NAVAIR 01-1A-509-2 TM 1-1500-344-23-2 TECHNICAL MANUAL CLEANING AND CORROSION CONTROL VOLUME II AIRCRAFT 15 APRIL 2009 This publication supersedes NAVAIR 01-1A-509-2/TM 1-1500-344-23-2, dated 01 March 2005. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. DESTRUCTION NOTICE - For unclassified, limited documents, destroy by any method that will prevent disclosure of contents or reconstruction of the document. PUBLISHED BY DIRECTION OF COMMANDER, NAVAL AIR SYSTEMS COMMAND Change 1 - 31March 2010
Transcript
NAVAIR 01-1A-509-2TM 1-1500-344-23-2
TECHNICAL MANUAL
CLEANING AND CORROSION CONTROL
VOLUME IIAIRCRAFT
15 APRIL 2009
This publication supersedes NAVAIR 01-1A-509-2/TM 1-1500-344-23-2, dated 01 March 2005.
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
DESTRUCTION NOTICE - For unclassified, limited documents, destroy by any method that will prevent disclosureof contents or reconstruction of the document.
PUBLISHED BY DIRECTION OF COMMANDER, NAVAL AIR SYSTEMS COMMAND
Change 1 - 31March 2010������������
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LIST OF EFFECTIVE PAGESDates of issue for original and changed pages are:
Original ........................ 0 ..........................15 Apr 2009(Includes IRAC 1)Change ....................... 1 ..........................31 Mar 2010Change x xx XXX 199XCha
Insert latest changed pages; dispose of superseded pages in accordance with applicable regulations.
NOTE: On a changed page, the portion of the text affected by the latest change is indicated be a vertical line, orother change symbol in the outer margin of the page. Change in illustrations are indicated by miniature pointinghands. Changes to wiring diagrams are indicated by shaded areas.
Total number of pages in this manual is 234, consisting of the following:
LIST OF ILLUSTRATIONS ........................................ ivLIST OF TABLES ........................................................ vHOW TO USE THIS MANUAL .................................. viiLIST OF TECHNICAL PUBLICATIONS
5-7. Troubleshooting .............................. 5-55-8. Expired Service Life ........................ 5-55-9. Post Treatment ................................ 5-55-10. Temporary Preservation ................. 5-6
TABLE OF CONTENTS
Chapter Page Chapter Page
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6 TREATMENT OF SPECIFIC AREAS
6-1. Introduction ..................................... 6-16-2. Air Intake Ducts for Jet Aircraft ....... 6-16-3. Battery Compartments, Boxes,
and Adjacent Areas ...................... 6-16-4. Beryllium-Copper Alloys .................. 6-26-5. Cables, Steel ................................... 6-36-6. Depleted Uranium
Counterweights ............................. 6-36-7. Electrical and Electronic
Equipment ..................................... 6-36-8. EMI Seals and Gaskets .................. 6-46-9. Fasteners and Attaching Parts ....... 6-66-10. Faying Surfaces, Joints, and
Seams........................................... 6-76-11. Fuel Tanks, Integral and External ... 6-76-12. Hinges, Piano Type ......................... 6-76-13. Relief Tube Areas ........................... 6-76-14. Rubber, Natural and Synthetic ........ 6-76-15. Springs ............................................ 6-86-16. Surfaces and Components
Exposed to Exhaust Gases,Gun Gases, and Rocket Blast ...... 6-8
6-17. Tanks, Potable Water ..................... 6-86-18. Thin Metal (0.0625 Inch
Thickness or Less) ....................... 6-86-19. Tubing, Non-Structural Members
and Assemblies ............................ 6-86-20. Tubing, Structural Members
and Assemblies .......................... 6-10
7 SEALANTS
7-1. Purpose ........................................... 7-17-2. Reasons for Sealing ........................ 7-17-3. Sealant Packaging .......................... 7-17-4. Sealing Compounds and
and Handling .............................. 7-107-7. Sealant Application Procedures .... 7-167-8. Sealing of Specific Areas .............. 7-207-9. Repair of Damaged Sealant .......... 7-257-10. Storage and Shelf Life .................. 7-27
8-5. Time Limitations of CPCs ............... 8-18-6. Description of CPCs ........................ 8-18-7. Preservation of Specific Areas ........ 8-58-8. Preservation Application
Methods ........................................ 8-58-9. Application of Polish and Wax ........ 8-98-10. Preservation of Assemblies and
Parts Removed fromAircraft During Maintenance ......... 8-9
9 EMERGENCY PROCEDURES
9-1. Purpose ........................................... 9-19-2. Responsibility .................................. 9-19-3. Emergency Preparations ................ 9-19-4. General Procedures ........................ 9-49-5. General Cleaning Procedures ........ 9-59-6. Removal of Fire Extinguishing
Agents ........................................... 9-69-7. Treatment After Landing on a
Foamed Runway .......................... 9-99-8. Treatment of Specific Areas............ 9-9
APPENDIX A. SUPPLEMENTAL REQUIREMENTSFOR NAVY AIRCRAFT
SECTION I. PAINT FINISHES ANDTOUCH-UP PROCEDURES................... A-1
A-1. Scope .............................................. A-1A-2. Safety .............................................. A-1A-3. Storage and Shelf Life .................... A-1A-4. Paint Systems ................................. A-2A-5. Paint Equipment .............................. A-4A-6. General Maintenance
Requirements for PaintSpray Equipment .......................... A-8
A-7. Preparation of Surfaces forPainting ......................................... A-9
A-8. General Paint ApplicationProcedures ................................. A-10
A-9. Touch-Up of Small Areas(Less Than Two Square Feet) .... A-18
A-10. Specific Paint ApplicationProcedures ................................. A-21
SECTION II. AIRCRAFT ANDENGINE CLEANING ............................. A-31
SECTION VII. PLASTIC MEDIABLASTING (PMB) FOR ARMYAIRCRAFT COMPONENTS ................. B-29
B-27. Plastic Media Blasting (PMB)for Army Aircraft Components .... B-29
SECTION VIII. CONSUMABLEMATERIALS.......................................... B-33
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2-1. Small Portable Foam GeneratingCleaning Unit (20 Gallons) ........................ 2-6
2-2. Large Portable Foam GeneratingCleaning Unit (45 Gallons) ........................ 2-7
2-3. Washing and Rinsing of Aircraft Surfaces .. 2-202-4. Use of Aircraft Washing Applicator ............. 2-202-5. Aircraft Cleaning Procedure ........................ 2-212-6. Automatic Water Spray Nozzle ................... 2-222-7. Aircraft at a Taxi-Through Rinse Facility .... 2-27
3-1. Fiber Optic Borescope .................................. 3-23-2. Measuring Corrosion with a Depth Gage...... 3-33-3. Optical Depth Micrometer ............................. 3-43-4. Usage of Straight Edge to
Determine if Suspect Areas HaveBeen Previously Reworked ....................... 3-7
3-5. Battery Compartment .................................... 3-93-6. Helicopter Bilge Area .................................... 3-93-7. Control Cables ............................................ 3-103-8. Jet Engine Frontal Area .............................. 3-103-9. Corrosion in Air Intake Duct ........................ 3-113-10. Corrosion Prone Points of
Air and Engine Inlet ................................. 3-113-11. Gun Blast Area ............................................ 3-113-12. Exhaust Trail Area....................................... 3-123-13. Corrosion Around Fasteners ....................... 3-123-14. Galvanic Corrosion of Aluminum Alloy
Sheet Adjacent to Steel Fasteners .......... 3-123-15. Flaps Lowered to Expose Recess Areas .... 3-133-16. Hinge Corrosion Points ............................... 3-133-17. Piano Hinge Lugs ........................................ 3-133-18. Typical Corrosion Around a
Relief Tube Vent ...................................... 3-143-19. Spot Welded Skin Corrosion Mechanism ... 3-143-20. Spot Weld Corrosion ................................... 3-143-21. Common Water Entrapment Areas ............. 3-143-22. P-3 Nose Landing Gear Wheel Well ........... 3-153-23. Wing Fold Joint ........................................... 3-15
4-1. Masking Around Area to be Stripped ............ 4-74-2. Bristle Discs Stacked on
Mandrel Assembly ................................... 4-134-3. Scotch-Brite™ Flap Brush and Mandrel ..... 4-154-4. Abrasive Flap Wheels with Spindle Mount . 4-15
4-5. Glove Box Unit Blast Cabinet ...................... 4-164-6. Portable Vacuum Blast Equipment ............. 4-164-7. Shaping Reworked Areas ........................... 4-214-8. Clean-Up of Pitting Corrosion on
Critical Structure ...................................... 4-224-9. Clean-Up of Limited Clearance Areas ........ 4-22
5-1. A Water Break-Free SurfaceCompared with One with Breaks ............... 5-1
5-2. Touch-N-Prep (TNP) Pen ............................. 5-35-3. Application of TNP Pen on
Non-Metallic Spatulaa ............................. 7-177-11. Faying Surface Sealing ............................... 7-207-12. Typical Fillet Seal ........................................ 7-217-13. Typical Injection Seal .................................. 7-217-14. Typical Methods of Sealing Fasteners ........ 7-227-15. Typical Lap Skin Sealing ............................. 7-237-16. Sealing Procedures for Typical
Aircraft Fitting .......................................... 7-237-17. Typical Spar Cap Sealing ........................... 7-247-18. Sealing of Access Doors ............................. 7-25
8-1. CPC Decision Tree ....................................... 8-8
Figure Title Page Figure Title Page
LIST OF ILLUSTRATIONS
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LIST OF TABLES
Table Title Page Table Title Page
1-1. Outline of Volume II ...................................... 1-21-2. Related Navy Publications ............................ 1-31-3. Related Army Publications ............................ 1-4
2-1. Water Quality Guidelines .............................. 2-22-2. Suggested List of Wash Rack Items ........... 2-122-3. Cleaning of Specific Areas and
Components ............................................ 2-142-4. Recommended Dilution of
Low Temperature Cleaner ....................... 2-262-5. Common Military Greases and
Their Uses ............................................... 2-30
3-1. Inspection Equipment and Techniques ......... 3-2
4-1. Recommended Non-PoweredAbrasives for Corrosion Removal ........... 4-10
4-2. Grades of Abrasive Mats ............................ 4-114-3. Grades of Steel Wool .................................. 4-114-4. Recommended Powered Abrasives for
B-1. Control of the Dissolving Action ofNitric-Hydrofluoric Acid Solution .............. B-12
B-2. Metal Identification Kit ................................. B-26B-3. Consumable Materials ................................ B-33
v/(vi Blank)
Figure Title Page Figure Title Page
LIST OF ILLUSTRATIONS (Cont.)
A-1. HVLP Spray Gun........................................... A-4A-2 HVLP Spray Gun Parts Breakdown .............. A-6A-3. 3M PPS Mounted on a Spray Gun ............... A-7A-4. Zahn No. 2 Viscosity Cup ............................. A-7A-5 Wet Film Thickness Gage ............................. A-8A-6. Paint Gun Washer ......................................... A-9A-7. Obtaining Correct Spray Pattern ................. A-11A-8. Estimating Distance to Work Surface ......... A-14A-9 Parallel Movement of Spray Gun ................ A-14A-10. Avoid Arcing the Spray Gun........................ A-14
A-11. Spraying Corners ........................................ A-14A-12. Improper Spray Angle ................................. A-14A-13. Triggering the Spray Gun ............................ A-14A-14. Proper Spray Pattern Overlap..................... A-15A-15. Sempens (Touch-up Pens) ......................... A-18A-16. Sempen Parts Breakdown .......................... A-18A-17. Sempen Application .................................... A-19A-18. Jet Engine Corrosion Control Cart .............. A-31A-19. Corrosion Control Spray Unit ...................... A-32
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HOW TO USE THIS MANUAL
1. This manual is one of a set. A complete set of manuals to perform aircraft cleaning and corrosion control functionsconsists of Volume I (Corrosion Theory), Volume II (this volume), and Volume IV (Consumable Materials andEquipment for Aircraft and Avionics).
2. The following major changes have been made in this revision. These changes should be reviewed forincorporation into local work documents, if applicable.
3. Specification and document references have been updated throughout the manual.
4. Cleaning and Corrosion Control questions may be directed to NAVAIR North Island, Code 4.3.4.6, 619-545-9759.
Report Control Number (RCN) LocationReport Control Number (RCN) Location
NADEP NORIS65888 2008 0837 Pg HMWS-5
HMM-76409402 2009 0001 Pg 3-6
VFA-12209355 2007 0030 Pg A-9
Army Aviation Support Division Pg B-29PRC #05P02079
Army Aviation Support Division Pg A-31PRC #08P01030
LIST OF TECHNICAL PUBLICATIONS DEFICIENCY REPORTS INCORPORATED
TPDR-1/(TPDR-2 Blank)
Army Aviation Support Division Pg B-19, B-22, B-23PRC #94A0982
Army Aviation Support Division Pg B-33PRC #05P01585
Army Aviation Support Division Pg B-5PRC #05P01586
Army Aviation Support Division Pg B-33PRC #98P01497
Army Aviation Support Division Pg 2-1PRC #01P01500
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TPDR-2
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HMWS-1
15 April 2009 NAVAIR 01-1A-509-2TM 1-1500-344-23-2
WARNINGS APPLICABLE TO HAZARDOUS MATERIALS
4. EXPLANATION OF HAZARDOUS MATERIALSICONS.
Chemical
The symbol of a liquid dripping onto ahand shows that the material will causeburns or irritation to human skin or tissue.
Cryogenic
The symbol of a hand in a block of iceshows that the material is extremelycold and can injure human skin or tissue.
Explosion
This rapidly expanding symbol showsthat the material may explode i fsubjected to high temperature, sourcesof ignition or high pressure.
Eye Protection
The symbol of a person wearing gogglesshows that the material will injure theeyes.
Fire
The symbol of a fire shows that thematerial may ignite or overheat and causeburns.
Poison
The symbol of a skull and crossbonesshows that the material is poisonous oris a danger to life.
Vapor
The symbol of a human figure in a cloudshows that material vapors present adanger to life or health.
1. Warnings and cautions for hazardous materialslisted are designed to apprise personnel of hazardsassociated with such items when they come in contactwith them by actual use. Additional information relatedto hazardous materials is provided in the NavyHazardous Material Control Program NAVSUPPINST5100.27, Navy Safety and Occupational Health (SOH)Program Manuals, OPNAVINST 5100.23 (Ashore)and OPNAVINST 5100.19 (Afloat), and the DoDHazard Communication (HAZCOM) program, DoDI6050.05. For each hazardous material used withinthe Navy, a Material Safety Data Sheet (MSDS) mustbe provided and available for review by users. Consultyour local safety and health staff concerning anyquestions regarding hazardous materials, MSDS,personal protective equipment requirements,appropriate handling and emergency proceduresand disposal guidance.
2. Under the heading HAZARDOUS MATERIALSWARNINGS, complete warnings, including relatedicon(s) and a numeric identifier, are provided forhazardous materials used in this manual. The numericidentifiers have been assigned to the hazardousmater ia l in alphabet ical order by mater ia lnomenclature. Each hazardous material is assignedonly one numerical identifier. Repeat use of a specifichazardous material references the numeric identifierassigned at its initial appearance. The approvedicons and their application are shown below.
3. In the text of the manual, the caption WARNING isnot used for hazardous material warnings. Hazardsare cited with appropriate icon(s), the nomenclatureof the hazardous material and the numeric identifierthat relates to the complete warning. Users ofhazardous materials shall refer to the completewarnings, as necessary.
This volume was prepared under the technical cognizance of theMaterials Engineering Division, NAVAIR North Island, San Diego, California.
1-1. GENERAL. Military aviation is recognized for itsunique and complex set of challenges, including maritimepatrol operation requirements and powerfulelectromagnetic operating fields. The highly constrainedmaintenance infrastructure available to deployed unitsto combat corrosion can limit the effectiveness ofprevention and corrosion control. The materials used toconstruct military aircraft also contribute to corrosion.High strength steels used in landing gear and launch/recovery systems are sensitive to pitting and stresscorrosion cracking, which can lead to catastrophic failure.Aluminum alloys susceptible to exfoliation andintergranular corrosion are commonly found on wingskin and other load carrying structures. Evenmagnesium, one of the most corrosion sensitive metalsknown, is still used in canopy frames and gear boxes.Added to this is the ever increasing age of militaryaircraft and the need to comply with stricter environmentalregulations. All of these factors combine to makecorrosion prevention and control a significant factor inthe safe and economic operation of military aircraft.
1-2. PURPOSE. The purpose of this manual is toprovide information on materials and procedures toprevent, control, and repair corrosion damage to aircrafton land or at sea.
1-3. SCOPE. The material in this manual containsbasic corrosion prevention and corrective maintenanceinformation to be used at Organizational, Intermediate,and Depot levels.
1-4. ARRANGEMENT OF MANUAL.
1-4.1. A complete set of manuals to perform aircraftcleaning and corrosion control functions consists ofVolumes I, II, and IV.
1-4.2. ARRANGEMENT OF VOLUME II. Volume IIconsists of nine chapters and two appendices, arrangedas shown in Table 1-1.
1-5. RELATED PUBLICATIONS. Tables 1-2 (Navy)and 1-3 (Army) list technical publications that may beused as supplemental references by personnel involvedin cleaning and corrosion control.
1-6. CONSUMABLES AND EQUIPMENT.Procurement information for ordering consumables andequipment referenced in this volume may be found inVolume IV (Navy and Army) of this manual.
2-1. INTRODUCTION. Cleaning is the first step inpreventing aircraft corrosion and wear. Dirt, salt airdeposits, and other contaminants can promote rapidcorrosion and wear of aircraft surfaces, and can have anadverse impact on aircraft systems performance.Effective cleaning requires knowledge of the appropriatematerials and methods needed to remove thesecontaminants.
2-2. REASONS FOR CLEANING. Aircraft should becleaned regularly in order to:
a. Prevent corrosion by removing salt deposits, othercorrosive soils, and electrolytes;
b. Maintain visibility through canopies and windows;
c. Allow a thorough inspection for corrosion andcorrosion damage;
d. Maintain turbine engine efficiency;
e. Reduce fire hazards by the removal ofaccumulations of leaking fluids;
f. Improve overall appearance;
g. Ensure aerodynamic efficiency of the aircraft;and
h. Maintain special paint scheme characteristics.
2-3. FREQUENCY OF CLEANING. All aircraft shallbe cleaned according to schedules required by theparent service organization. Navy aircraft shall becleaned in accordance with the schedule in the aircraftspecific manual. In the absence of aircraft specificrequirements, Navy aircraft shall be cleaned at leastevery 7 days when aboard ship and at least every 14days when ashore. Army requirements are given inAppendix B. Under certain conditions, depending onthe type of aircraft and usage, the normal wash cyclemay not be sufficient. More frequent cleaning may berequired for certain types of aircraft when:
a. Excessive exhaust gases or gun blast soilsaccumulate within impingement areas;
b. Paint is peeling, flaking, or softening;
c. Fluid leakage (coolant, hydraulic fluid, or oil)occurs; or
d. Exposure to salt spray, salt water, or othercorrosive materials occurs.
2-3.1. DAILY CLEANING. When deployed within threemiles of salt water or when flown below 3000 feet oversalt water, daily cleaning or wipe down is required on allexposed, unpainted surfaces, such as landing gearstruts and actuating rods of hydraulic cylinders.
NOTE
Optimum use of taxi-through rinse facilities isrecommended for removal of salt contaminationand light soils when operating near sea water.Rinsing does not satisfy aircraft washingrequirements, it only removes readily solublematter from exterior surfaces.
2-3.2. IMMEDIATE CLEANING. Affected areas mustbe cleaned immediately if:
a. Spilled electrolyte and corrosive deposits arefound around battery terminals and battery area;
b. Aircraft are exposed to corrosive fire extinguishingmaterials;
c. Salt deposits, relief tube waste, or other corrosivecontaminants are apparent;
d. Aircraft are exposed to significant amounts of saltwater;
e. Fungus growth is apparent; or
f. Chemical, biological, or radiological (CBR)contaminants are detected.
2-3.3. Procedures for decontamination of aircraftexposed to chemical, biological or radiological (CBR)materials are contained in FM 3-5 (Army) or or NAVAIR00-80T-121(Navy).
2-4. WATER QUALITY. Cleanliness of water can affectaircraft cleaning operations. Chlorides and pH have themost effect on corrosion. Recommended guidelines for
2-2
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the quality of fresh water used for cleaning and rinsingare shown in Table 2-1. The limits for chlorides and pHshown are approximately the same as for potable water.Adequate disinfection should be provided to control thegrowth of microorganisms in the water.
CAUTION
Authorized cleaning agents are listed in thischapter and Volume IV. Do not use unauthorizedcleaners. Although commercial cleaners mayappear to perform as well or better thanapproved products, these materials may becorrosive to aircraft alloys.
2-5. CLEANING COMPOUNDS. Cleaning compoundswork by dissolving soluble soils, emulsifying oily soils,and suspending solid soils. There are several types ofcleaning compounds, each of which clean by one ormore of these mechanisms. The following paragraphsdescribe the various authorized cleaning materials foraircraft surfaces. Paragraph 2-9 provides detailedcleaning procedures.
2-5.1. DILUTION. MIL-PRF-85570 Types I and II,MIL-PRF-85704 Types I, II and III, and MIL-D-16791detergent cleaning compounds should be diluted withwater as specified prior to use. Other detergent cleaningcompounds may also require dilution with water. Ingeneral, more concentrated solutions than thoserecommended do not clean better and are wasteful;MORE IS NOT ALWAYS BETTER. In fact, higherconcentrations can interfere with effective cleaning andrinsing processes. The solution merely becomesslippery, prevents the washing pad from loosening thesoil and makes rinsing more difficult. Do not exceed therecommended dilution.
CAUTION
High strength steels (typically 180 ksi andabove), some high strength aluminums, andsome stainless steels can develop a conditionknown as hydrogen embrittlement whenexposed to some highly alkaline materials, suchas unauthorized cleaners. Sudden catastrophicfailure may occur as a result of hydrogenembrittlement when the part can no longersustain the internal and/or applied stresses.See Volume I for additional information.
NOTE
Ozone depleting substances (ODS) are solventssuch as, but not limited to, 1,1,1 trichloroethane(MIL-T-81533) and trichlorotrifluoroethane(MIL-C-81302). These solvents, as well asproducts containing them, are still used in someaircraft maintenance processes, including highpressure oxygen systems cleaning and someavionics cleaning. Alternate materials continueto be identified. Wherever possible,specifications are being changed to eliminatetheir use automatically. Some products thathave been reformulated are now flammable.Pay close attention to all CAUTION/WARNINGlabels on solvents and solvent-based products.
2-5.2. MODERATELY ALKALINE CLEANERS. Highlyalkaline cleaning compounds (pH greater than 10) arenot authorized for Navy or Army aircraft, due toincompatibility with polyimide wiring insulation.Moderately alkaline cleaners (pH between 7.5 and 10),such as MIL-PRF-85570 Types I and II (Exterior AircraftCleaning Compound), are recommended. Both typescontain detergents and foaming agents, and work in thesame way as a detergent solution. Type I is a moreeffective cleaner for heavy oils and greases, includingwire rope lubricant, due to its solvent content, but itshould not be used in areas where ventilation is poor.Type IA is a premixed (1:4 dilution) Type I solutionavailable in a 16 oz aerosol can. Type II contains nosolvent but is an excellent cleaner for light oils andhydraulic fluids, and can be used in areas of reducedventilation (such as cockpits, cabins, bilges, andequipment bays). Type II RTU is a premixed (1:4dilution) Type II solution available in a 32 oz triggerspray bottle and a five gallon can.
retemaraP stimiL
sedirolhC xaml/gm004
Hp 5.8-5.6
)SDT(sdiloSdevlossiDlatoT xaml/gm005
)SST(sdiloSdednepsuSlatoT xaml/gm5
OCaC(ssendraH 3) l/gm051-57
)DOB(dnameDnegyxOlacigoloiB xaml/gm5
)HPT(nobracordyHmuelortePlatoT xaml/gm01
)ISL(xednInoitarutaSreilgnaL orezevobaylthgilS
Table 2-1. Water Quality Guidelines
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2-5.3. TURBINE ENGINE GAS PATH CLEANERS.MIL-PRF-85704 (Cleaning Compound, Turbine EngineGas Path) is specially formulated for cleaning thecompressor section of gas turbine aircraft engines andminimizing engine corrosion during wash cycles. Types I,II, and III are supplied as concentrates and must bemixed with water prior to use. Types II RTU and III RTUare premixed and ready to use upon receipt. Types I, II,and II RTU are intended for use with the engine off-line,with the starter motoring the engine. Type I (solventemulsion concentrate with hydrocarbon solvents) worksby softening oily soils so that they can be emulsified bythe detergent. Local air pollution regulations may restrictthe amount and methods of application of Type I cleaner:Types II or II RTU (aqueous cleaner without hydrocarbonsolvents) may be used as alternates. Types III andIII RTU are intended for use with the engine on-line(fired). Because purified water is required to mix theType III concentrate and may be unavailable, use ofType III RTU is recommended for on-line cleaning.
2-5.4. SPOT CLEANERS. The following three cleaners(to be used without dilution) are approved for specificlocalized applications in areas of heavy soil.
2-5.4.1. High Gloss Spot Cleaner. MIL–PRF–85570Type III is recommended for cleaning exhaust track andgun blast areas of high gloss paint systems. Thismaterial contains solvents, detergents, and suspendedabrasive matter to remove soil by wearing away thesurface that holds it. It shall not be used on aircraftpainted with tactical paint schemes since it raises thegloss of the surface.
2-5.4.2. Low Gloss Tactical Paint Scheme SpotCleaner. MIL-PRF-85570 Type IV is recommended forcleaning exhaust track and gun blast deposits, smudges,boot marks, and other embedded soils on low glosscoatings. This material contains solvents, detergents,and suspended rubber particles. When rubbed on asoiled surface, the rubber particles act like tiny erasers,removing soil by mechanically entrapping it in the rubber.The gloss of tactical paint coatings is unchanged. Formore information on tactical paint schemes, seeAppendix A.
NOTE
Solvents in MIL-PRF-85570 Type IV cleanermay be considered hazardous air pollutants(HAPs). Consult local regulations before use.MIL-PRF-85570 Type V may be used as analternate.
2-5.4.3. Thixotropic (Viscous) Cleaner.MIL-PRF-85570 Type V is recommended for cleaningwheel wells and wing butts, and replaces solvent cleaningwhere water rinsing can be tolerated. This cleanercontains solvents, detergents and some thickeningagents. When applied undiluted to an oily or greasysurface, the cleaner clings long enough to emulsify thesoil (about 5 to 15 minutes) and can then be rinsed awaywith fresh water. To perform most effectively, Type Vmust be applied to a dry surface. Do not prerinse areasof the aircraft that require application of Type V.
2-5.5. DETERGENT SOLUTION. MIL-D-16791(Detergents, General Purpose Liquid Nonionic)dissolved in water cleans by dissolving soluble salts,emulsifying low viscosity oils, and suspending easilyremoved dirt and dust. It is not very effective on grease,but is an excellent cleaner for interior lightly soiledareas, plastics, and instrument glass covers.
2-5.6. NON-AQUEOUS CLEANERS. MIL-PRF-32295(Cleaner, Non-Aqueous, Low VOC, HAP-Free) is anenvironmentally friendly chemical cleaner that is free ofhazardous air pollutants (HAP) and contains a very lowlevel of volatile organic compounds (VOC<25 g/l).Because these cleaners do not contain water, they canbe used in areas where water-based cleaners are notallowed. MIL-PRF-32295 can be used as a substitutefor MIL-PRF-680 in most applications. Type I isrecommended for removal of light soils (oils, dirt, CPCs).Type II is a more effective cleaner for removal of heavysoils (greases, carbonized oils, aged CPCs).
2-5.7. SOLVENTS. Cleaning solvents dissolve oils andgreasy soils so that they can be easily wiped away orabsorbed on a cloth. However, solvents differ significantlyin cleaning ability, toxicity, evaporation rate, effect onpaint, and flammability. MIL-PRF-680 Type IIDegreasing Solvent is the most common cleaning solventused on aircraft, due to its low toxicity, minimal effect onpaint, and relative safety. Other solvents, such asalcohols, ketones, and aliphatic naphtha, are specializedmaterials restricted for use.
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NOTE
The use of solvents for cleaning operations isdependent upon stringent environmental andsafety regulations. Determine localrequirements regarding limitations andrestrictions on materials, quantities, anddisposal from your work center supervisor,safety officer, or industrial hygienist.
Degreasing Solvent, MIL-PRF-680, replacesDry Cleaning and Degreasing Solvent, P-D-680.MIL-PRF-680 has been reformulated toeliminate Hazardous Air Pollutants, however,its high VOC content may prevent use in somelocations.
2-5.7.1. Degreasing Solvent (MIL-PRF-680). Thissolvent is used as a cleaner and degreaser for paintedand unpainted metal parts. It is also used to remove oilycorrosion preventive compounds. The solvent isavailable in four types. Although the degreasingeffectiveness is approximately the same for each type,the flash points as a measure of flammability differ asfollows: Type I, 100°F (38°C) minimum; Type II, 140°F(61°C) minimum; Type III, 200°F (93°C) minimum;Type IV, 140°F (61°C) minimum. A lower flash pointindicates greater flammability; however, all types willburn intensely once ignited. Type I is not authorized foruse as a general cleaner due to its flammability, but maybe used in parts washers that are designed for suchsolvents. Type II is the most common cleaning solventused on aircraft, and is intended for use where a solventwith a higher flash point is required. Type III is intendedfor use in confined atmospheric conditions where a veryhigh flash point is required. Type IV is used where ahigher flash point and strong solvency is desired. Thedwell time for all types should be held to a minimum(less than 15 minutes) to avoid damage to paint.
2-5.7.2. Isopropyl Alcohol (TT-I-735). This flammablesolvent is used as a disinfectant, and for removingfungus and mold from aircraft surfaces. It is a poordegreaser, but is a good solvent for removing fingerprints.
2-5.7.3. Methyl Ethyl Ketone (MEK) (ASTM D 740).This highly flammable solvent is used for cleaning priorto adhesive bonding. Most locations cannot use MEK asa wipe solvent for general cleaning or prior to paintingdue to restrictions on the use of solvents with vaporpressures greater than 45 millimeters of mercury (mmHg). As an alternate cleaner, use MIL-PRF-85570 Type IIAircraft Cleaning Compound (diluted 1 part cleaner to14 parts water), rinse thoroughly with fresh water and
allow surfaces to dry. Surfaces may be also be cleanedby solvent wiping with AMS 3166 (Solvents, CleaningPrior to Application of Sealing Compounds).
2-5.7.4. Aliphatic Naphtha (TT-N-95). This highlyflammable solvent is used for cleaning oils or greasydeposits and other soils from aircraft transparenciessuch as acrylic canopy materials. Other solvents maycause crazing and other damage to transparencies. It isalso effective at removing masking or preservation taperesidue. This material may be restricted in manygeographic locations for other cleaning operations dueto its high vapor pressure.
2-5.7.5. Thinner, Aliphatic Polyurethane Coatings(MlL-T-81772). This highly flammable solvent can beused for prepaint solvent cleaning as an alternative toMEK. MIL-T-81772 may be used at locations requiringa solvent vapor pressure less than or equal to 45 mm Hg.
2-5.8. PARTS WASHER CLEANING SOLUTION.MIL-PRF-29602 (Cleaning Compounds for Parts Washerand Spray Cabinets) is the recommended cleaningagent for use in high pressure cabinet-style parts washersto remove oils and greases from disassembledcomponents. It shall not be used for bearings unlessauthorized by part specific documentation. Also, due tothe high maximum allowable pH (pH 13.5) ofMIL-PRF-29602 cleaning compound, aircraft cognizantengineering authority approval is required beforecleaning aluminum alloy parts. MIL-PRF-29602 mustbe diluted with water in accordance with manufacturer’sinstructions, and the concentration must be testedperiodically (every 28 days is recommended).
2-5.9. MILDEW REMOVER. NAVCLEAN is a mildewremover developed by NAVAIR for cleaning mildew,mold, and fungus from aircraft surfaces. The mildewremover kit consists of four components (an oxidizingagent, a detergent, and corrosion inhibitors). Thecomponents are mixed with water immediately prior touse. The solution is effective for twenty four hours aftermixing. Surfaces cleaned with NAVCLEAN shall berinsed thoroughly with fresh water after application toremove residue.
2-5.10. MISCELLANEOUS CLEANING AGENTS.
2-5.10.1. Plastic polish (P-P-560), which contains mildabrasives, to polish out scratches in certain canopymaterials.
2-5.10.2. Optical glass cleaner (A-A-59199) for cleaninglenses.
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2-5.10.3. Ammonium hydroxide (O-A-451) to neutralizeurine.
2-5.10.5. Monobasic sodium phosphate (ANSI/AWWAB504) or boric acid (A-A-59282) to neutralize electrolytespills from nickel-cadmium batteries.
2-6. STEAM CLEANING. Steam cleaning is definedas super-heated water vapor delivered at relatively highpressure through a nozzle or wand. Steam cleaning canerode paint, craze plastic, debond adhesives, damageelectrical insulation, and drive lubricants out of bearings.Due to the potential for damage, it shall not be used onaircraft/missiles at the Organizational/Unit orIntermediate levels of maintenance. In addition, steamcleaning shall not be used on the following items removedfrom aircraft/missiles: honeycomb bonded structure,sealant, fiberglass composites, acrylic windows, orelectrical wiring.
2-7. CLEANING EQUIPMENT. Equipment specific toone type of aircraft is not covered in this manual. Thefollowing equipment is available for general cleaning.Ordering information for approved equipment can befound in Volume IV, Chapter 3. General operatinginstructions are found in paragraph 2-8. See specificoperating manuals for detailed instructions on automatedequipment.
CAUTION
No equipment which produces more than175 psi nozzle pressure shall be used for aircraftcleaning purposes unless specifically authorizedby the parent service organization. Thisrestriction includes portable pressure washers.High-pressure cleaning processes can erodepaint, drive lubricants out of bearings, drivewater into hidden areas, damage electricalinsulation, damage honeycomb bondedstructure and composite surfaces, and damagesealant.
NOTE
Use only cleaning materials or equipmentauthorized by the parent service organizationand as described in this manual.Experimentation with unauthorized cleaningmaterials or equipment may damage aircraft,reduce reliability and increase maintenancecosts.
2-7.1. SMALL PORTABLE FOAM GENERATINGCLEANING UNIT. The cleaning unit is compact, light,and ideal for cleaning hard to reach areas. It consists ofa 54 inch applicator wand, 50 feet of hose, and either a15 gallon stainless steel tank or a 20 gallon carbon steeltank. The tank assembly moves easily on rubber tirewheels (see Figure 2-1). The control system allows theoperator to adjust wetness of foam to fit any job. Thecleaning unit provides a foam capable of clinging tovertical surfaces to soften and dislodge soils. Generaloperating instructions for the cleaning unit are given inparagraph 2-8.1.
2-7.2. LARGE PORTABLE FOAM GENERATINGCLEANING UNIT. This cleaning unit is a simplified,pressure operated, foam-dispensing system (seeFigure 2-2). It uses available air supply for its powersource without using pumps. Air is metered directlyfrom the pressurized solution chamber into the hose tocreate foam. Units are available with a 45 gallon stainlesssteel tank or a 50 gallon carbon steel tank. Generaloperating instructions for the cleaning unit are given inparagraph 2-8.2.
2-7.3. TURBINE ENGINE COMPRESSOR CLEANINGEQUIPMENT. Equipment used for cleaning Navy aircraftturbine engines is contained in Appendix A. Army: referto specific engine technical manual.
2-7.4. MISCELLANEOUS LARGE CLEANINGEQUIPMENT. Other equipment such as truck or trailermounted spray or foam equipment may be available atcertain locations.
2-7.5. SPRAY GUN FOR CLEANING COMPOUNDS.This spray gun (AMS-G-952 Type I) has an extendednozzle/tube and requires approximately 14 cfm of air at50 psi to siphon cleaning compounds from a container.Do not use with solvents.
2-7.6. PNEUMATIC VACUUM CLEANER. Theair-operated vacuum cleaner is a small, portable unit forremoving debris and water from aircraft (Volume IV,Chapter 3).
2-7.7. UNIVERSAL WASH UNIT. The universal washunit is used for general purpose cleaning. Generaloperating procedures are given in paragraph 2-8.3.
2-7.8. CABINET-STYLE AQUEOUS PARTSWASHER. This method of cleaning utilizes an industrialpower washer that is comprised of an enclosed cabinetequipped with a system of spray impingement nozzles,cleaning solution heater, fluid pump, skimmer for oil and
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Figure 2-1. Small Portable Foam Generating Cleaning Unit (20 Gallons)
its residues, and separate reservoirs for cleaning solutionand waste. Cabinet-style parts washers have beenimplemented to replace the use of 1,1,1-trichloroethanevapor degreasing and to reduce the dependence uponMIL-PRF-680 Type II. They are suitable for degreasingdisassembled components. This cleaning processeffectively removes soils, oils/greases, corrosionpreventive compounds and other contaminants byapplying aqueous cleaner at varying combinations ofhigh temperature and pressure. The washers areequipped with oil skimming devices and particulatefiltration devices to extend the life of the cleaningsolution. Cognizant aircraft engineering authorityapproval is required prior to using cabinet-style partswashers for cleaning bearings or aluminum alloy parts.General operating instructions are given inparagraph 2-8.4.
2-7.9. MISCELLANEOUS EQUIPMENT. Accessoriesand consumable materials for manual operations, listedin Volume IV, Chapters 2 and 3, include the followingimportant items:
2-7.9.1. 3M No. 33 Aircraft Cleaning Pads and 3M No.261 Pad Holders are replacements for the 3M No. 251MWashing Kit for Exterior Aircraft Washing Operations.The wooden handle used with the No. 251M WashingKit can also be used with the 3M No. 261 Pad Holder;however, use of the A-A-1464 Aluminum Handle ishighly recommended because it is more ergonomic and
easily extendable from five to ten feet. The No. 33 padsare primarily used for general aircraft cleaning.
2-7.9.2. 3M "Jet Pad" Melamine Wash Pads are softfoam pads with a urethane foam backing and a polyesterattachment layer. These pads have demonstratedcleaning efficiency that is superior to conventional wovenpolyester cleaning pads. The Jet Pads are compatiblewith the 3M No. 261 Pad Holder, and are recommendedfor hard to clean soils; however, they will degrade overtime and generate debris during use.
2-7.9.3. Non-Metallic Cleaning and Polishing Pads(A-A-3100) are crimped polyester fiber pads for detergentand solvent cleaning aircraft surfaces. Do not use withpaint removers.
2-7.9.4. Brushes, Non-Metalic Bristles (MIL-B-23958,A-A-3080) are used with aircraft detergent cleaners,such as MIL-PRF-85570.
2-7.9.5. Cheesecloth (CCC-C-440) and non-wovencloth (CCC-C-46) are used for cleaning critical areaswhere an exceptionally clean cloth is required, such assolvent cleaning prior to painting, adhesive bonding, orsealing.
2-7.9.6. Plastic spray bottles are used for applyingdiluted MIL-PRF-85570 Type I or II or concentratedType V.
Figure 2-2. Large Portable Foam Generating Cleaning Unit (45 Gallons)
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2-8. EQUIPMENT OPERATING PROCEDURES. Thissection contains general operating instructions for themost commonly used large pieces of cleaning equipment.
2-8.1. SMALL PORTABLE FOAM GENERATINGCLEANING UNIT.
WARNING
Do not service the small portable foamgenerating cleaning unit without releasingpressure.
a. Release pressure prior to servicing.
NOTE
Refer to manufacturer's instructions to mix theproper ratio of solution to be used.
b. Remove tank fill cap and fill container withappropriate diluted cleaning compound. Allow adequateair space at the top of the tank. Replace filler plug.
c. Connect air supply to air inlet valve on air regulator.
d. Open compound metering valve to full openposition.
e. Open air inlet valve and set air pressure regulatorto 30-70 psi.
f. Open foam discharge valve and direct foam atobject to be cleaned.
g. If foam is too wet, close compound meteringvalve slightly.
h. If foam is too dry, open compound metering valveslightly and close air metering valve slightly.
i. Allow foam to remain on the surface for up to oneminute, but not long enough to dry, then scrub and rinse.
CAUTION
When cleaning task is completed, drain tankand flush with fresh water to prevent aconcentrated cleaning solution from being usedthat could be damaging to aircraft surfaces.
j. When cleaning task is completed, drain detergentsolution from tank and flush with fresh water.
2-8.2. LARGE PORTABLE FOAM GENERATINGCLEANING UNIT.
WARNING
Do not service the large portable foamgenerating cleaning unit without releasingpressure.
a. Release pressure prior to servicing.
b. If tank has been in prior use and is closed, closecleaning compound valve and air valve, then open airdump valve to bleed off retained air pressure.
c. Remove cover of tank. The cover is retained byseveral draw bolts.
NOTE
Refer to manufacturer's instructions to mix theproper ratio of solution to be used.
d. Fill with cleaning compound in appropriate dilution,allowing for adequate air space at the top of the tank.
e. Replace cover, being sure it is firmly locked inplace.
f. Close air and cleaning compound handle valves.
g. Attach air line to air inlet on side of unit. Fill andcheck air regulator to ensure proper pressure (30-70 psi).
h. Open air valve.
i. Open cleaning compound valve slowly untildesired foam consistency is reached.
j. Apply foam to surface to be cleaned. Generally,thin uniform layers perform best. During initial setting ofthe unit, air and cleaning compound valves should beadjusted to give the desired foam consistency.Combinations of less air and more cleaning compoundmake a wet foam. Combinations of more air and less
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cleaning compound make a drier foam. Dry foams givegreater dwell time and prolong cleaning action, but wetfoams clean better.
k. Allow foam to remain for up to one minute, but notlong enough to dry, then scrub and rinse.
CAUTION
Insure that tank is drained to prevent a build-upof highly concentrated solution, which maydamage aircraft surfaces.
l. When cleaning task is completed, drain detergentsolution from tank and flush with fresh water.
2-8.3. UNIVERSAL WASH UNIT.
WARNING
Use the universal wash unit in the horizontalposition only.
a. Connect the strainer unit to the intake hose.
b. Connect the wand and nozzle spray to the output(discharge) hose or connect the discharge quickdisconnect to the aircraft wash manifold quickdisconnect.
c. Insert the strainer unit into a container of water orcleaning solution.
d. Press and hold the start or remote start switch;observe the pressure gage. It should immediatelyindicate an increase in pressure.
e. After the pressure reaches approximately 10 psig,release the start switch. The unit should continue tooperate.
f. The unit will deliver approximately 2.5 gallons perminute at 30 psig.
g. Press the stop or remote switch to stop the unitfrom operating.
2-8.4. CABINET-STYLE AQUEOUS PARTSWASHER.
WARNING
The materials used and waste generated fromthis cleaning process may be hazardous tooperating personnel and the environment. Drainany entrapped solution back into the washer.Contact the local industrial hygienist,bioenvironmental engineer, or EnvironmentalOffice for guidance regarding personalprotective equipment (PPE) and other healthand safety precautions.
Parts will be very hot after the cleaning process.Handle with thermally protective and waterrepellent gloves.
CAUTION
High pressure parts washers shall not be usedfor cleaning bearings unless specificallyauthorized. Due to the maximum allowable pH(pH 13.5) that the required cleaning compound,MIL-PRF-29602, can reach, cognizantengineering authority approval is required beforecleaning aluminum alloy and IVD aluminumcoated parts.
a. Determine the reservoir capacity of the partswasher. Fill the reservoir with a solution ofMIL-PRF-29602 cleaning compound, diluted permanufacturer’s recommended concentration.
NOTE
Do not use the parts washer until the cleaningsolution has stabilized at the requiredtemperature. Agitation of the solution prior toreaching elevated temperatures may result inexcessive foaming of the cleaning solution.
b. Allow cleaning solution to stabilize atmanufacturer’s recommended temperature (usually140°F to 180°F).
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CAUTION
Caution shall be exercised when loadingcomponents with areas which can entrap water.Position parts in the cabinet and baskets suchthat the cavities which can hold or entrap waterare face down. It is imperative thatsuitable fixtures and/or baskets are used tosecure components during the cleaning cycle.Failure to do so may result in damage to thecomponents being cleaned by the high pressureimpingement spray.
c. Place components to be cleaned into parts washer.Components shall be secured to the turntable, or placedin a basket that is secured to the turntable.
CAUTION
Parts shall not be left unattended in the washingcabinet. Once the cleaning cycle is complete,the inside environment of the cabinet willbecome very hot and humid. Parts leftunattended, or not removed within the requiredtime, may develop corrosion. Follow therecommended manufacturer’s instructions forthe removal of cleaned parts.
d. Set the wash cycle timer for 3-30 minutesdepending upon the type of soil to be removed and thequantity of soil on the parts. For light degreasing, a3 minute cycle may be sufficient, while heavily soiledand baked on grease may require a full 30 minute cycle.Run the wash cycle, and allow components to coolbefore handling.
e. If the cleaned part is subjected to an immediateinline process, i.e., fluorescent penetrant inspection, orpainting, or in cases where precision cleaning is required,rinse the part with fresh clean water and thoroughly dry.
f. For bare steel parts which have been cleaned/rinsed and will not be processed immediately, wrap inVCI fi lm (MIL-PRF-22019) or apply CPCs(MIL-PRF-81309 Type II, followed by MIL-PRF-16173Grade 4).
2-9. CLEANING PROCEDURES.
2-9.1. WARNINGS AND CAUTIONS. The followingwarnings and cautions shall be observed during aircraftcleaning operations:
2-9.1.1. Electrical Warnings.
a. Aircraft and/or other equipment shall not bewashed, cleaned, or inspected on an outdoor wash rackwhen an electrical storm is in the immediate area.
b. Open all circuit breakers associated with batterypower (refer to applicable aircraft manuals) prior toapplication of flammable solvent cleaners.
c. In order to guard against the danger of staticelectricity, aircraft shall be electrically grounded duringall cleaning operations and when moored or parked.
d. Before cleaning electrical and avionic equipment,make sure electrical power is disconnected. Injury ordeath may otherwise result.
2-9.1.2. Personal Protection. Consult the local safetyoffice for personal protective equipment (PPE)requirements. The following Warnings apply.
a. Wear rubber gloves, chemical or splash proofgoggles, and water resistant boots during cleaningoperations using cleaning compounds MIL-PRF-85570or MIL-PRF-85704. Wet weather clothing is not requiredexcept during cold weather. If cleaner is splashed ineyes, rinse thoroughly with fresh water for 15 minutesand report to medical facility. Remove clothing saturatedwith cleaning solution immediately and flush exposedskin areas with fresh water.
b. Cleaning solutions are slippery. Maintenancestands shall be used where practical. Safety harnessand safety lines must be used when standing on uppersurfaces of aircraft during cleaning operations.
2-9.1.3. Solvent Warnings.
a. Do not use synthetic wiping cloths with flammablesolvents, such as aliphatic naphtha (TT-N-95), MEK, orMIL-T-87177 paint thinner. Synthetic cloths can generate
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static electricity which can result in sparks and fire.Cotton wiping cloths, such at terry cloth, flannel, orcheesecloth, are acceptable.
b. Solvents shall not be applied with atomizing sprayequipment. This is not only hazardous, but violatesenvironmental regulations in most areas.
c. Keep all solvents away from open flames and anylive electrical circuit or sources of electrical arcing.Ensure that residual solvent is removed from aircraft,engine bays, and equipment.
d. Use solvents in well-ventilated areas. Wear rubbergloves and chemical or splash proof goggles. Avoidskin contact. Consult the local safety office regardingrespiratory protection.
e. Do not mix cleaning compound with any solvent(e.g. MIL-PRF-680). The added solvents will create afire hazard and a serious disposal problem, and cancause damage to nonmetallic materials.
2-9.1.4. Cleaning Solution Cautions.
a. Steam shall not be used for cleaning aircraft orcomponents.
b. Do not apply MIL-PRF-85570 Types I, III, IV or V,or MIL-PRF-85704 Type I or II cleaning solutions or anyunauthorized solvents to electrical wiring or plasticaircraft canopies, as it may cause damage to insulationor crazing of transparent surfaces.
c. Do not use cleaning compounds at higherconcentrations than those recommended.
d. Do not allow cleaning solutions to dry on aircraftsurfaces. Such practices will cause streaking and candamage aircraft finishes and components.
2-9.1.5. Water Intrusion Cautions.
a. To prevent entrapment of water, solvents, andother cleaning solutions inside of aircraft parts andstructural areas, all drain holes and flap valves shall beopened before washing, and checked again afterwashing, to ensure that proper drainage occurs.
b. Do not wash or rinse aircraft with a solid streamof water. Use a soft spray pattern to avoid damagingfragile surfaces or causing water intrusion.
c. Water must not be directed at pitot tubes, staticports, or vents. These areas shall be adequatelyprotected.
d. Relubricate all fittings and other lube points inareas to which cleaning compounds have been applied,such as wheel wells, flap wells, and flight control wells.Ensure that these areas are adequately drained. Checkthe specific aircraft manual to determine lubricationrequirements.
2-9.1.6. Oxygen System Cautions. Observe warningsand cautions in specific oxygen system manuals.
2-9.1.7. Special Precautions. Use extreme care whencleaning and related treatment is performed aroundradomes, access doors to integral fuel tank cells, lightfixtures, electrical components, and antennas. Theseareas may be damaged by cleaning and relatedequipment.
2-9.2. PREPARATION FOR AIRCRAFT CLEANING.A list of recommended wash rack equipment andconsumables is provided in Table 2-2.
WARNING
Open all circuit breakers associated with batterypower (refer to applicable aircraft manuals)prior to application of any flammable solvent.
CAUTION
Cover acrylic or polycarbonate canopies duringshore based washing to prevent accidentalscratching or crazing by cleaning compounds.
2-9.2.1. Canopy. Cover canopy with flannel cloth(A-A-50129 Type II). Cover flannel with barrier material(MIL-PRF-131 Class 1), and tape to canopy frame orpainted surface near canopy using preservation tape(AMS-T-22085 Type II) or masking tape (AMS-T-21595Type III). Do not apply tape directly to transparentsurface.
a. To protect against cleaning solution entrapment,inspect all lubrication points that have exposure typelubrication fittings.
b. Prior to lubricating any components or parts,remove all foreign matter from joints, fittings, and bearingsurfaces, using non-woven cleaning cloth. Wipe up allspilled or excess oil and grease.
c. Lubricate all fittings which will be exposed towash solutions, in accordance with maintenancemanuals or maintenance cards. If fittings do not acceptlubrication, replace and lube prior to wash.
d. See applicable maintenance manual andparagraph 2-13 for lubrication of aircraft components.
2-9.2.3. Protection From Water/Cleaning CompoundIntrusion. Take the following steps to prevent water/cleaning compound intrusion during cleaning:
a. Close doors and emergency openings.
b. Refer to aircraft maintenance manuals forlocations of drain holes. Check drain holes. Make surethat all drain holes are clear by inserting a probe (suchas a pipe cleaner), except where pressurized flappervalves are located.
c. Cover vents, openings, and ports. Refer to aircraftmaintenance manuals for locations of vents to bemasked. Pitot static ports shall be covered. If covers arenot available, barrier material (MIL-PRF-131 Class 1)may be cut into circular pieces and taped in place withpreservation tape (AMS-T-22085 Type II). Covers mustbe removed prior to release of aircraft for flight. Particularcare shall be taken to ensure that static vents are notfouled by tape adhesive transfer. In the event ofsignificant adhesive transfer, clean with aliphatic naphtha(TT-N-95) or degreasing solvent (MIL-PRF-680 Type II).
CAUTION
Do not use a direct spray of water or cleaningcompound on carbon brakes, wheels or wheelhubs.
d. Cover wheels with locally fabricated covers toprevent water/cleaning compound contamination ofwheel bearings and carbon brakes. Carbon brakeshave temporarily reduced performance when subjectedto water, deicers, degreasers, and oil. Brakes should beprotected from direct impingement as much as practicalduring maintenance, aircraft cleaning or operations.Weak or spongy brakes (and in some cases, smoke)may result until the contaminants are burned off (normallyone flight). If contamination, corrosion, or loss of lubricantin wheel bearings is suspected, remove wheel bearingsand relubricate in accordance with applicablemaintenance instructions. If contamination of carbonbrakes is suspected, decontaminate in accordance withapplicable maintenance instructions.
2-9.3. CLEANING METHODS.
WARNING
Wear rubber gloves, chemical or splash proofgoggles, and water resistant boots duringcleaning operations using cleaning compoundsMIL-PRF-85570 or MIL-PRF-85704. Wetweather clothing is not required except duringcold weather. Open all circuit breakersassociated with battery power (refer toapplicable aircraft manuals) prior to applicationof flammable solvents.
2-9.3.1. The methods for cleaning aircraft varydepending upon the availability of fresh water. Thefollowing methods should be used for cleaning aircraftexterior surfaces. See Table 2-3 for instructions onspecific areas and components.
Table 2-3. Cleaning of Specific Areas and Components (Cont.)
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Figure 2-4. Use of Aircraft Washing Applicator
Figure 2-3. Washing and Rinsing of Aircraft Surfaces
2-9.3.2. Detergent Cleaning (Preferred Method). Thefollowing procedure shall be used where fresh water isavailable for rinsing purposes. Dilute cleaner asrecommended in Table 2-3. Where high outdoortemperatures are encountered (80°F (27°C) and above)and where shade is not available, cleaning operationsshould be scheduled for early morning and late afternoonor night. Wetting aircraft exteriors with fresh waterbefore cleaning will cool surfaces and help prevent fastevaporation during hot weather. For cold weatherprocedures, refer to paragraph 2-9.3.8.
CAUTION
Do not use abrasive mats (A-A-58054) forcleaning painted surfaces.
a. Rinse aircraft surfaces where necessary to reduceskin temperature. Streaking will occur if cleaningsolutions drip down hot painted surfaces.
Compound, Aircraft Cleaning 2MIL-PRF-85570
CAUTION
Do not use the 3M "Jet Pad" Melamine WashPads for cleaning transparency/canopymaterials such as plastic or glass.
NOTE
3M "Jet Pad" Melamine Wash Pads do not havethe durability of the traditional wash pad. It isrecommended that a thorough post-washinspection be completed to ensure that nosmall pieces of foam remain on the aircraft.
b. Apply diluted cleaning compound(MIL-PRF-85570 Type I or II) from a bucket, sprayingequipment, or foaming equipment (see Figure 2-3).Scrub surfaces with 3M No. 33 Aircraft Cleaning Pad or3M Jet Pad attached to the 3M No. 261 Pad Holder (seeFigure 2-4). Use nylon bristle scrub brushes(MIL-B-23958) or the 3M Jet Pad for hard to removesoils. To prevent streaking, start at the lower surfaces,working upward and out (see Figure 2-5). Surfacesbeing cleaned should be exposed to cleaning solutionfor 5 to 10 minutes.
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Figure 2-5. Aircraft Cleaning Procedure
LEGEND
Directionof Steps
Directionof Spray
Wash &Rinse Area
CoveredArea
STEP 1Clean the underside of the fuselage and tail section. Wash (allow detergent to dwell) and rinse, starting from the main landing gear and moving toward the forward and aft ends of the aircraft.
STEP 2
Clean the underside of the wings. Wash (allow detergent to dwell) and rinse, starting from the mid-section and moving outward to the wing tips.
STEP 3
Clean the center section of fuselage and topside of the wings. Wash (allow detergent to dwell) and rinse, starting from the center section of the fuselage and moving outward to the wing tips.
STEP 4
Clean the remaining topside area of the fuselage (except canopy). Wash (allow detergent to dwell) and rinse, starting from the mid-section and moving toward the forward and aft ends of the aircraft fuselage. Wash and rinse the tail section, starting at the bottom and moving up toward the top.
WARNINGSee applicable aircraft MIMs for no-step and water intrusion areas.
CAUTIONCanopies, windscreens and transparencies must be covered during washing to prevent scratching or crazing from aircraft cleaning detergents.
NOTEOpen doors and flaps to flapwells, intercoolers, oil coolers, speed brakes, spoilers, and controllable leading edges to permit cleaning of hidden areas.
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c. Rinse away the loosened soil and cleaner withfresh water. For rinsing, a rubber padded shut-off spraynozzle is recommended (see Figure 2-6). Rinse thecleaner and loosened soil from aircraft surface with afan spray nozzle, directed at an angle between 15 and30 degrees from the surface. Continue rinsing until allevidence of cleaner and soils have been removed fromaircraft.
d. For aircraft with gloss paint surfaces, ground-insoils (boot marks, smudges) can be cleaned withMIL-PRF-85570 Type III. Apply undiluted cleaner with adamp cloth. Rub area with a circular motion. Rinsethoroughly, then dry with a clean cloth. Do not allowcleaner to dry on surface.
NOTE
The 3M Jet Pad, used with MIL-PRF-85570Type I or Type II, will also adequately removeboot marks, smudges, and ground-in soils.
e. For aircraft painted with a tactical paint scheme,ground-in soils (boot marks, smudges) can be cleanedwith MIL-PRF-85570 Type IV spot cleaner. Blot undilutedcleaner on using a cleaning pad or sponge. After1-3 minutes, scrub these areas with the pad in a circularmotion. When the rubber particles in this cleaner arerubbed with the pad, removable soils are erased fromthe pores in the paint. Rinse thoroughly, then dry with aclean cloth. Do not allow cleaner to dry on surface.
Figure 2-6. Automatic Water Spray Nozzle
Mist
LightSpray
CoarseSpray
SolidStream
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f. Wheel wells, flap wells and other heavily soiledareas which can tolerate water rinsing can be cleanedwith MIL-PRF-85570 Type V gel cleaner. This cleanermay be sprayed on using a hand operated pump sprayor applied with a brush. Allow cleaner to dwell for fiveminutes. Brush if necessary, then rinse thoroughly witha coarse spray (see Figure 2-6).
2-9.3.3. Waterless Wipe Down. Waterless wipe downprocedures for spot cleaning shall be used only whenwater is not available for rinsing, or when cold weatherprevents the use of water. The preferred waterless wipedown method for removing soils and corrosive saltresidues is as follows:
Compound, Aircraft Cleaning 2MIL-PRF-85570
a. Using a plastic spray bottle, apply MIL-PRF-85570Type I or II (one part cleaner to 14 parts water) to theexterior surfaces of the aircraft (several square feet ata time).
b. After 30 seconds, scrub, then wipe cleaner andsoil from the surface with a clean cloth.
c. Rinsing with a cloth wet with fresh water followingthe use of cleaner is desirable.
d. Rinse the cleaned surface with fresh water whenit becomes available.
2-9.3.4. Alternate Waterless Wipe Down. Use onlywhen water is not available for rinsing or when coldweather prevents the use of water. The following is analternate method of waterless wipe down:
f. Apply MIL-PRF-81309 Type II and wipe with aclean, dry cloth.
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WARNING
Do not use synthetic wiping cloths withflammable solvents. Synthetic cloths cangenerate static electricity which can result insparks and fire. Cotton wiping cloths, such atterry cloth, flannel, or cheesecloth, areacceptable.
2-9.3.6. Solvent Cleaning. The use of MIL-PRF-85570for stubborn or exceptionally oily areas on exhausttracks, landing gears, wheel wells, and engine nacelleswill normally be sufficient. When this material has notcompletely cleaned these areas, MIL-PRF-680 Type IIor MIL-PRF-32295 Type I can be used in small quantities.The quantity used shall be limited to the minimumnecessary to accomplish the required cleaning. In usingMIL-PRF-680 for cleaning, remember that it will burnintensely once ignited. Solvent available at the aircraftor equipment shall not exceed three gallons under theuse or control of each person authorized to accomplishthe cleaning involved. The authorized person shall bethoroughly familiar with applicable safety precautionand disposal information. The time (dwell) the solvent isallowed to remain on painted surfaces shall be held toa minimum (10-15 minutes maximum) to preventsoftening of the paint. Control drain off of dirty solventresulting from the cleaning operation to preventunauthorized entry into the sewer. Minor spillage (lessthan one gallon) is not considered significant; however,solvent spillage should be cleaned up according to localregulations. In no instance shall the solvent be allowedto drain into or enter a public sewer or otherwise beallowed to contaminate streams or lakes.
2-9.3.6.1. The following guidelines shall be followed inusing MIL-PRF-680 Type II:
a. Use only in areas approved by the local safetyoffice.
b. Ensure that the area within 50 feet of the solventcleaning operation is clear and remains clear of allpotential ignition sources.
c. Use only explosion-proof electrical devices andpower equipment. Power units used in servicing shallbe placed upwind and beyond the 50 feet clearance.Ensure that the aircraft or equipment is grounded.
d. No smoking shall be allowed in the solvent cleaningarea.
e. Mixing of solvents with other chemicals, cleaningcompounds, or water is strictly prohibited except asspecified by this manual.
f. Suitable fire extinguishing equipment shall beavailable to the solvent cleaning area.
g. Wear ANSI Z87.1 Type II goggles, protective wetweather clothing, solvent resistant gloves, boots, andhead covering. Use a respirator fitted with organic vaporcartridges when working in an enclosed area. Ensurethat good ventilation is maintained. Consult the localsafety office for PPE requirements
a. Apply MIL-PRF-680 Type II (or MIL-PRF-32295Type I) using pad, cloth, or brush. Clean up spills asthey occur.
b. Ensure that no solvent/cleaner is trapped or hasentered the equipment interior. Remove by wiping withclean cotton wiping cloths or by blowing dry with clean,low pressure air (10-15 psi).
c. Collect waste solvent/cleaner and wiping ragsand dispose in accordance with local regulations.
d. After cleaning with MIL-PRF-680, rewash thearea using procedures in paragraph 2-9.3.2. to removeresidue left by the solvent.
2-9.3.7. Interior Cleaning. Dirt, dust, small loose objects,and paper can be removed from an area by use of anindustrial or domestic vacuum cleaner. A soft bristlebrush on the inlet of the vacuum cleaner will aid inremoval of soils.
a. Floor boards and areas underneath the floorboards (bilge) shall be inspected at depot-levelmaintenance and as necessary for cleaning and/orcorrosion treatment. Particular attention shall be givento urinal areas and other areas that may trap water.
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CAUTION
Accidental spills shall be investigatedimmediately after occurrence to determine ifingredients are corrosive. Neutralize corrosivespills by using procedures in Table 2-3. Failureto comply can result in extensive corrosiondamage and possible unsafe operation of theequipment.
b. When it is determined that harmful contamination,(e.g. dirt spillage, foreign material) is present, removethe floor boards as necessary to allow proper cleaningof the area.
c. Clean area by vacuuming all loose foreignmaterial, dirt, or spillage. The vacuum removal of dirt orsoil may be aided by agitating with the brush. Be carefulnot to sweep or wipe the dirt into oily or wet areas.
WARNING
Use MIL-PRF-680 Type II with adequateventilation and be sure bilge and/or other areasare properly ventilated (blown out) before floorboards are reinstalled or closed. Warning signsshall be conspicuously placed at all aircraftentrances to indicate that combustible materialsare being used. The guidelines cited inparagraph 2-9.3.6.1. for solvent cleaningprocedures apply.
d. Oily areas and/or spots may be cleaned by wipingarea with a clean cloth dampened with solvent,MIL-PRF-680 Type II or cleaner, MIL-PRF-32295 Type I,followed by immediate drying with a clean dry cloth. Donot over-saturate the cloth used for applying the solventbecause this may result in the solvent puddling orentering recessed areas and creating a fire hazard.Precautions to prevent entry shall be taken when usingthe solvent around electrical equipment.
CAUTION
Before starting the following cleaning operation,be sure that the spray or other methods ofapplication will not result in moisture damage toany components, especially electrical. Beforeusing the spray methods, ensure all drain holesare open, that the material will drain and that thecleaning solution will not be forced intoinaccessible areas. Do not apply the solution toany moisture absorbing material such asinsulation, sponge rubber (open cell), or felt.
e. If further cleaning is required, use 1 partMIL-PRF-85570 Type II mixed with 14 parts fresh water.The cleaning solution can be applied by spraying or witha mop, sponge, or brush, provided that the solution canbe adequately rinsed and/or removed from the surface.
f. After applying the cleaning solution with anon-metallic bristle brush, allow dwell time ofapproximately 10 minutes and flush or rinse with cleanwater. Check drain holes to assure that they are openand the water is draining properly. Remove anyremaining water using clean cloths. The surface shallthen be thoroughly dried using warm air or clean drycloths.
g. In those areas where the above procedures cannotbe used due to lack of drainage, or possible damage tocomponents, hand cleaning procedures shall be used.Apply 1 part MIL-PRF-85570 Type II mixed with 14parts water, by wiping or agitating the surface with a wetrag or sponge. Immediately following the application ofthe solution, wipe the same area with a rag wetted withclean water and then with a dry rag. The procedure mayhave to be repeated several times on extremely soiledareas.
h. Where corrosion is encountered or paint isremoved, treat in accordance with this manual and theapplicable maintenance instruction manual before thefloor boards are replaced or area is closed.
2-9.3.8. Low Temperature Cleaning. Routinescheduled cleaning should not be performed attemperatures below 40°F (5°C). Instead, aircraft shouldbe cleaned in an indoor wash rack. If such a facility is notavailable and aircraft are contaminated by corrosivematerials (such as runway deicer or salt water),contaminated areas shall be cleaned even if thetemperature is below 40°F (5°C). Normal cleaningsolutions cannot be used in freezing weather. When thetemperature is below or could drop below 32°F (0°C),clean as follows:
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WARNING
Deicing fluid (AMS 1424) is mildly toxic. Contactwith skin and eyes shall be avoided. Do notinhale deicing fluid mist. Operators should stayon the windward side of the aircraft duringspray or brush application. Chemical or splashproof goggles shall be worn by all maintenancepersonnel.
CAUTION
Isopropyl alcohol (TT-I-735) or any other alcoholshall not be used for deicing acrylic canopies.Use deicing fluid (AMS 1424) for theseapplications.
Deicing fluid (AMS 1424) is glycol-based andmay damage electrical/electronic circuitry withnoble metal (gold, silver) coatings.
a. If necessary, deice aircraft according to NAVAIR01-1A-520 (Navy), TM 55-1500-204-25/1 (Army), orapplicable maintenance manuals.
Solvent, Degreasing 13MIL-PRF-680
b. Solvent clean heavily soiled areas of aircraft bywiping or brushing with degreasing solvent(MIL-PRF-680 Type II).
Compound, Aircraft Cleaning 2MIL-PRF--85570
c. Dilute aircraft cleaning fluid (MIL-PRF-85570Type II) with diluted deicing fluid (AMS 1424) to make alow temperature cleaner. If necessary, both materialsshould be warmed until the detergent can be pouredinto the deicing fluid. Mix thoroughly.
d. Dilute this mixture as required by Table 2-4.
e. Scrub the aircraft using a brush or aircraft washingkit.
f. Rinse by deicing as in paragraph a. Heateddeicing fluid mixtures will speed up the rinsing process.
2-10. FRESH WATER RINSING. The purpose of freshwater rinsing is primarily to remove salt from aircraftsurfaces that have become contaminated due tooperations near salt water. Most salt deposits are readilydissolved and/or dislodged and flushed away by rinsing.Rinsing can be done in a taxi-through facility or by directmanual spraying.
CAUTION
Water in wheel wells, flap wells, or flight controlwells, necessitates relubrication. Ensure thatthese areas are adequately drained and checkthe specific aircraft manual to determinelubrication requirements.
NOTE
Fresh water rinsing does not satisfy aircraftwashing requirements.
2-10.1. TAXI-THROUGH RINSING. Deluge rinsefacilities are automatic installations located in a taxiwayarea for use by aircraft after flight through salt air (seeFigure 2-7). These installations provide multiple jetsprays of fresh water to cover the entire aircraft andrinse off salt and water soluble contaminants. Suchfacilities should be used as frequently as possible.
CAUTION
Do not rinse aircraft with a solid stream of water.Use a soft spray pattern to avoid damagingfragile sections or causing water intrusion. Watermust not be directed at pitot tubes, static ports,vents, or openings. Critical areas shall beadequately protected with ground plugs, covers,or barrier material.
2-10.2. MANUAL RINSING. The manual applicationof fresh water is accomplished through the use of ahand held hose or some piece of spraying equipment.
Table 2-4. Recommended Dilution ofLow Temperature Cleaner
erutarepmeTtneibmAnoituliD
)retawstrap:erutximstrap(
evobadnaF°03+ 4:1
F°03+otF°02+ 2:1
wolebdnaF°01+ 1:1
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The force or pressure used to apply the water is not ascritical as the amount of water. Satisfactory results areachieved with an amount of water that will create a fullflowing action over the surface. This will require aminimum flow rate of eight gallons per minute (gpm) ofwater at not less than 25 psi or standard pressure.Maximum nozzle pressure shall not exceed 175 psi.Rinse as follows:
a. Direct water at an angle of 15-30 degrees fromthe surface. Ensure that sufficient water flow is achievedon all surfaces.
b. Begin rinsing on lower surfaces and work upward(see Figure 2-5). Then rinse from the top down startingwith vertical stabilizer, then upper fuselage, upper wingsurfaces, and horizontal stabilizers. Lower areas will berinsed in the same order and manner as upper surfaces.
2-11. POST CLEANING PROCEDURES. Corrosionprevention depends on carrying out the prescribedpreservation and lubrication procedures. Strictcompliance with the following procedures is essential.Post-cleaning procedures shall be done in the followingorder.
a. Remove covers and masking from all static vents,pitot tubes, air ducts, heater ducts and openings.
b. Remove tape from all other openings sealed withmasking tape.
WARNING
Do not use synthetic wiping cloths withflammable solvents. Synthetic cloths cangenerate static electricity which can result insparks and fire. Cotton wiping cloths, such atterry cloth, flannel, or cheesecloth, areacceptable.
Naphtha, Aliphatic 11TT-N-95
Solvent, Degreasing 13MIL-PRF-680
c. Remove all tape adhesive residues with aliphaticnaptha (TT-N-95) or degreasing solvent (MIL-PRF-680Type II).
d. Clean all drain holes by inserting a probe, such asa pipe cleaner.
e. Ensure that all areas accumulating water havebeen drained. Whenever this is a recurring problem,procedures shall be developed and implemented toremove entrapped water and prevent accumulation.
Figure 2-7. Aircraft at a Taxi-Through Rinse Facility
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CAUTION
Lubrication must be accomplished as soon aspossible to prevent/minimize the occurrence ofcorrosion.
f. Upon completion of all cleaning operations,lubricate in accordance with applicable maintenancemanuals to displace any entrapped water or cleaningmaterials. Water which is not displaced can causecorrosion and failure of lubricated parts.
g. Apply operational preservatives (Chapter 8) whennecessary. Cleaning compounds tend to removepreservatives, making previously protected surfacesvulnerable to corrosion.
2-12. TREATMENT AND DISPOSAL OF WASHRACK WASTE.
NOTE
Cleaning solutions which remove greases andsurface contamination from aircraft andcomponents may exceed dischargeconcentration limits on oil and grease (especiallywhere oil/water separators are not installed ornot operating properly), naphthalene (fromcleaners containing aromatic hydrocarbons),chromium, cadmium, nickel or other heavymetals (from cleaning operations involvingengines or plated parts). If the wash rack is asource of hazardous waste, consult the basesafety or environmental office to determinecorrective action.
a. Precautionary measures shall be taken to preventwash rack waste from contaminating lakes, streams, orother natural environments. Some of the chemicalsused for cleaning require treatment or other specialcontrol prior to disposal.
b. The disposal of materials shall be accomplishedin accordance with applicable directives and in a mannerthat will not result in the violation of local, state, orFederal pollution criteria.
c. To mimimize the problems associated withdisposal and the actual cleaning process, all work shallbe accomplished on an approved wash rack. The onlyexception to this requirement shall be for those facilitieswhich are temporarily established to support combatoperations or special missions.
d. Aircraft wash rack cleaning waste shall receivethe equivalent of secondary sewage treatment. WhenMIL-PRF-85704 Type I solvent emulsion cleaningsolution is used, waste shall be released so that the totaleffluent entering the waste treatment plant does notcontain more than the amount limited by localenvironmental regulations or 100 parts per million (ppm)of cleaning compound.
2-13. LUBRICANTS. Lubrication performs a dualpurpose. It not only prevents wear between movingparts, but also fills air spaces, displaces water, andprovides a barrier against corrosive media. Thelubrication requirements contained in maintenancemanuals and maintenance cards are usually adequateto prevent corrosion of most lubricated surfaces undernormal operating conditions at shore bases. However,these required intervals shall be shortened whenoperating aboard ship, especially under foul weatherconditions. Aircraft lubrication shall be accomplished bypersonnel qualified in lubrication procedures. In theevent that the specified lubricant is not available, requestsubstitutions through the chain of command.
NOTE
Comply with relubrication time framerequirements outlined in the system specificmanual or maintenance cards.
2-13.1. CONVENTIONAL LUBRICANTS (GREASES).
CAUTION
Not all lubricating materials are compatible.Some are known to promote corrosion or causepaint or acrylic plastics to deteriorate. The useof the correct lubricating material is critical. Useonly lubricants specified by appropriate manualsor maintenance cards.
2-13.1.1. Conventional Lubricants shall not be used inthe following circumstances:
a. Do not use greases or oils with solid film lubricants.
b. Do not lubricate Teflon bearings and bushings.Clean Teflon bearings and bushings with degreasingsolvent MIL-PRF-680 Type II.
c. Lubricants containing graphite, either alone or inmixture with any other lubricants, shall not be used,since graphite is cathodic to most metals and will causegalvanic corrosion in the presence of electrolytes.
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CAUTION
The use of the correct lubricating material iscritical. Use only lubricants specified by theapplicable manual or maintenance card.
2-13.1.2. Table 2-5 contains the title, specification,intended use, and temperature range of the mostfrequently used conventional lubricating materials.
2-13.2. APPLICATION OF CONVENTIONALLUBRICANTS. The proper method of application isimportant. Apply lubricant as specified in the appropriatemaintenance manual. Lubricants can be applied by oneof the following methods:
a. Grease guns: lever or pressure type;
b. Oil, squirt, and aerosol spray cans; or
c. Hand or brush.
2-13.2.1. When lubricating hinges and pinned joints,apply MIL-PRF-81309 Type II or MIL-PRF-63460 beforeapplying lubricant.
2-13.2.2. Always apply generous quantities of lubricant,and actuate the joint several times to make sure that thelubricant penetrates all crevices thoroughly.
CAUTION
Excess lubricant can attract dust, dirt, and otherforeign material during aircraft service.
2-13.2.3. Wipe away any excess lubricant.
2-13.2.4. Grease Gun Application.
2-13.2.4.1. When applying lubricants through pressuretype fittings with a grease gun, clean grease fitting withdegreasing solvent (MIL-PRF-680) and a clean clothbefore applying lubricant.
2-13.2.4.2. Be certain the grease gun is properlyattached to the fitting prior to applying pressure.
2-13.2.4.3. Make sure the lubricant has emergedaround the bushing. If no grease appears, check thefitting and grease gun for proper operation.
2-13.2.4.4. When applying grease to a flush type (highpressure) fitting, make sure that the grease gun is fittedwith a flush type adapter and held perpendicular to thesurface of the fitting before applying pressure. If thefitting does not accept lubrication, replace the fitting andlubricate.
2-13.2.4.5. Wipe excess grease from fitting with aclean, dry cloth.
2-13.3. SOLID FILM LUBRICANTS. These lubricantsprevent galvanic coupling on close tolerance fittingsand reduce fretting. Solid film lubricants are used whereconventional lubricants are difficult to apply or retain, orwhere other lubricants may be contaminated with dust,wear products or moisture. Typical applications of solidfilm lubricants are sliding motion components such asflap tracks, hinges, turnbuckles and cargo latches. Solidfilm lubricants shall not be used in the followingcircumstances:
a. Do not use solid film lubricants in areas subject torotational speeds above 100 rpm under heavy loads.
b. Do not use solid film lubricants on roller bearingelements.
c. Do not use solid film lubricants in conjunction withoils or greases.
d. Do not use where there is a potential contact withliquid oxygen.
2-13.3.1. Surface cleanliness and preparation isextremely important to the service wear life of solid filmlubricants. They may be applied over bare metalsurfaces, or over surfaces that have been pre-coatedwith other films, such as anodized aluminum andphosphated steel. They have also been successfullyapplied over organic coatings such as epoxy primers.
2-13.3.2. SAE AS 5272 (Lubricant, Solid Film, HeatCured, Corrosion Inhibiting). This lubricant is a heatcured, corrosion-inhibiting solid film lubricant withextended wear life. AS 5272 Type I and Type II replacesMIL-L-46010 Type I and Type II. It can be used onaluminum, copper, steel, stainless steel, and titanium.AS 5272 Type II must be cured at 400°F (204°C) forone hour. If metallurgical damage is done at thistemperature, AS 5272 Type I, which cures at 300°F(149°C) for one hour, must be used. Due to thetemperature requirements, this lubricant is notsuitable for all applications. AS 5272 is recommendedfor use under the following conditions:
a. Sliding motion applications, such as plain sphericalbearings, flap tracks, hinges, threads, and cam surfaces;
b. Where conventional lubricants are difficult to applyor retain, or where other lubricants may be easilycontaminated by dirt or dust;
c. Where a solvent resistant lubricant is required.
d. If mechanisms are operated at infrequent intervalsor are lubricated for life.
e. When long term corrosion protection is requiredunder static conditions (2 years outdoor storage or 5years indoor storage).
2-13.3.3. MIL-PRF-46010 (Lubricant, Solid Film, HeatCured, Corrosion Inhibiting, Low VOC Content). Thislubricant is a heat cured, corrosion-inhibiting solid filmlubricant with extended wear life. MIL-PRF-46010replaces MIL-L-46010 Type III. Limitations and usesare the same as described for AS 5272 Type I above. Inaddition, engineering authorization to substituteMIL-PRF-46010 for AS 5272 is required prior to use.
2-13.3.4. MIL-L-23398 (Lubricant, Solid Film, Air Cured,Corrosion Inhibiting). This lubricant is an air-cured,corrosion-inhibiting solid film lubricant which may alsobe used to repair surfaces originally coated with AS 5272/MIL-PRF-46010. It can be used on aluminum, steel andtitanium. It provides moderate wear life and corrosionprotection in areas where it is not feasible to use a solidfilm lubricant that requires curing at elevatedtemperatures.
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2-14. INTRODUCTION. This section describes thespecial cleaning procedures required if an aircraft hasbeen exposed to volcanic ash (paragraph 2-15) orsand/desert environments (paragraph 2-16).
2-15. CLEANING AFTER EXPOSURE TOVOLCANIC ASH. The primary concern in removingvolcanic ash is the extreme abrasiveness of the ash. Itis not a significantly corrosive material. Aircraft thathave been exposed to volcanic ash shall be cleanedusing the following procedures after exposure andbefore the next aircraft operation or flight:
a. All static ports, fuel vents, engine inlets, and airconditioning inlets should be vacuumed to remove asmuch ash as possible and then suitably covered topreclude additional ash entry. Special emphasis shouldbe placed on ducting supplying cooling air to avionicsequipment.
b. After covering all openings where ash may enter,the exterior of the airframe or equipment shall have ashremoved initially using vacuum, low-pressure air, or bylightly dusting with clean rags. Avoid rubbing since thismay damage surfaces due to the abrasiveness of theash.
Compound, Aircraft Cleaning 2MIL-PRF-85570
c. Wash entire aircraft or equipment using one partaircraft cleaning compound (MIL-PRF-85570 Type II) in14 parts water and rinse thoroughly with low-pressurewater. Ensure that critical parts, such as flap screws,tracks, and exposed hydraulic actuators are adequatelycleaned. Caution should be taken when washing toavoid rubbing since ash is even more abrasive whencombined with water as slurry.
d. Wiper blades should be checked to ensure that allcontaminants are removed prior to operation.
e. If ash penetration is evident in the cockpit, cargo,or any other accessible interior areas, it should bethoroughly vacuumed.
f. Check lower aircraft structures for volcanic ashand water entrapment.
g. Clear all drains and air dry structures as much aspossible.
h. Uncover all openings that were covered duringparagraphs a. and b.
i. After washing, the aircraft shall be lubricated inaccordance with applicable maintenance instructionmanuals (MIMs).
2-16. CLEANING AFTER DESERT OPERATIONSOR EXPOSURE TO SAND ENVIRONMENTS.Environmental conditions in desert operations introducesalt-laden sand and other corrosive substances to theinterior of the aircraft. These substances, if allowed toremain, can accelerate the corrosion process and leadto premature corrosion damage. Aircraft that have beenexposed to sand/desert environments shall be inspectedand cleaned no later than 60 days after leaving thedesert environment, or as necessary during deployment.
2-16.1. VISUAL INSPECTION.
a. Open all access doors and remove all non-permanently installed panels and fairings. Visuallyinspect structural surfaces such as skins, frames, ribs,bulkheads, longerons, fittings, and stringers, for sandintrusion. Borescopes may be used to inspect interiorsurfaces not accessible to visual inspection.
b. Inspection should also include the followinggeneral areas and/or components: acrylic plastic parts,arresting gear and wheel wells, avionics components,battery compartments, bearings, bilge areas, brakes,canopy exterior, cockpit ducting, control cables, doors,ejection seats, elastomeric seals, electrical connectors,engines, equipment compartments, exterior surfaces,flap screws, hinges, hydraulic actuators, landing gearexposed piston surfaces, linkages, optical glass, oxygenlines, radomes, tracks, wire bundles, and wheels.
c. Inspect all drain holes and verify that they areopen and free of obstruction.
CHAPTER 2CLEANING
SECTION II. SPECIAL CLEANING
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2-16.2. GENERAL CLEANING PROCEDURES.
a. Vacuum clean all loose sand and contaminantsfrom all accessible areas inspected in accordance withparagraph 2-16.1.
b. Ensure sand is vacuumed from avionics bays,storage bays, and other enclosed compartments, suchas battery compartments and battery vent openings.Pay particular attention to air inlets.
c. Use a soft bristle brush and air pressure (not toexceed 10 psi) to dislodge sand between close-fittingcomponents. Repeat vacuum cleaning.
d. Hand wipe residual sand/dust film adhering tosurfaces with isopropyl alcohol (TT-I-735), degreasingsolvent (MIL-PRF-680 Type II), non-aqueous cleaner(MIL-PRF-32295 Type I), or cleaning compound (MIL-DTL-16791 or MIL-PRF-85570 Type II) on a clean cloth.If cleaning compound is used, dilute according toinstructions for light soil, use sparingly and ensure thatall areas are thoroughly dried.
e. Dry with wiping cloths or blow dry with air pressureless than 10 psi.
f. Wash aircraft exterior in accordance withparagraph 2-9. Remove all standing water and allowaircraft to dry thoroughly.
g. After washing, the aircraft shall be lubricated inaccordance with applicable maintenance instructionmanuals (MIMs).
h. Inspect for any remaining sand and re-clean untilall sand is removed.
2-16.3. TREATMENT OF SPECIFIC AREAS.
Detergent, Non-Ionic 9MIL-D-16791
a. Acrylic Plastic Parts (except Canopies). Wipewith cloth wet with cleaning solution (MIL-DTL-167911 oz cleaner per 1 gallon water) and follow with a flannelcloth wet with water. Dry with a clean cloth (A-A-50129).
Compound, Aircraft Cleaning 2MIL-PRF-85570
b. Arresting Gear and Wheel Wells. Clean usingMIL-PRF-85570 Type II RTU or mix one part aircraftcleaning compound, MIL-PRF-85570 Type II, to 4 partswater. Rinse thoroughly with fresh water.
c. Battery Compartments. Neutralize acid inaccordance with paragraph 6-2, using sodiumbicarbonate for lead acid batteries and sodium phosphatefor nickel-cadmium batteries. Rinse with fresh waterand dry with wiping cloths.
Solvent, Degreasing 13MIL-PRF-680
d. Bearings. Clean sand from exposed bearingswith degreasing solvent (MIL-PRF-680 Type II). Inspectbearings for sand damage. Contact cognizant bearingengineer for specific disposition if necessary.
e. Canopy Exterior. Flush with water to removeloose sand/dust. Clean using plastic polish (P-P-560)and flannel cloth (A-A-50129).
f. Control Cables. Clean using degreasing solvent(MIL-PRF-680 Type II) or non-aqueous cleaner(MIL-PRF-32295 Type I) and a clean wiping cloth.Preserve with CPC (MIL-PRF-16173 Grade 4) or asspecified by the applicable maintenance instructionmanuals.
g. Ejection Seats. Refer to specific Ejection SeatManual.
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Detergent, Non-Ionic 9MIL-D-16791
h. Elastomeric Seals. Wipe with cheesecloth(CCC-C-440) wet with detergent (MIL-DTL-16791 1 ozcleaner in 1 gallon water.) Rinse with cheesecloth wetwith water. Dry with clean cheesecloth.
i. Electrical Connectors and Avionics Components.If contamination is suspected, use an acid brush(A-A-289) to apply isopropyl alcohol (TT-I-735) liberallyto the internal and external sections of the connectors,both male and female. Mate and unmate connectorseveral times to clean. Rinse again with isopropylalcohol and allow to dry. Preserve with CPC(MIL-PRF-81309 Type III) or as specified by theapplicable maintenance instruction manuals.
Cleaning Compound 3Turbine Engine Gas PathMIL-PRF-85704
j. Engines. Wash engine with cleaning compound(MIL-PRF-85704) in accordance with the applicablemaintenance instruction manuals.
Fluid, Hydraulic 10MIL-PRF-83282
k. Landing Gear. Clean all sand from exposedreciprocating portions of landing gear shock struts bywiping with a clean, soft cloth (A-A-59323 Type II)moistened with hydraulic fluid (MIL-PRF-83282). Usecare not to scratch exposed piston shafts or damageseals.
l. Optical Glass. Spray cleaner (A-A-59199) onto aclean flannel cloth (A-A-50129) and wipe lens surface.Wipe dry.
m. Oxygen Lines. Refer to specific maintenanceinstruction manual.
2-16.4. CORROSION INSPECTION. Perform corrosioninspections as specified by the applicable maintenanceinstruction manuals.
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CHAPTER 3INSPECTION AND CORROSION PRONE AREAS
SECTION I. INSPECTION AND EVALUATION
3-1. GENERAL.
3-1.1. PURPOSE. Frequent corrosion inspections areessential to the overall corrosion control program. Thecosts resulting from corrosion can be minimized byearly detection, identification, and treatment. Withoutregular systematic inspections, corrosion will seriouslydamage aviation equipment. This chapter describesprocedures for basic visual inspection for corrosion andillustrates some of the signs of corrosion damage.
3-1.2. RESPONSIBILITY. Corrosion detection iseveryone’s responsibility. Since corrosion can occuralmost anywhere on aviation equipment, all maintenancepersonnel must be able to identify and report corrosionproblems. Personnel performing any scheduledinspections shall be qualified in corrosion detection andshall have attended appropriate corrosion preventionand control courses as established by the parent serviceorganization.
3-1.3. FREQUENCY OF INSPECTIONS. The minimumfrequency and extent of these inspections areestablished by the aircraft programs of the parent serviceorganization. However, during scheduled orunscheduled maintenance actions on aviationequipment or components, the area involved as well asthose within 3 feet or 36 inches (18 inches on each side)of the repair or treatment area shall be visually inspectedfor corrosion. Additional inspections may be necessaryin areas which are particularly prone to corrode, such asmagnesium gear boxes, wheel and flap wells, and bilgeareas. Areas which are corrosion prone are discussedin Section II of this chapter.
3-1.4. GENERAL INSPECTIONS. A general inspectionof aviation equipment or components is performed asfollows:
a. Clean the area thoroughly (as described inChapter 2) or, for water sensitive areas, wipe the areawith a clean cloth dampened with an approved solvent.
CAUTION
Prior to removing any access covers or panelsprimed with TT-P-2760 flexible primer, scorethe sealant at the edges of the cover/panel witha sharp plastic tool to prevent fraying the paintfinish when the panel is removed.
b. If corrosion is suspected, examine the area witha 10X magnifying glass and flashlight. Examine edgesof skin panels, rivet heads, and corrosion prone areas.If there are blisters, bubbles, or other coating irregularitiespresent, attempt to dislodge the paint by scraping witha sharp plastic tool. If paint does not easily dislodge andcorrosion is not suspected, the irregularity is probablyconfined to the paint film itself and no further actionshould be taken. When corrosion is suspected but noirregularities are present, apply a strip of ASTM D6123Type II flatback masking tape over the clean, dry area.Hand rub the tape for several strokes in order to assuregood adhesion, and remove the tape with an abruptlifting motion. Where paint is removed, inspect anddetermine the degree of corrosion (see paragraph 3-4).
c. Remove corrosion (Chapter 4), clean and treatthe surface (Chapter 5), and paint (Appendix A).
3-1.5. DETAILED INSPECTIONS. A detailed inspectionof aviation equipment or components shall be performedas a result of damage found during general inspectionsif extensive or severe corrosion is suspected, and asspecified in appropriate aircraft maintenance manuals.Parts shall be carefully inspected for signs of corrosionusing the tools and procedures listed in Table 3-1. SeeSection II of this chapter for information on commoncorrosion prone areas.
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3-2. INSPECTION METHODS.
3-2.1. VISUAL INSPECTION. Visual inspection is themost widely used method for the detection and evaluationof corrosion. It is very effective for detecting surface,exfoliation, pitting, and intergranular corrosion if donecarefully and with knowledge of where and what to lookfor. Read Volume I, Chapter 3 (Corrosion Theory) beforeperforming a corrosion inspection, paying particularattention to Table 3-1 of Volume I (Corrosion of Metals -Type of Attack and Appearance of Corrosion Products).
3-2.1.1. The following tools can be used to find andevaluate the extent of corrosion damage:
a. Flashlight.
b. 10X Magnifying Glass.
c. Plastic Scraper.
d. Borescope.
e. Depth Gage, Pin Micrometer Type.
f. Optical Depth Micrometer.
3-2.1.2. Evidence of Corrosion. Aluminum corrosionproducts will be white, gray, or black and may appear asa paste when wet, or a hard, adherent film or easilycrumbled deposits (i.e., powder) when dry. Magnesiumcorrosion products are white and form in large amountswith significant losses to the base metal. Steel corrosionproducts are red, brown, or black rust deposits whichare easily detected. Copper corrosion products are blueor blue-green and are also easily detected. Titaniumand stainless steels do not produce significant amountsof corrosion products but can exhibit stress corrosioncracking. When corrosion occurs beneath a paint system,the surface of the paint often appears blistered ordistorted.
3-2.2. VISUAL INSPECTION WITH BORESCOPE. Aborescope is an instrument with a small, high intensitylight that can be used in the inspection of interiorsurfaces (e.g. tubing, ducts, and pipes) which are notaccessible by any other method (see Figure 3-1).Examples of the different kinds of borescopes includeflexible, rigid, micro, video, and fiberscopes. Insert thehead assembly into any cavity having a large enoughopening. With the cavity illuminated, visually inspect itsinterior for defects, such as damage to the paint systemand corrosion.
3-2.3. DEPTH GAGE. Depth gages are tools formeasuring the depth of corrosion pits and reworkedareas to determine the extent of corrosion present andthe amount of metal removed during rework.
Table 3-1. Inspection Equipment and Techniques
noisorroCfoepyT
1 noisorrocecafrusmrofinU
2 noisorroclatemralimissidrocinavlaG
3 )lareneg(kcattaralunargretnI
4 )noitailofxe(kcattaralunargretnI
5 gnittiP
6 noisorrocgnitterF
7 gnikcarcnoisorrocssertS
8 eugitafnoisorroC
9 noisorrocmrofiliF
01 noisorroctoH
tnempiuqE rodetceteDepyTnoisorroCdetaulavE
)woleBepyTeeS(
epocseroB 01,5,4,3,2,1
egaGhtpeD 5,4,1
retemorciMhtpeDlacitpO 9,7,6,5,4,2,1
tnartenePtnecseroulF 8,7,5,4,3
tnerruCyddE 8,7,5,4,3,1
cinosartlU 8,7,4,3,1
tcetednac(yhpargoidaReromro%2fossolssenkciht
5,1
Figure 3-1. Fiber Optic Borescope
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NOTE
On thin sheet material, waviness in the materialmay result in false depth readings. Severalreadings may be necessary, or it may benecessary to improvise another method fordetermining the depth of the corrosion damage.The depth gage is not suitable for determiningthe depth of a corrosion crack due to therelatively large size of the indicator pin.
3-2.3.1. Use of Depth Gage. Several depth readingsshall be taken in the affected area. Select the deepestreading as the depth of the corrosion damage. Wherethere are several damaged areas in the same skin panelor component part, plot or sketch a diagram of the depthand location of each damaged area. This diagram willbe used for further evaluations, along with the applicableaircraft manuals, or when engineering assistance isrequired. The diagram should be forwarded to theengineer when requesting engineering assistance. Thebase of the depth gage shall be flat against theundamaged surface on each side of the corrosiondamaged area. When taking measurements on concaveor convex surfaces, place the base perpendicular to thesurface (see Figure 3-2).
3-2.3.2. If the pits or depth of rework are within allowabletolerances, as given in the specific aircraft manuals oras described in paragraph 4-8.3, the pits can beacceptably cleaned, and the reworked area will requirethe re-application of a protective coating system. If thepits or depth of rework are not within allowable tolerances,the part must be replaced or repaired, if allowed, or arequest for engineering assistance must be made.
NOTE
Wearing eyeglasses makes it difficult to placethe eye at the ideal distance from the eyepieceand the view is distorted by external glare andreflections. Rubber eyeshields on opticalinstruments (e.g. borescope, opticalmicrometer) are designed to shut out externallight, but are not as effective when glasses areworn. For these reasons, it is desirable that theinspector be able to adjust the instrument withoutwearing glasses to compensate for variationsin visual acuity.
3-2.4. OPTICAL DEPTH MICROMETER. Thisinspection tool measures the depth of scratches, cracks,and pits and the height on spurs and other protrusions
Figure 3-2. Measuring Corrosion with a Depth Gage
0 510
15
202520
15
10
5
Dial IndicatorMeasures0.001 Inch/Division
Indicator Pin
Wing Skin
A B
C
1. Take measurement readings at both edges (A and B) adjacent to groove.2. Take measurement at maximum groove depth (C).3. Subtract maximum groove depth (C) from average of edge measurements to obtain groove depth reading.
INSTRUCTIONS
�
GrooveDepth
= (A + B)2
C -
(see Figure 3-3). The micrometer is first focused on thehighest surface in the area of interest and a reading istaken. A second reading is taken when the lowestsurface is in focus. The difference between the readingsis the distance between the two surfaces. Opticalmicrometers are available with 100 and 200 powermagnification, reticle eyepieces, and accessory lighting.The procedures outlined below are to be used fordetermining the depth of corrosion pits and/or areasreworked due to corrosion damage on any surface.
a. Select the appropriate base to be used for thesurface (e.g., flat, curved, round, or inside/outside anglesurfaces) on which the measurement is to be made.
b. Position the micrometer solidly over surface A(undamaged surface close to surface B) with the lensdirectly over the area to be read. When the micrometeris set over the surface, a pinpoint of light will cover thearea to be measured.
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Figure 3-3. Optical Depth Micrometer
Partial View of Optical Depth Micrometer Showing Only the Optic and Base
Optical Depth Micrometer2
46
83
57
910
Enlarged View of Vernier Scales
Distance A
Surface A Flat Surface
Surface B
Distance B
INSTRUCTIONS
1. Place micrometer on an undamaged surface near the area of interest.
2. Focus on undamaged surface by adjusting the thimble on the micrometer.
3. Take reading from Vernier scales. This reading is Distance A.
4. Move micrometer and center over corrosion pit.
5. Focus on bottom of pit by adjusting the thimble on the micrometer.
6. Take reading from Vernier scales. This reading is Distance B.
7. Pit Depth = Distance B - Distance A
NOTEFor best results, the micrometer tripod should be stable and remain stationary when measuring distances.
24
68
35
79
10
Thimble
Eyepiece
ThousandthsScale
TenThousandths
Scale
HundredThousandths
Scale
Tripod Base forFlat Surfaces
Objective Lens
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c. Look through the eyepiece of the micrometer androtate the micrometer thimble clockwise orcounterclockwise until surface A comes into sharpfocus. Extreme care should be taken when focusing onthe surface to be measured in order to reduce inaccuracyin the measured values.
d. Obtain the reading for surface A located on thevernier scale. Since a vernier scale is not one that canbe easily read, an experienced, trained technician shouldread the scale or supervise/check the readings of lessexperienced personnel.
e. Position the micrometer over surface B (corrosionpit or area reworked due to corrosion damage) to bemeasured. When measuring the depth of corrosion pitsor reworked areas, ensure that the surface beingmeasured has a large enough area to be focused inorder to obtain an accurate reading.
f. Repeat procedures c. and d. on surface B.
g. Take the distance readings from surface A andsurface B and subtract the surface A reading from thesurface B reading to obtain the depth of the corrosiondamaged surface. Calculate the pit depth using thefollowing equation:
Pit Depth = Distance B - Distance A
h. Take several readings from the corrosiondamaged surface and select the deepest reading as thepit depth.
CAUTION
The apparent simplicity of the penetrantinspection is deceptive. Very slight variations inperforming the inspection process can invalidatethe inspection by failing to indicate seriousflaws. It is essential that personnel performingpenetrant inspection be trained and experiencedin the penetrant process.
NOTE
The following inspection methods are to beaccomplished only be NDI qualified and certifiedpersonnel (see COMNAVAIRFORINST 4790.2and AIA/NAS 410). Refer to NAVAIR 01-1A-16,TM 1-1500-335-23, or specific NDI manual formore detailed inspection procedures.
3-2.5. FLUORESCENT PENETRANT INSPECTION(FPI). In fluorescent penetrant inspections, thecomponent is cleaned and then treated with a fluorescentpenetrating liquid which is capable of entering surfacecracks or flaws. After removing the penetrant from thesurface, a developer (water-soluble, dry powder, ornon-aqueous) is applied to absorb penetrant trapped incracks. Under ultraviolet light, the absorbed penetrantis visible directly above the cracks from which it wasdrawn.
3-2.5.1. The penetrant inspection method is used todetect stress corrosion cracking and special cases ofintergranular corrosion. Intergranular corrosion attacksthe metallic grain boundaries and forms a network ofvery fine cracks. In the early stages, the crack indicationsare visible only under 10X or greater magnification.Penetrant indications of intergranular corrosion appearas a residual background and are resolved only undermagnification. Developer is not used when evaluating apenetrant indication using a magnifying glass.
3-2.5.2. In addition, penetrant inspection is often usedto monitor the surface for adequacy of corrosion removalby grinding. Caution must be exercised becausemechanical removal methods cause smearing whichmay obscure indications of remaining corrosion attack.In monitoring corrosion grind-out areas, a developer isnot used: following removal of excess surface penetrant,the area is examined using a low power magnifyingglass (10X). The examination should be repeated aftera minimum five minute dwell. When corrosion is nolonger detected, the inspection process shall be repeatedusing non-aqueous developer.
3-2.5.3. Limitations of Fluorescent PenetrantInspection.
3-2.5.3.1. Flaw Location. Penetrant inspection isapplicable to all solid, nonporous materials providedthat the flaw is open to the surface of the part. To detectsubsurface flaws, another inspection method must beused.
3-2.5.3.2. Restricted Flaw Openings. The penetrantinspection process depends upon the ability of thepenetrant to enter and exit the flaw opening. Any factorthat interferes with the entry or exit reduces theeffectiveness of the inspection. Organic surface coatings,such as paint, oil, grease, and resin are examples. Anycoating that covers or bridges the flaw opening willprevent penetrant entry. Even when the coating does
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not cover the opening, the material at the edge of theopening affects the mechanism of penetrant entry andexit and greatly reduces the reliability of the inspection.Coatings at the edge of the flaw may also retain penetrant,causing background fluorescence. An inspection methodother than penetrant must be used if the organic coatingcannot be stripped or removed from the surface to beinspected.
WARNING
Chemical etching shall only be performed bypersonnel trained and certified in the properhandling and application of the materials due totheir hazardous nature.
3-2.5.3.3. Smeared Metal. Mechanical operations,such as shot peening, machine honing, abrasive blasting,buffing, wire brushing, grinding, or sanding, will smearor peen the surface of metals. This mechanical workingcloses or reduces the surface opening of any existingdiscontinuities. Mechanical working (smearing orblending) also occurs during service use when partscontact or rub against each other. Penetrant inspectionwill not reliably indicate discontinuities when it isperformed after a mechanical operation or service usethat smears or peens the surface. Chemical etching(e.g. Flicks on aluminum alloys and Shantz on Inconels)prior to penetrant operations is recommended to improvetest sensitivity when smeared metal is present.
3-2.5.3.4. Porous Surfaces. Penetrant inspection isimpractical on porous materials with interconnectedsubsurface porosity. The penetrant rapidly enters thepores and migrates through the network. This results inan overall fluorescence or color that masks any potentialdiscontinuity indications. In addition, removal of thepenetrant may not be possible after the inspection.
3-2.6. EDDY CURRENT INSPECTION. The eddycurrent inspection method may be used to detect orevaluate surface and subsurface corrosion. This methodcan detect and evaluate uniform surface pitting,intergranular, exfoliation (corrosion around fasteners),and stress corrosion. Detection of corrosion with eddycurrent techniques is used on aircraft skins wherecorrosion may occur on inaccessible interior surfaces.Corrosion usually occurs in areas where moisture isentrapped. If relatively uniform thinning is expected,corrosion detection may be simply a matter of thicknessmeasurement. In most instances, corrosion is confinedto smaller localized areas of relatively small diameter.
As skin thicknesses increase, sensitivity to small areasand shallow depths of corrosion is reduced. Corrosionon either member of a faying surface may be detected.Eddy current can also be used for corrosion removalinspections, but is less sensitive than liquid penetrant.
3-2.7. ULTRASONIC INSPECTION. Ultrasonicinspection provides good resolution to evaluate materialloss and thickness. This method may be used to detectexfoliation, intergranular, uniform surface, and stresscorrosion. Ultrasonic thickness gaging is included inthis method. Ultrasonic inspection for far side pittingand internal exfoliation corrosion may be accomplishedusing shear ("S") wave and longitudinal ("L") wavetechniques. The use of a delay line transducer isrecommended for "L" wave inspection. The delay willimprove resolution of both near and far surface corrosion.Technique development is required for specificapplications.
3-2.8. RADIOGRAPHIC INSPECTION. Radiographicinspection provides the best resolution for detection ofsurface and subsurface corrosion flaws when no othermethod can accomplish the inspection. The drawbackof radiography is the high equipment cost and the highman-hour requirements to perform an on-aircraftradiographic analysis. Radiographic inspection is usedin combination with ultrasonics to determine the conditionof aluminum honeycomb.
3-3. EVALUATION OF CORROSION DAMAGE.Visually determine if corrosion is in an area which haspreviously been reworked. If the corrosion damage islocated in an area that has been previously ground out,measure the damage to include the material which haspreviously been removed. A straight edge and a 10Xmagnifying glass may be used to assist in determiningif an area has previously been reworked. Place thestraight edge across the area being examined at variousangles and check for irregularities, low spots, ordepressions (see Figure 3-4). If any irregularities, lowspots, or depressions are found, and a visualdetermination cannot verify previous rework, closelyexamine the suspected area and the surrounding areausing a 10X magnifier. After determining that the areahas been previously reworked, evaluate the depth ofthe previous rework (i.e., grind-out) to determine iffurther metal removal will exceed grind-out limitsspecified in the applicable aircraft manuals or as specifiedin paragraph 4-8.3. Depth measurements can be madeusing the depth gage as described in paragraph 3-2.3.
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3-4. DEGREES OF CORROSION. Corrosion must beevaluated after the initial inspection and cleaning todetermine the nature and extent of repair or reworkneeded. It is difficult to draw a distinct and specificdividing line among the degrees of corrosion.Consequently, the first requirement for a reliableevaluation is sound maintenance judgment. Use thefollowing categories in reporting degrees of corrosion.
3-4.1. LIGHT CORROSION. At this degree, theprotective coating is scarred or etched and the conditionof the metal is characterized by discoloration and pittingto a depth of approximately one mil (0.001 inch)maximum. This type of damage can normally be removedby light hand sanding.
3-4.2. MODERATE CORROSION. This appears similarto light corrosion, with the addition of blistering orevidence of scaling and flaking of the coating or paintsystem. The pitting depths may be as deep as 10 mils(0.010 inch). This type of damage is normally removedby extensive hand sanding or light mechanical sanding.
3-4.3. SEVERE CORROSION. Its general appearanceis similar to moderate corrosion, with the addition ofsevere intergranular corrosion, blistering, exfoliation,scaling, or flaking. The pitting depths are deeper than 10mils (0.010 inch). This damage must be removed byextensive mechanical sanding or grinding.
Figure 3-4. Usage of Straight Edge to Determine if Suspect Areas Have Been Previously Reworked
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3-5. COMMON CORROSION PRONE AREAS.There are certain corrosion prone areas common to allaircraft. Corrosion prone areas should be cleaned,inspected, and treated more frequently than lesscorrosion prone areas. The following paragraphsdescribe the areas and contain illustrations to aid ininspections. However, the list is not complete andshould be expanded by referencing the maintenancemanuals and maintenance cards for each specificaircraft, which will show other possible trouble spots.
3-5.1. BATTERY COMPARTMENTS AND BATTERYVENT OPENINGS. In spite of protective paint systems,corrosion preventive compounds, and ventingprovisions, battery compartments are severe corrosionproblem areas (see Figure 3-5). Fumes from overheatedbattery electrolyte will spread to adjacent internal cavitiescausing rapid corrosion of unprotected surfaces. If thebattery installation has an external vent opening to theaircraft skin, include this area in battery compartmentinspection and maintenance procedures. Frequentcleaning and neutralization of deposits will minimizecorrosion. Leakage of aircraft batteries with electrolytesof either sulfuric acid or potassium hydroxide will causecorrosion. Consult the aircraft maintenance manuals todetermine which type of battery is used. Refer to
CHAPTER 3INSPECTION AND CORROSION PRONE AREAS
SECTION II. CORROSION PRONE AREAS
Figure 3-5. Battery Compartment Figure 3-6. Helicopter Bilge Area
Chapter 6 and specific aircraft maintenance manualsfor instructions on cleaning and neutralizing batteryelectrolytes.
3-5.2. BILGE AREAS. These areas are naturalcollection points (i.e., lower point/areas of aircraft) forwater, dirt, loose fasteners, drill shavings, and otherdebris (see Figure 3-6). Keeping bilge areas free ofdebris and fluids, and application of recommendedcorrosion preventive compounds (CPCs) are the bestprotection against corrosion.
3-5.3. CONTROL CABLES. Control cables present acorrosion problem whether they are made of carbonsteel or stainless steel. As shown in Figure 3-7, thepresence of bare spots in the protective coating is oneof the main contributing factors to the corrosion ofcables. Dirt, dust, and grime that collect will lead tocorrosion and cable failure.
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Figure 3-7. Control Cables
3-5.4. ELECTRICAL CONNECTORS. Some electricalconnectors are potted with a sealant compound toprevent the entrance of water into the areas of connectorswhere wires are attached to pins. Rubber O-rings arealso used to seal moisture out of the mating area of pinconnections. Moisture will get into electrical plugs andcause failure. It is necessary that such plugs bedisconnected periodically for inspection and corrosiontreatment. The use of unauthorized sealants or pottingmaterials can cause severe damage to affectedconnectors or components. Refer to Volume III forauthorized avionic materials and procedures.
3-5.5. ENGINE FRONTAL AREAS AND AIR INLETDUCTS. Since these areas are constantly abraded bydirt, dust, and gravel, and eroded by rain, specialattention shall be given to:
a. Engine frontal areas (see Figure 3-8).
b. Leading edges of engine and air inlet ducts,including hardware inside ducts (see Figures 3-9 and3-10).
c. Due to heat dissipation requirements, oil coolercores are not usually painted. Engine accessorymounting bases may have small, unpainted areas onthe machined mounting surfaces. With moist, salt-ladenair flowing over these surfaces, they are vulnerable tocorrosion.
3-5.6. EXHAUST IMPINGEMENT AREAS. Exhaustimpingement areas include areas exposed to engine,rocket, and missile exhausts, gun blast, or any other
Figure 3-8. Jet Engine Frontal Area
surface that is exposed to exhaust gases of installedequipment. Exhaust gases cover the surface finish withdeposits (e.g. corrosive ash and residual solids) anddamage the finish. Surfaces located in the path of rocketand gun blasts, including gun compartment systemsand spent ammunition collection chutes, are particularlysusceptible to deterioration and corrosion (seeFigure 3-11). In addition to the corrosive effect of thegases and exhaust deposits, the protective finish isoften blistered by heat, blasted away by high velocitygases, or abraded by spent shell casings or solidparticles from gun and rocket exhausts (see Figure 3-12).These areas require more attention during inspectioncycles.
3-5.7. FASTENERS. There are thousands of fastenerson aircraft exterior surfaces, and areas around thesefasteners are trouble spots (see Figure 3-13). Theseareas are subject to high operational loads, moistureintrusion, and susceptibility of the skin material tocorrosion (see Figure 3-14). High operational loadscause the paint around the fasteners to crack, whichprovides a path for moisture intrusion. All paints willcrack to some degree around fasteners.
3-5.8. FAYING SURFACES AND CREVICES. Similarto corrosion around fasteners, corrosion in fayingsurfaces, seams, and joints is caused by the intrusion ofsalt water and other corrosive agents. Entry of fluids bycapillary action causes corrosive liquids to flow into thetightest of joints. The effect of corrosion resulting fromfluid intrusion is usually detectable by bulging of the skinsurface.
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Figure 3-9. Corrosion in Air Intake Duct
Figure 3-10. Corrosion Prone Points of Air andEngine Inlet
Figure 3-11. Gun Blast Area
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Figure 3-13. Corrosion Around Fasteners
Figure 3-12. Exhaust Trail Area
Figure 3-14. Galvanic Corrosion of Aluminum Alloy Sheet Adjacent to Steel Fasteners
MoistureEntrance
Points
Anode
Cathode
EntrappedMoisture
(Electrolyte)
GalvanicCorrosionProducts
1 2 3
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Figure 3-15. Flaps Lowered to Expose Recess Areas
Figure 3-16. Hinge Corrosion Points
Steel Hinge Pin
Aluminum AlloyExtrusions
Hidden corrosionoccurs here. Jointfreezes and lugsbreak off when
hinge is actuated.
Figure 3-17. Piano Hinge Lugs
3-5.9. FLAP AND SLAT RECESSES. Flap and slatrecesses (see Figure 3-15) and equipment installed inthese areas, which are normally closed, may corrodeunnoticed unless special inspections are performed.
3-5.10.HINGES. Hinges (see Figures 3-16 and 3-17)are highly susceptible to corrosion because of dissimilarmetal contact that results from wear and damage ofprotective metallic coatings. They are natural traps fordirt, salt, and moisture. Piano hinges, which areextensively used on aircraft, are especially vulnerableto attack.
3-5.11.MAGNESIUM PARTS. Magnesium parts areextremely corrosion prone. Special attention must begiven to proper treatment of their surfaces, insulation,and paint coatings. Magnesium is commonly used fortransmission and gearbox housings, and throughoutavionic systems (antennas and frames).
3-5.12.RELIEF TUBE AREAS. Human waste productsare very corrosive (see Figure 3-18). These areas shouldbe cleaned frequently and the paint finish kept in goodcondition. The relief tubes are usually made of plasticand should not present a corrosion problem.
3-5.13.SPOT WELDED ASSEMBLIES. Spot-weldedassemblies are particularly corrosion prone. As shownin Figure 3-19, corrosion is the result of the entrapmentof corrosive agents between the parts of the assemblies.Corrosive attack causes skin buckling or spot weldbulging (see Figure 3-20) and eventual spot weldfracture. Skin and spot weld bulging in their early stagesmay be detected by sighting or feeling along spot-welded seams. The only way to prevent this condition isby keeping the potential moisture entry points, includinggaps, seams, and holes created by broken spot-welds,filled with a sealant or suitable corrosion preventivecompound (CPC).
NOTE
Organizational and Intermediate levels shallnot drill drain holes unless authorized by theAircraft Controlling Custodians (ACC) or SystemProgram Manager (SPM) of the parent serviceorganization.
3-5.14.WATER ENTRAPMENT AREAS. Figure 3-21shows common water entrapment areas. Designspecifications require that aircraft have drains installedin all areas where water may collect. However, in manycases, these drains are ineffective either because ofimproper location or because they are plugged by
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Figure 3-18. Typical Corrosion Around aRelief Tube Vent
Figure 3-20. Spot Weld Corrosion
Figure 3-19. Spot Welded Skin Corrosion Mechanism
Corrosive agents travelbetween skins, aroundrivets and welds
Corrosion build-upcauses bulging of outer skin
Spot Weld
Corrosive agents enterat unsealed skin edges
Figure 3-21. Common Water Entrapment Areas
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sealants, fasteners, dirt, grease, and debris. Plugging asingle drain hole or altering the attitude of the aircraftcan cause a serious structural defect if salt water orother corrosives remain for any appreciable length oftime in one of these entrapment areas. Daily inspectionand cleaning of low point drains is a standardrequirement. These areas may accumulate waterfollowing washing or rinsing of aircraft. Where this is arecurring problem, procedures shall be developed toprevent water accumulation.
3-5.15.WHEEL WELL AREAS. Wheel well areasprobably receive more abuse than any other area on theaircraft (see Figure 3-22). They are exposed to mud,salt, gravel, and other flying debris from runways duringtaxiing, takeoff, and landing, and they are exposed to
salt water and spray when aircraft are parked aboardship. Because of the many complicated shapes,assemblies, and fittings in the area, complete coveragewith protective coatings is difficult to maintain.
3-5.16.WING-FOLD JOINTS AND LEADING EDGESOF WINGS AND CONTROL SURFACES.
a. Because wing and fin-fold areas are vulnerable tocorrosive attack when the wings are folded, they requirespecial attention (see Figure 3-23).
b. Both leading edges of wings and control surfacesare constantly exposed to salt laden air, thus specialattention should be given to these areas which arevulnerable to corrosion.
4-1. PURPOSE. This chapter covers instructions forcorrosion and paint removal. When corrosion is detected,a specific and immediate program for corrective actionis required. Each type of corrosion has its ownpeculiarities and will require special treatment. Completetreatment involves thorough inspection of all corrodedand adjacent areas and evaluation of the corrosiondamage (Chapter 3), paint and corrosion removal (thischapter), application of chemical surface treatments(Chapter 5), sealing (Chapter 7), and application ofpaint finishes: Appendix A (Navy) or TM 55-1500-345-23(Army). For additional procedures specific to Armymaintenance, see Appendix B.
4-2. RESPONSIBILITY. Personnel assigned tocorrective maintenance tasks must be specially trainedin the use of chemical paint remover, abrasive materials,powered tools, and damage limits. Inadequate trainingwill lead to further damage of equipment and poses asafety hazard to the individual.
4-3. CORRECTIVE MAINTENANCE.
4-3.1. Corrective maintenance depends on: (1) thetype of surface involved (metallic or composite); (2) thearea of damage (small corrosion spot or large heavilycorroded area); and (3) the degree of corrosion, asdetermined in Chapter 3.
4-3.2. Corrosion shall always be removed by the mildesteffective technique. Since composite materials do notcorrode, corrosion removal techniques are not applicableand shall not be used.
4-4. PAINT REMOVAL.
4-4.1. COMPOSITE SURFACES.
CAUTION
Propellers and helicopter blades have criticalbalance requirements. Refer to the appropriatepropeller or blade manual for evaluation andrepair limits of corrosion, erosion, and abrasiondamage.
4-4.1.1. Paint Removal. Paint shall be removed fromcomposite materials, such as fiberglass, carbon/epoxy,
graphite, and Kevlar using only mechanical paint removalequipment and techniques, unless specific exceptionsare provided in the appropriate maintenance manuals.Due to the irregularities in composite surfaces, removalof the complete paint system (e.g. topcoat and primer)can damage fibers in the surface layers. Therefore,paint removal by scuff sanding shall not go beyond theprimer coat unless repair is required.
4-4.1.2. Repair. Paint removed from compositesurfaces for the purposes of performing repairs shall beperformed by hand sanding or by using an orbitalsander in accordance with NAVAIR 01-1A-21. The useof other types of powered sanders is prohibited due tothe high potential for causing laminate damage. Paintsystem removal (to include removal of the majority ofthe primer) is required to prevent the compromising ofthe adhesive bond. Use extreme care during topcoatand primer removal to prevent sanding into the laminate.If the surface is to be subsequently prepared for structuraladhesive bonding, prepare surface in accordance withNAVAIR 01-1A-21.
4-4.2. METAL SURFACES. For areas of several squareinches, paint may be removed mechanically usingabrasive mats or flap wheels and brushes, taking carenot to remove underlying metal. Chemical paint removal,as specified in paragraph 4-6, may be used for areaslarger than several square inches. Plastic media blasting,as specified in paragraph 4-5.4, may be used atIntermediate and Depot level maintenance activities toremove paint.
4-5. MECHANICAL PAINT REMOVAL. Paint removalis authorized when corrosion is suspected/verified priorto magnetic particle or fluorescent penetrant inspection,or to replace damaged paint systems. For paint removalfrom small areas (less than several square inches), useof medium grade abrasive mats is authorized. Usecaution to remove as little metal as possible to properlyfinish the repair work. Abrasive wheels and brushes notspecified in this manual shall not be used for removingpaint.
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WARNING
Primers and paints may contain toxic materialssuch as chromates and lead. Use eye protection,gloves, and cartridge respirator duringmechanical paint removing operations. Contactthe local safety and health office for properpersonal protection equipment (PPE).
4-5.1. ABRASIVE MATS, FLAP WHEELS ANDBRUSHES. See paragraph 4-9 for a completedescription of authorized materials, equipment, andprocedures.
4-5.1.1. Composite Surfaces. Use medium grade(Grade C) abrasive mat (A-A-58054) for scuff sanding.The abrasive mat may be wet with fresh water or dilutedcleaning compound (MIL-PRF-85570) to preventclogging. See paragraph 4-4.1.1 for removal limits.
4-5.1.2. Metal Surfaces. Use a fine (Grade B) or veryfine (Grade A) abrasive mat on an orbital sander, or fineor very fine flap brushes on a pneumatic drill, for scuffsanding.
4-5.1.3. Cadmium Plated Steel Surfaces. Sanding tosmooth or remove paint from cadmium plated highstrength steel components shall be done with great careto avoid penetrating the cadmium, which can beextremely thin. If unprotected, high strength steel aircraftparts can experience detrimental levels of corrosionwithin just a few hours. Hand sand with 240 grit or finerabrasive paper or cloth until the primer coat is reached,then switch to 400 grit or finer paper or cloth.
CAUTION
Radial bristle discs are authorized for use onlyon aluminum, magnesium, high-strength steel,and titanium surfaces as a replacement/substitute for abrasive wheels and brushescited in this chapter. Use of the discs on othermetallic or composite surfaces is not authorizedand may result in damage to the surface orstructure.
4-5.2. 3M™ RADIAL BRISTLE DISC. The 3M™ radialbristle disc has been proven to be effective and lessaggressive than abrasive wheels and brushes and isintended for spot paint removal. The 400 grit (orange)disc may be used for spot paint removal and will leaveIVD aluminum or cadmium plating mostly intact on high-strength steel surfaces. Refer to paragraph 4-9.2.1 foroperating instructions.
4-5.3. PORTABLE VACUUM SANDING SYSTEMS.Air quality regulations mandate containment of airborneparticulates from sanding and grinding operations onmetallic and composite surfaces. Vacuum sandingsystems are suction-type equipment used for collectingpaint, metal, and carbon/epoxy dust from grinding andsanding operations. If appropriate filters (e.g. activatedcarbon) are used, then vapor, mist, gases, fumes, andodors can also be captured. Because the systems areportable, they allow for work to be done on locationrather than in a booth. These compact, self-containedunits are equipped with sanders, abrasives, adjustmenttools, air supply and vacuum hoses, vacuum hoseconnectors, supply air hose fittings and a high efficiencyfilter vacuum system for dustless sanding.
CAUTION
Abrasive blasting using glass beads oraluminum oxide shall not be used for removingpaint. Glass bead and aluminum oxide blastingmay be damaging to the underlying metal.
4-5.4. PLASTIC MEDIA BLASTING (PMB). PMB is anabrasive blasting method used to remove paint coatingson metal surfaces. PMB is a quick and environmentallypreferred alternative to most types of chemical paintremovers, but it can cause damage to underlying metaland injury to personnel if not performed by trainedoperators using approved methods. PMB of Army aircraftcomponents and parts shall be performed using therequirements and controls in Appendix B, Section VII.
4-5.4.1. PMB Training. Prior to using any PMBequipment, operators shall receive specializedon-the-job training conducted by qualified operators.Operators with limited training or who are newly trainedshall only perform PMB processes under the directsupervision of properly trained personnel.
a. Training shall include familiarization with thespecific equipment manufacturer’s operating andmaintenance manuals, and the guidelines andparameters as outlined in this chapter.
b. Training shall also include lectures anddemonstrations on equipment operation andmaintenance, masking and blasting techniques, processparameters, damage recognition, media contaminationprevention and removal, and safety requirements.
c. Training shall be documented in accordance withlocal requirements.
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4-5.4.2. PMB Restrictions. The following restrictionsapply to PMB operations:
a. PMB of aircraft component surfaces is authorizedfor use ONLY at Intermediate and Depot levelmaintenance activities.
b. PMB is NOT authorized for use at Organizationallevel maintenance activities.
c. PMB in a walk-in booth (open blasting) is notauthorized at Intermediate level maintenance activities.At the Intermediate level, only the PMB of aircraftcomponent surfaces in a blast cabinet (glove box)designed for plastic media is authorized.
d. PMB of aircraft component surfaces atIntermediate maintenance level activities is restricted tometallic surfaces 0.032 inch thick or greater.
e. Nonmetal surfaces, such as composites orfiberglass, and metal bonded structures are notauthorized for PMB at the Intermediate level.
f. Corroded steel components shall not beprocessed in equipment used for aluminum andmagnesium components without first removing allcorrosion products (rust). Plastic media used to removepaint from rusted steel parts should be completelypurged from blasting equipment, and the equipmentshould be thoroughly cleaned prior to blasting aluminumor magnesium parts. Best practice is to maintain anduse separate equipment for steel components.
g. Plastic media used to remove non-slip, walkwaycoatings (such as A-A-59166), is consideredcontaminated and the media must be replaced prior toblasting aluminum or magnesium parts.
4-5.4.3. Fluorescent Penetrant Inspection Limitations.Because PMB can peen or smear soft metals, it shallnot be used to remove paint from aluminum ormagnesium components requiring subsequentfluorescent penetrant inspection for cracks (see NAVAIR01-1A-16) unless specifically directed by the engineeringauthority for that component. Distortion caused by PMBcan limit crack detection. PMB is permitted prior to eddycurrent inspection. Chemical etching may be used toreopen cracks after PMB by removing distorted metal,however, this process shall be performed only inaccordance with specific engineering authority, approval,and written detailed process and application instructions.Chemical etching also removes protective coatingssuch as anodize and chromate conversion coatings.
Instructions for reapplication of these protective coatingsmust also be provided by the engineering authority.
WARNING
Hearing protection and air respirator shall beworn during plastic media blasting operations.Contact the local safety and health office forproper personal protection equipment (PPE).
4-5.4.4. Operator Safety. Operational safetycompliance shall be in accordance with local regulationsand the following:
a. PMB creates airborne particles which may behazardous if inhaled or allowed to contact eyes or skin.Both eye protection (goggles) and respirator are requiredfor all operating personnel. Do not allow unprotectedpersonnel to come in contact with dust. Wash handsthoroughly before eating or smoking.
b. The PMB process is noisy; typically greater than80 decibels. Hearing protection is mandatory.
c. All PMB equipment and components being blastedshall be properly grounded to dissipate static electricity.
4-5.4.5. PMB Equipment. The blast cabinet (glovebox) shall be specifically designed for use with plasticmedia meeting the requirements of NA 17-600-191-6-2.The blast cabinet shall be the pressure pot design,capable of maintaining constant blast pressure andmedia flow using a 1/4 inch to 3/8 inch I.D. nozzle. Theblast cabinet shall be equipped with an air pressureregulator and pressure gage to provide easy adjustment.The equipment shall allow for several successive cycles,and shall be equipped with a dust collection system toremove dust particles (recommend 60 mesh or finer).The dust collection system shall be accessible forremoval of the collected dust to facilitate proper wastedisposal. A magnetic particle separator shall be anintegral part of the system to remove ferrous particlesfrom recirculated media.
4-5.4.6. PMB Preparation.
4-5.4.6.1.Prior to PMB, all components to be blastedshall be thoroughly cleaned to remove dirt, oil, grease,and other soils. Refer to Chapter 2 for cleaning methodsand materials. If not removed, these soils will contaminatethe plastic media, causing possible damage to thesurface(s) being blasted and leading to malfunction ofthe blasting equipment. Allow the surfaces to drycompletely prior to blasting.
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4-5.4.6.2.Surfaces or areas which are sensitive tocontamination or impact damage from PMB shall bemasked or covered to prevent damage. These surfacesinclude precision bearings and gears; grease fittings;fuel, oil, and hydraulic lines; tanks, pumps, passages,and actuators; nonmetal surfaces (i.e., glass, plastic,fiberglass); electrical wiring and connectors; and avionicscomponents. Masking may be accomplished using oneor more of the following materials:
CAUTION
Hydraulic, oil, pneumatic, and fuel system linesshall be protected from contamination asspecified in NAVAIR 01-1A-20.
a. Plastic, rubber, or metal plugs and caps, asspecified in NAVAIR 01-1A-20.
b. Aluminum or paper backed masking tapes, kraftpaper, and plastic sheeting. These materials are notresistant to direct impact by PMB.
c. Impact resistant tape (3M No. 500 or IntertapeBT-100).
d. Hot glue and hot glue gun to seal edges of impactresistant tape.
4-5.4.7. PMB Procedures.
4-5.4.7.1. Conduct pre-operational inspection of glovebox in accordance with NAVAIR 17-600-191-6-1.
4-5.4.7.2. To prevent surface damage during blasting,the blast nozzle shall be kept moving at all times in asweeping motion and shall not be allowed to dwell inone place. Do not continue blasting if any surfacedamage is suspected.
4-5.4.7.3. The following parameters shall be adheredto in the operation of PMB cabinets:
a. Plastic bead media shall conform to MIL-P-85891Type V (acrylic), size 20-30 mesh material.
b. Blasting pressure shall be no higher than 50 psioutput pressure, which corresponds to approximately40 psi at the blast nozzle.
c. Distance from nozzle tip to surface being blastedshall be greater than 10 inches. A distance of less than10 inches may damage the surface and reduce the rateof coating removal.
d. Nozzle angle shall be 80 degrees from horizontal.
CAUTION
Particulate residues from PMB operations canlead to catastrophic failure of aircraft systems.
4-5.4.8. Post-PMB Cleaning. All PMB residue must beremoved following blasting operations to preventdamage.
CAUTION
Do not use compressed air to blow off partsoutside of a glove box or with the glove boxdoors open.
a. Inspect all openings to ensure no internal residuesremain. Remove internal residue using a HEPA vacuumor oil-free compressed air. Reclean as necessary.
b. Surface residue may impact downstreamprocessing, such as painting operations. Clean surfaceresidue using detergent washing methods and materialsspecified in Chapter 2. Reclean as necessary.
4-5.4.9. PMB Quality Control. Heavy particles, such assand, steel or rust particles, and glass beads, shall bekept out of the plastic media. PMB with heavy particlecontamination may decrease the overall fatigue life offatigue critical materials. If contamination is suspected,an impact test may be performed to confirmcontamination. The impact test is performed by blastinga bare (unclad) 2024 aluminum (AMS QQ-A-250/4)panel, approximately 3 inches x 5 inches x 0.040 inch,once over to simulate paint removal. Inspect the panelfor evidence of nicks/pitting. If nicks/pitting are visuallyevident (without magnification), the media is consideredcontaminated and must be replaced prior to furtherblasting. Additionally, to prevent buildup of contaminants,blast cabinets will be thoroughly cleaned prior to eachaddition of new plastic media. Information concerningdetection of contamination and equipment maintenanceis provided in paragraph 4-5.4.2. and NAVAIR17-600-191-6-2.
4-5.4.10. PMB Waste Disposal. Due to toxic materialscommonly found in paint, residue generated from PMBprocesses must be considered a hazardous materialunless otherwise directed by local environmental office.Dispose of used PMB in accordance with localenvironmental regulations.
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4-6. CHEMICAL PAINT REMOVAL. Paint removal isauthorized when corrosion is suspected/verified prior tomagnetic particle or fluorescent penetrant inspection,or to replace damaged paint systems. Larger areas ofmetal aircraft surfaces shall be stripped using TT-R-2918Type I or MIL-R-81294 Type I paint removers. The useof TT-R-2918 Type I is recommended if the use ofmethylene chloride, phenol, and/or chromate basedpaint removers is restricted/prohibited. Aircraftcomponents (except honeycomb and composite parts)may be stripped by tank immersion using AMS-C-19853,which contains methylene chloride, phenol, andchromates. Alternatively, MIL-PRF-83936 (NMP andmonoethanolamine based) hot tank paint remover maybe used. This product requires a heated stripping tank.
CAUTION
Use of acid based paint strippers is notauthorized.
Hydrogen embrittlement. When high strengthsteels (typically 180 ksi and above), some highstrength aluminum, and some stainless steelsare exposed to acid paint removers, platingsolutions, and other acidic chemicals and somealkaline materials, a cathodic reaction on themetal surface produces hydrogen. If the part isunder load or contains residual manufacturingstresses, sudden catastrophic failure may occurwhen the part can no longer sustain the internaland/or applied stresses. See Volume I foradditional information.
4-6.1. TYPES OF CHEMICAL PAINT REMOVERS.
4-6.1.1. MIL-R-81294 Remover, Paint, Epoxy,Polysulfide, and Polyurethane Systems. This materialis a methylene chloride based paint remover that isapplied using a nylon bristle brush or by immersing thepart into a small covered metal tank. Use this chemicalin accordance with paragraphs 4-6.2 through 4-6.4.MIL-R-81294 is not suitable for paint removal fromcomposite materials as it attacks the resin, resulting inloss of strength in the composite fibers. MIL-R-81294covers the following types of paint removers, whichhave been established for specific types of paint.
NOTE
Types I and II are available with phenols(Class 1) and without phenols (Class 2). Class 1products remove paint slightly quicker thanClass 2 products, but may present a greaterdisposal problem because of the phenol content.
a. Type I. For epoxy primer and polyurethane topcoatsystems.
b. Type II. For polyurethane topcoat systems.
c. Type III. For polysulfides (sealants).
d. Type IV. For paint systems with an elastomericpolyurethane intermediate coat.
4-6.1.2. TT-R-2918 Remover, Paint, No HAPs. Thismaterial is a nonhazardous air pollutant (non-HAPs)paint remover, ideal for use in areas where methylenechloride is restricted or prohibited. Type I is used forremoving epoxy/polyurethane systems, while Type IIproducts are designed to remove polysulfide based(sealant) systems. Comply with manufacturer’sguidelines. TT-R-2918 is not suitable for paint removalfrom composite materials.
4-6.1.3. AMS-C-19853 Immersion Tank PaintRemover. This material is a liquid carbon remover usedin immersion tank applications. Type I (phenolic) of thisproduct can also function effectively as a paint remover.The material has a water seal top layer which preventsrapid evaporation of the methylene chloride. Dry blisteredpaint can be removed by brushing with a heavy nylonbristle brush and then rinsing with water. Spent stripperand rinse water are hazardous waste and shall beprocessed accordingly.
4-6.1.4. MIL-PRF-83936 Hot Tank Paint Remover. Thismaterial is a di-phase n-methyl- 2-pyrrolidone (NMP)and ethanolamine based hot tank paint remover with amineral oil seal top layer. MIL-PRF-83936 is limited tointermediate level and above maintenance activities.The following shop practices shall be observed:
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CAUTION
Do not attempt to use MIL-PRF-83936 if shopfacilities do not have heated (minimum 140°F)stripping tanks. Do not introduce water into thestripping tank, as MIL-PRF-83936 is extremelysensitive to water. Parts should be thoroughlydry before they are allowed into the strippingtank. Deviations from the following shoppractices will degrade the performance of thischemical.
a. Use in a heated tank with a thermostat temperaturecontroller.
WARNING
Never exceed the manufacturer’srecommended temperature for heating andmaintaining stripper solution.
b. Use per manufacturer’s instructions.
c. Blistered paint can be removed by brushing witha heavy nylon bristle brush and then rinsing with water.
d. Spent stripper and rinse water may be hazardous.Check with local hazardous waste management officeprior to disposal.
CAUTION
Chemical paint removers shall be stored in aprotected area, out of direct sunlight, in atemperature controlled environment maintainedbetween 40°F and 100°F to prevent freezing orexposure to excessively high temperatures. Attemperatures out of the aforementioned range,chemical removers rapidly deteriorate, cannotbe remixed to form a homogeneous solution,and will become corrosive/acidic.
4-6.2. SHELF LIFE. Chemical paint removers with anexpired shelf-life can seriously degrade the structuralproperties of high strength metals, through hydrogenembrittlement resulting in a loss of ductility and crackingof the metal. On high strength steel aircraft componentsand structural fittings, do not use MIL-R-81294(methylene chloride based) or TT-R-2918 (benzyl alcoholbased) paint removers that are more than 12 monthspast the manufacture date unless otherwise authorized.On aluminum components and structures, MIL-R-81294
paint remover that is within 3 years of the manufacturedate may be used. As a general rule, if there is evidencethat the paint remover has separated into distinct layersor has become liquefied, do not use. Dispose of removeras hazardous waste.
4-6.3. PROTECTIVE MEASURES. Contact the localsafety and health office for proper personal protectiveequipment (PPE).
WARNING
Containers of chemical paint removers are underpressure, even when cold. If pressure is notbled off slowly, remover may splatter violently.
Chemical strippers are toxic and containingredients harmful to skin and eye tissues. Noeating, drinking, or smoking is allowed in areaswhere paint removers or solvents are beingused or stored. Prolonged breathing of vaporsfrom organic solvents or materials containingorganic solvents is dangerous. In addition togood tank ventilation, use cartridge respiratorand ensure good ventilation when in confinedareas.
4-6.3.1. When opening a can of chemical remover orwhen applying chemical remover, the following itemsshall be worn:
a. Chemical and splash proof goggles;
b. Rubber gloves;
c. Protective clothing (e.g. rubber apron and rubberboots); and
d. Cartridge-type respirator with organic vaporcartridge.
4-6.3.2. When opening, cover the cap or bung of thecontainer with a rag to reduce splatter and turn cap onlyfar enough to break the seal. Allow internal pressure torelease slowly and completely before removing cap.
4-6.3.3. First Aid.
4-6.3.3.1. If chemical remover is splashed on the skin,proceed immediately as follows:
a. Rinse affected area with water.
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b. Wash affected area thoroughly with soap andwater.
c. Flush affected area again with fresh water for atleast three minutes.
d. Get medical aid. Do not apply salves or othermedications without specific medical department direction.
4-6.3.3.2. If chemical remover is splashed in the eyes,immediately do the following:
a. Flood the eyes with water for at least 15 minutes.
b. Get medical attention immediately.
4-6.4. CHEMICAL PAINT REMOVAL PROCEDURES.The following procedures shall be followed when usingpaint removers MIL-R-81294 and TT-R-2918:
WARNING
Whenever possible, paint removal shall beaccomplished in a corrosion control facilitydesigned for paint removal. If not available,ensure adequate ventilation. Army and Navypersonnel shall read paragraphs 4-6.2 and4-6.3 prior to using any chemical remover.
CAUTION
Paint removers shall not be used on plastics,fiberglass or graphite composites, or otherorganic matrix structural composite surfaces.Keep paint removers away from fuel or watertightseam sealants, since they will tend to softenand destroy the integrity of sealants. Syntheticrubber parts, aircraft tires, fabrics, and acrylicplastics must be completely protected againstpossible contact with paint removers.
a. Mask acrylic and plastic surfaces, rubber hosesand tubing, exposed wiring, and any other surfaces thatcan be damaged from contact with the paint remover.Use barrier material (MIL-PRF-131 Class 1) andaluminum foil tape (AMS-T-23397 Type II).
b. To chemically paint strip small surface areas,mask around the area to be stripped using barriermaterial and aluminum foil tape. Raise the tape about1⁄2 inch along the bottom of the area as shown inFigure 4-1.
c. Prior to application of paint remover, removeexcess sealant with a sharp plastic scraper. Thenremove the remaining residue using the paint remover.
d. Application.
(1) MIL-R-81294: Apply a thick, continuouscoating of paint remover to cover the surface to bestripped using a nylon bristle brush or equivalent.
(2) TT-R-2918: Apply a thin coating of paintremover using an acid or paintbrush. Keep material wetby reapplying thin coats of additional TT-R-2918 paintremover periodically.
NOTE
Parts which are only coated with an epoxyprimer are very difficult to strip and need to bescrubbed with nylon brushes. Parts coated withan epoxy primer and a topcoat are easier tostrip.
e. Allow paint remover to remain on the surface fora sufficient length of time to wrinkle and completely liftthe paint, usually 10-40 minutes depending on thetemperature, humidity, and type of paint being removed.Paint removal rates may vary with temperature andhumidity. The strip rate of the TT-R-2918 material isslower than that of MIL-R-81294. Reapply paint removeras necessary in the areas where paint remains tight orwhere the material has dried. Micarta scrapers, abrasivepads (A-A-58054) or fiber brushes (A-A-3118) may beused to assist in removing persistent paint. Do not rinsewith water until all paint has been loosened. Watergreatly reduces the paint stripping efficiency of theremover.
Figure 4-1. Masking Around Area to be Stripped
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WARNING
Rinsing of epoxy paint removers shall beconducted in a suitable area specified by localsafety and environmental directives.
f. Remove loosened paint and residual paintremover by washing and scrubbing the surface withfresh water and a stiff nylon bristle brush or an abrasivepad. If water spray is available, use a low pressurestream of water applied directly to the surface while it isbeing scrubbed. Do not allow rinsed paint remover orcontaminated rinse water to contact other paintedsurfaces.
g. After thorough rinsing, remove masking materialsand thoroughly clean the area in accordance with thecleaning processes outlined in Chapter 2, usingMIL-PRF-85570 Type II (general cleaning) orMIL-PRF-29602 (aqueous parts washer).
h. Disposal. Process spent stripper and rinse wateras hazardous waste in accordance with local regulations.
4-7. MINOR PAINT DAMAGE REPAIR. Minor nicksand scratches in paint films can be easily and quicklyrepaired as follows:
a. Clean the area around the damage to ensure thatall traces of oil, dirt, salt, or other contaminants havebeen removed. Use a cleaning cloth dampened withMIL-T-81772 paint thinner or an approved solvent.
b. Remove any paint film not firmly adhering to thesurface using a nonmetallic scraping tool.
c. Lightly abrade the area around the damage witha fine abrasive mat (A-A-58054 Grade B) or 320 gritabrasive cloth (ANSI B74.18). Feather the edge of thepaint film while using care to prevent removal of metal,especially aluminum cladding.
d. Clean the area to be refinished usingMIL-PRF-85570 Type II (diluted one part cleaner to14 parts water) and rinse thoroughly with clean, freshwater. Ensure that all traces of oil and other contaminantshave been removed from the metal skin For watersensitive areas, use an approved cleaning solvent.
e. Apply chemical conversion coating (use ofTouch-N-Prep Pen is recommended) to the clean, barealuminum surface as described in Chapter 5.
f. Apply primer coating using a small, touch-upbrush, a Sempen™, or an approved aerosol touch-uppaint system as described in Appendix A (Navy) or TM55-1500-3554-23 (Army).
g. Apply topcoat paint film, using the sametechniques as described for primer. Two or three thincoats are preferred, rather than one heavy coat. Therepaired area should have the same paint thickness asthe surrounding area.
4-8. CORROSION REMOVAL. There are certain factorsthat must be considered prior to starting any corrosionremoval operation. The most important of theseconsiderations is that the removal of the corrosion productsmust be completed while not causing additional damageduring the process. This can be accomplished by firstremoving all corrosion visible through a 10X magnifyingglass, then removing an additional two mils (0.0020 inch) toensure that all deposits have been eliminated. Failure toremove all the corrosion may allow the corrosion to continueafter affected surfaces are refinished.
4-8.1. CLEANING. Before attempting to removecorrosion products, the surface must be stripped ofpaint and cleaned. Surface contaminants will interferewith corrosion removal procedures and increase thedifficulty of the operation.
4-8.2. PROTECTION. Adjacent components and partsmust be protected from corrosion residue and possibledamage that could be caused by the removal operation.Corrosion residue can cause additional corrosion anddamage the surface finish of the surrounding area. Anaccidental slip of a corrosion removal tool can quicklyresult in additional damage.
4-8.3. DAMAGE LIMITS. Complete removal ofcorrosion products may result in metal removal thatexceeds the amount allowed by specific aircraft orequipment repair handbooks. Prior to corrosion removal,the allowable limits specified in aircraft and equipmentmanuals and technical orders must be checked. Metalremoval damage is cumulative: prior metal removal,including areas on the opposite side of the part, must beconsidered when assessing corrosion damage. Whenremoving corrosion on critical aircraft structure, thefollowing steps shall be taken:
a. If allowable metal removal or damage limits willnot be exceeded, remove corrosion completely.
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b. If allowable limits will be exceeded, repair orreplacement of the part shall be coordinated with theAircraft Controlling Custodians (ACC) or SystemProgram Manager (SPM).
c. If a critical structural component is affected, repairsshall be coordinated with the ACC/SPM in order todetermine if the part should be repaired or replaced.
4-8.4. METHODS OF REMOVAL. There are variousmethods of mechanical corrosion removal from metalsurfaces. Chemical corrosion removal techniques arenot authorized for Navy organizational or intermediatelevel maintenance. Army: refer to Appendix B, Section III,for chemical corrosion stripping procedures.
4-8.4.1. The method used will depend on the type ofmetal, the location and accessibility of the corrodedarea, the degree of damage, and the type of corrosioninvolved. These factors will determine the types of toolsand equipment selected for the removal operation. It isvery important that the removal method and the toolsand equipment selected be compatible with the metalsurface. Compatibility involves two considerations:
a. The mechanical effect of the equipment on thesurface and
b. The compatibility of metallic particles worn off theremoval equipment which might become trapped in themetal surface.
4-8.4.2. Mechanical Compatibility. Mechanicalcompatibility refers to the selection of the right tools andequipment to prevent additional damage from occurringas a result of the removal process. Often it is necessaryto select a series of removal techniques involving theuse of different grades or classes of equipment andmaterial to effectively remove the corrosion products.The initial use of a rapid and coarse removal methodfollowed by a slower and finer removal method willproduce a smooth metal surface finish (for example, theuse of a vacuum blaster at first, and, once the surfaceis exposed, the use of a fine abrasive cloth or paper).
4-8.4.3. Material Compatibility. Material compatibilityrefers to using a cleaning medium during brushing,abrading, or blasting, that will not be the cause ofadditional corrosion. Material compatibilities are assuredby using like metals during corrosion removal operations.For example, only aluminum wool shall be used toremove corrosion from aluminum alloys. Using steelwool is prohibited because it can embed in the surfaceand cause galvanic corrosion of the aluminum alloy.
4-8.5. NOTES ON MECHANICAL CORROSIONREMOVAL.
4-8.5.1. Aluminum. Intergranular exfoliation corrosionis not removed by abrasive blasting; however, blastingmay be used in conjunction with powered corrosionremoval to determine whether all exfoliation corrosionhas been removed.
4-8.5.2. High Strength Steel. Use only the radial bristledisc, flap brush and wheel, or abrasive mat to removecorrosion on high strength steel parts. Other powertools are prohibited because of the danger of localoverheating and the formation of notches which couldlead to failure. Refer to specific maintenance manualsfor additional corrosion removal procedures.
4-8.5.3. Stainless Steels and Nickel Alloys. Useabrasive blasting only on heavily corroded parts as aprecursor to acid pickling.
4-8.5.4. Fasteners. Corrosion occurring on installedfasteners shall be removed using dry honing machine(i.e., vacu-blaster) or hand held abrasive materials
4-9. CORROSION REMOVAL EQUIPMENT ANDMATERIALS.
4-9.1. NON-POWERED TOOLS AND MATERIALS.Refer to Table 4-1 to determine the correct non-poweredabrasive to use on various aircraft metals.
4-9.1.1. Abrasive Mats. Abrasive mats (9" x 11" sheets)are nylon webs containing various grades of aluminumoxide abrasive material (A-A-58054 Type I Class 1Grade A - Very Fine, Grade B - Fine, Grade C - Medium).These mats are used by hand or with mandrels toremove small areas of corrosion and/or paint where theuse of powered tools would be impractical or preventedby the shape or accessibility of the area. Table 4-2 is aguide to grades of abrasive materials.
4-9.1.2. Abrasive Cloth. Aluminum oxide and siliconcarbide (ANSI B74.18) grit bonded to cloth are used fordry sanding of light to moderate corrosion products. Thecloth is available in sheets (9"X11") and rolls (2" or 3"wide X 150" long) in 240 grit (Fine) and 320 grit (VeryFine) grades. Use of aluminum oxide is prohibited oncomposite surfaces.
4-9.1.3. Abrasive Paper. Silicon carbide grit bonded toheavy paper (ANSI B74.18) is used for wet or drysanding of light to moderate corrosion products. It isavailable in sheets in 240 grit (Fine) and 320 grit (Very
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Table 4-1. Recommended Non-Powered Abrasives for Corrosion Removal
Fine) grades. Use of aluminum oxide is prohibited oncomposite surfaces. Silicon carbide is usually moreeffective than aluminum oxide on harder metals such asferrous alloys. Other abrasives are available on paperor cloth (emery and flint) but suffer from poor efficiencyand short working life.
4-9.1.4. Metallic Wools. Metallic wool is an abrasivematerial used for removing corrosion that is not tightlybonded to a metal surface. The four major types ofmetallic wools are: aluminum, copper, stainless steel,and steel. Metallic wools are available in five grades,ranging from very fine to extra coarse. Table 4-3 is aguide to help select the correct grade of metallic wool.These materials are very good for corrosion removal ontubing or extruded parts.
CAUTION
The use of metallic wools which are notgalvanically compatible with the metal surfacebeing treated is not authorized.
a. The type of corroded metal must be known beforeusing metallic wool. Steel wool is used on ferrousmetals; aluminum wool is used on aluminum, aluminum
alloys, magnesium, and magnesium alloys; copperwool is used on copper alloys, bronze, and brass; and,stainless steel wool is used on stainless steel.
b. After using metallic wools, remove all residuefrom the metal surface with a vacuum cleaner.
4-9.1.5. Wire Brushes. Wire brushes are used toremove heavy corrosion deposits or paint that is nottightly bonded to the metal surface. They are availablewith aluminum, steel, stainless steel, or brass bristles.Thick, short, and/or stiff bristles are more effective forrapid corrosion removal. The brushes must becompatible with the metal surface to prevent galvaniccorrosion. Stainless steel can be considered to beneutral, and can be used on all aviation equipment. Donot use a wire gage or diameter above 0.010 inch, asgouging of the surface may occur. Remove the corrosionwith a linear motion; do not cross-hatch. This willunnecessarily damage the surface. After wire brushingsoft metal (such as aluminum or magnesium) the surfaceareas must be polished with fine abrasive paper.
4-9.1.6. Pumice Powder. Pumice powder is a very fineand soft abrasive used to remove stains or to removecorrosion on thin metal surfaces where minimum metal
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removal is allowed. It is mixed with water and thenrubbed over the area with a soft cloth. After drying, thepowder is wiped off.
4-9.1.7. Scrapers. Scrapers are used primarily for theinitial removal of heavy corrosion deposits in cornersand crevices that cannot be reached with otherequipment. Scrapers of this kind may be locallymanufactured from phenolic plastic, fiberglasscomposites, aluminum or carbide-tipped steel. Plasticscrapers may be used on any metal surfaces; aluminumscrapers shall be used only on aluminum or magnesiumsurfaces; and steel scrapers shall be used only on steelsurfaces. Failure to use the correct metal scraper canlead to galvanic corrosion after the part is returned toservice. Normally, surface areas must receive furtherfinishing after corrosion removal with scrapers due tothe gouging action of scrapers and the difficulty indetermining complete corrosion removal.
WARNING
Power tool operations create toxic airborneparticles often containing heavy metals, suchas chromium (in the form of chromates), titanium,nickel, and beryllium, depending on the surfacebeing treated. Eye protection, ventilation, andan adequate respirator for dust control isrequired. Do not use hands to probe for airpressure leaks, as injury can result. Beforeusing any powered equipment, remove clothingwhich might become entangled in theequipment, as well as rings and other jewelry.Always wear proper personal safety equipment,such as goggles, faceshield, and/or respirator.Ensure that all electrical equipment is grounded.
CAUTION
Corrosion removal accessories, such as bristlediscs, flap brushes, or rotary files, shall only beused on one type of metal. For example, a flapbrush used to remove aluminum shall not beused to remove magnesium or steel.
4-9.2. POWERED TOOLS AND MATERIALS. Powertools are used to remove heavy corrosion from metalsurfaces, or mild to severe corrosion over large surfaceareas. Their use results in savings of time and money.However, care must be exercised when using powertools. Application of excessive pressure can easilydamage metal surfaces and cause internal metallurgicalchanges in the metal due to excessive heat buildup.Powered tools are an aggressive method which shallonly be used when authorized by cognizant aircraftengineering authority and where the extent of corrosionmakes non-powered corrosion removal impractical. Theindiscriminate use of powered corrosion removalmethods will result in damage to protective surfacefinishes and excessive metal removal. Refer to Table 4-4to determine the correct powered tools to use on variousaircraft metals.
CAUTION
Radial bristle discs are authorized for use onlyon aluminum, magnesium, high-strength steel,and titanium surfaces as a replacement/substitute for abrasive wheels and brushescited in this chapter. Use of the discs on othermetallic or composite surfaces is not authorizedand may result in damage to the surface orstructure.
4-9.2.1. 3M™ Radial Bristle Disc. Bristle disctechnology has been proven to be effective and lessaggressive than abrasive wheels and brushes and isintended for small corrosion repairs and paint removal.Other commercial off-the-shelf radial bristle discs areavailable, however, they have not been approved for
edarG tnelaviuqE)AC(evisarbAdetaoC
esraocartxE 001-08
esraoC 021-001
muideM 051-021
eniF 022-081
eniFyreV 023-082
eniFrepuS 004-023
eniFartlU 005-004
tnilF 006-005
Table 4-2. Grades of Abrasive Mats
epyT edarG esU
I eniFyreV gnihtoomslaniF
II eniF desuylnommoctsoM
III muideM esopruplareneG
VI esraoC krowhguoR
V esraoCartxE krownoitarotseR
Table 4-3. Grades of Steel Wool
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Table 4-4. Recommended Powered Abrasives for Corrosion Removal
NAVAIR use. Thus, they are strictly prohibited for useon Navy aircraft. Use of non-approved discs on aircraftmay result in serious damage to the substrate. It isrecommended that only one disc be utilized at a time onthe mandrel assembly. However, for larger surfaceareas, discs can be ganged/stacked on the mandrelassembly up to 4 discs thick (see Figure 4-2).
4-9.2.1.1. Two types of radial bristle discs with adiameter of 3 inches are available for corrosion repairand paint removal from aluminum, magnesium,high-strength steel, and titanium surfaces: 3M SPA(orange in color) is designed for light surface corrosiondiscrepancies such as filiform corrosion, and 3M 360(green in color) is designed for heavier corrosiondiscrepancies, light sealant removal, and light tomoderate surface pitting.
4-9.2.1.2 Radial Bristle Discs on High-Strength Steel(HSS). The 360 grit green disc is for removing lightsurface oxidation and corrosion, but it will also removethe IVD aluminum or cadmium plating. The 400 gritorange disc will leave the IVD aluminum or cadmiumplating mostly intact. Therefore, it is recommended thatthe 400 grit orange disc be used where only paintremoval is required, and the 360 grit green disc be usedas a replacement for abrasive wheels and flap brushesto perform small corrosion repairs down to bare metal.Examples of high-strength steel material locations onaircraft include the nose and main landing gears, launchbars, and tail/arresting gear assemblies.
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WARNING
Improper mounting of the radial bristle disc onthe grinder-mandrel assembly can causepersonal injury due to separation of the discfingers from the tool hub. Additionally, damageto the substrate and disc can occur.
4-9.2.1.3. Disc Mounting Procedures. Note thedirectional rotation arrow on the disc hub. The disc mustbe positioned on the mandrel assembly with the arrowpointing in the direction of the tool’s rotation (clockwise).Also, note the angle of the tips of the disc fingers. Thedisc fingers should be angled away from the direction ofthe grinder rotation. Placing the disc on the mandrel ina counterclockwise direction will damage the aluminumsubstrate and the tool. Also, if the disc fingers areangled toward the direction of the grinder rotation, theywill separate from the disc hub. Operating the tool in thismanner will damage the substrate and personal injurywill result from disc finger separation.
WARNING
Utilization of the radial bristle disc generatesdust particles that may contain chromates fromprimers. Therefore, eye protection is requiredwhen operating this tool. Consult with the localIndustrial Hygienist (IH) concerning properrespiratory protection equipment.
4-9.2.1.4. Operation of Radial Bristle Disc. Discoperation requires an air source of 90-110 psig, alongwith a high-speed pneumatic grinder rated from20,000-25,000 rpm and a 3M™ No. 990 mandrelassembly. The mandrel assembly includes two differentend caps, one silver and one black, for thin or thickstacks. The silver cap is used to mount one or two discs
and the black cap is used to mount three or four discs.Operating the grinder at its maximum rated speed isrequired to ensure maximum efficiency and effectivenessof the radial bristle disc. In addition to speed, light handpressure during operation is required to achieve optimumstripping results. The tips of the bristles are the workingelement of the tool. Therefore, to achieve the bestoverall result, maintain a light pressure on the grinderand move the grinder over the affected area on the worksurface. Exerting hand pressure on the disc at a force of2 pounds or greater will fold the bristle tip fingers makingthe tool inoperative. The disc is no longer effective whenthe bristle fingers are worn down to the disc hub. At thispoint, the disc must be replaced with a new disc.
4-9.2.2. Pneumatic Drill Motors. Pneumatic drill motorsare the preferred power tools for removing heavycorrosion or reworking large surface areas. The drillmotor is normally used with wire brush wheels, rotaryfiles, flap brushes, sanding pads, abrasive wheels, orbuffing wheels. These drills are available in many shapesand sizes to satisfy almost any requirement. Prior touse, check all pneumatic equipment air hoses for breaksor bulges in the coverings. The maximum chuck capacityof the portable powered drill is usually 1/4 inch. Insertthe tool shank and tighten chuck securely with the chuckkey prior to use. When it is difficult or impossible toreach the work area with a straight drill, use a flexibleshaft or angle adapter. The flexible shaft permits workingaround obstructions with a minimum of effort.
a. To prevent the rotary file, abrasive wheel, orsanding disc from digging into the metal, keep the tooloff the metal when initially starting the drill. When theabrading stroke is finished, lift the tool from the metalbefore releasing the power to the motor.
b. Holding the drill motor with both hands, applymoderate pressure while holding the rotary file, sandingdisc, or abrasive wheel against the work. When usingthe pneumatic tool as a sander, be sure to check thesize and type of the abrasive disc. Ensure that the typeof disc is compatible with the metal. Keep the sandingdisc tilted to approximately a 10 degree angle so thatonly one side of the disc is in contact with the metalsurface. If the entire disc surface is in contact with thesurface, a "bucking" effect will occur. Excessive pressurewill cause a "chattering" effect.
c. Move the tool over the surface with slightlyoverlapping strokes. Do not grind, sand, or file in onearea for any length of time without stopping and allowingthe metal to cool. Excessive heating of the metal willalter its metallurgical structure.
Figure 4-2. Bristle Discs Stacked on Mandrel Assembly
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4-9.2.3. Pneumatic Sanders. The proper technique forusing pneumatic sanders with oscillating heads shallinclude the following:
a. To prevent the sander from digging into the metal,start the sander before it touches the metal. When thesanding strokes are finished, lift the sander from themetal before engaging the stop switch. Do not lay theunit down with the motor running.
b. For best results, apply moderate pressure whileholding the sander against the work. Move the sanderover the surface with parallel and slightly overlappingstrokes. Move it as slowly as possible without overheatingthe metal. Generally, the cleaning rate should be abouttwo square feet per minute.
CAUTION
Do not use flap brushes down to within 2 inchesof core. Continued use beyond this limit maycause gouging due to loss of flexibility of fiber.Excessive pressure on flap brushes will causepolyurethane paint to melt, gum up, and streakaround the area being worked. Do not use onnonmetallic surfaces.
4-9.2.4. Scotch-Brite™ Finishing Flap Brushes. Flapbrushes are made of non-woven, nylon, aluminumoxide webbing. The brushes are very effective forremoving mild surface corrosion and prepping surfaces.They can also be used for mechanical removal andfeathering of paint systems. The brushes are comprisedof a series of flaps attached to a mandrel, with each flapimpacting the surface as it spins. When used correctly,the brushes will lead to minimal metal removal. The flapbrush and mandrel (see Figure 4-3) shall be assembledso that the arrow, painted on the brush, is facing theoperator or the arrow is pointed in the direction ofrotation (clockwise). When using flap brushes, applyminimal pressure to remove maximum paint andminimum metal. To achieve maximum effectiveness,use the specified RPM.
4-9.2.5. Abrasive Flap Wheels. Flap wheels(MIL-W-81319) are made of nylon paper impregnatedwith aluminum oxide abrasives (Figure 4-4). Thesewheels usually come with a spindle mount. Dependingon grit size, the flap wheels can be used to removemedium to severe corrosion from thick materials. Thewheels will also remove metal. Thus, caution must beused to minimize the amount of metal removal. For themost effective use of this equipment, use the specifiedRPM.
4-9.2.6. Abrasive Cloth and Paper. Aluminum oxideand silicon carbide cloth and paper can be used withsanders and buffers by cutting suitable pieces fromstock.
CAUTION
Unless authorized by the cognizant aircraftengineering authority, rotary wire brushes arenot authorized for corrosion removal on softmetals, such as aluminum and magnesium.
4-9.2.7. Rotary Wire Brushes. Powered wire brushesare available with various types of wire (straight, twisted,or crimped), various lengths of wire (short, medium, orlong), and various wire densities (light, medium, orheavy). Different actions can be obtained by varyingwire type, trim length, and density.
CAUTION
Improper use of the rotary file can damagealuminum structure by creating thin spotsexceeding damage limits. Use of rotary files isauthorized only for severe granular or exfoliationcorrosion removal by qualified structural repairtechnicians. Do not use rotary files to removecorrosion from installed fasteners.
4-9.2.8. Rotary Files. Since it is one of the fastest waysto remove corrosion and underlying metal, a rotary fileshould be only handled by an experienced structuralrepair technician. This tool is a tungsten carbide cylinderor cone into which cutting edges have been machined.When installed in the chuck of a pneumatic drill, rapidmetal removal can be achieved.
4-9.3. ABRASIVE BLASTING. During abrasive blasting,abrasive media is propelled toward the work piece withair pressure (conventional or vacuum blasting) or water(wet blasting).
WARNING
Abrasive blasting operations create airborneparticles which may be hazardous to the skinand eyes. A hood, gloves with gauntlets, andadequate ventilation are required.
4-9.3.1. Conventional Equipment. Two types ofequipment are used to propel dry abrasives: directpressure feed and suction feed. In direct pressureequipment, the abrasive holding tank is a pressurevessel from which abrasive media is forced, through a
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Figure 4-4. Abrasive Flap Wheels with Spindle Mount
metering device, into the pressurized blast line to theblast nozzle. In suction equipment, the abrasive holdingtank is unpressurized and provides media, through ametering device, into a passing airstream which thenpropels it through the blast hose to the blast nozzle.Blast cabinets (Figure 4-5), built to accommodate smallparts, have a recycling system which removes dust andlight particle contaminants, such as paint or corrosionproducts. Blasting rooms, designed for largecomponents, use a recycling and ventilating system.The operator works within the room, using a blast gun.
NOTE
Suction feed (also known as venturi equipment)requires higher nozzle pressure than directpressure equipment to obtain the requiredabrasive action.
4-9.3.1.1. Blast Media. A wide variety of materials andsizes (usually measured by mesh size) are available forblasting applications. Some of the recommendedabrasives include aluminum oxide (A-A-59316) andglass bead (MIL-PRF-9954). Table 4-4 specifies thecorrect material, mesh size, and air pressure at the blastnozzle to be used in blasting each type of alloy. Pressures
Figure 4-3. Scotch-Brite™ Flap Brush and Mandrel
WheelFlange
WheelFlange
WheelNut
Washer(Optional)
Washer(Optional)
Mandrel
Use Limit2 Inches
FlapBrush
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Figure 4-6. Portable Vacuum Blast Equipment
given in Table 4-4 are for direct pressure equipment. Asa general rule, increase the nozzle pressure by 50%when using suction feed equipment.
4-9.3.1.2. Air Hoses. The nozzle pressure of the blaststream is affected by the length and inside diameter ofthe air hoses. It is best to use the shortest hose possible,so that there will not be an excessive pressure drop. Ifit is necessary to couple lengths of hose, quick connect/disconnect external couplers are recommended.
4-9.3.1.3. Blast Nozzles. In general, larger nozzle sizesare preferable to smaller ones, because more area canbe cleaned per hour with the same amount of labor.High efficiency nozzles (e.g. tungsten carbide) shouldbe used, since they have a longer use life, require lessreplacement time, and direct the blasting particles moreefficiently. Nozzles should be periodically inspected forwear and discarded when the orifice is worn to adiameter which is 50 percent greater than the diameterwhen new. A worn nozzle, like a larger nozzle, willrequire a larger volume of air flow from the compressorto sustain the needed pressure at the nozzle.
4-9.3.1.4. Air Supply. Frictional losses in the hosesreduce the pressure at the nozzle, and nozzle wearincreases the volume of air needed to maintain thedesired nozzle pressure. To allow for nozzle wear, it isgenerally good practice to have a compressor capableof twice the pressure required for a new nozzle. Moistureand oil in the air stream is collected in the abrasiveduring blasting operations and gradual accumulationswill cause the abrasive to clog the blaster. A water andoil separator must be used in the compressed air supplyline to reduce excessive moisture or oil.
4-9.3.2. Portable Vacuum Blast Equipment. Also knownas a vacu-blaster or dry honing machine, these devices
Figure 4-5. Glove Box Unit Blast Cabinet
are portable machines designed to recover the abrasiveas it rebounds from the work piece. Vacu-blasters havean abrasive hopper, a reclaimer, a dust collector, avacuum pump and a blast gun which contains both ablast nozzle and a vacuum duct for recovery of themedia (Figure 4-6). This equipment is most effective onflat or slightly curved surfaces so that the media reboundsnear the vacuum duct surrounding the blast nozzle.Refer to NAVAIR 17-5BM-1, 17-5BM-2, and 17-5BM-3,for Navy equipment and TM 55-1500 series manuals forArmy equipment.
4-9.3.3. Wet Abrasive Blasting. Wet blasting is atechnique using high pressure water as the medium forthe delivery of abrasives. This method is not as harmfulto the base metal as dry abrasive blasting, due to thecushioning effect of the water medium. Unfortunately,this effect inhibits the speed with which coatings andcorrosion products are removed. The abrasive materialis normally not recoverable in wet blasting operations,and only sand (MIL-A-22262), aluminum oxide(A-A-59316), or No. 13 glass beads (MIL-G-9954) shallbe used. A corrosion inhibitor solution must be added tothe water or applied to the blasted surface immediatelyafter blasting to give some protection from rusting untilthe part can be painted.
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4-10. CORROSION REMOVAL PROCEDURES.
4-10.1. WARNINGS AND CAUTIONS. The followingwarnings and cautions shall be observed duringcorrosion removal operations.
4-10.1.1. Personal Protection.
WARNING
Many materials, such as copper alloys(especially beryllium-copper), cadmium plate,chromate conversion coatings, paints containingchromates, lead, barium, and strontium, aretoxic. Use approved respirators, eye protection,and skin protection. Take proper safetyprecautions to avoid inhalation or ingestionduring corrosion removal. Wash handsthoroughly before eating or smoking.
4-10.1.1.1. All powered corrosion removal procedurescreate airborne particles. Respirators and eye protectionare required. Consult with the local Industrial Hygienist(IH) concerning proper respiratory protection equipment.Wear leather gloves when using metallic wools toprevent hand injuries.
4-10.1.1.2. Do not use flap brushes, abrasive wheels,or wire brush wheels above their authorized RPM.These tools can fly apart, causing serious injury. Exercisecaution when using sharp or pointed tools to preventinjury.
4-10.1.1.3. Depleted uranium is extremely toxic andshall be worked only under a license from the NuclearRegulatory Agency (NRA). Machining or other work,such as surface sanding, may be done only by thelicensee. No drilling, sanding, or other mechanical workis permitted on depleted uranium by any servicemaintenance activity. If the protective finish (plating)which covers the depleted uranium is chipped, peeled,or otherwise removed so the dark gray or black depleteduranium (or uranium oxide) is visible, the part must bereturned to the licensee for rework or disposal. Packagingand shipping procedures shall conform to currentregulations for handling radioactive materials. Abrasivecleaning or sanding shall not under any circumstancesbe applied to depleted uranium.
4-10.1.2. Mechanical Damage.
WARNING
Use extreme care to ensure that blast mediadoes not contaminate hydraulic, fuel, oil, coolant,or oxygen systems. Blockages in flight criticalcomponents caused by abrasive media particlescan result in loss of life and aircraft.
CAUTION
Do not use flap brush down to within two inchesfrom the center of the hub. Continued usebeyond this limit may cause gouging due to lossof flexibility of the fiber. Follow direction ofrotation, as indicated by arrow imprinted onside surface of core.
4-10.1.2.1. Excessive pressure on the flap brush willcause polyurethane paint to melt, gum up, and streakaround the area being worked.
4-10.1.2.2. When using abrasive blasting on aluminumor magnesium alloys, do not allow the blast stream todwell on the same spot longer than 15 seconds. Longerdwell times will cause excessive metal removal.
4-10.1.2.3. Use of rotary files on aircraft or missile skinthinner than 0.0625 inch is prohibited unless authorizedby the ACC/SPM.
4-10.1.2.4. Vigorous, heavy, continuous rubbing (suchas with power driven wheels, discs, or flap brushes) cangenerate enough heat to cause metallurgical damage.Protect surfaces from severe abrasive action. Do notuse rotary files to remove corrosion from installedfasteners.
4-10.1.2.5. Mechanical removal of corrosion fromdepleted uranium shall not be attempted atOrganizational unit or Intermediate level maintenanceactivities.
4-10.1.2.6. Protect areas adjacent to corrosion removaloperations from chips, dust, and other debris whichcould produce dissimilar metal corrosion on previouslyuncorroded surfaces.
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4-10.1.2.7. Use only the materials recommended inTables 4-1 and 4-4. Dissimilar metal particles maybecome embedded in surfaces, leading to rapid galvaniccorrosion.
4-10.1.2.8. Be careful when removing corrosion fromsoft plated surfaces (such as zinc or cadmium). Softplating is easily damaged or removed by mechanicalmethods.
4-10.2. NON-POWERED CORROSION REMOVAL.This method is accomplished by hand rubbing thecorroded surface with tools or abrasives to remove thecorrosion. This method is normally used to remove mildsurface corrosion by scraping or wearing away thecorrosion products and some base metal. The basicsteps are:
a. Prior to removing corrosion, determine whethercorrosion can be removed without exceeding theauthorized allowable damage limits. See paragraph4-8.3.
b. Protect adjacent components from scale, chips,corrosion products, and chemical agents. Mask lapjoints, hinges, faying surfaces, access doors, air scoops,and other openings which would allow chips, dust, orother debris to enter interior areas. Use barrier paper(MIL-PRF-131) and masking tape.
c. Clean the affected area to remove grease andsoil (see Chapter 2).
d. Using materials in Table 4-1, remove all corrosionusing the mildest effective method. To determine whethercorrosion has been completely removed, inspect with a10X magnifier. A more sensitive evaluation can bemade using fluorescent penetrant with a 10X magnifier.
e. When complete corrosion removal has beenattained, blend or fair out the edges of the damagedareas using fine abrasive paper or cloth.
f. After removal of all corrosion, ensure that theallowable damage limits have not been exceeded.
g. Treat the surface in accordance with Chapter 5and apply protective coatings in accordance withAppendix A (Navy) or TM 55-1500-345-23 (Army).
4-10.3. POWERED CORROSION REMOVAL.Powered corrosion removal is generally done usingpneumatic drills with bristle disc, flap brush, rotary file,sanding pad, or abrasive wheel attachments. This
method is normally used to remove heavy corrosion bywearing away the corrosion products. Part of the basemetal is abraded away with the corrosion productsusing this procedure. The basic steps in corrosionremoval are:
WARNING
All powered corrosion removal procedurescreate airborne particles. Adequate ventilation,respiratory protection, and eye protection arerequired.
a. Prior to corrosion removal, determine whethercorrosion can be removed without exceeding theauthorized allowable damage limits. See paragraph4-8.3.
b. Protect adjacent components from scale, chips,corrosion products, and chemical agents. Mask lapjoints, hinges, faying surfaces, access doors, air scoops,and other openings which would allow chips, dust, orother debris to enter interior areas. Use barrier paper(MIL-PRF-131) and masking tape.
c. Clean the affected area to remove grease andsoil (see Chapter 2).
d. Using only recommended materials in Table 4-4,remove all corrosion using the mildest effective method.To determine whether corrosion has been completelyremoved, it may be necessary to use fluorescentpenetrant inspection with a 10X magnifier.
e. When complete corrosion removal has beenattained, blend or fair out the edges of the damagedareas using fine abrasive paper or cloth (see paragraph4-11)..
f. After removal of all corrosion, ensure the allowabledamage limits have not been exceeded.
g. Treat the surface in accordance with Chapter 5and apply protective coatings in accordance withAppendix A (Navy) or TM 55-1500-345-23 (Army).
4-10.4. ABRASIVE BLASTING.
4-10.4.1. Safety Precautions. Before beginningabrasive blasting operations, observe the followingsafety precautions. Failure to comply with theseprecautions may result in harm to personnel andequipment.
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(2) Examine all corroded areas for corrosionblisters. If intergranular exfoliation is present, use otherrecommended mechanical removal methods.
(3) Blasting shall not be performed on surfaceswhere there is a danger of warping or distorting the basematerial. Sheet metal, 0.0625 inch (16 gage, U.S.Standard) or thinner, shall not be blasted withoutengineering approval. See the applicable aircraftmanuals for limits on metal removal for the particularpart.
b. Determine what areas should be protected fromthe blast stream and from entrapment of the media, andtake action to mask or seal these areas. Compositesurfaces and those requiring a high gloss surface finishmust be effectively protected from the blast. Use impactresistant PMB tape (3M No. 500 or Intertape BT-100).
c. Static ground the blaster and equipment to beblasted.
d. Blast corroded areas using the pressures andmaterials given in Table 4-4. Do not attempt to usepressures higher than those specified, since higher airpressures tend to smear the metal and entrap corrosionproducts. When cleaning nonferrous (e.g. aluminum,magnesium) alloys, never use media which has beenused for cleaning ferrous metals. Abrasives used forcleaning ferrous metals will contain many particles ofmetal which will remain in the abrasive and willcontaminate any nonferrous metal being cleaned. Referto applicable abrasive blasting equipment instructions.
(1) Direct the blast stream at an angle to sweepacross the surface being cleaned (30-40 degrees fromthe surface). Several short passes over the corrodedarea with the blast nozzle are more effective than onesustained effort. The passes should start a few inchesbefore and end a few inches beyond the area to becleaned.
(2) Maintain the nozzle distance from the surfacebeing cleaned wherever the best cleaning is obtained.The normal nozzle distance range is from two to sixinches.
(3) Continue blasting with short passes over thecorroded area to be cleaned until a near-white blastcleaned surface is obtained. A near-white blast cleanedfinish is a surface finish from which all oil, grease, dirt,mill scale, rust, corrosion products, oxides, paint, orother foreign matter have been removed.
WARNING
Use extreme care to ensure that blast mediadoes not contaminate hydraulic, fuel, oil, coolant,or oxygen systems. Blockages in flight criticalcomponents caused by abrasive media particlescan result in loss of life and aircraft.
4-10.4.1.1. Operators shall be adequately protectedwith complete face and head covering equipment, andprovided with pure breathing air meeting therequirements of AFOSH Standard 161-1 and NAVOSHStandard A1-NAVOSH-SAF-000/P-5100-1 whenblasting in confined areas.
4-10.4.1.2. Finely divided dry particles of manymaterials (metallic, organic, and inorganic) can formexplosive mixtures with air. In dust form, certain metallicmaterials, notably titanium and magnesium, are capableof igniting spontaneously when exposed to air. Due topotential fire and explosion hazards, one should becareful with these materials when dry abrasive blasting.
4-10.4.1.3. Dry abrasive blasting of titanium alloysand high strength steel creates sparking. Take care toensure that there is no hazardous concentration offlammable vapors present.
4-10.4.1.4. After blasting in confined areas, it isessential that all blasting media and other residue becompletely removed. The blasting media can be veryslippery and can cause dangerous falls.
4-10.4.2. Abrasive Blasting Procedures. The blastingoperation should be accomplished in the following steps:
CAUTION
When blasting aluminum alloys or magnesiumalloys, do not allow the blast stream to dwell onthe same spot longer than 15 seconds. Longerdwell times will cause excessive metal removal.
a. Inspect areas and surfaces to be blasted anddecide what techniques will be used. Clean oil andgrease from surfaces with diluted MIL-PRF-85570 TypeII or an approved cleaning solvent (e.g. MIL-PRF-680Type II or MIL-PRF-32295 Type I).
(1) Blasting shall not be used in areas or underconditions that would allow any escaped abrasiveparticles to contaminate any system, engine, or othercomponent.
Change 1 - 31 March 2010
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CAUTION
Refer to the individual aircraft manuals for limitson metal removal. Do not exceed these limitswithout engineering approval.
(4) In critical areas it is necessary to fair out andsmooth edges of pits to reduce stress concentrations(see paragraph 4-11). The most effective manner is torotate the blast nozzle around the outer edge of the pit,keeping the nozzle at a constant distance from the workpiece and moving at a constant rate. Several shortpasses over the corroded area with the blast nozzle aremore effective than one sustained effort.
e. Upon completion of blasting, inspect for thepresence of corrosion in the blasted area. It may benecessary to use fluorescent penetrant inspection witha 10X magnifier. Particular attention shall be given toareas where pitting has progressed into intergranularattack. This is necessary because abrasive blasting hasa tendency to close up streaks of intergranular corrosionrather than remove them if the operator uses an improperimpingement angle. If corrosion has not been removedin a total blasting time of 60 seconds on any one specificarea, other mechanical methods of removal should beutilized.
f. Ensure that the limits of metal removal have notbeen exceeded, thereby affecting the structural integrityof the piece.
g. Completely clean all residue from the surface andexposed areas using a vacuum cleaner or low pressureair. The vacuum cleaner nozzle shall be plastic orcovered with masking tape to protect surfaces frommechanical damage. Clean surface using materials
and procedures recommended in Chapter 2. Treat andprotect all blasted areas as soon as possible afterblasting in accordance with the procedures outlined inChapter 5.
4-11. SURFACE FINISH. All depressions resulting fromcorrosion removal shall be blended smoothly and evenlywith the surrounding original surfaces. In critical andhighly stressed areas, all pits remaining after removal ofcorrosion products, by any method, shall be blendedout to prevent stress risers which may cause stresscorrosion cracking.
4-11.1. PITTING ON A NON-CRITICAL STRUCTURE.On noncritical structure it is not necessary to blend outpits remaining after removal of corrosion products sincethis results in unnecessary metal removal. Check specificaircraft manuals for maximum allowable depth ofdepressions. The general guidelines for shaping andblending corrosion grindouts are shown in Figure 4-7.For additional information, contact ACC/SPM forblendout procedures.
4-11.2. PITTING ON A CRITICAL STRUCTURE. Oncritical structure having a large number of closely spacedpits, intervening material may be removed to minimizesurface irregularity or waviness. The resulting depressionshall have no sharp corners and shall be saucer-shaped,wherever clearance permits, with its major axis runningspanwise on wings and horizontal stabilizers,longitudinally on fuselages, and vertically on verticalstabilizers (Figure 4-8). In areas where a true saucershaped depression cannot be formed due to inadequateclearance, blend out a depression as nearly as possibleto that shape so that there are no abrupt or sharp edges(see Figure 4-9).
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Figure 4-7. Shaping Reworked Areas
Corrosion Damage Before Rework
Pit has been cleaned up to the extent that all loose corrosion products have been removed.
Depression After Corrosion Removal
Rough edges have been smoothed and allcorrosion has been removed.
However, depression has not been shaped.
Dish-Out After Blending
Blending has been accomplished.
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Figure 4-9. Clean-Up of Limited Clearance Areas
Do Not GrindInto AdjacentStructure or Weld
Blended Area
StiffenerEdge Face
StiffenerEdge Face
Figure 4-8. Clean-Up of Pitting Corrosion onCritical Structure
A. Pitting Corrosion
B. Acceptable Clean Up
C. Non-Acceptable Clean Up
Location of Corrosion Pits
Top View
Blended Area
Cross Sectional View
Top View
Cross Sectional View
Blended AreaWidth of Clean Up Area (10 Times Pit Depth, Min.)
Depth ofClean Up
AreaLength of Clean Up Area
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CHAPTER 5SURFACE TREATMENT
5-1. PURPOSE. A critical step in the corrosionprevention and control process is treating the surface ofthe metal with a prescribed chemical to form a protectiveoxide film. Properly applied chemical treatment impartsconsiderable corrosion resistance to the metal, andgreatly improves the adhesion of subsequently appliedpaints or other coatings. Epoxy primers, for example,which do not adhere well to bare aluminum, adhere verywell to chemical conversion coatings.
5-2. SURFACE PREPARATION. After completingcorrosion removal in accordance with Chapter 4, proceedas follows:
a. Feathering Edges of Paint. Feathering of paintalong the edge of areas that have been chemically ormechanically stripped is required prior to pre-treatmentand repainting to ensure a smooth, overlapping transitionbetween the old and new paint surfaces. A smooth,overlapping paint film will ensure the absence of arough, soil accumulating junction between the old andnew paint films. Feathering shall be accomplished using240 or 320 grit aluminum oxide abrasive cloths (ANSIB74.18), fine or medium aluminum oxide abrasive mats(A-A-58054), or a fine or very fine powered finishingbrush (3M Radial Bristle Disc with 240 or 320 gritaluminum oxide abrasive).
NOTE
Aircraft that have been waxed, particularly withsilicone based material, may require specialcleaning to obtain a surface free of water breaks.When silicone wax is suspected, solvent cleanusing an approved cleaning solvent.
b. Clean surface with MIL-PRF-85570 Type II aircraftcleaning compound (dilute 1 part cleaner to 14 partswater) and an abrasive mat, then rinse with clean water.For water sensitive areas, use an approved cleaningsolvent.
c. Lightly abrade the bare or clad surface with a fineor very fine abrasive mat (A-A-58054) to remove theoxide layer and any residual chemical conversioncoating. This is the most effective means of preparingthe surface so that it will accept a new chemicalconversion coating. Care shall be taken to ensure thatclad surfaces are not compromised during mechanicalcleaning, as this can reduce the overall corrosionresistance of the alloy.
d. After abrading the surface, rinse the area byflushing with clean, fresh water. Particular attentionshould be given to fasteners and other areas whereresidues may become entrapped. At this stage of thecleaning process, the surface should be water break-free (see Figure 5-1). A surface showing water breaks(water beading or incomplete wetting) is indicative ofcontamination, which will later interfere with conversioncoating, sealing, plating, and/or painting.
e. If the surface is not free of water breaks, recleanthe area by repeating paragraphs b, c, and d.
5-3. PRECAUTIONS. Observe the followingprecautions when applying chemical conversion coatingsolutions on aluminum or magnesium surfaces:
5-3.1. Chemical conversion coating materials are acidicand require the use of chemical resistant gloves andchemical or splash proof goggles by personnel duringhandling and application. If the material accidentallycontacts the skin or eyes, flush immediately with plentyof clean, fresh water. Report to dispensary and/orconsult a physician if eyes are affected or skin is burned.
5-3.2. Mixing and application should be done in anadequately ventilated area. Avoid prolonged breathingof vapors.
5-3.3. Some chemical conversion coating materialsare strong oxidizers and a fire hazard when in contactwith combustible materials. Therefore, oxidizers must
Figure 5-1. A Water Break-Free SurfaceCompared to One with Breaks
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be stored separately. Rags and other materialscontaminated with conversion coating materials shouldbe containerized and properly disposed of as soon aspossible.
5-3.4. Do not use chemical conversion coating materialson high-strength steel. Catastrophic failure may occurdue to hydrogen embrittlement.
5-3.5. Do not allow any aluminum or magnesiumchemical conversion coating materials to enter fayingsurfaces or other areas where the solutions cannot beadequately removed by rinsing as the residue cancause corrosion.
5-3.6. Do not use steel, lead, copper, or glass containersfor holding/storing chemical conversion coatingmaterials. Use only acid-resistant plastic, rubber, orstainless steel. Brushes with tin plated steel handles orferrules may be used, but contact with the treatmentsolution should be minimized.
5-4. CHEMICAL CONVERSION COATING. Alsoknown as conversion coating, chemical film, paintpretreatment, "Accelagold", or "Alodine", thesetreatments are aqueous acid solutions of active inorganiccompounds that convert aluminum or magnesiumsurfaces to a corrosion resistant film. This film improvesthe adhesion of paint coatings. The process specificationgoverning aluminum conversion coating isMIL-DTL-5541, and MIL-DTL-81706 is the materialspecification for aluminum conversion coating materials.The process and material specification for pretreatmentand prevention of corrosion on magnesium alloys isAMS-M-3171.
5-4.1. APPLICATION METHODS. Chemicalconversion coating application methods include spray,brush-on or wipe-on, immersion, and applicator pens orpre-saturated applicator devices.
5-4.2. APPLICATION TOOLS. Chemical conversioncoatings may be applied by Touch-N-Prep pens, pre-saturated wipes, acid resistant brushes, sponge stickmoisteners, non-atomizing sprayers, or dip tankimmersion.
5-5. MIL-DTL-81706 CHEMICAL CONVERSIONCOATING FOR ALUMINUM ALLOYS. MIL-DTL-81706is a chemical treatment for both bare and clad aluminum
surfaces, including touch-up of scratched/damagedanodized aluminum. MIL-DTL-81706 has two types(Type I and II) and two classes (Class 1A and 3), and sixforms. The majority of aircraft chemical conversioncoating requirements are Type 1 Class 1A.
5-5.1. TYPES. Type I materials contain hexavalentchromium and Type II materials do not containhexavalent chromium. Type II coatings may not besubstituted for Type 1 coatings without engineeringauthorization.
5-5.2. CLASSES. Class 1A coatings provide maximumprotection against corrosion when left unpainted andsuperior adhesion when paint systems are applied.Type 1 Class 1A coatings can be iridescent yellow,golden brown or iridescent blue in color and rarelyexceed 0.005 mils in thickness. Class 3 coatings areintended for use as a corrosion preventative film forelectrical and electronic applications where lowresistance contacts are required. Class 3 coatings areoften much thinner than Class 1A coatings and usuallylighter in color. Type II coatings are the same thicknessas Type I, but are an iridescent blue to gray color forboth Class 1A and Class 3.
5-5.3. FORMS. Aluminum chemical conversionmaterials are available in the following forms:
NOTE
Form I concentrate and Forms II and V powdershall be mixed in accordance with themanufacturer’s instructions.
a. Form I (Concentrated Liquid). When water,preferably deionized (DI), is mixed with the concentrate,a solution equivalent to Form III is created. The unusedportions of the mixed solution may be stored in acontainer and used as required. Once mixed, servicelife is six months if the solution is not contaminated.Service life may be extended if solution successfullypasses the test in paragraph 5-8.
b. Form II (Powder). When water, preferablydeionized (DI), is mixed with the powder, a solutionequivalent to Form III is created. The unused portions ofthe mixed solution may be stored in a container andused as required. Once mixed, service life is six monthsif the solution is not contaminated. Service life may beextended if solution successfully passes the tests inparagraph 5-8.
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c. Form III (Premixed Liquid). Ready to use liquid forbrush (wipe-on/wipe-off), spray, and immersionapplications. The premixed liquid is the most commonlyused form of MIL-DTL-81706.
d. Form IV (Premixed Liquid, Thixotropic).Thickened, ready to use liquid for touch-up brushapplications on vertical or underlying surfaces.
e. Form V (Premeasured Powder, Thixotropic). Afteraddition of water, a thickened liquid is created that isequivalent to Form IV.
f. Form VI (Premixed Liquid). Ready to use liquidfor touch-up in a self-contained applicator device (e.g.Touch-N-Prep pens or pre-saturated wipes).
5-5.4. APPLICATION OF MIL-DTL-81706 FORMS I-V.
NOTE
Cleaning shall take place immediately beforeapplication of the chemical conversion coatingsolution because oxides will form on thealuminum surface and interfere with thechemical reaction.
a. Surfaces to be treated must be clean and free ofoils, greases, fingerprints, dirt, and corrosion productsprior to treatment. Refer to paragraph 5-2 for surfacepreparation.
Coating, Chemical Conversion 7MIL-DTL-81706
b. Immediately following cleaning, apply aluminumconversion coating material to surface. Keep the surfacewet with treatment material until a color change oriridescence is noted (approximately 2-6 minutes).Depending upon the aluminum alloy, the color changewill vary from a light iridescent color to a darker goldenbrown in color for Type I. The color will range from a faintiridescent to a light blue, gray, or purple for Type II.
c. After the color change, rinse treated surfaces withclean, fresh water and allow to dry completely beforepainting.
NOTE
Expiration dates for the Alodine 1132 Touch-N-Prep (TNP) pens are noted on the individualpens. As a general rule for pens stored at roomtemperature, it is usually two years from thedate of manufacture or one year after it is firstused. However, the cap must be on the penwhen not use to prevent evaporation.
5-5.5. APPLICATION OF MIL-DTL-81706 FORM VI(TOUCH-N-PREP (TNP) PENS). The repair of damagedchemical conversion coatings on aluminum surfacescan be accomplished by using Touch-N-Prep (TNP)pens (see Figure 5-2). The TNP pens are authorized fortouching-up small surface areas requiring eitherClass 1A or Class 3 solution. Use of TNP pens does notrequire water rinsing or wiping-off following applications,thereby minimizing hazardous waste generation. Emptypens can be returned to manufacturer for recyclingusing the self-addressed adhesive label and the originalbox.
5-5.5.1. To use the TNP pen, remove cap and chargethe tip by firmly pressing tip against a flat surface for10-15 seconds. The conversion coating solution in thepen will saturate the tip. Do not over-saturate tip. Refreshsolution during use by pressing tip against the surface.The acrylic tip of TNP pen can be modified or altered toform any shape to allow touch up of hard to reach areas.
5-5.5.2. Repair damaged coating as follows:
a. Clean the damaged area and prepare the surfaceto be repaired in accordance with paragraph 5-2. Surfacemust be water break free and dry prior to using the TNPpen.
Figure 5-2. Touch-N-Prep (TNP) Pen
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Coating, Chemical Conversion 7MIL-DTL-81706
b. Immediately following cleaning, use the TNP pento apply a chemical conversion coating solution inoverlapping parallel strokes (see Figure 5-3). Do notover apply the solution or allow puddles, drips, or runsto form.
c. Apply one coat of solution and allow coating to dryfor 5-10 minutes.
CAUTION
The newly formed conversion coating is softand can be easily damaged. Do not disturb thecoated surface until coating is completely dry.
d. The treated surface does not require rinsing orwiping-off, and can be air or forced dried with hot air.Maintain drying temperatures below 140°F to avoidcompromising the integrity of the film. Minimum dry timeis one hour. Once completely dried, the coating is readyfor subsequent priming and/or painting.
e. If bare surface areas still exist, repeat paragraphsb through d.
f. If treated surface does not turn to an iridescentyellow color shortly following application, re-cleansurface and re-apply (paragraphs a through d).
5-5.6. POWDERY CONVERSION COATING. Allowingthe chemical conversion coating to dwell too long on thealuminum surface can result in a powdery coated surface.Aluminum prepaint treatments shall be rinsedimmediately after the allotted pretreatment time. Abrownish color, or dry/matte finish indicates too long adwell time and produces a powdery coating. This will notprovide a good surface to which the paint system canadhere. If a powdery coating is formed, clean thesurface in accordance with paragraph 5-2 and reapplythe solution with a shorter pretreatment time.
5-6. AMS-M-3171 CHEMICAL CONVERSIONCOATING FOR MAGNESIUM ALLOYS.
CAUTION
Aluminum conversion coating solution (MIL-DTL-81706 Type I) is not authorized for treatingmagnesium surfaces.
5-6.1. AMS-M-3171 TYPE VI. This material, also knownas Dow #19, is a brush-on chemical surface treatmentfor magnesium alloys that provides corrosion protectionand improved paint adhesion. This material is primarilyused to touch-up and repair small areas on magnesiumparts such as transmission housings and gearboxes. Itis available in ready-to-use plastic bottle kits (seeFigure 5-4). Each kit contains an 8 ounce bottle ofpremixed magnesium surface treatment solution, two250 ml polyethylene beakers for dispensing material toprevent contamination of the 8 ounce bottle, a 16 ouncetrigger spray bottle for water rinsing, and two reusablenylon brushes. If the premixed AMS-M-3171 Type VIsolution is not readily available, the solution may beprepared using the mixing instructions provided below.
Figure 5-3. Application of TNP Pen onAluminum Substrate
Figure 5-4.Magnesium Treatment Kit
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Contact the Materials Engineering Laboratory at a depotlevel maintenance activity for assistance if necessary.
a. Obtain a clean container made of stainless steel,aluminum, or acid-resistant plastic (such as polyethyleneor polypropylene) that is at least one gallon in capacity.
b. Add 1⁄2 gallon of water, preferably distilled ordeionized (DI) water, to the container.
WARNING
Chromic acid can cause burns of the skin, eyes,and mucous membranes, including irritationand ulcers of the nasal septum. Use rubbergloves, goggles, and a dust filter mask whenmixing.
Chromic acid is a strong oxidizer and may igniteon contact with organic materials and reducingagents.
c. Add 11⁄3 ounces (37.8 grams) of chromic acid(A-A-55827) to the water and allow to dissolvecompletely.
d. Add 1 ounce (28.3 grams) of calcium sulfate(O-D-210) to the chromic acid/water mixture.
e. Top off with enough distilled or DI water to bringtotal volume to one gallon. Mix solution thoroughly untilchromic acid and calcium sulfate are completelydissolved. Once mixed, the solution has a service life ofabout two years if not contaminated. The solution canbe service life extended if it has not changed color,separated into different layers, and is tested successfullyon a scrap part (see paragraph 5-8).
5-6.2. APPLICATION OF AMS-M-3171 TYPE VI.
a. Surfaces to be treated must be clean and free ofoils, greases, fingerprints, dirt, and corrosion productsprior to treatment. Refer to paragraph 5-2 for surfacepreparation.
Chemical Conversion Coating 8for Magnesium AlloySAE AMS-M-3171
b. Immediately following cleaning, apply magnesiumconversion coating solution to surface using a brush.Keep the surface wet with treatment solution until a
color change is noticed (approximately 1-3 minutes).Depending upon the magnesium alloy, the color canchange to golden-brown, greenish-brown, brassy orgray.
c. After the color change, rinse treated surfaces withclean, fresh water and allow to dry completely beforepainting.
5-7. TROUBLESHOOTING. If chemical conversioncoatings do not form properly, check for one of thefollowing causes.
a. The metal surface is insufficiently cleaned.Cleaning must provide a water break-free surface.Refer to paragraph 5-2.
b. There was insufficient dwell time. As the solutionapproaches its one year service life, or at temperaturesbelow 50°F (10°C), more time may be required to formgood films.
c. The pretreatment solution has been allowed tocontact lead, steel, copper, glass, or other incompatiblematerials that can reduce the effectiveness of the solutionand may prevent adequate pretreatment.
5-8. EXPIRED SERVICE LIFE. The following test maybe performed to determine if a chemical conversionsolution is acceptable for use.
a. Apply test solution to a small aluminum ormagnesium coupon.
b. Allow solution to react for up to five minutes.
c. For aluminum, if a yellow to gold coating isproduced the material is still usable. For magnesium, acolor change to golden-brown, greenish-brown, brassyor gray indicates that the solution is acceptable for use.
d. If the solution has separated into different layersor a color change is not noticed after five minutes, thesolution is not acceptable for use and shall be disposedof in accordance with local hazardous materialregulations.
5-9. POST TREATMENT. Allow the chemicalconversion coated surface to dry for a minimum of onehour before applying paint or other coatings. More timemay be required at low temperature or high humidity.The coating is soft until completely dried. Do not wipethe area with a cloth or brush when coating is still wet,since wiping will remove the coating.
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5-9.1. To avoid contamination of the treated surface,apply primer according to procedures in Appendix A(Navy) or TM 55-1500-345-23 (Army) within 72 hoursafter conversion coating or perform temporarypreservation procedures (see paragraph 5-10) as soonas possible.
5-9.2. If the surface becomes dirty or accumulates oil,grease, fingerprints, or other contaminants, wipe priorto painting with clean cheesecloth (CCC-C-440) and anapproved solvent.
5-9.3. If the surface is scratched or the conversioncoating is damaged, clean (refer to paragraph 5-2) andretreat the surface before applying paint coatings orsealants.
5-10. TEMPORARY PRESERVATION. Under adverseconditions or when the restriction of operations will notpermit the application of a chemical conversion coating,apply a temporary corrosion preventive compound (CPC)in accordance with Chapter 8.
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CHAPTER 6TREATMENT OF SPECIFIC AREAS
6-1. INTRODUCTION. This chapter describes theprocedures recommended for treating and protectingagainst corrosion in specific, corrosion prone areas.The following paragraphs describe the treatment ofthese areas. The information in this chapter is general,and should be amplified and expanded by reference tothe applicable maintenance instruction manuals forspecific aircraft.
WARNING
Observe precautions listed in other chapters orreferences when using cleaning compounds,solvents, surface treatments, sealants, andpaints.
6-2. AIR INTAKE DUCTS FOR JET AIRCRAFT. Airintake ducts are fabricated from materials (usually5000 series aluminum) which have high corrosionresistance. Certain components of these ducts may becast aluminum or magnesium. Frequent cleaning of theducts is usually sufficient to preclude attack by corrosion.Activities operating aircraft performing low level missionsor take-off and landings over salt water or in highlysaline atmospheres may need to paint the ducts toreduce corrosion attack. A requirement for a coating asdetermined by the operating activity shall be coordinatedwith the parent service organization. The standardepoxy primer/polyurethane topcoat paint system isrecommended for painting the ducts.
6-3. BATTERY COMPARTMENTS, BOXES, ANDADJACENT AREAS. The battery, battery cover, batterybox, and adjacent areas (especially areas below thebattery compartment where battery electrolyte mayhave seeped) are subject to the corrosive action of theelectrolyte. Two different types of batteries areencountered on aviation equipment: lead acid, havinga sulfuric acid electrolyte; and nickel-cadmium, havinga potassium hydroxide electrolyte.
6-3.1. PREPARATION OF SOLUTIONS FORCLEANING AND NEUTRALIZING BATTERYELECTROLYTES. Neutralizing solutions are requiredfor cleaning areas contaminated with battery electrolyte.
6-3.1.1. Sodium Bicarbonate Neutralizing Solution. Forsmall areas, pour one pint of fresh water into a 500 mlpolyethylene wash bottle. Add two ounces of sodiumbicarbonate (ASTM D928) and mix thoroughly. Forlarge areas, pour one gallon of fresh water into a
bucket. Add six ounces of sodium bicarbonate (ASTMD928) and mix thoroughly.
6-3.1.2. Boric Acid Neutralizing Solution. For smallareas, pour one pint of fresh water into a 500 mlpolyethylene wash bottle. Add one-half ounce of boricacid powder (A-A-59282) and mix thoroughly. For largeareas, pour one gallon of fresh water into a bucket. Addfour ounces of boric acid powder (A-A-59282) and mixthoroughly.
6-3.1.3. Monosodium Phosphate Neutralizing Solution.For small areas, pour one pint of fresh water into a500 ml polyethylene wash bottle. Add two ounces ofmonosodium phosphate (AWWA B504) and mixthoroughly. For large areas, pour one gallon of freshwater into a bucket. Add six ounces of monosodiumphosphate (AWWA B504) and mix thoroughly.
6-3.2. CLEANING AND NEUTRALIZING PROCE-DURES.
WARNING
When handling electrolytes, splash proofgoggles, rubber gloves, and rubber apronsshall be worn. If any electrolyte contacts theskin or eyes, flood the affected area immediatelywith water and consult the Base Medical Service.An emergency shower and an eye wash stationin the area where work is being performed arerequired.
CAUTION
Both lead acid and nickel-cadmium batteryelectrolytes will cause severe corrosion ofmetallic structure. Do not allow contaminatedgloves, rags, or sponges, to come in contactwith aircraft structure. Place all itemscontaminated with electrolyte in a leak-proofplastic container prior to removing them fromthe aircraft. Remove any battery box whichcontains spilled electrolyte from the aircraftprior to cleaning it. Electrolyte spilled on aircraftstructure shall be cleaned up as soon as possibleafter it has been detected.
a. Apply the proper indicator to the spill area. Forspills from lead-acid batteries, apply a strip of bluelitmus paper to the wet surface. A color change to red
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indicates an acid contaminated area. For spills fromnickel-cadmium batteries, apply a strip of red litmuspaper to the wet surface. A color change to blue indicatesan alkaline contaminated area.
b. Apply the correct neutralizing solution to the areaswhere the litmus paper has been applied. Use a 10percent sodium bicarbonate solution (see paragraph6-3.1.1) to neutralize sulfuric acid from lead acidbatteries. Use a boric acid solution (see paragraph6-3.1.2) or a monosodium phosphate solution (seeparagraph 6-3.1.3) to neutralize potassium hydroxidefrom nickel-cadmium batteries. Ensure that the area iswell-saturated including all seams and crevices whereelectrolyte could collect. Use care to prevent neutralizingsolutions from spreading to adjacent areas, and ensurethat bilge area drains are open to allow fluids to flowoverboard. Allow the neutralizing solution to remain onthe surface for at least five minutes or until all bubblingaction ceases, whichever is longer.
c. Rinse the area thoroughly with a liberal amount ofclean water.
d. Remove any standing liquid or puddles with asqueeze bulb type syringe, absorbent cloth, or sponge.Place the used items in a leak-proof container fordisposal to prevent the contamination of other areas.
e. Reapply the litmus paper, as in paragraph a. Ifthe litmus paper does not change color, rinse the area,as in paragraph c, and dry the areas with clean cloths orrags. If the litmus paper changes color, repeatparagraphs b and c.
f. Apply chemical conversion coating treatment(Chapter 5), sealant (Chapter 7), or paint coatings(Appendix A), as required.
6-3.3. PAINT SYSTEMS. Special acid and/or alkaliresistant coatings are usually required for batterycompartments, boxes, and areas. Refer to the applicableaircraft manuals.
6-4. BERYLLIUM-COPPER ALLOYS. Surfacediscoloration of beryllium copper alloys is normal andremoval is not advised. If removal is required, minimizethe generation of fine beryllium dust particles as muchas possible.
a. Wear disposable coveralls, gloves, hood, andcartridge respirator. Consult local safety office forrequirements.
Solvent, Degreasing 13MIL-PRF-680
b. Dampen abrasive mat (A-A-58054) withdegreasing solvent (MIL-PRF-680).
WARNING
Dust, corrosion products, and other fine particlesgenerated by beryllium and beryllium-copperalloys are toxic when inhaled or allowed tocontact the skin. Severe poisoning can result ifberyllium dust is inhaled. Beryllium-copperalloys shall be cleaned only in strict accordancewith the following procedure or the procedure ofthe applicable maintenance manual.
c. To prevent the spread of toxic dust, keep mat wetthroughout the corrosion removal process.
d. Clean fitting with disposable towels dampenedwith MIL-PRF-680 after the completion of corrosionremoval.
e. Apply corrosion preventive compound,MIL-PRF-81309 Type II, on bushings, or MIL-PRF-81309Type III, on contacts.
Solvent, Degreasing 13MIL-PRF-680
f. Wipe work area clean with disposable towelsdampened with degreasing solvent (MIL-PRF-680).
g. Place disposable towels, abrasive mats, andcoveralls in a plastic bag marked "Berylliumcontaminated waste".
h. Seal plastic bag with tape (AMS D6123 Type II).
i. Discard plastic bag in accordance with localenvironmental protection directives.
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j. Wash hands with soap and water immediatelyafter completion of task.
6-5. CABLES, STEEL.
WARNING
Consult maintenance manuals for cabledetensioning and tensioning requirements priorto performing any maintenance.
6-5.1. If the surface of a cable is corroded, relieve cabletension and carefully force the cable open by reversetwisting. Visually inspect the interior. Corrosion on theinterior strands constitutes failure, and the cable mustbe replaced.
CAUTION
Do not use metallic wool to clean installedcables. The use of metallic wool will causedissimilar metal particles to become embeddedin the cables and create further corrosionproblems (galvanic corrosion).
6-5.2. If no internal corrosion is detected, remove looseexternal rust and corrosion with a clean, dry,coarse-weave rag or fiber brush.
CAUTION
Excessive solvent will remove internal cablelubricant and allow cable strands to abrade andfurther corrode.
6-5.3. To clean control cables, use a clean clothdampened with degreasing solvent (MIL-PRF-680Type II) or cleaner (MIL-PRF-32295 Type I).
Compound, Corrosion Preventive 6MIL-PRF-16173
6-5.4. After thorough cleaning, apply MIL-PRF-16173Grade 4 corrosion preventive compound (CPC) liberally.Wipe off excess. If excessive CPC is allowed to build up,it will interfere with the operation of cables at fair-leads,pulleys, or grooved bellcrank areas.
6-6. DEPLETED URANIUM COUNTERWEIGHTS.
6-6.1. Some aircraft have depleted uranium balanceweights incorporated in the airframe. Refer to applicablemaintenance manuals (Scheduled Depot LevelMaintenance) to determine the location of depleteduranium parts.
WARNING
Do not abrade or sand depleted uranium underany circumstances. Depleted uranium isextremely toxic and shall be worked only undera license from the Nuclear RegulatoryCommission. Machining or other work, such assurface sanding, may be done only by thelicensee. No drilling, sanding, or othermechanical work is permitted on depleteduranium by any service maintenance activities.If the protective finish (plating) which covers thedepleted uranium is chipped, peeled, orotherwise removed so the dark gray or blackdepleted uranium (or uranium oxide) is visible,the part must be returned to the licensee forrework or disposal. Packaging and shippingprocedures shall conform to current regulationsfor handling radioactive materials.
6-6.2. Mechanical removal of corrosion from depleteduranium shall not be attempted at Organizational/Unitor Intermediate level maintenance activities. If corrosionoccurs, apply a liberal, continuous coat of AMLGUARD(MIL-DTL-85054) and contact the local radiation safetyofficer immediately.
6-7. ELECTRICAL AND ELECTRONICEQUIPMENT. Avionic and electrical equipment areeasily damaged by contamination with corrosion removaldebris and by application of improper corrosion controlmaterials. Many of the conventional corrosion treatmentmethods used on airframe components are also usedon areas adjacent to or supporting avionic equipment,electrical equipment, wire bundles, and other electricalparts. Personnel performing airframe corrosion controltasks shall be familiar with avionic corrosion controlmaterials and procedures to ensure that no damage toelectrical or avionic equipment will occur. For morespecific information, refer to Volume III, as well as thespecific equipment maintenance manuals.
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6-7.1. GROUNDING AND BONDINGCONNECTIONS. After the grounding or bondingconnection has been made, overcoat the entireconnection, including all bare areas on the metal surface,with MIL-PRF-81733 sealant.
6-7.2. CONDUIT AND JUNCTION BOXES. Ifcorrosion is found, remove by mechanical methodsoutlined in Chapter 4. Before applying primer, reworkedand bare metal areas shall be treated withMIL-DTL-81706 for aluminum alloy parts or AMS-M-3171for magnesium alloy parts. Electrical conduit (exterior)and junction boxes (interior and exterior) shall be primedwith two coats of epoxy primer (MIL-PRF-23377 orMIL-PRF-85582) in accordance with Appendix A (Navy)or TM 55-1500-345-23 (Army).
6-7.3. WIRES AND CABLES. Electrical wires andcables having plastic jacket insulation or braided wireexterior shielding shall not be painted except as requiredfor moisture and fungus proofing (see Volume III).
6-7.4. ELECTRICAL CONNECTORS AND LEAD-INATTACHMENT POINTS. Almost all corrosion problemson electrical and electronic equipment are caused bymoisture intrusion at the connector or lead-in attachmentpoints on cases and covers. While the design of thisequipment is fixed, corrosion can be prevented byspraying MIL-PRF-81309 Type III corrosion preventivecompound into the pin and/or pin receptacle end ofconnectors prior to mating the connector halves and onthe connector shells after mating the connector halves.External electrical connectors and clamps that arecadmium plated may become discolored or tarnishedduring service. This is normal for cadmium plate andshould not be removed. Loss of cadmium plating isevident by rusting or pitting. Consult Volume III foradditional information.
6-7.5. MOISTURE AND FUNGUS PROOFING OFELECTRICAL AND ELECTRONIC EQUIPMENT. SeeVolume III.
6-7.6. ANTENNAS. Dissimilar metal corrosion(galvanic corrosion) often occurs at antenna attachmentpoints. Refer to Volume III for repair and replacementinformation on conductive gaskets and sealants, and tothe maintenance instruction manuals for information onpaint touch-up and finishing.
6-8. EMI SEALS AND GASKETS. To preventmalfunctions caused by electromagnetic interference(EMI), electrically conductive shielding is either built
into the avionic device or must be added to accesspanels, doors, or covers to: 1) prevent emission of EMIfrom its own circuits and; 2) prevent susceptibility tooutside EMI. EMI seals and gaskets may also act asenvironmental seals in certain locations, especiallyaround doors and access panels. However, since theseals must provide a conductive path to an aluminum orgraphite/epoxy skin, corrosion often occurs at thejunction of these dissimilar metals. When corrosionoccurs, the conductive path is lost and so is the EMIprotection, making the aircraft susceptible to electricalmalfunctions caused by external radiation. Refer toVolume III for additional information on EMI causes andeffects.
6-8.1. EMI SHIELDING MATERIALS. The followingare typical EMI shielding materials: elastomeric sealsand gaskets with an embedded or attached conductor(Figure 6-1), conductive elastomer gaskets (Figure 6-2),metallic screens installed under composite covers(Figure 6-3), bonding cables for access doors(Figure 6-4), and bonding washers for avionics enclosure(Figure 6-5).
6-8.2. TREATMENT OF EMI SEALS AND GASKETS.When corrosion is observed in such areas, disassembleonly the affected area and remove the corrosion usingthe mildest available method.
Alcohol, Isopropyl 1TT-I-735
a. Carefully clean the area with cloths wet withisopropyl alcohol (TT-I-735). Dry with a clean cloth.
b. If replacement seals are available, install them inaccordance with aircraft maintenance instructions orbulletins.
c. If replacement seals are not available or do notexist, spray the contacting surfaces with a light coatingof MIL-PRF-81309 Type III, then reassemble.Periodically inspect repaired areas and areas known tobe chronic problems.
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Figure 6-2. Dorsal Longeron EMI Seal
Figure 6-1. Beryllium-Copper Spiral Contact withEnvironmental Fluorosilicone Seal
Figure 6-3. Stainless Steel EMI Screen
Figure 6-4. Bonding Cable From Airframe toGraphite/Epoxy Avionics Bay Door
Figure 6-5. EMI Bonding Washers in Avionics Bay
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6-9. FASTENERS AND ATTACHING PARTS.
NOTE
The following does not apply to parts which arelubricated in the joint areas immediately beforeor after installation, or to close tolerance boltsand parts which are removed frequently formaintenance requirements. Additionalinformation concerning wet installation withsealant can be found in Chapter 7, and wetinstallation with primer can be found inAppendix A.
6-9.1. Attaching parts, such as nuts, bushings, spacers,washers, screws, self-tapping screws, sleeves forshake-proof fastener studs, self-locking nuts, speednuts, clamps, and bolts, do not need to be paintedexcept when dissimilar metal contact is involved withthe materials being joined. However, all parts shall beinstalled wet with sealant. For permanent installations,use MIL-PRF-81733 sealant and coat the entire matingsurface of the parts. For removable installations, useAMS 3284 sealant and coat only the lower side of theheads of screws and bolts with sealant. For removableinstallations, coat the threads and shanks of screws andbolts or the holes into which they are inserted with acorrosion preventive compound (see Table 8-3).
6-9.2. CLOSE TOLERANCE PARTS. Close tolerancebolts and parts shall be coated with corrosion inhibitingsolid film lubricant. Use AS 5272 (heat curing) onnon-aluminum parts when 400°F (204°C) ovens areavailable. Use MIL-L-23398 (air curing) on aluminumparts and on all types of metallic parts when 400°Fovens are unavailable. The solid film lubricant shall beapplied and completely cured prior to assembly. Boltsshall be coated on shanks and threads only. A thin beadof sealant shall be applied under the bolt head to imparta wet seal. If possible, bolt head, nut, and end shall befillet sealed with MIL-PRF-81733 sealant afterinstallation.
6-9.3. RIVETS, GENERAL. All rivets shall be installedwet with MIL-PRF-81733 sealant, except those in fuelcontact areas.
6-9.4. RIVETS, MONEL. Corrosion of nickel-copperalloy (Monel) is evidenced by green corrosion products.Removal of this corrosion is not required. If desired,corrosion may be removed as follows:
a. Scrub with a brush wet with solution of one cup ofsodium bicarbonate (ASTM D928) per gallon of water.
b. Thoroughly rinse the affected area with freshwater and dry with clean cloth or oil free, low pressureair.
6-9.5. FASTENERS AND MAGNESIUM. All machinescrews, countersunk fasteners, bolts (head end) andnuts which are used in contact with magnesium shall beinstalled with 5056 aluminum alloy washers. Theseparts and washers shall be installed wet withMIL-PRF-81733 sealant and shall be completely filletsealed with the same material after installation.
6-9.6. ADJUSTABLE PARTS. Adjustable parts, suchas tie rod ends and turnbuckles:
a. If possible, surfaces and threads shall be lubricatedand protected before assembly with corrosion inhibitingsolid film lubricant (AS 5272 or MIL-L-23398) whichshall be completely cured prior to assembly. Afterinstallation, apply a thin coating of DOD-L-25681lubricant to all surfaces of these parts located in hightemperature areas, or a thin coating of water displacing,corrosion preventive compound (MIL-PRF-81309 TypeII) to all surfaces of these parts located in other areas.
b. If solid film lubricants cannot be applied, use athin coating of DOD-L-25681 lubricant on all surfacesbefore and after assembly when located in hightemperature areas. Apply a thin coating of waterdisplacing lubricant (MIL-PRF-81309 Type II) beforeand after assembly, when parts are located in otherareas.
6-9.7. SLIP FIT PARTS. Slip fit parts shall be assembledwith MIL-PRF-81733 sealant between the matingsurfaces. If this is not possible, coat the ID of the hole inthe receiving part, which is normally the larger structure,with MIL-L-23398 and coat the OD of the mating partwith AS 5272 or MIL-L-23398. The solid film lubricantshall be applied and completely cured prior to assembly.
6-9.8. PRESS FIT PARTS. Press fit parts shall beinstalled with MIL-PRF-81733 sealant between the fayingsurfaces, and the edges of these parts shall be filletsealed with the same sealant after installation. Thesealant should also be applied to the ID of the hole intowhich the part will be installed.
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6-9.9. CUT EDGES AND HOLES. All cut edges andholes drilled or reworked for bolts, screws, rivets, studs,and bushings of aluminum and magnesium structure orparts shall receive chemical conversion coatingtreatment prior to the installation of the fasteners orbushings and prior to installing or refinishing the structureor parts. Apply MIL-DTL-81706 to aluminum parts andAMS-M-3171 to magnesium parts in accordance withChapter 5.
6-9.10.SEVERELY CORRODED (RUSTED)HARDWARE. Severely corroded screws, bolts, andwashers shall be replaced. When a protective coating,such as cadmium plating on bolts or screws is damaged,immediate action shall be taken to apply an appropriateprotective finish to prevent further corrosion (rusting).Refer to Chapter 8 for proper corrosion preventivematerials.
6-10. FAYING SURFACES, JOINTS, AND SEAMS.
NOTE
Treat and process faying surfaces of parts,components, or structures which are assembledby adhesive bonding in accordance with theapplicable equipment structural repair manualfor adhesive bonding.
6-10.1. When repairs are made on equipment oraccessories, or when components are installed orstructures are reinstalled, the attaching or faying surfacesshall be protected by sealing all metal-to-metal contactsand composite-to-metal contacts.
6-10.2. REMOVABLE STRUCTURES. All removablestructures (components requiring frequent removal formaintenance requirements) shall be installed at thefaying surfaces with AMS 3284 sealant. Fillet seal allexterior seams on removable structure with AMS 3284sealant (see Chapter 7 for details on sealant application).
6-10.3. PERMANENT STRUCTURES. All permanentstructures shall be installed with MIL-PRF-81733 sealantat the faying surface. Fillet seal all exterior seams (thoseexposed to the outside environment) of permanentstructures to make it flush with the adjoining surface.
6-10.4. The coating system on all attaching parts shallbe touched up after installation to match the surroundingstructure in accordance with Appendix A (Navy) orTM 55-1500-345-23 (Army).
6-11. FUEL TANKS, INTEGRAL AND EXTERNAL.For Navy materials and procedures, see NAVAIR01-1A-35. For Army materials and procedures, see TM55-1500-204-25/1 or applicable maintenance manuals.
6-12. HINGES, PIANO TYPE. Corrosion inhibitingsolid film lubricants are often applied to hinge pins andnodes to provide lubrication and to reduce corrosionproblems. See Chapter 2 for procedures on touch-upand replacement of these lubricants when hinges aredisassembled.
6-12.1. Each time equipment is washed, make sure allhinges are cleaned in accordance with Chapter 2.
6-12.2. After washing, apply a coating of a waterdisplacing corrosion preventive compound. Apply eitherMIL-PRF-63460, or MIL-PRF-81309 Type II andMIL-PRF-32033, to the node and hinge pin areas of allpiano hinges, including those coated with solid filmlubricants.
6-13. RELIEF TUBE AREAS. Interior and exteriorrelief tube areas shall be inspected and cleaned aftereach flight. Cleaning shall be accomplished inaccordance with procedures outlined in Chapter 2. Aftercleaning, the areas shall be treated with a disinfectant(O-D-1435 or TT-I-735). After cleaning and disinfecting,if the treated areas have exposed bare metal, applychemical conversion coating material for the specificmetal or alloy as outlined in Chapter 5.
6-14. RUBBER, NATURAL AND SYNTHETIC.Natural and synthetic rubber shall not be painted oroiled. As a general rule, grease should not be applied torubber parts, but some parts, such as "O" rings, requirea grease coating (consult the appropriate maintenancemanual). Many types of rubber are subject to fungusgrowth (e.g. mold, mildew) which can cause deteriorationof the rubber and corrosion of surrounding metalsurfaces. If fungus is noted on rubber parts, clean theparts and remove the fungus in accordance withChapter 2.
6-15. SPRINGS. Springs which are so tightly coiledthat the areas between the coils cannot be plated orpainted for corrosion protection shall be coated withwater displacing corrosion preventive compound(MIL-PRF-81309 Type II) by spraying or dipping, andallowed to dry for at least one hour. After drying, applya coating of MIL-PRF-16173 Grade 4 to the springs byspraying or dipping. These requirements do not apply tosprings operating in oil or hydraulic fluids.
6-16. SURFACES AND COMPONENTS EXPOSEDTO EXHAUST GASES, GUN GASES, AND ROCKETBLAST. Residues from exhaust gases, gun gases, androcket blast are very corrosive and can causedeterioration of paint systems. Frequent cleaning ofthese areas to remove residue is required and shall beaccomplished in accordance with Chapter 2.
6-17. TANKS, POTABLE WATER. The interiorsurfaces of aluminum alloy potable water tanks shall notbe painted or conversion coated. Remove corrosion byusing the mechanical methods outlined in Chapter 4.Flush thoroughly with clean fresh water and ensure alldebris is removed.
6-18. THIN METAL (0.0625 INCH THICKNESS ANDLESS).
6-18.1. Severe pitting, intergranular, and exfoliationcorrosion on thin metal requires removal by mechanicalmethods specified in Chapter 4 as appropriate for thetype of metal involved. Use extreme care and consultthe applicable maintenance manual for structuraldamage limits when removing corrosion from thin metal.When stains, surface corrosion, and mild to moderatepitting are found on thin structural skins (i.e., aircraft andmissile skins), chemical methods, as appropriate to thetype metal involved, are authorized for Army personnel(see Appendix B). Chemical methods are not authorizedfor Navy use. A convenient and effective mechanicalmethod for the removal of minor corrosion or stains onall metals is as follows:
CAUTION
Do not allow metallic or corrosion particles tobuild up around the polishing area or polishingtool (cloth or grit paper) during the polishingoperation. Damage to thin metal may result.
a. Mix ground pumice abrasive (SS-P-821) withclean tap water to form a paste. Using a clean, soft cloth(such as cheesecloth, CCC-C-440), apply the paste tothe area being treated and abrade the area with a lightrubbing motion.
b. When pumice has dried to a white powder, wipeoff with a clean, dry, soft cloth. If corrosion products(observed as stubborn stains) still exist, use number600 grit wet or dry abrasive paper and water to removethe remaining corrosion. Wipe clean with a clean, soft,dry cloth.
c. Refer to Chapter 5 for the required surfacetreatment, and paint in accordance with Appendix A(Navy) or TM 55-1500-345-23 (Army).
6-19. TUBING, NON-STRUCTURAL MEMBERSAND ASSEMBLIES. Non-structural tubing is tubingthat transfers a functional fluid (e.g. oxygen, hydraulicfluid, engine oil). Use the same procedures and materialsspecified for corrosion removal on structural tubingmembers and assemblies specified in paragraph 6-20.
6-19.1. ALUMINUM TUBING.
WARNING
Due to the possibility of combustion, do not usedegreasing solvent (MIL-PRF-680) or othersolvents that are not oxygen compatible onareas of oxygen storage, transfer systems, orsurfaces of missiles using liquid propellant.Failure to observe these precautions can resultin serious or fatal injury to personnel.
6-19.1.1. Treat aluminum tubing according to thefollowing procedure.
a. Clean in accordance with Chapter 2.
b. Remove corrosion using non-powered mechanicalmethods specified in Chapter 4. Polish to a smoothsurface.
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c. Apply chemical conversion coating(MIL-DTL-81706) to the interior and exterior surfaces oftubing (see Chapter 5). Do not apply chemical conversionto the interior of oxygen tubing. Apply conversion coatingafter fabrication and prior to the installation of newtubes. If corrosion has been removed from tubing, applyconversion coating to all bare, reworked areas.
CAUTION
Use extreme care to prevent the contaminationof interior surfaces of hydraulic, oxygen, and airspeed indicator tubing during paintingoperations.
d. Paint or corrosion preventative compound shallnot be applied to the interior surfaces of non-structuraltubing. Apply the specified exterior finish system to allexterior surfaces or reworked areas of tubing exposedto the environment. Take necessary precautions toprevent primer or paint from entering the interior areasof tubing. Where double flares are used (e.g. oxygensystems), cap the end and apply the finish system afterthe flaring operation. Paint end fittings after installationon the aircraft or equipment. Touch-up any coatingsystems damaged during tubing installation. Paint inaccordance with Appendix A (Navy) or TM55-1500-345-23 (Army).
6-19.2. STAINLESS STEEL TUBING. Austenitic (3XXseries) stainless steels are highly susceptible to pitting,crevice corrosion, and stress corrosion cracking whenexposed to moist, salt-laden air and when deposits ofdirt and debris are allowed to collect on tubing areascovered by metal brackets or parts. Treat stainless steeltubing according to the following procedure.
WARNING
Due to the possibility of combustion, do not usedegreasing solvent (MIL-PRF-680) or othersolvents that are not oxygen compatible onareas of oxygen storage, transfer systems, orsurfaces of missiles using liquid propellant.Failure to observe these precautions can resultin serious or fatal injury to personnel.
a. Clean in accordance with Chapter 2.
b. Remove corrosion using non-powered mechanicalmethods specified in Chapter 4. Polish to a smoothsurface.
WARNING
AMS 3166 wipe solvent is flammable and toxicto the skin, eyes, and respiratory tract. Eye andskin protection is required. Use only in a wellventilated area. To control solvent odor, usedrags should be immediately placed in sealedbags or covered containers and disposed perlocal directives.
c. Immediately before painting, wipe areas whichwill be painted with a lint free cloth moistened with AMS3166 or an approved wipe solvent, and dry with a cleancloth. Do not allow drying by evaporation, since soils willredeposit on the surface.
d. Apply the specified finish system for stainlesssteel tubing (consult the applicable maintenancemanual). Paint in accordance with Appendix A (Navy)or TM 55-1500-345-23 (Army).
6-19.3. CADMIUM PLATED STEEL TUBING. Barecadmium plating deteriorates rapidly when subjected toabrasion, most bases (alkali) and acids, and marine,industrial, and very humid environments. It should alwaysbe protected with a paint system to prevent corrosion.Treat cadmium plated steel tubing according to thefollowing procedure.
a. Clean in accordance with Chapter 2.
b. Remove deteriorated plating and corrosion onbase metal (steel) using non-powered mechanicalmethods specified in Chapter 4. Polish to a smoothsurface.
WARNING
AMS 3166 wipe solvent is flammable and toxicto the skin, eyes, and respiratory tract. Eye andskin protection is required. Use only in a wellventilated area. To control solvent odor, usedrags should be immediately placed in sealedbags or covered containers and disposed perlocal directives.
c. Immediately before painting, wipe areas whichwill be painted with a lint free cloth moistened with AMS3166 or an approved wipe solvent, and dry with a cleancloth. Do not allow drying by evaporation, since soils willredeposit on the surface.
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d. Apply the specified finish system for steel tubing(consult the applicable maintenance manual). Paint inaccordance with Appendix A (Navy) or TM55-1500-345-23 (Army).
6-19.4. TUBING FITTINGS AND SLEEVES. Corrosionoften occurs on sleeves and their fittings or on the tubingin contact with them, due to the crevices present at theattachment points. Galvanic corrosion often occursbecause the type of sleeve or fitting chosen is notelectrochemically compatible with the tubing. Whencorrosion is found on these areas, or when tubing,fittings, or sleeves are replaced, consult the applicablemaintenance manual to determine the proper types ofsleeves and fittings. Fittings located in areas which areinaccessible for inspection and refinishing duringoperational service shall be fillet sealed at the joint areawith MIL-PRF-81733 sealant at the time of installationand prior to painting. After the sealant is tack-free, paintthe tubing, fittings, and sealant in accordance withAppendix A (Navy) or TM 55-1500-345-23 (Army).
a. Clean all old preservative coatings and dirt fromthe fitting, sleeves, and tubing ends with degreasingsolvent (MIL-PRF-680 Type II) or cleaner(MIL-PRF-32295 Type I) before reinstalling tubing andtightening fittings.
b. Do not apply the finish system on fittings andadjacent tubing for a distance of one inch from the backend of the fittings on tubing areas requiring periodicremoval and/or opening during service.
WARNING
Do not use corrosion preventive compounds onoxygen line fittings. These materials containpetroleum solvents which are not liquid oxygen(LOX) compatible. Explosion may occur ifoxygen contacts these materials.
c. Except for oxygen line fittings, apply waterdisplacing, corrosion preventive compound(MIL-PRF-81309 Type II) by spray or brush to all fittingsurfaces after they are tightened, including the exposedareas of the sleeves and the unfinished areas of thetubing. Allow the CPC to dry for at least one hour, andapply MIL-PRF-16173 Grade 4 or MIL-DTL-85054 overthe same area by spraying or brushing.
d. After installation, apply the exterior paint systemto exposed tubing, sleeves, and back portions of the Bnuts of the fittings.
6-20. TUBING, STRUCTURAL MEMBERS ANDASSEMBLIES. Structural tubing is used as a supportingmember in a structure. It does not transport fluids. Onlynon-powered mechanical procedures and materialsspecified in Chapter 4 shall be used to remove corrosionon structural tubing. Reworked areas shall always bepolished to a smooth surface, using 400 to 600 gritabrasive paper or cloth, as the final step in the corrosionremoval procedure. The following steps outline generalpractices for the protection of structural tubing.
6-20.1. STRUCTURAL ALUMINUM ALLOY TUBING.
6-20.1.1. Apply chemical conversion coating (seeChapter 5) and paint to the exterior and interior surfaces
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6-11/(6-12 Blank)
of structural tubing in accordance with the finish systemdesignated in the applicable maintenance manual. Paintin accordance with Appendix A (Navy) or TM55-1500-345-23 (Army). All bolted or riveted caps orcomponents shall be installed with faying surfaces andfasteners wet using MIL-PRF-81733 sealant.
6-20.1.2. Interior surfaces of tubing having closedend(s) shall be coated with corrosion preventivecompound (MIL-PRF-16173 Grade 2 or 4) using thefill-and-drain method of application through holes locatednear each end of the tubes. These holes shallsubsequently be closed by installing blind rivets usingMIL-PRF-81733 sealant and overcoating the rivet headwith the same after installation.
6-20.2. STRUCTURAL MAGNESIUM ALLOY TUBING.All surfaces of tubing shall be treated with magnesiumconversion coating (AMS-M-3171) in accordance withChapter 5 and painted with the finish system designatedin the applicable maintenance manual. Install all partsonto the tubing with all faying surfaces and fastenerswet with MIL-PRF-81733 sealant.
6-20.3. STRUCTURAL COPPER ALLOY, STAINLESSSTEEL ALLOY, AND HEAT RESISTANT ALLOYTUBING. The interior and exterior surfaces of thesetypes of tubing do not require a finish system. However,to prevent galvanic corrosion of other metals with whichthese types of tubing are in contact, install parts and
attach tubing with faying surfaces and fasteners wetusing MIL-PRF-81733 sealant, or AMS 3374 sealantfor high temperature areas.
6-20.4. STRUCTURAL CARBON STEEL TUBING.
6-20.4.1. Exterior. All exterior surfaces of steel tubingassemblies shall be finished with one coat ofMIL-PRF-23377 or MIL-PRF-85582 primer, followed bytwo coats of MIL-PRF-85285 polyurethane topcoat.The topcoat color is specified in the applicablemaintenance manual. Apply primer and topcoat materialsin accordance with Appendix A (Navy) or TM55-1500-345-12 (Army).
6-20.4.2. Interior. For tubing assemblies without weldedor crimped ends, coat all interior surfaces withMIL-PRF-23377 or MIL-PRF-85582 primer using afill-and-drain procedure. Where practical, in lieu offill-and-drain procedure, two coats of primer may bespray applied to interior surfaces of all assemblies.
6-20.4.3. After coating the interior, clean the exteriorsurfaces to remove any residual primer. Seal all holesin tube walls by installing blind rivets wet withMIL-PRF-81733 sealant in the holes and overcoat therivet heads with the same after installation. Assembleall tubing assemblies manufactured by riveting or boltingmembers together on fittings with faying surfaces andfasteners wet with MIL-PRF-81733 sealant.
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CHAPTER 7SEALANTS
7-1. PURPOSE. This chapter covers recommendedmaterials and procedures for the application of sealingcompounds to aircraft structures. Sealants prevent theintrusion of moisture, rain, salt water, dust, and aircraftfluids, which can lead to extensive corrosion and possiblyequipment failure. Sealants are one of the most importanttools for corrosion prevention and control. For sealantsto be effective, it is critical that the correct sealant bechosen for a specific area/situation and that it be appliedcorrectly. Only qualified personnel thoroughly familiarwith sealants and their application shall be permitted tohandle and apply them.
7-2. REASONS FOR SEALING. Sealants are used forthe following purposes:
a. Fuel sealing (integral fuel tanks).
b. Pressure area sealing (cabin areas and accessdoors).
c. Weather sealing (exterior skin surfaces).
d. Firewall sealing (engine and ordnance areas).
e. Electrical insulation and sealing (bulkhead wiring,electrical connectors, and electrical components).
f. Acid-resistant sealing (battery compartments andrelief tanks).
g. Window sealing (windshield and canopy).
h. High temperature sealing (engine areas, anti-icingducts, and some electronics).
i. Aerodynamic smoothing (void filling) and sealing(exterior skin surfaces).
j. Sealing conductive gaskets (communication andnavigation antennas and static wicks).
k. Corrosion inhibition.
7-3. SEALANT PACKAGING. Sealants are generallypackaged and available as three different units of issue(U/I):
CAUTION
Sealants are sensitive to mix ratio and will notcure or perform properly if incorrectly mixed.
a. Two Part Can Kit (KT): Package consists of acuring agent (part A) and a base compound (part B) thatare pre-measured into separate containers. The entirecontents of both containers are intended to be mixed atone time. Accurate weighing equipment shall be used toachieve the correct mix ratio for smaller mixes.
b. Semkit Cartridge (CA): A complete plasticcartridge assembly that stores, mixes, and appliessealant materials. Semkit packages are convenientbecause they eliminate the need to measure and handlematerials, prevent contamination when opening andclosing can kits, and reduce air entrapment whichcauses voids in mixed sealant.
c. Premixed and Frozen (PMF): Sealant that ispre-measured, mixed, and frozen at extremely lowtemperatures. PMF sealants are the most convenientpackage configuration for high usage applications;simply thaw material according to manufacturer’sinstructions and use. PMF sealants are available in avariety of sizes, but the 21⁄2 ounce and 6 ounce are themost common.
7-4. SEALING COMPOUNDS AND MATERIALS.Table 7-1 lists approved sealing compounds, availabletypes, classes, groups, properties, and intended use.Refer to the applicable aircraft/equipment maintenancemanual and paragraph 7-7 for specific informationconcerning proper application of sealing compounds.Also, observe the warnings and cautions in paragraph7-7 when using any sealing compound. If use of asealant is required, and no specific instructions areavailable, the Sealant Decision Tree (Figure 7-1) maybe used as a guideline to determine the most appropriatesealant.
7-4.1. POLYSULFIDE AND POLYTHIOETHERSEALING COMPOUNDS. These materials consist oftwo components: the base compound (containing theprepolymer) and the accelerator (containing the curingagent). When thoroughly mixed, the accelerator curesthe prepolymer to a rubbery solid. Rates of cure dependon the type of prepolymer, accelerator, temperatureand humidity; full cure may not be achieved for as longas 7 days.
CAUTION
MIL-A-46106 materials shall not be used onaircraft or components. MIL-A-46106 can beidentified by its vinegar-like smell. If RTVsealants are required by the structural repairmanual (SRM), ensure that the sealant conformsto MIL-A-46146, or is a noncorrosive, authorizedsealant.
7-4.2. SILICONE SEALING COMPOUNDS. Roomtemperature vulcanizing (RTV) silicones generallyconsist of one component which cures by reacting withmoisture in the air. If silicones are applied too thickly orin such a way as to prevent moisture from entering thematerial, they may not cure at all. In addition, manyunauthorized silicone sealing compounds produce aceticacid (identified by a vinegar smell) while curing, whichcan lead to severe corrosion problems. There are twosilicone sealant specifications, MIL-A-46146 andMIL-A-46106. Only MIL-A-46146 materials arenoncorrosive.
NOTE
Use of the ePTFE sealing tape requiresauthorization from the cognizant Type, Model,Series (TMS) engineering authority for theaircraft.
7-4.3. ePTFE SEALING TAPE (AMS 3255). The ePTFE(expanded polytetrafluoroethylene) sealant tapeconsists of an extruded gasket with a pressure sensitiveadhesive backing. No mixing is required and there areno application life constraints or cure times. The sealingtape does not require removal and replacement unlessdamaged. The adhesive backing is only required to holdthe sealing tape in place until an access panel is(re)installed. Tapes may be special ordered withoutadhesive backing for use in areas where fluid exposure(e.g. hydraulic fluid or fuel) is expected; such tape isapplied with a fluid resistant rubber cement such asMMM-A-189.
7-4.4. REINFORCED POLYURETHANE GELSEALING TAPE. These tapes consist of a preformedpolyurethane gel reinforced with a loose fiberglassweave and a thin translucent backing. No mixing isrequired and there are no application life constraints orcure times. The sealing tape does not require removaland replacement unless damaged. Integrity of the tapeis affected by long-term exposure to hydraulic fluids andoils, which cause swelling and softening. Exposure tofluids will not degrade corrosion protection but mayreduce reusability and make removal messy. Tapesmay be ordered in a variety of widths, indicated by thelast three numbers in the part number (i.e. IS-HT3000-015 is 11⁄2 inches wide).
7-4.5. CONDUCTIVE GASKETS. Sealants andconductive gaskets used for weather sealing antennasand static discharge wicks and materials for weathersealing mated connectors are discussed in Volume III.
CAUTION
Use only those primers or adhesion promotersrecommended by the manufacturer for theirproducts.
NOTE
Solvent based adhesion promoters arehygroscopic (absorb moisture) and must bekept away from moisture. Discard material if itbecomes cloudy or a precipitate is formed.
7-4.6. ADHESION PROMOTERS. Some sealingcompounds require the application of a special primeror adhesion promoter prior to sealant application inorder to develop a good adhesive bond with the surface.Adhesion promoters are one part, water or solvent-basedcompounds which, after drying, leave behind couplingagents which promote adhesion with certain sealants.Adhesion promoters are especially important whenusing AMS 3277 Type I, AMS 3276, and most siliconebased sealants. It is essential that AMS 3100 adhesionpromoter be used before new sealant is applied overaged, fuel soaked polysulfide sealant. In all caseswhere polythioether sealants (e.g. AMS 3277) areapplied over polysulfide sealants (e.g. AMS-S-8802),especially in integral fuel tanks, a polythioether adhesionpromoter is required for use at the sealant interface.
7-4.7. RELEASING/PARTING AGENT. VV-P-236(Petrolatum) or MIL-PRF-32033 (light lubricating grease)can be used as release agents for sealant applicationsby applying a very thin film. Do not allow release agent
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Model 850 Manual Sealant Dispensing Gun
Notes:1. Requires no air or power supply.2. Rugged, heavy guage metal construction.3. Easy to operate.4. Dipenses a wide range of sealants, adhesives, or other materials.5. Handles thick, viscous materials.
Figure 7-3. Manual Sealant Gun
Figure 7-2. Pneumatic Sealant Gun
2.5 oz. Disposable Plastic Cartridge(incl. plunger, seal, and cap)
6 oz. Disposable Plastic Cartridge(incl. plunger, seal, and cap)
2.5 or 6 oz. Metal Retainer Barrel
KnobAssembly
Gun HandleAssembly
Air Hose (5, 10, 20, or 25 feet)
Typical Application Nozzles
Hansen Quick Disconnect
Model 250-A Pneumatic Sealant Dispensing Gun (With Handle)
Available in 2.5 oz. or 6 oz. Metal Retainers
Notes:1. All parts interchangeable.2. Plastic cartridge and metal retainer determine capacity. All other parts are identical.3. Pistol grip handle may be removed to convert to lever throttle for more clearance, better manipulation, and use in confined areas.4. 2.5 oz. capacity recommended for most field repairs.
2.5 oz. Metal Retainer
6 oz. Metal Retainer
1 16 " Orifice (No. 252)
3 32 " Orifice (No. 430)
1 8 " Orifice (No. 480)
to contact any surface(s) where sealant is to adhere.Sealant will not adhere to surfaces coated with releaseagent. If contact surface to be sealed becomescontaminated with the release agent, removecontaminant using a clean cloth moistened with anapproved solvent. Reapply adhesion promoter asnecessary.
7-5. SEALING EQUIPMENT. The following sealingequipment is available.
7-5.1. SEALANT GUN. Sealant guns are available forboth pneumatic and manual application of sealants,adhesives, and potting compounds (see Figures 7-2and 7-3). The Semco Model 250-A gun, or equivalent,is fitted with one of the nozzles from Figure 7-4 andused for the application of fillet seals. When using asealant gun, the nozzle tip must be pointed into theseam and maintained at a 45 degree angle to the line oftravel, forcing the bead of sealant to precede the gun tipto minimize entrapment of air. Use fairing/smoothingtools (i.e., spatulas and spreaders) shown in Figure 7-5to work sealants into seams.
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Figure 7-4. Sealant Application Nozzles
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Figure 7-5. Sealant and Adhesive Smoothing Tools
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CAUTION
Care should be taken when using rivet nozzlesto prevent sealant material from filling fastenerholes.
7-5.2. APPLICATION NOZZLES. In addition to thestandard, fillet, and ribbon nozzles in Figure 7-4, thecountersink and rivet nozzles in Figures 7-6 and 7-7,respectively, can also be used with the sealant guns.Countersink nozzles are used to apply sealants into thecountersink of fastener holes prior to fastener installation.Rivet nozzles are used to apply sealants through thehole prior to fastening parts with rivets. The rivet nozzleshave a spring-loaded tip, which serves as a check valveand allows for dispensing a precise amount of sealantmaterial.
7-5.3. HIGH-PRESSURE INJECTION GUN. Figure 7-8illustrates injection guns used for injecting sealant intoconfined holes, slots, structural voids, and joggles,including channel sealing. Follow the procedures outlinedin the aircraft SRM for the proper preparation and useof these guns. For hard to reach areas, attach anextension nozzle to the injection tip.
7-5.4. SEALANT KITS (SEMKIT OR TECHKIT). Mostsealants are available as ready to use kits (Semkits orTechkits). These kits are compact, two-part mixingapplication units designed for convenient storage, easymixing, and proper application of the sealant in smallquantities. The base sealant is packaged in standard21⁄2 ounce and 6 ounce cartridges which are placed in asealant gun for application. There are two styles: theBarrier style, which holds proportioned amounts of thetwo components separated by an aluminum barrier;and the Injection style, which stores the acceleratormaterial within the injection rod to separate it from thebase compound prior to use (Figure 7-9). When usingSemkits or Techkits, note that the handle or dashercontains a pre-measured amount of accelerator andshould be retained until the ramrod has been operatedto release the seal at the bottom of the dasher. All of thematerial contained inside the two-component Semkit orTechkit package is mixed within the cartridge.
7-5.5. SEALANT APPLICATION TOOLS. Whenapplying or fairing out sealants and adhesives, use thesmoothing tools shown in Figure 7-5. These tools are
commonly used in sealing maintenance work, but othertools may be manufactured/fabricated as needed to fita specific situation. Only phenolic/plastic material shallbe used to manufacture sealant application tools.
7-6. TWO COMPONENT SEALANT MIXING ANDHANDLING. The proper weighing and mixing ofcomponents is essential to assure proper curing andadhesion of sealants. Use a weight scale to accuratelymeasure the materials before mixing. Mixing shall beaccomplished in one central area in each organization.Polysulfide and polythioether sealants consist of twoseparately packaged components, a base compound(part B) and an accelerator (part A) in 6 ounce, 12 ounce,and 24 ounce kits. The base-to-accelerator ratio varieswith different manufacturers. It is important, therefore,to mix the material according to the manufacturer’sinstructions. The accelerator should be added to thebase in the correct ratio and mixed until a uniform coloris obtained. Difficulties with polysulfide and polythioethersealants are frequently caused by incomplete mixing orinaccurate weighing. The two-part sealants arechemically cured and do not depend on solventevaporation for curing. Slow mixing by hand isrecommended for two-part can kits. A high speedmechanical mixer should not be used as internal heatwill be generated, reducing application life andintroducing air into the mixture. Mix Semkit or Techkit inaccordance with manufacturer's mixing instructions.
CAUTION
Do not use any two-part sealant after it hasbeen mixed and its rated application time hasexpired, as poor adhesion may result.
7-6.1. APPLICATION TIME AND CURE TIME. Sealantapplication time and cure time are dependent uponambient environmental conditions. Maintenancepersonnel should be aware of the effects of temperatureand humidity on the application time of a sealant. Mixonly the amount of material that can be applied duringthe rated application (work) time of the sealant. Thistime (in hours), known as a dash number, is denoted asthe last number in a sealant designation (e.g.MIL-PRF-81733 Type II-2 has an application time oftwo hours). Table 7-2 indicates application times, tack-free times, and full cure times for each sealant type anddash number at 75°F (24°C) and 50% relative humidity.
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Figure 7-6. Countersink Application Nozzles
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Figure 7-7. Rivet Application Nozzles
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Figure 7-8. High-Pressure Sealant Injection Guns
Semco Model #507-A
Semco Model #510
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Figure 7-9. Injection Style Semkit
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Table 7-2. Time Requirements for Two Component Sealants
7-6.1.1. Effect of Temperature. Increases intemperature will shorten application and cure time.Conversely, lower temperatures will lengthen applicationtime and cure time. For polysulfide sealants, each 18°F(10°C) increase in the temperature above 75°F (24°C),cuts the application time by approximately half, with asimilar reduction in tack-free and cure time. Similarly,for each 18°F (10°C) decrease in the temperaturebelow 75°F (24°C), the application time is approximatelydoubled with a similar increase in tack-free and curetime. Tack-free and cure times may increase forpolyioether sealants (e.g. AMS 3277) at temperaturesbelow 40°F (4°C).
7-6.1.2. Effect of Humidity. When sealants, especiallypolysulfides, are applied in an environment where thehumidity is greater than 50% RH, application time isshortened to some degree; when humidity is less than50% RH, application time and cure time may beextended. Polythioether sealants (e.g. AMS 3277) cureindependent of humidity conditions.
7-6.1.3. Tack-Free Condition. Sealant is considered tobe in a tack-free condition if, when lightly touched, thesealant does not transfer onto the skin.
7-6.2. STORAGE INSTRUCTIONS. When largequantities of sealant are used, it may be advantageousto pre-mix and freeze the sealant to provide a readysupply of mixed sealant when it is needed.
7-6.2.1. Two-part kits and Semkit or Techkit packagesealants should be stored according to instructions onthe container.
7-6.2.2. Polysulfide sealants in a pre-mixed and frozen(PMF) form should be stored in a freezer at -40°F(-40°C) or below for optimal retention of applicationproperties.
7-6.2.3. Polythioether sealants (e.g. AMS 3277) requireextremely low temperature refrigeration at -80°F (-62°C)or below for optimal retention of application properties.
7-6.2.4. Thawing of PMF can be accomplished in twoways.
a. For ambient temperature thaw, place the PMFcartridge in a vertical position. Let stand at ambienttemperature for approximately 30 minutes. Dry anycondensation from the exterior of the cartridge prior touse.
b. For water bath thaw, place the PMF cartridgeupright in a 120°F (49°C) water bath for approximately4-6 minutes with plunger cup out of water bath. Uponremoval from the bath, carefully dry the exterior of thecartridge before using.
WARNING
MIL-T-81772 Type I thinner solvent isflammable. Never store, open, or apply nearignition sources (e.g. lighted cigarettes, sparks,electrical arcing, or heat sources).
7-6.3. MIXING MIL-PRF-81733 TYPE III.MIL-PRF-81733 Type III has a tendency to settle outduring storage. The base compound must be thoroughlymixed, using a standard paint shaker, to obtain auniform consistency before the addition of theaccelerator. After both components, base andaccelerator, have been mixed separately, add the properamount of accelerator to the base compound and mixthe combined materials, preferably with a paint shaker,for at least five minutes. For proper application time andcure, the base compound and accelerator must becombined in the proper ratio and mixed prior to theaddition of any thinners (solvents). After mixing, thesealant may be thinned for spraying to a viscosity of 20to 25 seconds in a Zahn No. 2 cup (refer to Appendix A)using MIL-T-81772 Type I. A 20 to 30 volume percentaddition is usually required. The application time andtack-free time will not change using this solvent blend.
7-7. SEALANT APPLICATION PROCEDURES.
WARNING
To control solvent odor, used rags should beimmediately placed in an appropriate HAZMATcontainer and disposed of per local directives.
7-7.1. CLEANING. If the surfaces to be sealed havebeen contaminated following surface treatment, cleanthe area with a clean cheesecloth (CCC-C-440), cleaningcloth (AMS 3819), or nonwoven cleaning cloth(CCC-C-46) saturated with solvent (AMS 3166,A-A-59281 Type I or II, or equivalent), beginning at thetop of the area to be sealed and working downward.Always pour solvent on the cloth to avoid contaminatingthe solvent. Dry the surfaces immediately with a cleancloth. Do not allow surface to air dry, as the oil or dirt mayremain on the surface and is impossible to remove witha dry cloth. Use a stiff bristle brush to clean around bolts,rivets, or fasteners. Always use a clean cloth as eachnew area is cleaned.
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7-7.2. PRIMING. All surfaces to be sealed, with theexception of internal fuel tank surfaces, shall be primedwith MIL-PRF-23377 or MIL-PRF-85582 in accordancewith Appendix A (Navy) or TM 55-1500-345-23 (Army),and allowed to dry one to two hours at ambienttemperatures before sealing.
CAUTION
After surface treatment and primer application,do not contaminate areas to be sealed withhands or tools.
7-7.3. MASKING. To prevent sealant from contactingadjacent areas during application and smoothing outoperations, the surrounding area not being sealed canbe masked off with AMS-T-21595 Type I masking tape(Figure 7-10). In cases where the tape is likely to remainin place for more than two days on items exposed todirect sunlight and where tape residue on the surfacecannot be tolerated, use AMS-T-22085 Type IIpreservation and sealing tape. An example wheremasking tape may be useful is during fillet sealing ofexterior surface lap and butt seams.
NOTE
Always pour solvent onto a new cloth to avoidcontaminating the solvent supply. Clean onesmall area at a time. Reclaimed solvents orsoiled cleaning cloths shall not be used.
7-7.4. ADHESION PROMOTER. If adhesion promoteris required, the surfaces shall be cleaned with a solvent(AMS 3166, A-A-59281 Type I or II, or equivalent)immediately before applying adhesion promoter.Contaminants such as dirt, grease, and/or lubricantsmust be removed to insure good adhesion. Apply a verythin coat of the adhesion promoter to the solvent cleanedsurface with a clean cloth (AMS 3819), wipe off anyexcess with a clean cloth, and allow the surface to dryfor 30 minutes to one hour. If surface becomescontaminated or sealing is not accomplished within anhour after application and drying of adhesion promoter,repeat cleaning procedure and reapply adhesionpromoter.
WARNING
Sealants, with the exception of ePTFE sealingtapes, are toxic; therefore, rubber orpolyethylene gloves and goggles shall be wornwhen using these materials. Wash handsthoroughly with soap and water before eating orsmoking.
7-7.5. BRUSH, SPATULA, OR SEALANT GUNAPPLICATION. Prior to masking and sealing, preparesurface in accordance with paragraphs 7-7.1 and 7-7.2
CAUTION
After surface treatment and primer application,do not contaminate areas to be sealed withhands or tools.
a. To prevent sealant from contacting adjacent areasduring application and smoothout, outline the areasbeing sealed with masking tape (AMS-T-21595 Type I)so that each tape strip is 1⁄8 to 1⁄4 inch from the edge of theseams (see Figure 7-10).
b. If required, apply adhesion promoter in accordancewith paragraph 7-7.4.
c. Apply sealant between tape strips.
Figure 7-10. Application of Sealant withNon-Metallic Spatula
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(1) Paste sealants may be applied with anonmetallic spatula or spreader as shown in Figure 7-10.Avoid the entrapment of air. Work sealant into recessesby sliding the edge of the spatula firmly back over therecesses. Smoothing will be easier if the nonmetallicspatula is first dipped in water.
(2) Sealant applied with a brush is applied andsmoothed until the desired thickness is reached.
(3) Sealant applied with a sealant gun will notusually require masking and is especially adaptable tofilling seams or the application of form-in-place gaskets.
d. Remove masking tape after the sealant has beenapplied and before it becomes tack-free. Cure time willdepend upon the application life of the materials used.
e. If tape residue on these surfaces is excessive,remove residue using aliphatic naphtha (TT-N-95Type II) or equivalent.
f. When sealant no longer feels tacky, prime withMIL-PRF-23377, MIL-PRF-85582 or other primers asspecified. Apply topcoat if specified.
7-7.6. SPRAY GUN APPLICATION. Prior to maskingand sealing, prepare surface in accordance withparagraphs 7-7.1 and 7-7.2.
CAUTION
After surface treatment and primer application,do not contaminate areas to be sealed withhands or tools.
NOTE
The dried film of the spray sealant shall have aminimum thickness of 6 mils (0.006 inch).
a. Mask off adjacent areas with barrier material(MIL-PRF-131) held in place with masking tape(AMS-T-21595 Type I).
Sealing and Coating Compound 12Corrosion InhibitingMIL-PRF-81733
b. Apply MIL-PRF-81733 Type III sealant in a solid,continuous pattern when spraying over seams whoseconfiguration is less than 14 inches apart. On seamconnections greater than 14 inches apart, minimizeoverspray to adjacent areas.
c. Allow at least four hours for the spray sealant todry before subsequent processing.
7-7.7. ePTFE SEALING TAPE (Skyflex™), PEEL ANDSTICK APPLICATION. Prior to application, preparesurface in accordance with paragraphs 7-7.1 and 7-7.2.
CAUTION
After surface treatment and primer application,do not contaminate areas to be sealed withhands or tools.
a. Examine faying surfaces to be sealed and buildup any uneven areas on the aircraft frame withcompensation tape (P/N: GSC-21-95158-011 orequivalent) to create a level faying surface for panelsealing.
b. Select from Skyflex™ P/Ns: GSC-21-95201-0111,GSC-21-95241-011, GSC-21-95261-011, GSC-21-98006-021, GSC-21-95811-022, GUA-1059-1, GUA-1301-1,or equivalent. The sealant tape should cover the fullwidth of the faying surface to be sealed.
c. Measure and cut the desired length of ePTFEsealant tape that is required. Excess tape width shouldbe trimmed to the width of the faying surface.
d. For corners on aircraft/panels, cut ends of tape atapproximately a 30 degree angle so that the sealanttape from the converging side will overlap by a minimumof one quarter to one half inch. The overlap is requiredto assure a complete perimeter seal; butt joints are notacceptable and will allow moisture intrusion and potentialcorrosion. Do not fold the tape in corners. This will result
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in triple layer thickness which may adversely affectenvironmental sealing capability.
e. Tape may be applied to either the aircraft frameor panel faying surface. Application of tape to the panelfaying surface is recommended, especially for panels incorrosion prone areas of the aircraft, for ease ofsubsequent airframe corrosion inspections.
CAUTION
Use care not to pull or stretch the ePTFE tapeas it is applied. The stretched ePTFE tape willretract even if it is clamped between fayingsurfaces which may reduce or eliminate overlapsand allow water intrusion.
f. Peel the nonstick backing paper off the sealanttape a little at a time as the tape is applied to the aircraft/panel.
(1) Applying extra pressure to the sealant tapewill cause the pressure sensitive adhesive to betteradhere to the faying surface and will create indentations/discoloration at the fastener holes allowing for easyidentification.
(2) For some areas and fasteners, it may benecessary to pre-punch holes in the sealant tape at thefastener locations. To locate holes and avoid mismatch,either use the panel as a template for hole locations orhold sealant tape in place and use pressure to creatediscoloration at fastener holes. Pre-punch using a leatherpunch with a diameter no greater than 1⁄4 inch more thanthe fastener hole diameter.
g. If sealant without adhesive backing has beenordered for use in areas where fluid exposure is expected,MMM-A-189 plastic adhesive, or equivalent, may beused to hold the ePTFE sealing tape in place. Applyadhesive to airframe sill or panel and apply ePTFEsealing tape within 20 minutes or before adhesive istack free.
h. After applying the full length of the sealant tape,run fingers back and forth on the sealant to press tapeagainst the aircraft structure/panel surface to activateadhesive and identify fastener holes. No curing time isrequired.
i. Puncture all fastener holes using an object with asharp point such as an awl/scribe or scissors.
NOTE
As fasteners are installed, the ePTFE sealantmaterial pushed into the fasteners will help toseal against moisture intrusion.
j. Install access panel. All fasteners should be wetinstalled with corrosion preventive compound(MIL-PRF-16173 Grade 4 or equivalent) as specified inthe aircraft maintenance manual.
7-7.8. REINFORCED POLYURETHANE GELSEALING TAPE (HI-TAK TAPE® TUFSEAL™), PEELAND STICK APPLICATION. These materials arecurrently approved only for floorboard applications onplatforms where their use has been authorized. Prior toapplication, prepare surface in accordance withparagraphs 7-7.1 and 7-7.2.
CAUTION
After surface treatment and primer application,do not contaminate areas to be sealed withhands or tools.
Sealing and Coating Compound 12Corrosion InhibitingMIL-PRF-81733
a. Examine surfaces to be sealed and build up anyuneven areas on the floorboard frame withMIL-PRF-81733 Type II-1/2 sealant (preferred),AMS 3255 compensation tape (P/N GSC-21-95158-011or equivalent), or AMS 3277 sealant to create a levelfaying surface for sealing.
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Figure 7-11. Faying Surface Sealing
Apply sealant to entire fayingsurface approximately1/32 inch thick
Sealant must beextruded continuously
along entire joint
Application of Faying Surface Seal Finished Faying Surface Seal
Complete fastenerinstallation withinwork life of sealant
b. The reinforced polyurethane gel sealant tapeshould cover the full width of the surface to be sealed.Apply tape directly from supplied roll onto floorboardsupport structure/spar.
c. Install tape with the tacky polyurethane side of thetape applied to the surface. The top side of the tape iscovered with a translucent protective film that remainson the tape.
d. Create butt joints at floorboard spar joints. Do notoverlap tape sections, but make sure gaps greater than1⁄
8inch are not created at butt joints. A slight excess of
tape (1⁄8 to 1⁄
4 inch) is preferred over insufficient tape to
cover mating surface.
e. There is no need to pre-punch fastener holesprior to installation of floorboard panels.
NOTE
As fasteners are installed, the polyurethane gelwill help to seal against moisture intrusion.
f. Install floorboard panels. All fasteners should bewet installed with corrosion preventive compound(MIL-PRF-16173 Grade 4 or equivalent) as specified inthe aircraft maintenance manual. Fasteners may bepushed through the tape by applying pressure to thefastener with the installation tool.
7-8. SEALING OF SPECIFIC AREAS.
CAUTION
Do not use any two-part sealant after it hasbeen mixed and its rated application time hasexpired, as poor adhesion may result.
To determine if a sealant is suitable for aspecific application, review the guidelinesprovided in Table 7-1 and Figure 7-1.
7-8.1. FAYING SURFACE SEALING. Faying surfacesare sealed by applying sealants to the contactingsurfaces of two or more parts (Figure 7-11). It is a veryeffective seal and should be used for all assembly orreassembly. When possible, it should be used inconjunction with fillet sealing. There are two types offaying surface seals, removable and permanent.Removable seals are used around access doors,removable panels, and inspection plates. A removableseal can be formed using a standard sealant on onesurface and a parting agent on the mating surface.Permanent seals are created using sealants betweenpermanently fastened structures. To create a permanentseal, coat both mating surfaces with sealant beforeassembling part. Apply enough sealant to force a beadto squeeze out along the joint after assembly. Assembleparts and torque fasteners within the rated applicationlife of the sealant.
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NOTE
Avoid air bubbles as much as possible duringthe sealing operation. Allow the sealant to cureto, at least, the tack-free stage before movingthe assembly.
Sealing and Coating Compound 12Corrosion InhibitingMIL-PRF-81733
a. All faying surfaces, seams, and lap joints shall beprotected with MIL-PRF-81733 sealant (or sealantspecified in aircraft specific manual). Apply the sealingcompound to one or both surfaces and squeeze the parttogether to ensure the complete coating of the entiresurface. Excess material squeezed out shall be removedso that a fillet seal remains. The fillet width shall not beless than 1⁄4 inch. Joint areas which could hold watershall be fillet sealed with MIL-PRF-81733 (or aircraftspecific) sealant (see paragraph 7-8.2). If sealing isimpossible because of mechanical or other factors,prime both surfaces with two coats of MIL-PRF-23377or MIL-PRF-85582 in accordance with Appendix A(Navy) or TM 55-1500-345-23 (Army).
b. Faying surfaces that are to be adhesively bondedshall be treated and processed as specified by theapproved bonding procedure in the applicablemaintenance manual.
Figure 7-12. Typical Fillet Seal
Figure 7-13. Typical Injection Seal
c. For plastic components, the joint shall be suitablysealed and faired into the adjacent surfaces withMIL-PRF-81733 sealant, unless otherwise specified inthe applicable maintenance manuals, to stop theformation of pockets which will entrap moisture and dirt.MIL-PRF-81733 sealant shall be used for rivets thatrequire wet installation on plastic components.
7-8.2. FILLET SEALING. The fillet, or seam seal, shownin Figure 7-12, is the most common type found on anaircraft. Fillet seals are used to cover structural joints orseams along stiffeners, skin butts, walls, spars, andlongerons, and to seal around fittings and fasteners.This type of seal is the most easily repaired. Filletsealing shall be used in conjunction with faying surfacesealing, or alone if the assembly sequence restricts theuse of faying surface sealing.
7-8.3. INJECTION SEALING. This type of seal, shownin Figure 7-13, is used primarily to fill voids created bystructural joggles, gaps, and openings. Use only thosesealants recommended by the aircraft/equipmentmanufacturer. Force sealant into the area using asealant gun. This method produces a continuous sealwhen it becomes impossible to lay down a continuousbead of sealant while fillet sealing. Clean the voids of alldirt, chips, burrs, grease, and oil before injection sealing.
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CAUTION
AMS 3284 may only be used for wet installationof fasteners. Do not use AMS 3284 sealants inhigh temperature areas or for structuralinstallations.
7-8.4. FASTENER SEALING. Figure 7-14 illustratestechniques used to seal different types of fasteners.Fasteners are sealed either during assembly or afterassembly.
a. To seal during assembly, apply the sealant to thehole or dip the fastener into sealant, and install fastenerwhile sealant is wet. Fasteners in permanent structuresshall be wet installed in accordance with the aircraftmaintenance manual. For removable parts, coat thelower side of the fastener head only. Do not coat thehole or the fastener shank or threads, as this makesfuture removal almost impossible without damage tothe part.
b. To seal after assembly, cover the pressure side ofthe fastener with sealant after installation. As a generalrule, sealant should be approximately 1⁄8 inch thick overthe top of the fastener, and extend a minimum of 1⁄4 inchfrom the edge of the fastener onto the surface of the part(see Figure 7-14).
c. Corrosion damaged areas in the countersinksaround removable and fixed fasteners may be filled withthe fastener in place. Cadmium coated fasteners thathave been blasted or abraded during corrosion removalshall be primed in accordance with Appendix A (Navy)or TM 55-1500-345-23 (Army) and coated withMIL-PRF-81733 sealant.
WARNING
MIL-PRF-81733 is not suitable for use on theinsides of integral fuel tanks and shall not beused for these applications. AMS-S-8802 orAMS 3276 is the authorized sealant for theinsides of integral fuel tanks of most aircraftplatforms. AMS 3277 may be used for repair ofintegral fuel tanks only if recommendedadhesion promoter is used during the repair.Adhesion of repair sealant is critical as disbondof repair sealant during aircraft operation couldcause clogging of fuel filters and result in loss ofaircraft or personnel.
CAUTION
AMS-S-8802, AMS 3276, or other fuel tanksealants should not be exposed to fuel orovercoated until tack-free.
Figure 7-14. Typical Methods of Sealing Fasteners
A. Rivet C. High Shear Rivet
B. Bolt D. Huck Lock
HeadEnd
CollarEnd
HeadEnd
CollarEnd
ManufacturedHead
BuckedHead
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7-8.5. FUEL CELLS. Refer to NAVAIR 01-1A-35,TM 55-1500-204-25/1, or applicable Structural RepairManual (SRMs) for sealant procedures.
7-8.6. EXTERNAL AIRCRAFT STRUCTURE. If, duringnormal maintenance, it becomes necessary to removeand replace components (wing planks, skin, spar caps,fasteners, or fittings), they shall be sealed whenreinstalled, even if they were not sealed originally. Theonly exception to this requirement is temporary repairaccomplished for a one time flight to a Depot or overhaulfacility. See Figures 7-15 through 7-18 for typical sealingmethods.
7-8.7. DEPRESSIONS. When the thickness of metalis reduced by more than 15 mils (0.015 inch) duringremoval of corrosion damage, fill the depression with
Figure 7-15. Typical Lap Skin Sealing
1. Assemble lap joint with MIL-PRF-81733 in faying surfaces2. Install fasteners wet with MIL-PRF-817333. Fillet seal all external seams with MIL-PRF-817334. Apply appropriate paint system
1. Fillet seal all external seams with MIL-PRF-817332. Install fasteners wet with MIL-PRF-817333. Apply appropriate paint system
1. Remove corrosion and surface treat in accordance with Chapter 4 and 5.
2. Apply MIL-PRF-81733 sealant to all faying surfaces.3. Install all fasteners wet with MIL-PRF-81733.
4. Fillet seal all external joints with MIL-PRF-81733.5. Coat with appropriate paint system.
1
2
3
3
5
4
4
4
MIL-PRF-81733 Type II sealant after applying chemicalconversion coating (MIL-DTL-81706) and priming(MIL-PRF-23377 or MIL-PRF-85582). Depressions onsurfaces that will be sealed with AMS 3255 sealing taperequire filling with compensation tape (see paragraph7-7.7). Depressions on the inside of integral fuel tanksdo not require filling.
7-8.8. EXTENSIVE CORROSION REPAIR. Ifcorrosion damage is so extensive that structural repairis necessary, all faying surfaces between patches (ordoublers) and skins shall be painted with one coat of
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Figure 7-17. Typical Spar Cap Sealing
MIL-PRF-23377 or MIL-PRF-85582 primer. When theprimer is dry, coat with MIL-PRF-81733 sealant prior toinstallation of patch. Permanently installed fastenersshall be wet installed with MIL-PRF-81733 prior toinstallation. Removable panel fasteners shall be wetinstalled with AMS 3284.
7-8.9. HIGH TEMPERATURE AREAS. In areas wherehigh temperatures are expected, MIL-A-46146 Group III,AMS 3374 Type I, or AMS 3277 Type I should be used
for sealing. Adhesion promoter is required when sealingwith AMS 3277. Application of these sealants is similarto spatula-applied sealants (refer to paragraph 7-7.5).
7-8.10. LOW TEMPERATURE CURING. When coldclimates interfere with sealing operations by prolongingthe sealant curing reaction, use AMS 3277 Type I.Adhesion promoter is required when sealing withAMS 3277. AMS 3255 (ePTFE sealing tape) may beused in approved applications, as it does not requirecuring.
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Figure 7-18. Sealing of Access Doors
Dry bay/otheraccess doors,semi-permanent fittings (fillet seal after tightening fasteners)
Fuel tank access doorwith "O" ring(install "O" ringand fillet seal)
Fuel tank access doorwithout "O" ring(seal fayingsurfaces andfillet seal)
1. Install all fasteners wet with AMS 3284, under head only2. Seal edge with AMS 3284 as shown below
AMS 3284
"O" RingAMS 3284
AMS 3284
7-9. REPAIR OF DAMAGED SEALANT.
7-9.1. DAMAGED SEALANT. Many areas on aircraftare sealed either at the factory or by Depots duringrework. Fresh sealant shall be applied whenever thepreviously applied sealant is damaged. Remove thedamaged sealant with a plastic scraper or mechanicalsealant removal tool (paragraph 7-5.5.) and, if necessary,prepare the metal surface in accordance with Chapter 5.Slightly roughen a strip of the undamaged sealantapproximately one inch wide around the boundary ofthe stripped area using an abrasive cloth and then cleanwith solvent (AMS 3166 or approved equivalent) usinga clean cloth (AMS 3819) or cheesecloth (CCC-C-440).Apply the new sealant by brush or spatula (see paragraph7-7.5) onto smaller areas, or by spraying (see paragraph7-7.6) onto larger areas. The new sealant should overlapthe existing coating onto the roughened area.
7-9.2. FORM-IN-PLACE SEALANT REPAIR. Afterremoval of all loose sealant material, thoroughly cleanthe area to be resealed (see paragraph 7-7.1). Areas ofold seal to which new sealant will be added must becleaned and abraded using an abrasive mat or abrasivecloth to expose a clean, fresh surface.
Sealing and Coating Compound 12Corrosion InhibitingMIL-PRF-81733
a. Apply MIL-PRF-81733 Type II-1/2 or aircraftspecific sealant, preferably with a sealant gun. The newsealant should match the configuration of the removedsealant but should be of sufficient depth to ensurecontact with the mating surface.
b. Apply a very thin film of release agent (VV-P-236or MIL-PRF-32033) to the nonstick mating surface andclose the access door.
c. Do not open the door for a minimum of 24 hoursor the published tack free time of the aircraft specificsealant, if applied at 75°F (24°C) and 50% relativehumidity (RH).
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7-9.3. ePTFE SEALING TAPE (Skyflex™) REPAIR. Inorder to preserve sealant integrity, it is necessary toinspect the sealant tape each time an access panel isremoved.
NOTE
The main function of the adhesive backing is tohold the ePTFE sealant tape in place. Peeling/delamination of the adhesive from the aircraftstructure/panel requires replacement of anysection of the sealant tape that is not located inthe faying surface.
a. Visually inspect ePTFE sealant material for nicks,cuts, gouges and delamination/separation.
b. Cut and remove only the damaged section of thesealant tape. Lift damaged tape section from surface tocut with scissors; do not cut tape directly on surface toavoid damage to airframe.
c. Measure and cut a new piece of sealant tapeapproximately one inch longer than the removed section.
CAUTION
Ends of repair splice must overlap the existingsealant to ensure sealant integrity. Use carenot to pull or stretch the ePTFE tape as it isapplied. The stretched ePTFE tape will retracteven if it is clamped between faying surfaces,which may reduce or eliminate overlap andallow water intrusion.
d. Install new sealant tape so it overlaps thepreviously installed sealant by 1⁄4 to 1⁄2 inch on each sideof the repair site.
e. Once sealant tape is applied, run fingers backand forth on tape to further activate the adhesive. Nocuring time is required.
(1) Applying extra pressure to the sealant tapewill cause the pressure sensitive adhesive to betteradhere to the faying surface and it will create indentations/discoloration at the fastener holes allowing for easyidentification.
(2) For some fasteners, it may be necessary topre-punch holes in the sealant tape at the affectedfastener locations. Locate holes in repair section andpre-punch using leather punch with diameter no greaterthan 1⁄
4 inch more than the fastener hole diameter.
f. If sealant without adhesive backing is used forrepair in areas where high fluid exposure is expected,MMM-A-189 plastic adhesive or equivalent may beused to hold the ePTFE sealing tape in place. Applyadhesive to entire length of repair section and applyePTFE sealing tape within 20 minutes or before adhesiveis tack free.
g. Puncture any affected fastener hole with a sharppointed object such as an awl/scribe or scissors.
NOTE
As fasteners are installed, the ePTFE sealantmaterial pushed into the fasteners will help sealagainst moisture intrusion.
h. Install access panel. All fasteners should be wetinstalled with corrosion preventive compound(MIL-PRF-16173 Grade 4 or equivalent) as specified inthe aircraft maintenance manual.
7-9.4. REINFORCED POLYURETHANE GELSEALING TAPE (HI-TAK® TAPE TUFSEAL™)REPAIR. In order to preserve sealant integrity, it isnecessary to inspect the sealant tape each time afloorboard is removed.
a. Visually inspect reinforced polyethane gel sealanttape on floorboard spars for nicks, cuts, gouges, dryappearance, missing gel, and other indications ofdamage which might compromise sealing integrity.
b. Cut and remove only the damaged section of thesealant tape. Lift damaged tape section from surface tocut with scissors; do not cut tape directly on surface toavoid damage to airframe.
c. Clean any residue from the surface using a solvent(AMS 3166, A-A-59281 Type I or II, or equivalent) andcheesecloth (CCC-C-440) or a clean cloth (AMS 3819or equivalent).
d. Measure and cut a new piece of sealant tapeapproximately the same length as the removed section.
e. Install new sealant tape, creating a butt joint withremaining tape sections. Gaps greater than 1⁄8 inch shallnot be created at butt joints. A slight excess of tape(1⁄8 inch to 1⁄4 inch) is preferred over insufficient tape tocover the exposed surface.
f. If the repaired section is over a fastener hole,there is no need to pre-punch fastener holes prior toinstallation of floorboard panels.
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7-10. STORAGE AND SHELF LIFE. All sealants havea specified shelf life. The date of manufacture and theexpiration date or inspect/test date are listed on eachcontainer. The shelf life is dependent on storing thesealant in its original, unopened container in an areawhere the temperature does not exceed 60°F (27°C),unless otherwise specified on the package. Prior to use,sealant containers shall be visually inspected todetermine if the material has exceeded its expirationdate. If the sealant has exceeded the expiration date,dispose of the container in accordance with localregulations. If the sealant has exceeded its inspect/testdate, then it shall not be used until update testing hasbeen performed. Procedures for update testing areusually provided in the sealant specification. No sealantshall be used if it fails testing. Minimum update testingcan be performed as follows:
a. Select one sample of sealant from eachmanufacturer’s batch of material to be tested for updating.
b. Visually examine the content of each componentin the sample. No separation, layering, or settling thatwill not disperse to a homogeneous mixture when mixedis allowed. If the base compound is lumpy, partiallycured, or cannot be mixed with the curing agent, dispose
of the opened sample and all kits from that batch ofsealant in accordance with local regulations.
c. If the sample can be blended to form ahomogeneous mixture, determine whether theapplication time is suitable for the intended purpose byapplying the mixture to a clean piece of scrap aluminumat the application time of the sealant (i.e., B-1/2, applyafter 30 minutes). If the sealant is too thick or does notstick to the metal at application time, the sealant is notacceptable. Dispose of the opened sample and allothers from that batch in accordance with localregulations.
d. If the application time is acceptable, periodicallycheck the applied sealant for cure time by checking itshardness. The batch of sealant represented by theapplied sealant can be extended if it achievesapproximately the same hardness as sealants whichare not overaged.
e. This updating process may be repeated for amaximum of three extensions (1⁄2 original shelf life,1⁄3 original shelf life, and 1⁄6 original shelf life). Affix anextension label to the container in accordance withFED-STD-793.
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8-1. INTRODUCTION. Corrosion preventivecompounds (CPCs), or preservatives, are used to protectmetal aircraft parts and components. They function bypreventing corrosive materials from contacting andcorroding bare metal surfaces. Many of thesecompounds are also able to displace water, sea water,and other contaminants from the surfaces to beprotected. Some provide lubrication, as well as corrosionprotection. Generally, CPCs are mixtures of specialadditives in petroleum derivative bases (special oils orgreases). CPCs range in appearance and consistencyfrom the thick, black types, such as MIL-PRF-16173Grade 1, to light oils, such as MIL-PRF-32033 (formerlyVV-L-800). The thicker CPCs provide the best corrosionprotection, are longer lasting, and are more difficult toremove. The thinner materials provide some lubricationand do not crack, chip or peel but must be removed andreplaced regularly to provide continuing protection.Navy: refer to NAVAIR 15-01-500 for detailed informationon preservation of aircraft and components.
8-2. OPERATIONAL PRESERVATION. The day today application of CPCs to prevent corrosion onoperational aircraft is known as operational preservation.Areas which are corrosion prone or where paint hasbeen damaged should be routinely protected by CPCsuntil more permanent treatment (such as paint touchupor sealing) can be accomplished.
8-3. NON-OPERATIONAL PRESERVATION.Preservation of aircraft or components during periods ofprolonged inactivity, storage, or shipment is known asnon-operational preservation.
8-4. TYPES OF CPCS. CPCs can be separated intotwo major categories: water displacing and non-waterdisplacing compounds.
8-4.1. WATER DISPLACING COMPOUNDS. Waterdisplacing CPCs can be used to remove water, seawater, or other electrolytes from metal surfaces.MIL-PRF-81309, MIL-DTL-85054, MIL-PRF-63460, andMIL-PRF-32033 are examples of water displacing CPCs.These CPCs are able to penetrate into cracks, crevices,voids in faying edges, around fastener heads, and intohinges. They usually provide very thin coatings, one mil(0.001 inch) or less in thickness (a dollar bill is five milsthick), and are usually clear or translucent. Most waterdisplacing compounds are soft, oily compounds which
cannot provide long term protection outdoors or inareas which are frequently handled. MIL-DTL-85054differs from the other water displacing compounds byforming a relatively hard, dry film, and can be used forprotection outdoors and in areas of frequent handling.
8-4.2. NON-WATER DISPLACING COMPOUNDS.Non-water displacing CPCs may be used on driedsurfaces or on surfaces which have been first treatedwith a water displacing CPC. MIL-PRF-16173, Grades 1,2 and 4, are examples of non-water displacing CPCs.They are heavier bodied oils or greases which providelong term corrosion protection. These CPCs providethicker coatings and are light brown to very dark brownin color, with a waxy greasy appearance. They providegood corrosion protection in areas where large amountsof water collect on or run off of structures. MIL-L-87177Grade B is a corrosion inhibiting and lubricating CPCthat provides longer outdoor protection thanMIL-PRF-81309 and MIL-PRF-32033 and can be usedfor corrosion protection when ultra-penetrating propertiesare not required.
8-5. TIME LIMITATIONS OF CPCS. Because of theirtemporary nature, CPCs must be regularly removedand replaced to provide continuing corrosion protection.Table 8-1 provides the recommended time intervals forindoor and outdoor CPC application. Navy: Refer toNAVAIR 15-01-500 for further information on usage ofCPCs.
8-6. DESCRIPTION OF CPCS. A list of CPCs andtheir intended uses is summarized in Table 8-2.
WARNING
MIL-PRF-81309 and MIL-DTL-85054 have beenrevised to eliminate Ozone DepletingSubstances (ODS). Some products that havebeen reformulated are now flammable. Payclose attention to all CAUTION/WARNINGlabels on solvents and solvent-based products.
8-6.1. MIL-PRF-81309 (CORROSION PREVENTIVECOMPOUND, WATER DISPLACING, ULTRA THINFILM). MIL-PRF-81309 is a general purpose corrosionpreventive compound which can be used whenever aCPC or a water displacing compound is called for but nospecification is referenced. MIL-PRF-81309 is used for
CHAPTER 8PRESERVATION
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indoor protection and short term protection wheresurfaces can be recoated when required.MIL-PRF-81309 materials are excellent water displacingcompounds which provide an ultra thin (0.5 mil or less),soft film. The specification covers two types, both ofwhich can be applied by dipping, spraying, brushing, oraerosol container. They provide temporary protectionfrom corrosion and are easily removable with a solvent.They should not be used around liquid oxygen fittings.
8-6.1.1. Type II. A soft, thin film for general use,particularly on moving or sliding parts where somelubrication is needed, such as hinges or bomb racks. Itmay be washed away by rain or wash procedures. TypeII shall be used to protect areas which cannot beproperly drained or contain recesses that are particularlydifficult to reach.
8-6.1.2. Type III. An ultra thin, soft film primarily for useon avionics and electronic equipment. Although thiscoating is nonconductive, it will allow electrical contactbecause it is soft and very thin.
8-6.2. MIL-DTL-85054 (CORROSION PREVENTIVECOMPOUND (AMLGUARD)). AMLGUARD is a waterdisplacing CPC which forms a clear, dry, flexible film. Itis intended for use as a protective coating until paintingis practical. Because of its paint-like characteristics, itprovides no lubrication.
CAUTION
Ensure that all areas where MIL-DTL-85054 isapplied are fully dried before sealing an area.Although MIL-DTL-85054 is a corrosionpreventive compound, its solvent vapors maycause corrosion if not allowed to dissipate.
8-6.2.1. AMLGUARD can be applied by dipping,brushing, spraying, or from aerosol containers; however,dipping provides a very thin coating with less corrosionprotection. AMLGUARD is primarily applied by sprayingfrom aerosol cans. After each use of an aerosol can,invert the can and spray until spray tip (nozzle) is clearof entrapped material. If an aerosol can does not spray,invert and depress the spray tip several times to clearthe delivery tube and spray head. If the can still does notspray, remove and clean the plastic spray head thenspray again to clear the delivery tube.
8-6.2.2. AMLGUARD should be removed if it isdamaged due to abrasion, when there are cracks in thecoating, or if there is evidence of corrosion below thecoating. Since AMLGUARD buildup is difficult to remove,especially after prolonged exposure to direct sunlight,previously applied coatings should be removed beforereapplication. If the solvents do not remove old films ofAMLGUARD, spraying on fresh AMLGUARD to softenthe film and wiping or rubbing while wet is often effective.
8-6.3. MIL-PRF-16173 (CORROSION PREVENTIVECOMPOUND, SOLVENT CUTBACK). MIL-PRF-16173covers five different grades of CPCs which can beapplied by brushing or dipping. Grades 1, 2, and 4 do notdisplace water and must be applied to dried surfaces orto surfaces which have first been treated withMIL-PRF-81309.
8-6.3.1. Grade 1. A thick, hard, black CPC which canbe removed with difficulty using mineral spirits or paintremovers. It offers the most corrosion protection of allthe CPCs indoors and outdoors, and may be used attemperatures down to 0°F (-18°C).
8-6.3.2. Grade 2. A thick, soft, greaselike, brown CPCthat remains tacky and can be removed with mineralspirits. It protects under relatively severe conditionsand, given adequate maintenance touch-up asnecessary, can be used for most maximum protectionrequirements. It may be used at temperatures down to-40°F (-40°C).
8-6.3.3. Grade 3. A thin, soft film, water-displacingCPC. It is not recommended for use on aluminum ormagnesium parts. Use MIL-PRF-81309 Type II as asubstitute.
NOTE
Remove MIL-PRF-16173 Grade 4 withdegreasing solvent (MIL-PRF-680 Type II) ifthe coating is dark and prevents visual inspectionof the underlying surface for cracks and hydraulicleaks.
8-6.3.4. Grade 4. A thin, relatively dry, semitransparentfilm through which identification can be read. It may beused at temperatures down to -40°F (-40°C).
CAUTION
If MIL-PRF-63460 is used in an area which willlater be sealed, allow at least 4 hours for thesolvent to evaporate prior to sealing. AlthoughMIL-PRF-63460 is a corrosion preventivecompound, its solvent vapors may causecorrosion if not allowed to dissipate.
Do not use MIL-PRF-63460 on rubber or otherelastomeric parts. MIL-PRF-63460 containssolvents which attack rubber "O" rings andother elastomeric parts. Do not use as a directsubstitute for MIL-PRF-32033.
8-6.4. MIL-PRF-63460 (LUBRICANT, CLEANER, ANDPRESERVATIVE FOR WEAPONS AND WEAPONSYSTEMS). MIL-PRF-63460 is a thin, water displacing,protective, penetrating lubricant used for cleaning,lubrication, and preservation of aircraft hinges andsmall or large caliber weapons. This material has goodlubricating properties between -65° and 150°F (-54°and 65°C). It may be applied by brushing, dipping,spraying, or from an aerosol container.
CAUTION
MIL-PRF-32033 suffers a loss of viscosity atvery low temperatures; therefore, it shall not beused when temperatures can drop below -40°F(-40°C).
8-6.5. MIL-PRF-32033 (LUBRICATING OIL,GENERAL PURPOSE, PRESERVATIVE (WATERDISPLACING, LOW TEMPERATURE)).MIL-PRF-32033 (supersedes VV-L-800) is a generalpurpose, water displacing, lubricating oil withpreservative properties, and is intended for the lubricationand preservation of aircraft components. It may beapplied by brushing, dipping, spraying, or from anaerosol container. It should not be used in fuel cells orfuel systems.
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NOTE
Current formulation of MIL-L-87177 Grade Bcontains Halon 141B, which may be subject toenvironmental restrictions in some locations.
8-6.6. MIL-L-87177 (LUBRICANTS, CORROSIONPREVENTIVE COMPOUND, WATER DISPLACING,SYNTHETIC). MIL-L-87177 Grade B is a syntheticlubricant with added corrosion inhibitor. This materialcreates a non-tacky film on the surface. MIL-L-87177does not displace water or penetrate as thoroughly asMIL-PRF-81309 or MIL-PRF-32033 and should only beused on surfaces that have been wiped dry. Tightcrevice locations should have a coating ofMIL-PRF-81309 applied prior to use of MIL-L-87177 toensure proper protection.
CAUTION
Do not use corrosion preventive compounds onthe interior of fuel tanks or fuel cells, engines, orengine fuel systems.
Do not use corrosion preventive compounds onengine parts or accessories which exceed 800°F(427°C). Hot corrosion reactions may occur.
CPCs are not compatible with liquid oxygenand should not be used on oxygen equipment,lines, fittings or storage bottles.
NOTE
Use only corrosion preventive compounds(CPCs) authorized by the parent serviceorganization and described in this manual.
8-7. PRESERVATION OF SPECIFIC AREAS.Table 8-3 provides procedures for the preservation ofspecific areas and components where the use of a CPCon exposed metal surfaces is generally recommendedfor reducing corrosion. This list does not constituteauthority to use CPCs on specific equipment. The useof some or all types of CPCs in certain areas or onequipment may be detrimental. Therefore, consult theappropriate corrosion and maintenance manuals beforeapplying a CPC in a new area and determine which, ifany, compounds should be used in that area. Ifapplication of a CPC is required, and no specificinstructions are available, the CPC Decision Tree(Figure 8-1) may be used as a guideline to determinethe most appropriate CPC.
WARNING
CPCs and solvents can produce toxic vapors.Use only in well ventilated areas. Avoid contactwith skin. Consult local safety office for personalprotective equipment requirements. Do not usesynthetic wiping rags or cloths with thesematerials. Keep CPCs and solvents away fromopen flames or sparks.
8-8. PRESERVATION APPLICATION METHODS.CPCs can be applied by brushing, dipping, or spraying.The area of application, viscosity of the material, andconditions under which they need to be applied arefactors which determine which method of application touse. Low viscosity (thin) materials are best applied byspraying, whereas high viscosity (thick) materials aremore suited for brushing or dipping. Dipping can beused for all types of materials, but the thickness of thecoating obtained with low viscosity materials may be toothin to provide adequate corrosion protection. Prior toapplication of preservatives, remove old preservativecoatings, then apply using one of the following methods.
8-8.1. BRUSHING. Brushing may be accomplishedusing an ordinary paint brush. This method is mostappropriate for applying thick materials, for use on smallareas, or where it is necessary to prevent material fromgetting on surrounding areas or nearby equipment.
8-8.2. DIPPING. Dipping may be accomplished usingany suitable container for the CPC. It is most suitable forsmaller disassembled parts. It cannot be used forassemblies which contain any part or area adverselyaffected by the CPC.
CAUTION
For spray application, do not thin or dilute bulkpreservative unless absolutely necessary. Donot use synthetic wiping cloths. Mask offadjacent areas to prevent overspray.
8-8.3. SPRAYING. Spraying may be accomplishedusing paint spraying equipment, various types of triggersprayers, or aerosol containers. This method is veryeffective for application to large areas and whereconfinement is not a problem. The viscosity of thematerial will determine which type of spraying equipmentto use.
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Table 8-3. Preservation of Specific Areas and Components
MIL-PRF-81309 Type II.Infrequent disassembly, use MIL-PRF-81309 Type II then
MIL-PRF-16173 Grade 4.
Thick or ThinFilm?
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8-9. APPLICATION OF POLISH AND WAX. Polishingand waxing of aircraft exterior surfaces is prohibitedunless authorized by parent service organizationdirectives.
8-10. PRESERVATION OF ASSEMBLIES ANDPARTS REMOVED FROM AIRCRAFT DURINGMAINTENANCE.
8-10.1. SHORT TERM STORAGE (30 DAYS ORLESS). Short term storage shall be defined as anyperiod up to 30 days for the purposes of this manual.When assemblies or parts are removed from the aircraftfor repair, or to gain access to areas of the aircraft formaintenance, they shall be treated to prevent corrosionprior to placement into short term storage. All items shallbe stored indoors in a covered area to protect them fromthe elements. Navy shall refer to NAVAIR 15-01-500 orto the applicable maintenance or equipment storagemanuals for specific details on storage of a particularpart or assembly. In the absence of other requirements,the following procedures apply:
a. Clean part or assembly in accordance withChapter 2.
b. Assemblies or parts having bare metal surfaces,such as internal and working surfaces on landing gearcomponents, shall be properly lubricated with the aircraftgreases or oils normally applied in service.
c. High strength steel components which are strippedof their protective coatings shall be protected using oneof the following methods:
(1) Apply a film of CPC (MIL-PRF-81309 TypeII) to all bare surfaces whenever there is a lapse of twohours or more in the repair cycle. The part shall then beloosely overwrapped with barrier material(MIL-PRF-131 Class 1).
(2) Wrap part in VCI film, MIL-PRF-22019 orVCI paper, MIL-PRF-3420, and seal with tape, SAEAMS-T-22085.
d. Completely painted parts need no other specialprotective measures, except in marine or high humidityenvironments. In these cases, the part shall be looselyoverwrapped with barrier material (MIL-PRF-131Class 1).
e. Prior to rework or reapplication of protectivecoatings, remove CPC with degreasing solvent (MIL-PRF-680 Type II or III) or non-aqueous cleaner(MIL-PRF-32295 Type I) as required. Reapply theappropriate aircraft lubricant to areas requiringlubrication. CPCs shall not be used for lubrication in lieuof the lubricant specified for use on a particular part orassembly.
8-10.2. LONG TERM STORAGE (OVER 30 DAYS). Ifthe storage of assemblies or parts will exceed 30 days,increased protective measures are required, particularlyon critical parts and high strength steel components. Allitems shall be stored indoors in a covered area toprotect them from the elements. Refer to the followingmanuals, or to the applicable maintenance or equipmentstorage manuals, for specific details on storage of aparticular part or assembly: NAVAIR 15-01-500 (Navy)or TM 743-200-1 (Army). In the absence of otherrequirements, the following procedures apply:
a. Clean part or assembly in accordance withChapter 2.
b. All bare metal surfaces, and surfaces withdamaged plating or paint, shall be protected using oneof the following methods:
(1) Apply water displacing CPC(MIL-PRF-81309 Type II) followed by long term CPC(MIL-PRF-16173 Grade 4). The part shall then beoverwrapped with barrier material (MIL-PRF-131 Class1) and sealed with tape (SAE AMS-T-22085 Type II).
(2) Wrap part in VCI film, MIL-PRF-22019, orVCI paper, MIL-PRF-3420, and seal with tape, SAEAMS-T-22085.
c. Completely painted parts need no other specialprotective measures, except in marine or high humidityenvironments. In these cases, the part shall beoverwrapped with barrier paper (MIL-PRF-131 Class 1)and sealed with tape (SAE AMS-T-22085 Type II).
d. Depending upon the length of time in storage,reapplication of protection may be required.
(1) Refer to Table 8-1 for time limitationinformation on CPCs.
(2) Replace torn or damaged VCI film or paper.Intact VCI film or paper has a storage limit of one year.
e. Prior to returning the part or assembly to service,remove CPCs with degreasing solvent (MIL-PRF-680Type II or III) or non-aqueous cleaner (MIL-PRF-32295Type I) as required. Reapply the appropriate aircraftlubricant to areas requiring lubrication. CPCs shall notbe used for lubrication in lieu of the lubricant specifiedfor use on a particular part or assembly.
Change 1 - 31 March 2010
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CHAPTER 9EMERGENCY PROCEDURES
9-1. PURPOSE. This chapter describes the emergencyprocedures to be followed after aircraft incidents oraccidents involving exposure to vast amounts of saltwater or fire extinguishing agents. The proceduresdescribed herein are used to prevent further damageand will usually require further treatment at a higherlevel of maintenance.
9-2. RESPONSIBILITY.
CAUTION
Exposure of metal surfaces to salt water, Purple-K-Powder (PKP), and protein foam requiresimmediate action to prevent serious corrosiondamage.
NOTE
In cases involving aircraft accidents, permissionmust be obtained from the senior member ofthe accident investigation board prior to theinitiation of emergency procedures.
9-2.1. Under emergency conditions, all personnel shallassume responsibility for minimizing damage. Removalof equipment shall be supervised by the MaintenanceOfficer (MO). Each reporting custodian shall designatea Corrosion Prevention and Control Program Managerto supervise the emergency reclamation team.Maintenance control shall direct the team to accomplishsalvage operations or corrosion control action. The sizeand composition of the team depends on the urgency ofthe situation and/or workload. If required, additionalsquadron personnel shall be selected and placed underthe direction of the Corrosion Prevention and ControlProgram Manager. In case of fire damage, the MaterialsEngineering Division of the Fleet Support Team (FST)shall be contacted to determine the effects of heat orexcessive salt water contamination prior to continueduse or repair of affected parts or components.
9-2.2. (N) AIRCRAFT FIREFIGHTING. Firefighting inand around crashed aircraft is highly specialized. Referto NAVAIR 00-80R-14 (NATOPS U.S. Navy AircraftFirefighting and Rescue Manual) for approved fireextinguishing agents, methods of application, and
firefighting equipment. Naval Air Systems Command’sPMA-251 has sole responsibility and authority toestablish policy for all aircraft fire fighting programs forthe Office of the Chief of Naval Operations. PMA-251serves as the Navy and Marine Corps technical authorityfor aircraft fire fighting and manages this program inaccordance with OPNAVINST 5100.8G and DODI6055.06.
9-3. EMERGENCY PREPARATIONS. In preparationfor an emergency, priority lists shall be developed forremoval of equipment, emergency reclamation planning,and the required materials and equipment.
9-3.1. PRIORITY REMOVAL LIST OF AIRCRAFTCOMPONENTS.
CAUTION
Magnesium parts are particularly susceptibleto corrosion attack when exposed to salt wateror fire extinguishing materials. Avionic, electrical,and ordnance equipment known to containmagnesium components shall be given highpriority for cleaning.
9-3.1.1. Table 9-1 is a list of aircraft component groupsarranged in order of recommended priority for treatment.Among the factors to be considered when removingequipment are dollar value, corrosion rate, availabilityof replacement parts, and probability of successfulsalvage. Whenever manpower or facility shortagesprohibit simultaneous processing of all components,treatment shall be given in the order of the prioritylisting. The table should be considered as a guide, andoperations may deviate from the assigned priority whendirected by qualified production planning or engineeringpersonnel or the cognizant maintenance officer.
9-3.1.2. Variations in aircraft designs, configurations,and mission equipment installations may make itnecessary to contact custodians of the aircraft to obtaina listing of equipment and the preferred priority ofremoval and treatment. Priority of removal and treatmentshould always be oriented toward recovery ofsalvageable equipment.
Table 9-1. Recommended Priority Removal Guide for Emergency Treatment of Aircraft
9-3.2. INTERMEDIATE LEVEL EMERGENCYRECLAMATION TEAM. The intermediate levelemergency reclamation team shall provide expertiseand facilities for processing equipment received fromoperational activities. This team shall be responsible forprocessing equipment received from Organizational/Unit activities. The size of the team, its organization,and the specific equipment requirements will be gearedto the needs of the units supported. Recommendedequipment includes wash/rinse facilities, drying ovens,dip tanks (for water displacing compounds andpreservatives), and cleaning compounds.
9-3.3. EMERGENCY RECLAMATION EQUIPMENT.The availability of the necessary tools, materials, andequipment for prompt removal, cleaning, and drying willsignificantly aid in reducing damage. Refer to materialand equipment lists (see Table 9-2) and Volume III.Additional items of equipment that may be useful are:
a. Drying ovens.
b. Portable air blowers.
c. Heaters.
d. Dehumidifiers.
9-3.4. PRODUCTION PLANNING. Whenever possible,all salvageable components of the aircraft shall betreated simultaneously. To minimize damage and ensurethat the work is accomplished in a thorough andcompetent manner, the most experienced personnelavailable shall be assigned to disassemble and processthe aircraft. Whenever possible, examination andevaluation personnel shall be assigned to work with thedisassembly and preservation crew in order that thoseitems obviously beyond reclamation may be scrappedimmediately; and that only those areas exposed tocorrosive water or fire fighting chemicals aredisassembled and treated. The time saved by thisprocedure may be utilized in preserving salvageablecomponents.
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Table 9-2. Recommended List of Emergency Reclamation Items
Before starting emergency treatment,particularly in those instances where fuel cellshave been ruptured and fuel or fuel vapors arepresent, it is imperative that a GFE, GFET, orthe safety officer supervise purging or inertingprocedures and certify that the aircraft is fireand explosion safe. Qualified ordnancepersonnel shall be assigned to handle allordnance and associated items, such asammunition and pyrotechnics.
9-4.1. For cases involving aircraft accidents, permissionfor any treatment shall be obtained from the seniormember of the accident investigation board prior toinitiating procedures for emergency reclamation. Failureto obtain permission will jeopardize the ability of theaccident investigation team to determine the cause ofthe incident.
NOTE
Procedures for decontamination of aircraftexposed to chemical, biological, or radiological(CBR) materials are contained inNAVAIR 00-80T-121 (Navy) or FM 3-5 (Army).
a. The fire department shall determine whichextinguishing agent was used on the aircraft. A reviewof photographs taken by public affairs or other mediapersonnel may provide information concerning areasthat had corrosive extinguishing material exposure.
b. Ensure that the aircraft is safe for maintenance.Electrically ground the aircraft. Attach the ground leadto the aircraft at a point outside the area which couldcontain explosive vapors. Turn off all electrical powerand disarm aircraft, including the ejection seat.
c. Closely inspect the aircraft to determine areasaffected. Traces of foam type extinguishing agents maynot be present; however, moist residues often indicateprevious foam application. Dry powders may be presentin joints and faying surfaces, so a careful examinationwill be necessary.
d. Wherever possible, remove components fromaffected areas. Open, loosen, or remove covers, accessplates, and inspection doors. Allow accumulated saltwater to drain thoroughly wherever possible. If drychemical fire extinguishing materials have been used,refer to paragraph 9-6.
e. Remove gross amounts of contaminants byflushing with fresh water and draining.
f. Remove components in accordance withparagraphs 9-4.2 and 9-4.3.
g. Clean the aircraft in accordance with paragraph9-4.4.
h. Inspect the aircraft and determine whether it canreturn to flight status following local maintenance actionor whether additional maintenance will be necessary.
9-4.2. REMOVAL OF CONTAMINATED EQUIPMENT.After salt water immersion, salt water entry, or exposureto any corrosive agents, equipment must be cleanedpromptly and thoroughly. Follow the procedures in thischapter for decontaminating specific areas andequipment. Refer to Table 9-1 for assigning priority toequipment removal and treatment.
9-4.3. REMOVAL OF COMPONENTS.
9-4.3.1. The mechanical cutting of fuel, hydraulic andoil lines, and electrical leads, and other drastic operationsnecessary to expedite removal of components are leftto the discretion of the MO directing the operations.
9-4.3.2. When aircraft are involved in water crashes, itshall be assumed that all components, including hollowstructural and mechanical members, are contaminatedinternally. All components shall be disassembled andtreated or forwarded to the next highest level ofmaintenance for disassembly and treatment as required.It shall be established that contaminants have beenremoved and that all corroded surfaces have beeneffectively inhibited against further attack prior toreturning to operational status.
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9-4.4. CLEANING. Equipment and components shallbe cleaned by the team, in accordance with paragraphs9-5, 9-6, and 9-8, and then delivered to the designatedshops for further inspection and maintenance.Equipment that cannot be removed shall be cleaned inplace and inspected.
9-4.5. TAGGING. All parts and components removedfrom the aircraft shall be tagged for identification (seeVolume IV for Water/Crash/Fire Tags and Labels).Indicate preservation method (e.g. CPC) used oncomponent.
9-4.6. PROCESSING. All equipment subject toemergency reclamation team procedures must becertified operationally ready before returning toserviceable status. Inspect equipment for corrosion,cracks and heat damage. Obtain the maximum availableengineering assistance to determine evaluation ofdamage. Particular attention shall be given to dissimilarmetal joints. Avionic electrical equipment will most likelycontain dissimilar metals.
9-5. GENERAL CLEANING PROCEDURES.
CAUTION
Do not expose plastic items, avioniccomponents, wiring, or other componentssusceptible to heat damage to temperatures inexcess of 130°F (54°C) during emergencycleaning procedures. Also, do not expose anyother areas to temperatures in excess of 150°F(66°C) during emergency cleaning procedures.
NOTE
The mildest chemical and cleaning cycle whichwill assure proper decontamination shall beused at all times. Even though fresh water/detergent wash should not significantly affectaccident investigations, permission must beobtained from the senior member of appointedaccident investigation board before cleaning.
9-5.1. Use the specified methods in paragraph 9-8 foremergency treatment of specific areas. Do not use thefollowing general procedures when specific methodsare available.
9-5.2. Contaminated areas may be cleaned by severalmethods. The primary method is fresh water flushing.Alternate methods may be used when fresh water is notavailable.
9-5.3. PRIMARY CLEANING METHOD. The primarymethod of removing salt water is as follows:
a. Immerse removed unit or component in clean,fresh water whenever possible.
b. Flush all areas with clean fresh water and allow todrain.
c. Dry the item or areas by vacuum cleaning excesswater, blotting with cloth or paper, or blow-drying with airpressure not greater than 10 psi. If visual evidence ofsalt remains, a second cleaning should be accomplishedas follows:
Compound, Aircraft Cleaning 2MIL-PRF-85570
(1) Mix a solution of one part aircraft cleaningcompound (MIL-PRF-85570 Type II) in 14 parts water.
(2) Apply the solution to the affected areas andscrub with soft bristle brushes, sponges or cloths.
(3) Flush thoroughly with clean fresh water anddrain thoroughly.
(4) Dry the item or areas as before.
Compound, Corrosion Preventive 4MIL-PRF-81309
d. After flushing and drying, apply water displacingpreservative (MIL-PRF-81309 Type III) on all avioniccomponents and connectors. Ensure that all areas andcrevices are coated. Liberally apply water displacingCPC (MIL-PRF-81309 Type II) to all other areas thatcannot be properly drained or contain recesses whichare difficult to reach. Ensure that all surfaces are coated.
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NOTE
Water displacing CPC (MIL-PRF-81309 Type II)will deposit a thin, non-conductive film thatmust be removed prior to use for proper functionof contact points and other electro-mechanicaldevices where no slipping or wiping action isinvolved. Water displacing CPC is easilyremoved using degreasing solvent(MIL-PRF-680 Type II) or non-aqueous cleaner(MIL-PRF-32295 Type I).
9-5.4. ALTERNATE CLEANING METHODS. Use onlywhen fresh water is not available or is available only inlimited supply or when time prevents immediate flushingwith fresh water.
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9-5.4.1. Method One (Preferred). Spray, brush, or wipethe exterior of the affected areas and components withliberal amounts of water displacing CPC(MIL-PRF-81309 Type II).
9-5.4.2. Method Two (Alternate).
Compound, Aircraft Cleaning 2MIL-PRF-85570
a. Apply a solution of one part aircraft cleaningcompound (MIL-PRF-85570 Type II) in 14 parts water.
b. Brush over affected areas until contaminants andcleaner become intermixed or emulsified.
c. Wipe-off thoroughly with clean cloth, removingboth contaminants and cleaner.
Compound, Corrosion Preventive 4MIL-PRF-81309
d. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to affected areas.
9-6. REMOVAL OF FIRE EXTINGUISHING AGENTS.
NOTE
Refer to NAVAIR 00-80R-14 for approved fireextinguishing agents usable on aircraft.
9-6.1 PURPLE-K-POWDER (PKP) AND OTHER DRYCHEMICAL FIRE EXTINGUISHING AGENTS.
9-6.1.1 Purple K Dry Chemical Powder. The principalbase chemical for Purple-K-Powder (PKP) is potassiumbicarbonate. Since it is a purple powder, the PKP fireextinguishers are marked with a purple band around thetank. PKP is primarily used to extinguish flammableliquid and gas fires such as gasoline, greases, oils, andpaints. When combined with water, PKP could corrodeor stain surfaces. As soon as possible, PKP should becompletely removed from all surfaces.
9-6.1.2. Removing Purple K Powder (PKP) and OtherDry Chemical Fire Extinguishing Agents. To removepowdered extinguishants, proceed as follows:
a. Remove as much extinguishant as possible byvacuum cleaning.
b. Use a soft bristle brush and air pressure notgreater than 10 psi to dislodge contaminants betweenclose-fitting components.
c. Vacuum clean again.
Compound, Aircraft Cleaning 2MIL-PRF-85570
d. Remove the residual film of dry powder adheringto the surface by wiping, brushing, or spraying with asolution of one part aircraft cleaning compound(MIL-PRF-85570 Type II) in 14 parts of water.
e. Rinse thoroughly with fresh water.
f. Dry with cloths or paper towels, or blow dry withair pressure not greater than 10 psi.
Change 1 - 31 March 2010
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Compound, Corrosion Preventive 4MIL-PRF-81309
g. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to affected areas.
h. Enter location of affected areas and listcomponents that were exposed to PKP fire extinguishingagent in the appropriate section of the aircraft logbook,corrosion folder, or other appropriate documents toensure that the area is re-inspected in the future as acorrosion prone area.
9-6.1.3. Treatment Procedures for Engines ExposedTo or Contaminated with Fire Extinguishing Powder(i.e., PKP).
a. With the ignition off/disconnected, vacuum cleanall excess and loose material, then crank the engine andrinse thoroughly with water.
Cleaning Compound 3Turbine Engine Gas PathMIL-PRF-85704
b. Flush all surfaces and passages with either asolution of one part engine gas path cleaner(MIL-PRF-85704 Type II) in four parts fresh water oruse the ready-to-use form of the cleaner(MIL-PRF-85704 Type II RTU).
c. Drain engine lubricant and refill.
d. At the next inspection, re-check previouslycontaminated areas and, if necessary, repeat the aboveprocedure.
9-6.2. AQUEOUS FILM-FORMING FOAM(MIL-F-24385).
9-6.2.1. Aqueous Film-Forming Foam (AFFF). AFFF isa specially formulated synthetic concentrate made fromsurfactants, solvents, and additives. When mixed witheither fresh or salt water, it will form a dense foam overthe liquid fuel to rapidly smother and cool hydrocarbonfuel fires such as gasoline, kerosene, and diesel.
9-6.2.2. Removing Aqueous Film Forming Foam(AFFF). To remove residues of salt water solutions ofAFFF fire extinguishing agent, proceed with paragraphsa. through h. below. To remove residues of fresh watersolutions of AFFF, use the same procedure but omitparagraphs b. through d.
NOTE
The following procedure applies to AFFF andsalt water mixtures normally used aboard ship.AFFF and fresh water mixtures usually do notpresent a corrosion problem. However, cleanupof all residues after a fire is required for corrosionprevention due to water intrusion into gaps,joints, cracks, and crevices.
a. Flush all affected areas with clean, fresh waterwhile draining. Whenever possible, units or componentswhich have been removed should be immersed in freshwater and then flushed thoroughly with fresh, cleanwater. Drain away the water.
b. Mix a solution of one pint of AFFF fire extinguishingagent in 10 gallons of fresh water.
c. Apply solution to affected areas using one of thefollowing methods:
(1) Use any type of spray equipment such as afoam generator, solvent wash gun, or back pack.
(2) Use an applicator such as aircraft washingpads, sponges, or low lint cloths, or pour AFFF solutiondirectly over affected areas if foaming equipment is notavailable.
d. Keep affected areas wet with AFFF solution for 3to 5 minutes.
Compound, Aircraft Cleaning 2MIL-PRF-85570
e. Clean surfaces with a solution of one part aircraftcleaning compound (MIL-PRF-85570 Type II) in 14 partsof water. Scrub affected areas and rinse with clean,fresh water. Drain away excess water.
f. Dry with cloths, paper towels, or air pressure notgreater than 10 psi.
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g. Apply water displacing preservative(MIL-PRF-81309 Type III) to all avionic componentsand electrical connectors. Liberally apply waterdisplacing CPC (MIL-PRF-81309 Type II) to all otherareas that cannot be properly drained or have recesseswhich are difficult to reach.
h. Enter location of affected areas and listcomponents that were exposed to AFFF fireextinguishing agent in the appropriate section of theaircraft logbook, corrosion folder, or other appropriatedocuments to ensure that the area is re-inspected in thefuture as a corrosion prone area.
9-6.3. CARBON DIOXIDE, HFC-125, AND HALONFIRE EXTINGUISHING AGENTS.
9-6.3.1. Carbon Dioxide (CO2). Carbon dioxide is a
dry, non-corrosive, inert gas that is used on flammableliquids and electrical fires because it does not leave anyresidues which might further harm the damaged electricalequipment. Also, CO2 is ideal for use on fires when it isimportant to avoid water damage. CO2 works by reducingthe amount of oxygen available for combustion bysmothering it. Although CO2 is non-poisonous,asphyxiation can result from breathing it and suppliedair must be worn when CO2 is used below decks or inconfined spaces.
9-6.3.2. HFC-125 (Pentafluoroethane). HFC-125 is afluorocarbon fire extinguishant that is electrically non-conductive, non-corrosive, free of residue, has zeroozone depletion potential (ODP), and is anenvironmentally approved replacement for Halonsystems. HFC-125 works by absorbing the heatgenerated from the combustion reaction.
9-6.3.3. Halon 1211 (Bromochlorodifluoromethane)and Halon 1301 (Bromotrifluoromethane). Halons arecolorless, odorless gases. They will extinguish mosttype of fires without leaving a residue and are suitablefor discharge in confined spaces. Typically, they areused in areas that contain sensitive or irreplaceableequipment that could be damaged or destroyed bywater, foam, dry chemical, or carbon dioxide. Like PKP,Halons do not extinguish by smothering or cooling,instead they interrupt the chemical reaction of the fire as
it decomposes upon contact. Halons have been foundto be an ozone depleting agent; however, some Halonsare still required for aircraft and shipboard applicationsas no safe and effective alternative exists. Halon 1211extinguishers are marked with a reflective silver bandaround the tank.
NOTE
Carbon Dioxide, HFC-125, or Halon fireextinguishing agents will not leave residues.However, smoke, smudges, or other grimefrom a fire is corrosive and shall be removedfrom affected items that are to be retained forfuture use.
9-6.3.4. CO2, HFC-125, Halon 1211 and Halon 1301
evaporate rapidly. Therefore, no cleanup is requiredunless moisture or high temperature was present at thearea of application. However, ventilation should alwaysbe provided to remove the vapors. If moisture or hightemperature was present, use the following clean-upprocedures.
a. After fire has been extinguished, purge area andsurface with clean, dry air (dust free, low moisturecontent, compressed air).
Compound, Aircraft Cleaning 2MIL-PRF-85570
b. Clean surfaces with a solution of one part aircraftcleaning compound (MIL-PRF-85570 Type II) in 14 partsof water. Scrub affected areas and rinse with clean,fresh water. Drain away excess water.
c. Dry with cloths, paper towels, or air pressure notgreater than 10 psi.
Compound, Corrosion Preventive 4MIL-PRF-81309
d. Apply water displacing preservative(MIL-PRF-81309 Type III) to all avionic componentsand electrical connectors. Liberally apply waterdisplacing CPC (MIL-PRF-81309 Type II) to all otherareas that cannot be properly drained or have recesseswhich are difficult to reach.
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e. Enter location of affected areas and listcomponents that were exposed to fire extinguishingagent in the appropriate section of the aircraft logbook,corrosion folder, or other appropriate documents toensure that the area is re-inspected in the future as acorrosion prone area.
9-6.4. PROTEIN FOAM AND SODA ACID.
9-6.4.1. Protein Foam. A general category of fireextinguishing agents that use protein based foamconcentrate. When mixed with water, protein foam ishighly effective on fuel fires and provides excellent heatresistance. Types of firefighting foams include AFFF,AR-AFFF, Protein Foams, Fluoroprotein Foams, ClassA Foams, and Training Foams.
9-6.4.2. Soda Acid. Soda acid and other inverted foamextinguishers are not approved portable fire fightingequipment for use on or around aircraft because theyare very corrosive. Soda acid type extinguishers operateby turning the extinguisher upside down. Acid spills outof a glass jar and reacts with the soda contents.
9-6.4.3. Removing Protein Foam and Soda Acid. Theresidues left from the use of these materials can beextremely corrosive to aircraft and equipment. Removeresidues as follows:
a. Thoroughly flush the affected area with freshwater. Ensure that the rinse water is completely flushedfrom the aircraft or equipment.
Compound, Aircraft Cleaning 2MIL-PRF-85570
b. Clean surfaces with a solution of one part aircraftcleaning compound (MIL-PRF-85570 Type II) in 14 partsof water. Scrub affected areas and rinse with clean,fresh water. Drain away excess water.
c. Dry with cloths, paper towels, or air pressure notgreater than 10 psi.
Compound, Corrosion Preventive 4MIL-PRF-81309
d. Apply water displacing preservative(MIL-PRF-81309 Type III) to all avionic components
and electrical connectors. Liberally apply waterdisplacing CPC (MIL-PRF-81309 Type II) to all otherareas that cannot be properly drained or have recesseswhich are difficult to reach.
e. Enter location of affected areas and listcomponents that were exposed to fire extinguishingagent in the appropriate section of the aircraft logbook,corrosion folder, or other appropriate documents toensure that the area is re-inspected in the future as acorrosion prone area.
9-7. TREATMENT AFTER LANDING ON A FOAMEDRUNWAY. Materials used to foam runways are corrosiveto aircraft. As soon as possible after a landing on afoamed runway, exterior areas, wheel wells, any interiorareas exposed, and engines shall be cleaned. Cleanthe exterior and wheel wells, interior areas, and enginesin accordance with Chapter 2.
9-8. TREATMENT OF SPECIFIC AREAS.
9-8.1. SPECIFIC INTERNAL AREAS. The followinginternal areas require special emergency cleaning.
9-8.1.1. Avionic and Electrical Equipment. Effectivecleaning ensures that salt water, fire fighting chemicals,and other corrosive agents are completely removed toprevent corrosion damage. Refer to Volume III forspecific cleaning procedures.
9-8.1.2. Cockpit Area. Emergency cleaning proceduresfor the cockpit are as follows:
a. If the interior is undrainable, drill out fasteners atlow point. If still undrainable, drill a hole at the low point.
b. Remove avionics equipment, relay boxes, circuitbreakers, and switches, and clean as specified inaccordance with Volume III.
c. Turn over avionic equipment to the activity thathas the authority and capability to disassemble.
d. Dry equipment that has been cleaned as much aspossible with air pressure (less than 10 psi), dryingmachines, electric fans, or hand fans in a hot room of150°F (66°C) maximum, or in a well ventilated roomwhere the humidity is low.
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e. Apply water displacing CPC (MIL-PRF-81309Type II) by spraying or brushing onto all areas thatcannot be properly drained or contain recesses whichare difficult to reach.
9-8.1.3. Ejection Seats. The following emergencycleaning procedure shall be used for cleaning ejectionseats.
WARNING
Disarm ejection seat mechanism beforecleaning. Ensure that only authorized personneldisarm seats and perform cleaning operations.
a. Remove parachutes, drogue parachutes (whereapplicable), and seat pans. Return to local work centerfor cleaning or replacement.
b. Remove ejection seat in accordance with theapplicable maintenance manual.
c. Rinse seat thoroughly with fresh water. Continuerinsing while directing water into crevices and closefitting parts until contaminants are removed.
d. Wipe down cartridge activated devices, rockets,and inertia reels with a clean cloth wet with fresh water.Disarm and remove from seats. Metal cap all gas linesand ports.
e. Remove as much water as possible fromequipment with vacuum or low-pressure, clean, dry air.
f. Dry excess water deposits with clean cloth orclean paper towels.
Compound, Corrosion Preventive 4MIL-PRF-81309
g. Apply water displacing CPC (MIL-PRF-81309Type II) by either spray or brush application to criticalmetal surfaces and recess areas that may not becompletely dry. Water displacing CPC will protectequipment during necessary inspections and duringtransfer to repair custodian.
h. Wash all survival gear and pilot safety equipmentwith fresh water and dry thoroughly. Refer to applicablemaintenance requirements for detailed preservationprocedures. Lubricate and control corrosion inaccordance with maintenance cards.
i. If necessary, send ejection seat to next highestlevel of maintenance.
j. Aircraft mounted escape system components(mechanically activated CADS) shall be wiped anddried with a clean cloth and fresh water. If internalcontamination is suspected, remove and replace.Forward to a Depot Level Maintenance Activity forfurther disassembly, inspection, and repair.
9-8.1.4. Fluoroelastomer (Viton™) Hazards. Viton is arubber-like compound used in aircraft applications forits excellent resistance to heat, abrasion, and aircraftfluids. It is used as an engine duct coating for firesuppression, and as gaskets on the backside of doorsand access panels (e.g. F/A-18s). Viton poses no harmunder normal temperature conditions. However, attemperatures encountered during an aircraft fire, Vitonwill break down and produce small amounts of toxichydrogen fluoride gas. Hydrogen fluoride can combinewith water to produce hydrofluoric (HF) acid, which isextremely corrosive to human tissue. Refer to NAVAIR00-80R-14 and/or aircraft specific maintenanceinstruction manuals for guidance as to the appropriatePPE, handling, clean-up, and first aid procedures whendealing with decomposed Viton or contaminatedequipment.
9-8.1.5. Photographic Equipment. The followingprocedure is applicable for cleaning photographicequipment.
a. Immediately rinse with fresh water, drain, andrinse again.
Compound, Corrosion Preventive 4MIL-PRF-81309
b. Apply water displacing preservative(MIL-PRF-81309 Type III).
c. Return to the appropriate photographic technicianfor prompt servicing.
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9-8.2. SPECIFIC EXTERNAL AREAS. The followingexternal aircraft areas require special emergencycleaning.
9-8.2.1. Airframes. The following procedure isapplicable for cleaning airframes:
a. If the aircraft fuselage, hull, or wings are in asalvageable condition, drain holes may be made fordraining water by drilling out rivets at the lowest points.All repairable/reusable parts shall be collected andreturned with the aircraft when shipment is made.
b. Flush all areas with clean, fresh water whiledraining. If possible, units or components that havebeen removed should be immersed in fresh water andthen flushed thoroughly with fresh water. Drain awaythe water and dry the areas with cloths, paper towels, orair pressure less than 10 psi.
Compound, Aircraft Cleaning 2MIL-PRF-85570
c. Clean surfaces with a solution of one part ofaircraft cleaning compound (MIL-PRF-85570 Type II) in14 parts of water. Scrub affected areas using the solution.Flush thoroughly with fresh water and drain away theexcess water. Dry with cloths, paper towels, or airpressure less than 10 psi.
Compound, Corrosion Preventive 4MIL-PRF-81309
d. To aid in the removal of water, liberally applywater displacing CPC (MIL-PRF-81309 Type II) to allother areas that cannot be properly drained or haverecesses which are difficult to reach.
e. All repairable/reuseable parts shall be collectedand returned with the aircraft when shipment is made.
9-8.2.2. Antennas. Remove the antenna according toinstructions in the aircraft maintenance manual. Treat inaccordance with Volume III. In-place cleaning may beaccomplished as follows:
a. Check antenna insulators for damage or cracks.
Compound, Aircraft Cleaning 2MIL-PRF-85570
b. Brush or spray a solution of one part aircraftcleaning compound (MIL-PRF-85570 Type II) in 14 partswater onto the affected area.
c. Scrub the area with a small, soft brush or wipingcloth dipped in the above cleaning solution.
d. Rinse with clean, fresh water.
e. Dry the area with a clean, dry cloth.
9-8.2.3. Armament. The following instructions are forinitial treatment of armament equipment that has beenimmersed in salt water or subjected to fire extinguishingchemicals.
9-8.2.3.1. Safety Precautions. Before performing anycleaning tasks, make certain that preliminary safetyprecautions are followed:
a. Ensure that the aircraft is safe for maintenance.
b. Disconnect all electrical power and ensure that allarmament switches are in the OFF or SAFE positions.
NOTE
For removal of armament equipment, refer tothe applicable manual for the respective aircraft.
c. Remove all ordnance from the armamentequipment and dispose of contaminated ammunition asrequired.
b. Disassemble as required and remove excess oilsand greases using a clean cloth dampened withdegreasing solvent (MIL-PRF-680 Type II) ornon-aqueous cleaner (MIL-PRF-32295 Type I).
Compound, Aircraft Cleaning 2MIL-PRF-85570
c. Immerse and agitate parts in a solution of one partaircraft cleaning compound (MIL-PRF-85570 Type II)in 14 parts of fresh water.
d. Rinse with fresh water to ensure complete removalof contaminants.
e. Wipe away excess water with clean, dry cloth.
f. Blow dry the cleaned equipment as thoroughly aspossible with clean, dry air pressure less than 10 psi.
Compound, Corrosion Preventive 4MIL-PRF-81309
g. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to disassembled parts.
h. Inspect disassembled parts to determine whetherthe equipment can be returned to service or should beforwarded to a higher maintenance activity for rework.
Compound, Corrosion Preventive 4MIL-PRF-81309
i. If shipment to a higher level of maintenance isrequired, reassemble parts and apply water displacingCPC (MIL-PRF-81309 Type II) to the outer surfaces.Permit excess CPC to drain off, then wrap gun in barriermaterial (MIL-PRF-131 Class 1) sealed with tape(AMS-T-22085) and prepare for shipping.
9-8.2.4. Composite Materials, Graphite or Carbon/Epoxy.
WARNING
The inhalation of carbon composite fibersresulting from aircraft fires and/or aircraftmaterial damage may be harmful to personnel.Wear a full facepiece respirator when exposedto these materials, and, in addition, wear closeweave cotton gloves when handling thesematerials.
CAUTION
Aircraft construction utilizing carbon/epoxy fibercomposite materials and metal structure orsubstructure creates a high potential forestablishing galvanic corrosion cells. This canresult in corrosion of the metal components ifthe structure is exposed to an electrolytemedium, such as salt water.
9-8.2.4.1. The carbon fibers of composite materialsmay be released into the atmosphere if their epoxybinder burns; this occurs at temperatures in excess of600°F (316°C). In addition, fibers may be released byan explosion or a high impact crash. The procedures fortreating fire damaged composite materials are listed inNAVAIR 01-1A-21 (Navy) or TM 55-1500 series (Army).
NOTE
Appropriate ship maneuvering, to direct thesmoke and debris away from parked aircraftand the island structure, can materially reducefiber contamination and reduce the cleanupprocess.
9-8.2.4.2. Cleanup. When damaged aircraft havecomposite surfaces that are broken or burned, thefollowing procedures should be followed.
Change 1 - 31 March 2010
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WARNING
Do not put power to or start up aircraft orelectronic/electrical equipment that has beenexposed to debris until decontamination byvacuuming and/or washing is completed. Failureto observe these procedures may result inelectrical short circuits and fires.
NOTE
It is recommended that industrial hygiene/safetypersonnel be contacted to provide specificinformation regarding hazards to personnelduring cleanup.
a. If ventilation inlets are known to be exposed todebris, take immediate action to ensure that the filtrationsystem is properly operating. If the system is notoperating properly, shut down the system and providetemporary filtration at outlets leading to compartmentswith electrical and electronic equipment.
b. Warn adjacent aircraft and ships that the smokemay contain hazardous electrical contaminants.
Compound, Corrosion Preventive 4MIL-PRF-81309
c. Spray water displacing CPC (MIL-PRF-81309Type II) on damaged composite surfaces. This willprevent the spread of carbon fiber contamination bycausing the fibers to stick to the damaged surface.Cover damaged surfaces securely with thick plasticsheets (A-A-3174) and seal with tape (AMS-T-22085Type II).
d. Aircraft, equipment, clothing and facilities thathave been exposed to carbon fiber or other debris froman aircraft fire must be vacuumed and/or washed downprior to reuse or prior to moving to another location.
e. Decontamination of the immediate area of theaircraft wreckage may require vacuuming, washing,and bagging of composite material fragments. Use asealed industrial vacuum cleaner. Store collected debrisin sealed, plastic bags for the accident investigation.Dispose of in accordance with applicable environmentaland safety regulations when so directed by theinvestigation team.
f. If wrapping and secure taping of the aircraftwreckage is not possible, transportation of the wreckagemust be planned. Bypass heavily populated andindustrial areas. Aircraft parked along the planned routemust have their canopies and access doors closed andengine inlet and exhaust covered. In addition, the doorsand windows of surrounding buildings should be closedto minimize the probability of having wind-blown fibersenter areas containing electrical and electronicequipment.
9-8.2.5. Composite Materials, Boron/Tungsten. Theextinguishing, containing, and cleaning practices forboron fibers are the same as those for carbon/epoxyfibers.
9-8.2.6. Engines, Reciprocating.
a. Determine the extent of contamination.
b. Drain all fluids. Partial disassembly is authorizedto accomplish thorough draining. Ensure that pressuresystems and cylinders are drained.
c. Thoroughly flush all surfaces and passages withclean, fresh water.
Solvent, Degreasing 13MIL-PRF-680
d. Apply dry cleaning solvent (MIL-PRF-680 Type II).
Cleaning Compound 3Turbine Engine Gas PathMIL-PRF-85704
e. Flush all surfaces and passages with either asolution of one part engine gas path cleaner(MIL-PRF-85704 Type II) in four parts fresh water or usethe ready-to-use form of the cleaner (MIL-PRF-85704Type II RTU).
f. Thoroughly rinse all areas with fresh water.
g. Allow to drain thoroughly. Dry using paper towels,cloths, or air pressure less than 10 psi.
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Compound, Corrosion Preventive 4MIL-PRF-81309
h. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to all surfaces. This may beaccomplished by fill and drain (preferred), flushing, orspraying. Rotate the propeller shaft to coat cylinderwalls. Drain excess CPC.
i. Reassemble engine finger tight.
j. Lubricate any pressure lubrication points tocompletely displace all contaminated lubricant.
k. For shipping, place engine in an approveddehydrated metal container, using twice the normalamount of desiccant.
9-8.2.7. Engines, Turbine. Engines that arecontaminated with small amounts of seawater enteringthe intake shall be cleaned using engine gas pathcleaner (MIL-PRF-85704) in accordance with Table 2-3.For engines which have been completely submerged inwater or seawater, decontaminate as follows:
a. Drain all fluids. Partial disassembly is authorizedto accomplish thorough draining.
b. Thoroughly flush all surfaces and passages withfresh water.
Cleaning Compound 3Turbine Engine Gas PathMIL-PRF-85704
c. Flush all surfaces and passages with either asolution of one part engine gas path cleaner(MIL-PRF-85704 Type II) in four parts fresh water or usethe ready-to-use form of the cleaner (MIL-PRF-85704Type II RTU).
d. Thoroughly rinse all areas with fresh water.
e. Drain thoroughly.
Compound, Corrosion Preventive 4MIL-PRF-81309
f. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to all surfaces. This may beaccomplished by fill and drain (preferred), flushing, orspraying. Drain excess CPC. Repeat this procedureuntil all traces of water have been removed.
g. Lubricate any pressure lubrication points tocompletely displace all contaminated lubricant.
h. For shipping, install in an approved dehydratedmetal container, using twice the normal amount ofdesiccant. Notify the Aircraft Controlling Custodians(ACC) or System Program Manager (SPM) to arrangespecial handling as required.
9-8.2.8. Helicopter Blades, Main and Tail Rotor.Helicopter blades that have been exposed to anexcessive amount of salt water or fire fighting chemicalsshall be treated as follows:
a. Thoroughly flush all contaminated surfaces withclean, fresh water. Pay particular attention to recessesthat tend to trap debris such as mud, dirt, or saltdeposits.
CAUTION
Some rotor blades have areas commonly knownas pockets or blade boxes with very small drainholes. If blades have been immersed in saltwater, the drain holes may require enlargementto facilitate decontamination of the blade spar.Enlarging drain holes destroys the affectedpockets or blade boxes and requires repair at aDepot Level Maintenance Activity before theblade can be reused.
b. Allow water to drain. Enlarge drain holes in pocket/blade box if required. Enlargement of pocket/blade boxrequires authorization from the appropriate ACC/SPMfor each blade involved.
Compound, Aircraft Cleaning 2MIL-PRF-85570
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c. Wash with a solution of one part aircraft cleaningcompound (MIL-PRF-85570 Type II) in 14 parts freshwater.
d. Rinse thoroughly with fresh water.
e. Dry with cloth, paper towels or air pressure lessthan 10 psi.
Compound, Corrosion Preventive 4MIL-PRF-81309
f. Where possible, flush with water displacing CPC(MIL-PRF-81309 Type II). Preserve and package bladebefore sending to the appropriate ACC/SPM forengineering evaluation and repair.
9-8.2.9. Helicopter Transmission, Rotor Head, andRotor Hub. Helicopter transmission, rotor head, androtor hub cases are often constructed of magnesium.Magnesium parts exposed to salt water or fire fightingchemicals require immediate and thoroughdecontamination and preservation.
9-8.2.9.1. External Surface Contamination. Treathelicopter transmissions, rotor heads, and rotor hubswith external surface contamination as follows:
a. Rinse with fresh water.
Compound, Aircraft Cleaning 2MIL-PRF-85570
b. Wash with a solution of one part aircraft cleaningcompound (MIL-PRF-85570 Type II) in 14 parts freshwater and rinse thoroughly.
Compound, Corrosion Preventive 4MIL-PRF-81309
c. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to all affected areas.
d. Lubricate all pressure lubrication points tocompletely displace all contaminated lubricant.
9-8.2.9.2. Internal Surface Contamination. If internalsurface contamination of helicopter transmission rotorheads and gearboxes is suspected, immediately contactthe appropriate ACC/SPM for assistance anddecontamination procedures. Treat helicoptertransmissions, rotor heads, and rotor hubs havinginternal contamination as follows:
a. Drain all fluids. Partial disassembly is authorizedto accomplish thorough draining. Ensure that pressuresystems are drained.
b. Thoroughly flush all surfaces and passages withfresh water.
Compound, Aircraft Cleaning 2MIL-PRF-85570
c. Flush all surfaces and passages with a solution ofone part aircraft cleaning compound (MIL-PRF-85570Type II) in 14 parts fresh water.
d. Thoroughly rinse all areas with fresh water.
e. Allow to drain thoroughly.
Compound, Corrosion Preventive 4MIL-PRF-81309
f. Liberally apply water displacing CPC(MIL-PRF-81309 Type II) to all surfaces. This may beaccomplished by fill and drain (preferred), flushing, orspraying. With the housing full of CPC, rotate the mainshaft approximately five revolutions. After the CPC hasremained in the housing for 4 hours, drain and replaceplugs.
g. Service transmission in accordance withmaintenance instruction manuals (MIMs) if going backin service or leave as preserved if shipping out.
h. Lubricate all pressure lubrication points tocompletely displace all contaminated lubricant.
9-8.3. AIRCRAFT FUEL SYSTEMS. For emergencytreatment of aircraft fuel systems contaminated withseawater through means other than water, crash, or firedamage, refer to NAVAIR 01-1A-35 (Navy) orAppendix B, Section V (Army).
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APPENDIX ASUPPLEMENTAL REQUIREMENTS FOR NAVY AIRCRAFT
SECTION I. PAINT FINISHES AND TOUCH-UP PROCEDURES
A-1. SCOPE. This section describes materials andprocedures used for applying protective paint finishesto interior and exterior surfaces of Navy and MarineCorps aircraft. This information is intended for use inconjunction with system specific paint finishinginstructions. This section describes the following:
a. Safety precautions when storing and handlingpaint materials;
b. Storage and shelf life considerations;
c. Paint systems used on Navy and Marine Corpsaircraft;
d. Paint application equipment;
e. Preparation of surfaces prior to painting;
f. Paint application techniques; and
g. Specific mixing and application information forstandard paint finishing materials.
A-2. SAFETY. Paint materials, including primers andsolvents, are toxic and flammable. It is essential toproperly store, handle, and apply these materials toprevent fires and to minimize exposure to solventvapors and paint overspray mist. All personnel involvedwith paint operations shall read, understand, and followOPNAVINST 5100.23. Consult the local OccupationalSafety and Health Office or Industrial Hygiene Activityfor these references and appropriate safety precautionspertinent to specific sites. Consult applicable materialsafety data sheets (MSDSs) supplied by themanufacturer for information on specific materialhazards. Additional safety information may be obtainedfrom the Hazardous Material Users Guide (HMUG) andDoDI 6050.05.
A-2.1. RESPIRATOR USE. Respiratory protectionprograms shall be established per OPNAVINST5100.23. Whether painting operations are performedindoors or outdoors, it is necessary to avoid inhalationof vapors and dust. Solvents and thinners used for paintprocesses, including those used for equipment cleanup,are harmful if inhaled for prolonged periods and shouldbe handled with the same care as paint materials.
Contact the local Industrial Hygiene Activity orOccupational Safety and Health Office for properselection of respiratory protection equipment. Refer toVolume IV for ordering information for various respiratorsand supplied air devices.
A-2.2. PROTECTIVE CLOTHING. Eye and skin contactwith paint materials and solvents shall be avoided.Wear protective goggles or face shield, rubber gloves,and coveralls. If paint materials or solvents contact theeyes, rinse with fresh water for 15 minutes and seekimmediate medical attention. If contact with the skinoccurs, wash affected area with soap and water; if thereis excessive exposure or a severe reaction, seek medicalattention immediately.
A-2.3. VENTILATION. Adequate ventilation shall beprovided in all painting and storage areas to prevent thebuildup of solvent vapors. Painters and all otherpersonnel involved in the paint operation shall takeappropriate precautions to minimize exposure to solventvapors and paint overspray mist.
A-2.4. FIRE PREVENTION. Paint materials areextremely flammable. These materials shall be stored,mixed and applied in approved areas away from heat,flame, sparks, and other sources of ignition. Ensure thatfire fighting equipment is readily available and in workingorder. Consult the local Fire Department, Fire Marshall,or Occupational Safety and Health Office for specificfire prevention and safety requirements during paintingoperations.
A-3. STORAGE AND SHELF LIFE. All paint materialsshall be stored in tightly closed containers away fromexcessive heat and cold. As a general rule, store paintmaterials between 40°F and 100°F, away from directsunlight. Extreme storage temperatures can degradematerial quality and will reduce the effective shelf life ofpaint materials.
A-3.1. IDENTIFICATION. All paint materials shall beproperly identified when stored. Containers should berelabeled when necessary to ensure legibility. Previouslyopened containers shall be closed and sealed tightly.Paint thinners shall be stored with the same care aspaints.
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A-3.2. SHELF LIFE. The shelf life or storage life of paintmaterials can vary from several months to severalyears. The manufacturer’s recommended shelf life isusually printed on the container label. However, ifproperly stored, material usability may exceed theserecommendations. Additional shelf life information maybe obtained from https://www.shelflife.hq.dla.mil.
A-3.3. SHELF LIFE EXTENSION. Shelf life action codesdetermine how long the shelf life can be extended if thematerial passes testing.
A-3.3.1. If the inspect/test date of the material has beenexceeded, shake the container, or containers as in thecase of multicomponent paint materials, and examinethe contents. The material shall be homogenous with noskinning and lumps. The resin component ofmulticomponent materials shall be clear with no visiblecloudiness, white precipitate, or sediment. Containersshall be free from rust and other contaminates. Discardany unsuitable materials according to local regulations.
A-3.3.2. If the material appears satisfactory, mix andapply it to aluminum test coupons. Periodically checkthe coating on the test specimens for appropriate dryingand film characteristics.
a. If the material dries properly, the shelf life may beextended for a period of six months (first extension),four months (second extension), or two months (thirdextension). Affix an extension label to the container inaccordance with FED-STD-793.
b. If the coating does not dry in the specified time,dispose of the material according to local regulations.
A-3.3.3. Shelf life for paint-type materials can beextended three times if the material is found suitable, fora total extension period of 12 months.
A-4. PAINT SYSTEMS. The primary objective of anypaint system is to protect exposed surfaces againstcorrosion and other forms of deterioration. Operationaluses for particular paint schemes include:
a. Flat (lusterless or non-specular) coatings for glarereduction;
b. Special finishes for heat reduction and thermalprotection;
c. Camouflage/stealth (LO) and other detectioncountermeasures;
d. Corrosion protection;
e. Dissipation of static charge;
f. Resistance to abrasion, rain erosion, fungus, andoperational fluids;
g. High visibility requirements; and
h. Identification markings.
A-4.1. PAINT SYSTEM MATERIALS. Aircraft paintsystems usually consist of a primer and topcoatcombination applied over a properly prepared surface.The primer contains corrosion inhibitors and alsopromotes adhesion of the paint system. The primer mayalso provide low infrared reflectance properties. Thetopcoat provides durability to the paint system, includingweather and chemical resistance, along with coloringnecessary for tactical requirements. On some aircraft,spray sealant is applied between primer and topcoat toimprove paint system flexibility and to add additionalcorrosion protection. Aircraft paint systems often makeuse of specialty coatings, such as conductive paintsand low-observable coatings. Consult specificmaintenance instructions for guidance on specialtycoatings application and repair.
A-4.1.1. Environmentally Compliant Coatings. TheEnvironmental Protection Agency (EPA), along withmany local and state air pollution control districts, hasimplemented rules that limit the volatile organiccompound (VOC) content, or solvent content, of paintsapplied to aircraft. VOC content is reported as grams ofsolvent per liter of paint or "g/l". Currently, the nationalmaximum permissible VOC content is 340 g/l for aircraftprimers, and 420 g/l for aircraft topcoats. These limitsmay be less in certain local or state air pollution controldistricts. It is the responsibility of the user activity toensure that applicable rules are understood and obeyed.Failure to comply with current rules can result in largefines and revocation of air emission permits. Consultthe local Environmental Affairs Office or appropriatepermitting authority for guidance.
A-4.1.2. Common Materials. Table A-1 lists the primarycoatings used on Navy aircraft and some specific materialcharacteristics.
A-4.2. PAINT COLORS. FED-STD-595 (color fandeck)provides a list of paint colors represented by five digitnumbers. The first digit describes gloss value:1 = high gloss, 2 = semigloss, and 3 = flat (lusterless).The second digit describes the color family: 0 = browns,
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1 = reds, 2 = oranges, 3 = yellows, 4 = greens,5 = blues, 6 = grays, 7 = blacks, whites, and metallics,and 8 = fluorescent. The remaining three digits describethe color value or hue. For example, color number36440 is a flat, gray color and color number 17925 is ahigh gloss, white color. See Volume IV for informationon ordering a color fandeck.
A-4.3. PAINT SYSTEM IDENTIFICATION. Paint finishmaterials, application date, and application activity areidentified by decal or stencil located on the aft starboardside of the aircraft fuselage, and should be used as aguide for selection of materials when paint systemrepair is necessary. Refer to MIL-STD-2161 or systemspecific instructions for paint color schemes, aircraftmarkings/MODEX, and specific material requirements.
A-4.4. TOUCH-UP. Table A-2 lists original coatingmaterials and specified touch-up materials used forcommon aircraft paint systems. All activities shall befamiliar with paint scheme requirements, particularlythe importance of using appropriate materials. Refer toMIL-STD-2161 and system specific instructions for paintfinishing details.
A-4.5. COSMETIC PAINTING. Repainting solely forthe sake of cosmetic appearance is not authorized.Since common paint materials may take as many asseven days to completely cure, a faded or stained butwell-bonded paint finish is more durable than a freshtouch-up treatment. Refinishing shall be performedonly when existing paint finishes have deteriorated orhave been damaged, or when removal of the existingpaint system is necessary for corrosion correctiveactions.
A-4.6. TEMPORARY MARKINGS. Where localenvironmental regulations permit, lacquer paint such asMIL-PRF-81352 Type I may be used for temporarymarkings. Lacquer can be easily removed using solvents,
such as MIL-T-81772 Type I Aircraft Paint Thinner,without affecting the underlying paint system. Ininstances where local environmental regulations do notpermit the use of lacquer, use only the prescribedenvironmentally compliant coatings listed in Table A-2.
NOTE
Non-approved aerosol coatings are notauthorized for aircraft touch-up and painting.
A-4.7. AEROSOL COATINGS. Aerosol paint deliverysystems using approved coatings are recommendedfor small touch-up processes. Refer to Table A-2 andparagraph A-9 for authorized materials. Non-approvedaerosol coatings do not provide adequate corrosionprotection, weather resistance, and durability, nor arethey resistant to operational fluids.
A-4.8. WET INSTALLATIONS. Fasteners and bushingsare often wet-installed with corrosion inhibiting primeror sealant to provide additional corrosion protection.Waterborne materials, such as MIL-PRF-85582Waterborne Epoxy Primer, shall not be used for wetinstallation of fasteners and bushings since entrappedmoisture may promote corrosion. In general,MIL-PRF-23377 Epoxy Primer and MIL-PRF-81733Polysulfide Sealant are preferred materials for wetinstallation purposes. Consult specific maintenanceinstructions for appropriate selection of materials.
A-4.9. SPECIAL SURFACES. Some aircraft surfacesrequire specialized coatings to satisfy service exposureand operational needs. Radomes, antenna covers, andparts with similar elastomeric coatings shall be repairedin accordance with NAVAIR 01-1A-22 andsystem-specific repair instructions. Coatings on propellerblades, helicopter rotor blades, leading edge erosionresistant coatings, and anti-chafe coatings shall also berepaired in accordance with system-specific repair
Table A-1. Primary Coatings Used on U. S. Navy Aircraft
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instructions. Refer to Volume III for touch-up of avionicsequipment. Refer to NAVAIR 17-1-125 for touch-up ofground support equipment.
A-5. PAINT EQUIPMENT. Paint coatings are typicallyapplied using brushes, touch-up pens, rollers, andspray guns. Selection of an appropriate applicationmethod depends upon the size of the area to be painted,where the paint is to be applied, and what equipment isallowed. Specific coating application procedures arecontrolled by environmental and safety regulations, andsome equipment may be prohibited. Therefore, anyoneperforming painting operations shall be knowledgeableabout local, state, and federal regulations governingequipment and procedures. Consult the localEnvironmental Affairs Office for specific requirements.
A-5.1. HIGH-VOLUME LOW-PRESSURE (HVLP)GUN. HVLP spray equipment (see Figure A-1) atomizespaint into a soft pattern of low speed particles using anair cap pressure up to 10 psi maximum. Due to the lowvelocity of the coating particles, more of the coating isdeposited on the intended object with less overspray.
Table A-2. Original Coating Systems and Corresponding Touch-up Systems
Figure A-1. HVLP Paint Spray Gun
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Since there is less overspray, it is easier to see thesurface being coated. Film build is faster than withconventional spray equipment due to higher transferefficiency. Benefits include less material usage and lesspaint booth maintenance due to less overspray. Theproper working distance of an HVLP gun is usuallycloser than with a conventional paint spray gun. Due toenvironmental regulations, an HVLP system must notbe operated at air cap pressures exceeding 10 psi.Refer to manufacturer’s literature supplied with thepaint gun for proper operation and adjustment.Figure A-2 illustrates the components of a typical HVLPpaint spray gun. Refer to Volume IV for orderinginformation of the HVLP paint spray guns.
A-5.1.1. Transfer Efficiency. Application methods shallbe selected to minimize the amount of paint waste andsolvent emissions. Transfer efficiency is used to gagethe effectiveness of paint equipment and is representedas a percentage of the amount of paint deposited on thesurface compared with the total amount of paint used.Spray painting produces overspray and has much lesstransfer efficiency than brush or roller application, butproduces a more uniform, higher quality paint film. TheEPA has established specific requirements for paintspray equipment used on aircraft surfaces. High-volumelow-pressure (HVLP) spray equipment or electrostaticspray equipment is recommended since they havehigher transfer efficiencies than conventionalhigh-pressure spray equipment. In addition, conventionalhigh-pressure spray equipment is no longer allowed inmost localities for use on aircraft surfaces due toenvironmental restrictions. Consult the localEnvironmental Affairs Office for guidance on selectionof proper paint spray equipment.
A-5.1.2. HVLP Equipment Options. HVLP spray gunsare suitable for painting both large areas and smallcomponents. These guns can be fitted with a small cup,usually a pint or quart capacity, or a pressure pot. Apressure pot holds two or more quarts of paint and ispressurized to force paint through a hose to the paintspray gun. The amount of pressure supplied to the potis determined by the paint viscosity and length of paintsupply hose. Follow manufacturer’s recommendationsto set pot pressure.
A-5.2. TOUCH-UP SPRAY GUN. A touch-up spraygun is used to apply paint to small areas using a smallspray pattern. Since these guns are used for smallareas, they are often acceptable under environmentalregulations. Consult the local Environmental AffairsOffice for guidance on the use of touch-up spray guns.
A-5.3. 3M PAINT PREPARATION SYSTEM (PPS).PPS is a closed paint system that connects to bothsiphon and gravity feed HVLP spray guns, allowingmixing and spraying of paint materials from the samedisposable liner bag (see Figure A-3). Adapters areavailable to convert existing spray guns to use PPS.Instead of traditional rigid cups made of polyethylene,aluminum, or stainless steel, the PPS includes acollapsible liner bag in a plastic cup fitted with a lid andbuilt-in filter. As paint is sprayed, the liner bag collapses,allowing the spray gun to function at any angle (i.e.,sideways, upside down). This multi-angle capability isespecially useful for painting inside compartments, underwings, or the bottom of the fuselage. Collapsed linerbags and lids with built-in filter are disposable, leavingonly the spray gun and adapter to be cleaned. Unusedpaint can be sealed in the liner with a sealing cap andstored appropriately. PPS provides an efficient meansof applying paint materials, thus reducing paint wasteand minimizing time and cleaning solvents required forcleaning paint spray gun assemblies.
A-5.4. ELECTROSTATIC EQUIPMENT. Electrostaticpaint spray equipment deposits paint on surfaces bymeans of static electric attraction. The surface to bepainted and the coating material have opposing chargeswhich causes the coating to be attracted to the surface.Electrostatic painting is useful for painting large areasand, if used properly, produces little overspray with hightransfer efficiency. Due to electrical conductivityrequirements, this equipment is highly dependent uponthe type of coating (i.e., waterborne vs. solvent based)and substrate conditions (i.e., metallic or nonmetallic).Follow manufacturer’s recommendations and safetyprecautions when operating this equipment.
A-5.5. BRUSH AND ROLLER. Brushes and rollers areenvironmentally preferred alternatives for touch-uppainting since they produce little paint waste and do notrequire solvent clean up. However, spray painting ispreferred where allowed by local regulations andavailability of proper personal protective equipment(PPE), since the quality and uniformity of the paint filmis better than that achieved by brush or roller application.Brushes and rollers must be constructed of durablematerials that will not be affected by solvents in thecoatings. Do not use foam brushes or foam rollers sincethey are not solvent resistant. Refer to Volume IV forappropriate brushes and rollers. Note that in addition tothe standard 1" wide brush, there are "acid brushes"and "artist brushes" available for small or hard to reachareas. Use rollers with the shortest nap possible in orderto achieve the best surface finish. Brushes and rollers
are considered disposable. As such, they should not becleaned or reused.
A-5.6. ZAHN NO. 2 VISCOSITY CUP. Viscosity ofpaint materials can be checked by measuring the timerequired for the material to flow from a cup with aspecified volume through a specified orifice size in thebottom of the cup (see Figure A-4). A Zahn No. 2 Cupis constructed of corrosion resistant steel. This cup willhold 44 milliliters (1.47 ounces) of material and has acalibrated orifice in the bottom. The cup must not bedamaged or altered to ensure consistent volume; thesize of the orifice must also remain the same. Do not useabrasive materials or metallic objects to clean the cupssince damage to the volume or orifice may occur.Viscosity is measured using the Zahn No. 2 Cup asfollows:
a. Prepare the paint to be tested. Mix and strain permanufacturer’s recommendations.
b. Fill the cup by submerging it into the material.Make sure that enough material is available to completelyfill the cup.
c. When the cup is full, raise it completely out of thematerial and immediately start a stopwatch. Carefullyobserve the flow of paint from the orifice.
d. When the constant stream or flow of the materialbreaks, stop the watch. The time required (in seconds)for the stream to break is the viscosity value. Viscosity
values will vary among coatings. Primers are usuallyapplied at lower viscosities (15-25 seconds), andtopcoats, such as MIL-PRF-85285, are usually appliedat higher viscosities (18-30 seconds). Refer to theapplication instructions for specific coating requirements.To avoid exceeding VOC limits, do not add additionalpaint thinner unless specifically authorized by themanufacturer’s instructions.
A-5.7. WET FILM THICKNESS GAGE. Wet filmthickness of coatings is used to estimate the dry filmthickness. Wet film thickness is easily obtained using acomb-type thickness gage (refer to Figure A-5). As ageneral rule, dry film thickness will be approximately 50percent of the wet film thickness. Wet film thickness isobtained as follows:
a. Place gage on wet paint film at a 90° angle. Thisis done on test panels sprayed at the same time as theactual component or on masking tape adjacent to theactual component just after the coating is applied.
b. Press gage into film. Withdraw and note deepesttooth having paint on it and next higher tooth that is notcoated.
c. The wet film thickness lies between these tworeadings.
d. Clean gage with a suitable solvent immediatelyafter use.
Figure A-3. 3M PPS Mounted on a Spray Gun Figure A-4. Zahn No. 2 Viscosity Cup
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A-5.8. DECAL MARKING EQUIPMENT. The GerberEdge adhesive stencil making system and AveryTechniflex adhesive vinyl are the recommended productsfor aircraft decal markings; however, any equivalentsystem may be used.
A-6. GENERAL MAINTENANCE REQUIREMENTSFOR PAINT SPRAY EQUIPMENT. Proper maintenanceis necessary to preserve the life of the paint sprayequipment and ensure high quality results. The spraygun requires little maintenance if kept clean. Two partcatalyzed coatings cure or harden by chemical reactionin addition to solvent evaporation. The curing processbegins when the two components are mixed. Over a fewhours, the coating will gel and harden regardless ofwhether or not it is exposed to air. If catalyzed materialsare allowed to remain in the equipment too long, theequipment will become inoperative. For this reason,paint equipment shall be thoroughly cleaned immediatelyafter use or at least every four hours.
A-6.1. PAINT EQUIPMENT CLEANING. Paint sprayequipment cleanup procedures are controlled by EPAregulations. Local and state pollution control districtsmay also have specific requirements. Consult the localEnvironmental Affairs Office for specific requirements.Generally approved cleaning solvents and methods arelisted below.
A-6.1.1. Paint Cleaning Solvent. To effectively removeresidue, paint equipment cleaning solvents must be
compatible with the type of coating material. In general,residue from polyurethane coatings such asMIL-PRF-85285 and TT-P-2760 can be removed usingMIL-T-81772 Type I Thinner. Residue from epoxycoatings such as MIL-PRF-22750 and MIL-PRF-23377can be removed using MIL-T-81772 Type II Thinner.Uncured residue from waterborne coatings such asMIL-PRF-85582 can be removed using a combinationof water and TT-I-735 (Isopropyl Alcohol). To preventcorrosion, do not allow water to remain in the paintequipment. Consult specific manufacturer's instructionsfor guidance on cleaning solvents for each individualcoating.
WARNING
Eye protection and solvent proof gloves (nolatex) must be worn during use and maintenanceof the paint gun washer.
Rags and other cleaning materials saturatedwith waste solvent are a potential fire hazardand therefore shall be deposited in a suitablecontainer immediately after use. The containershall be covered with a tight fitting lid and keptclosed except when depositing or removingcleaning materials.
A-6.1.2. Paint Gun Washers. These washers consist ofan automated, close-loop spray system that flushesand cleans both interior and exterior of HVLP paint guns
Figure A-5. Wet Film Thickness Gage
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and other painting equipment (refer to Volume IV forrecommended units). These stainless-steel tankwashers (see Figure A-6) provide an alternative to thelabor intensive method of manually cleaning paint guns,and minimize worker exposure to potentially harmfulsolvents. The only exposure is during loading andunloading of paint guns, solvent replenishment, andreplacing and disposing of the spent filters. A filtrationsystem allows the cleaning solvent to be reusednumerous times before disposal is required, therebyreducing the quantity of spent solvent and rags thatmust be disposed of as hazardous waste. Solventsselected for use in the unit should be based on the typeof coatings to be removed. Operate and service systemper manufacturer’s instructions. Lid shall be kept closedat all times except for loading and unloading paint sprayequipment or servicing system. Do not use thisequipment if leaks are present. Spent solvents shall bedisposed as necessary to ensure proper equipmentoperation.
A-6.1.3. Non-Atomized Cleaning. Clean the paint spraygun by placing solvent into the pressure pot or cup andforcing solvent through the spray gun into a suitablewaste container. Do not atomize/spray the cleaningsolvent. The waste container shall be closed when notin use to prevent solvent evaporation.
A-6.1.4. Manual Gun Cleaning. Clean the disassembledpaint spray gun by hand or by soaking the parts in acontainer filled with solvent. Brushes may be used toassist in cleaning detailed parts. The container shall beclosed while parts are soaking and when not in use. Donot immerse the entire paint spray gun.
A-6.2. REMOVAL OF DRIED PAINT. After severalmonths of use or when clogged with dried paint, the
spray gun may be cleaned by completely dismantlingand soaking metal components, such as the air nozzle,fluid nozzle, and needle assembly, in MIL-PRF-83936tank-type paint remover (see Chapter 4). Do not immersethe entire paint spray gun or any plastic componentsinto a paint remover tank.
A-7. PREPARATION OF SURFACES FORPAINTING. Much of the effectiveness of a paint finishdepends on careful preparation of the surface prior toapplying the coatings. Surface preparation includesscuff sanding of old existing paint, cleaning, and chemicalconversion coating of any bare metal.
WARNING
Some coatings contain chromium compounds,lead compounds, and other heavy metalpigments. Wear eye and respiratory protectionand ensure adequate safety precautions are inplace to prevent exposure to dust during sandingoperations. Contact the local Industrial HygieneActivity or Occupational Safety and Health Officefor guidance on the proper selection ofrespiratory protection and other personal safetyrequirements.
CAUTION
When scuff sanding and feathering paintcoatings, avoid damage to metal and compositesubstrates. Abrasion of substrate materials candamage structural integrity.
NOTE
Proper surface preparation is essential. Mostpoorly adherent paint coatings are caused bypoor surface preparation. Carefully follow allcleaning, corrosion removal, surface treatment,and solvent wipe-down procedures beforeapplying any coatings.
A-7.1. PREPARATION OF AGED PAINT. Aged paintcoatings (those allowed to cure seven days or more)must be scuff sanded prior to repainting to ensureadhesion of additional paint coatings. Scuff sand using150 grit or finer aluminum oxide cloth (ANSI B74.18),abrasive mat (A-A-58054), or random orbital sanderwith aluminum oxide paper. Scuff sanding requires acomplete roughening of the paint surface; however,avoid aggressive scuff sanding, which can expose thesubstrate and promote corrosion of metal anddegradation of composite materials. Unevenly matched
Figure A-6. Paint Gun Washer
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faying surface joints or fasteners and sharply protrudingobjects or corners shall be scuff sanded by hand toavoid sanding through the coating. After scuff sanding,remove dry residue using clean cheesecloth(CCC-C-440) dampened with water, followed by wipingwith clean cheesecloth dampened with thinner(MIL-T-81772 Type I).
A-7.2. DRYING. All surfaces to be painted shall bethoroughly dry prior to painting. After cleaning, specialprecautions shall be taken to assure proper drainage ofall liquids from between faying surfaces, crevices, andpockets, preferably by permitting the aircraft orcomponent to stand for a sufficient time to permit suchdrainage. If necessary, isopropyl alcohol (TT-I-735)may by sprayed into seams or fastener patterns aftercleaning to ensure displacement of water in theseareas. Ensure that areas surrounding the area to bepainted, especially crevices and faying surfaces, arealso dried prior to painting to prevent drainage onto thework surface.
A-7.3. FINAL INSPECTION AND PREPARATION.
a. Inspect surface to be painted to ensure allcorrosion has been properly removed. Surfaces mustbe cleaned and properly treated using chemicalconversion coating (see Chapters 2 and 5, respectively).If chemical conversion coating is scratched or damaged,the area must be retreated in accordance with Chapter 5.
b. Replace any seam sealants if necessary, asdescribed in Chapter 7.
c. Mask surrounding areas to protect from paintoverspray. Paint masking tape (AMS-T-21595 Type I)and brown masking paper (A-A-203) are suitable formost masking requirements. For touch-up sprayapplications, it is often desirable to mask to a seam orline to prevent the appearance of a paint edge aftermasking material is removed.
A-7.4. SOLVENT WIPE. Surfaces must be completelyclean prior to painting. Failure to remove all oils, greases,aircraft fluids, fingerprints, or other contaminants willlead to coating adhesion problems and prematurecorrosion.
A-7.4.1. Clean surfaces immediately prior to paintingby solvent wiping with clean cheesecloth (CCC-C-440Class 2) or cleaning cloth (AMS 3819 Grade A orequivalent) dampened with an approved solvent(MIL-T-81772 Type I, AMS 3166, or equivalent).
A-7.4.2. Environmentally Compliant Solvents.Environmental regulations in most locations prohibit theuse of wipe solvents with vapor pressures greater than45 millimeter of mercury (mmHg). The vapor pressureof MIL-T-81772 Type I and AMS 3166 is approximately35 mmHg or less.
A-8. GENERAL PAINT APPLICATIONPROCEDURES. The following procedures are generalrules to be followed when applying paint. For moredetailed information on the application of paint finishes,refer to MIL-STD-7179 (Finishes, Coatings, and Sealantsfor the Protection of Aerospace Weapons Systems).
WARNING
Aircraft shall be electrically grounded during allpainting procedures in order to guard againstthe danger of fire from static electricity.
A-8.1. GENERAL SPRAYING TECHNIQUES.
a. Prior to spraying, the gun should be checked toensure that it produces the proper spray pattern.Figure A-7 shows correct spray patterns and tips onhow to achieve them. Table A-3 shows incorrect patterns,causes, and suggested remedies.
b. Always have the spray gun in motion beforespraying.
c. Keep the spray gun at a consistent distance fromthe work during application.
d. Move the spray gun across the work at a consistentspeed.
e. For large surfaces, trigger the spray gun afterbeginning and before ending each stroke.
f. Start the first stroke at the same point on eachsimilar object.
g. Always overlap half of the pattern of the previousstroke.
h. On similar pieces of work, always try to use thesame number of strokes or passes.
i. End the last stroke in the same place on similarobjects.
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A-8.2. SPRAY GUN DISTANCE.
a. Keep the spray gun at the same distance from thework during application. The proper distance of thespray gun from the work varies with the spray patternand type of application. When the spray gun is close tothe surface being painted, it must be moved morerapidly to prevent runs and sags. For most processes,spray gun distance from the work should beapproximately 6-10 inches (see Figure A-8).
b. A full coat of paint through which most materialscannot be seen is called a full wet coat. For a wet, heavycoat, move the spray gun closer to the surface or movethe gun more slowly across the surface to increase thevolume of paint being applied.
c. A light coat of paint through which most materialscan be seen is called a mist coat. For a light film build orfor a mist coat, move the spray gun further away ormove the gun more quickly across the surface todecrease the volume of paint being applied.
A-8.3. SPRAY APPLICATION.
a. Hold the paint gun parallel to the work surface sothat the spray is always perpendicular to the surfacebeing painted (see Figure A-9).
b. Move the spray gun parallel to the surface tomaintain the same distance from the surface. Moveboth your arm and shoulder, along with the paint gun, toavoid "arcing" and tilting the spray gun (see Figures A-10,A-11, and A-12). Overlap approximately half of thepattern of the previous stroke.
c. Slow gun travel gives a wet, heavy film build; fastgun travel gives a light film build.
d. Trigger the spray gun after the stroke has beenstarted (see Figure A-13). Release the trigger beforethe end of the stroke. This reduces paint loss, preventsheavy build up of paint on the corners and edges ofwork, and prevents runs and drips at the beginning andend of the stroke. If the trigger is not completely pulled,only air will flow through the gun.
e. To achieve the desired film thickness, primerscan usually be applied in one spray coat; topcoatsusually require two coats with specific dry time betweencoats to allow proper solvent evaporation, film leveling,and curing properties. The second coat should beapplied in a cross coat to ensure adequate coverage(see Figure A-14). A paint thickness gauge should beused to check the actual film thickness. Manymanufacturers' primer products have different levels ofopacity when applied at the proper 0.6-0.9 mils dry filmthickness (DFT).
A-8.4. SPRAY PAINTING DEFECTS. During sprayapplication of paints, certain defects may appear on thefinish due to faulty application methods or poorapplication conditions. The most common defects,probable causes, and remedies are listed in Table A-4.
For spray touch-up processes, an exact color or glossmatch is extremely difficult to obtain and shall not beused as criteria for quality control. Slight orange peelthat does not affect operational conditions oraerodynamic smoothness (as defined in MIL-STD-7179)is also acceptable. If unacceptable defects in the paintfilm are found, repair the defects as follows:
a. For dried defective paint, scuff sand per paragraphA-7 and refinish in accordance with instructions providedin this section for the specific coating being used.
b. For wet, freshly painted surfaces, removedefective paint by wiping with a cloth dampened with anapproved solvent. In general, residue from polyurethanecoatings such as MIL-PRF-85285 and TT-P-2760 canbe removed using MIL-T-81772 Type I Thinner. Residue
from epoxy coatings such as MIL-PRF-22750 andMIL-PRF-23377 can be removed using MIL-T-81772Type II Thinner. Residue from waterborne coatingssuch as MIL-PRF-85582 can be removed using acombination of water and TT-I-735 (Isopropyl Alcohol).Consult the local Environmental Affairs Office forguidance on pertinent regulatory requirements.
A-8.5. BRUSH AND ROLLER APPLICATION. Brushor roller application of paint may be used when paintingsmall areas or when spray painting is not convenient orpermitted. The advantage of brush and roller applicationis that the paint does not become atomized and airborne,thus minimizing safety and health concerns.
A-8.5.1. Brush Application. Brush application shall belimited to small nicks, chips, or scratches. When brushing,the coating should be applied in one direction, thencross brushed to completely cover the area. Near theend of each stroke, the brush should be gradually liftedto prevent excessive roughness from brush marks. Thecoating material should be stirred frequently during useto avoid settling. A brush applied coat should be allowedto dry completely before applying subsequent coats.
A-8.5.2. Roller Application. In roller application, thecoating material should be placed in a paint tray havinga sloping bottom. The tray must be sized to accommodatethe roller and coating material. The roller is dipped intothe tray and rolled back and forth until it is coated.Excess material on the roller is removed by rolling outon the tray grid. The coating is applied by slowly rollingit back and forth across the surface until uniform coverageis obtained. Once a uniform coating is achieved, allowit to dry completely before applying additional coats.During roller application, adjacent strips should beoverlapped as in other methods of painting. Since theroller will not fit into corners or other tight areas, thesesurfaces may be coated using a brush before beginningthe roller application. The roller should follow the brushingpromptly to avoid lap marks. When applying paint byroller, several coats may be necessary to achieveadequate film thickness.
A-8.6. ADHESION TESTING. Adhesion testing maybe used for quality control of newly applied coatingswhen it is directed by aircraft/component specific manualor local directives, or when poor adhesion or poorsurface preparation is suspected. Adhesion testing canalso be used to evaluate quality characteristics of old/existing coatings. If the primer coat is the only coatapplied, then this test applies to the primer. If the primercoat is to be topcoated, then this test applies to the
topcoat only. This test is applicable to primed/paintedareas greater than 2 square feet in total area.
A-8.6.1. Wet Tape Adhesion Test. Allow the primer/paint to dry at least 48 hours before performing the tapetest. Use 4" X 4" square cut cheesecloth (CCC-C-440)layers to equal a pad 1/8" thick. Saturate the pad inwater and place it against the surface to be tested.Overlay a larger sheet of polyethylene (A-A-3174 Type IClass 1) over the wet pad and tape the edges down,using AMS-T-21595 Type I masking tape or equivalent.Mark the polyethylene sheet with the date and time.Allow 24 hours dwell time and then remove the cloth andwipe the area dry with clean, dry cheesecloth. Beforeone minute passes, apply a one inch wide by six incheslong piece of ASTM D6123 Type II flatback maskingtape (adhesive side down) across the test area. Ensurethat four inches of the tape covers the test area andtwo inches are left unattached for gripping purposes.Press the tape down in the test area with a firm handpressure (use of tape and decal applicator is alsoauthorized). Grip the two inch loose end of the tape andremove the tape in one abrupt motion.
A-8.6.2. Pass/Fail Criteria. If no paint/primer wasremoved, the adhesion test passed. If more than onesquare inch (total) of paint/primer was removed, the testfailed and the entire surface must be stripped andre-coated in accordance with this manual. If paint/primer was removed but the total area removed wasless than one square inch, then a retest must beperformed in accordance with the following paragraph.
NOTE
It may be more economical to strip and recoatrather than retest.
A-8.6.3. Retest of Failed Area Less Than One SquareInch. Perform three additional wet tape tests in adjacentareas to the failed area. All three tests must pass (nocoating removed). The coating is considered to havefailed adhesion requirements if any coating was removedin the three retests. If this is the case, the surface mustbe stripped and re-coated in accordance with thismanual. If no coating is removed in the retest, touch upthe removed coating from the first test and continueprocessing.
A-8.6.4. Adhesion Testing for Touch-up Areas. In orderto test for proper adhesion of small areas of touch-upcoating (less than two square feet, total), a dry tape testis authorized. Allow the coating (primer/paint) to dry for
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Figure A-16. Sempen Parts Breakdown
Figure A-15. Sempens (Touch-Up Paint Pens)
48 hours before testing. Apply a 1 inch wide by 6 incheslong piece of ASTM D6123 Type II flatback maskingtape across the touch-up area and proceed with the testas described in paragraph A-8.6.1. Any coating removaldefines a test failure. Strip and re-coat the touch-uparea in accordance with this manual.
A-9. TOUCH-UP OF SMALL AREAS (LESS THANTWO SQUARE FEET). The following paragraphsprovide instructions and guidelines for touch-up of smallareas using touch-up pens, aerosol sprays, and brushapplicators.
A-9.1. TOUCH-UP PEN (SEMPEN™). MIL-PRF-23377(Epoxy High Solids Primer), MIL-PRF-85582 (EpoxyWaterborne Primer), and MIL-PRF-85285 Type I(Polyurethane Coating) are available in touch-up pens(see Figure A-15). These self-contained touch-upapplicators are available by national stock numbers(refer to Volume IV for ordering information). Theapplicator is designed for convenient storage, mixing,and application of pre-measured two component coatingmaterials, and is ideal for touch-up of small areas wherespraying is impractical or not allowed. Each applicatorcontains 10 milliliters (1/3 fluid ounce) of material andwill cover an area of approximately 1 to 2 square feet.The two components are separated by a barrier (seeFigure A-16). The material is mixed and applied asfollows:
a. Before mixing, ensure the applicator is at roomtemperature. Read and follow manufacturer’sinformation, including MSDS, supplied with theapplicator.
b. Slide the collar all the way to the back of theapplicator to displace the barrier between the twocomponents.
c. With the brush cap in place, shake the applicatorvigorously by hand until the two components arethoroughly mixed (approximately one minute).
d. After mixing, remove the brush cap and press theapplicator against a scrap surface to bleed off anyinternal pressure that may have formed during storage.Make sure the applicator is not pointing toward anyone.
e. Depress the applicator brush against the worksurface. This opens the spring-loaded valve that allowsthe coating material to flow when the tube is gentlysqueezed. Use the brush to apply a uniform coating tothe surface. See Figure A-17.
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Figure A-17. Sempen Application
f. Replace the brush cap when the applicator is notbeing used. The useful pot life of the mixed material isapproximately 8 hours. Do not store the applicator in ashirt pocket or any other clothing article.
g. If a different size brush is required, followmanufacturer’s instructions for changing brushes.Change brushes only after the material in the applicatorhas been mixed.
WARNING
Prior to application, observe all safetyregulations and use proper personal protectiveequipment (PPE) such as gloves, eye protection,and respirator. Contact the local IndustrialHygiene Activity or Occupational Safety andHealth Office for guidance on the properselection of respiratory protection and otherpersonal safety requirements.
NOTE
Two component aerosols are not authorized forspraying large areas. These sprayers areintended only for small repairs of less than twosquare feet.
Do not remove red button or cap until product isused. Red button is required to activate theaerosol can.
A-9.2. TWO COMPONENT AEROSOL. Twocomponent aerosols provide spray gun performancefrom a can using approved coatings, such asMIL-PRF-23377 (Epoxy High Solids Primer) and MIL-PRF-85285 Type I (Polyurethane Coating). Theseaerosol cans are ideal for small touch-up processes asthey minimize many of the problems associated withhazardous waste disposal, equipment clean up, andrelated safety hazards. The aerosol can has a 48 hourpot life once mixed. Refer to Volume IV for the twocomponent aerosol can ordering information. Thematerial is mixed, applied, and cleaned as follows:
a. Remove red button from the cover cap and put iton the plastic pin at the bottom of the aerosol can.
b. Place can upright on a flat surface and push downcompletely on the red button to break the inner seal.After red button is removed, if done correctly, the plasticpin (at the bottom of the can) should move easily whenpushed with finger. Properly dispose of red button toavoid FOD.
c. Invert can and shake contents vigorously for twominutes to mix the catalyst and base materials. Allow 30minutes to elapse before use. Shake can prior to eachuse to insure complete mixing.
d. After proper surface preparation (refer toparagraph A-7), apply coating in a manner similar to thatused in conventional spray gun painting processes.Standing distance from surface should be 6 to 10 inches.Make full sweeps across and stop spraying at the endof each sweep.
e. Use an overlap stroke pattern for uniformapplication. Delivery of paint is faster than other aerosolsand the fan is larger. Rotate spray tip to select eithervertical or horizontal spray fan.
f. After use, invert aerosol can and spray until clear.This will keep the feed tube from clogging during nextuse.
g. The remainder of the can must be used within48 hours. After that time, the contents of the can will geland will no longer be sprayable.
h. Properly dispose of used paint cans in accordancewith local environmental regulations.
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NOTE
PreVal sprayers are not authorized for paintinglarge areas. These sprayers are intended onlyfor small, spot repairs.
A-9.3. PREVAL AEROSOL TOUCH-UP PAINTSYSTEMS. PreVal sprayers provide a simple methodof applying approved coatings for small, touch-upprocesses. These sprayers minimize many of theproblems associated with hazardous waste disposal,equipment cleanup, and related safety hazards. Manyof the commonly used primers and topcoats(MIL-PRF-23377, MIL-PRF-85582, MIL-PRF-85285Type I, and MIL-PRF-81352 Type III) are available insmall 2 ounce bottles that attach directly to the PreValsprayer. Refer to Volume IV for ordering information.
NOTE
Primers and topcoats in 2 ounce bottles mayalso be applied by brush for small, touch-upapplications.
A-9.3.1. PreVal Aerosol Touch-Up Primers. BothMIL-PRF-23377 and MIL-PRF-85582 Epoxy Primersare available in small 2 ounce kits that can attachdirectly to PreVal sprayers. These kits are supplied astwo part materials (catalyst and base components) thatmust be mixed prior to use. Follow manufacturer’sinstructions printed on the container label for propermixing procedures. See paragraph A-9.3.3 for additionalmixing and application instructions.
A-9.3.2. PreVal Aerosol Touch-Up Topcoats. BothMIL-PRF-85285 Type I polyurethane coating andMIL-PRF-81352 Type III one component aircrafttouch-up coating are available in small 2 ounce kits thatcan attach directly to PreVal sprayers.
a. MIL-PRF-85285 Type I topcoat kits are suppliedas two part materials (catalyst and base components)that must be mixed prior to use. Follow manufacturer’sinstructions printed on the container label for propermixing procedures. See paragraph A-9.3.3 for additionalmixing and application instructions.
b. MIL-PRF-81352 Type III is supplied as a singlecomponent topcoat that is ready to use. See paragraphA-9.3.4 for additional mixing and application instructions.
WARNING
The PreVal sprayer has an air vent on thecoupling. To avoid leakage and personal injury,never shake the sprayer once it has beenattached to the bottle. Eye protection and properprotective equipment are required whenhandling, mixing and applying coatings usingPreVal sprayers.
NOTE
To prevent leaking, do not tilt PreVal sprayersbeyond a 45 degree angle. Spray angles of45 degrees or less will ensure the properdischarge of coatings. During any continuousspray application, PreVal sprayers may "freezeup" and cause irregular spray patterns. Toavoid freezing up, limit each spray applicationto a pattern of 36 square inches (6" X 6"), thenpause and continue with spraying. Repeat asnecessary until repair area is properly coated.
A-9.3.3. Two Component Primer and Topcoat Mixingand Application Instructions.
a. Two component primers and topcoats must bemixed carefully prior to use. Follow manufacturer’sinstructions printed on the container label for propermixing procedures for base and catalyst components.Some vendors supply two separate bottles for the twocomponents, others supply the catalyst in a small internalbottle (as a bottle within a bottle) under the cap. Mixentire contents of each kit.
b. Replace cap on larger bottle and shake mixturethoroughly for two minutes. After shaking, allow coatingto rest for two minutes to dissipate any air bubbles.
c. Attach pick-up tube to the PreVal sprayer.
d. Remove cap from coating bottle and attachbottle to the PreVal sprayer. To prevent leakage, do notshake the bottle once it is attached to the PreValsprayer.
e. After proper surface preparation (refer toparagraph A-7), apply coating in a manner similar toconventional spray gun painting processes, making fullsweeps and stopping the spray at the end of eachsweep.
f. Clean PreVal sprayer after each use. Refer toparagraph A-9.3.5 for cleaning procedures.
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g. Properly dispose of empty PreVal sprayers andcoating bottles in accordance with local environmentalregulations.
A-9.3.4. One Component Topcoat Mixing andApplication Instructions.
a. With screw cap firmly attached, shake topcoatbottle thoroughly for two minutes. After shaking, allowcoating to rest for two minutes to dissipate any airbubbles.
b. Attach pick-up tube to the PreVal sprayer.
c. Remove cap from topcoat bottle and attachbottle to the PreVal sprayer. To prevent leakage, do notshake the bottle once it is attached to the PreValsprayer.
d. After proper surface preparation (refer toparagraph A-7), apply coating in a manner similar toconventional spray gun painting processes, making fullsweeps and stopping the spray at the end of eachsweep.
e. Clean PreVal sprayer after each use. Refer toparagraph A-9.3.5 for cleaning procedures.
f. Partially used one component topcoat bottlesmay be recapped and stored for later use.
g. Properly dispose of empty PreVal sprayers andcoating bottles in accordance with local environmentalregulations.
A-9.3.5. Cleaning of PreVal Sprayer. The PreValaerosol sprayer is a small, hand-held canister containingenough propellant to spray two, 2 ounce bottles ofprimer or topcoat, provided the sprayer is cleanedimmediately after each use. Clean as follows:
a. Remove the sprayer head from the coating bottle.
b. Cap and properly store the unused coating.Catalyzed, two part coatings have a limited pot life oncemixed. In general, these coatings must be used within4-8 hours after mixing.
c. Clean the sprayer head by placing the pick-uptube into a small amount of MIL-T-81772 or otherapproved cleaning solvent. When using a waterbornecoating (e.g. MIL-PRF-85582 Epoxy WaterbornePrimer), remove residual material with deionized ordistilled water first, followed by rinsing with TT-I-735
Isopropyl Alcohol. Spray just enough cleaner throughthe sprayer to disperse the remaining coating materialand produce a clear spray pattern. Alternatively, cleanthe pick-up tube by hand with cleaning solvent, theninvert the sprayer head and depress button to clear thesprayer.
A-9.4. ONE OUNCE PAINT BRUSH TOUCH-UPAPPLICATOR. TT-P-1757 (Alkyd Base Primer) andMIL-PRF-81352 Type III (Aircraft Touch-Up Coating)are available in small, one ounce brush-top bottles(similar to "White-Out" bottles). These materials areappropriate for very small touch-up processes that canusually be done concurrently with other maintenanceoperations. Consult the local Industrial Hygiene Activityor Occupational Safety and Health Office for detailedsafety requirements.
WARNING
Appropriate safety precautions must be takenwhen working with coating materials. Refer toparagraph A-2 for additional safety information.Consult the local Industrial Hygiene Activity orOccupational Safety and Health Office fordetailed safety requirements.
A-10. SPECIFIC PAINT APPLICATIONPROCEDURES. The following are instructions andguidelines for specific materials, primers, topcoats, andcommonly used specialty coatings.
A-10.1. AIRCRAFT PAINT THINNER (MIL-T-81772).This specification covers three types of paint thinnerscompatible with various coating materials. Due tochemical incompatibility, no single paint thinner isacceptable for all types of coatings. Environmentalregulations restrict the amount of thinner that can beadded to aircraft coatings. Fortunately, newer coatingsand application technologies do not usually requireadditional thinner. As stated in paragraph A-4.1.1, aircraftcoatings must meet strict VOC requirements. Do notadd thinner to coatings unless specifically indicated onthe container label or on manufacturer’s literaturesupplied with the material. MIL-T-81772 Thinner isavailable in the following types:
a. Type I – Polyurethane coating thinner;
b. Type II – Epoxy coating thinner; and
c. Type III – Acrylic and alkyd coating thinner.
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A-10.2. EPOXY HIGH SOLIDS PRIMER(MIL-PRF-23377).
A-10.2.1. Description. MIL-PRF-23377 is a VOCcompliant (340 g/l maximum) epoxy high solids primerwith corrosion inhibitors. This specification covers twotypes and three classes of materials. Type I, Class C1or C2, is the standard yellow or light green primer usedprimarily in high gloss paint systems and on interiorcomponents and surfaces. Type II, Class C1 or C2, isthe dark green low infrared reflective primer used intactical paint schemes on exterior surfaces. Each typeis available in three classes: Class C1 (barium chromatebased corrosion inhibitor), Class C2 (strontium chromatebased corrosion inhibitor), and Class N (non-chromatebased corrosion inhibitor). Class N materials, especiallyType I, may be a variety of colors, such as white, tan,blue, black, or bright green. They will not have the samecoloration as Type I, Class C1 or C2 materials. Consultspecific maintenance instructions for guidance on theselection of primers for each weapons system. ClassC1 shall be selected when no class is specified. ClassN shall not be substituted for Class C1 or C2 unlessauthorization for its use is given by the engineeringauthority for the system or item to which the primercoating is to be applied. These primers can be appliedto properly treated metal surfaces and to cured, scuffsanded primers and topcoats. They dry to durable,chemical resistant films and offer excellent protectionagainst corrosion, particularly when coupled with acompatible topcoat.
A-10.2.2. Temperature Requirements. Ensure thetemperature for each primer component is between60°F and 90°F before mixing and application. Surfacetemperature of the area to be coated must be between50°F and 95°F. Do not apply this material if the ambienttemperature is below 50°F.
A-10.2.3. Material Preparation. MIL-PRF-23377 primeris supplied as a two component kit. The two componentsmust be mixed together in the proper proportions priorto use. One component contains the pigment within anepoxy vehicle, while the other component contains theresin solution. These components are packagedseparately and have excellent storage stability. Oncemixed, however, the two components undergo achemical reaction to achieve proper film characteristics.Over a few hours, the coating will gel and hardenregardless of whether or not it is exposed to air. Pot lifeis a measure of the length of time a catalyzed coatingremains useful for application. In general, the pot life ofepoxy primer is 4 hours. During hot or humid conditions,the pot life will decrease. Only mix the amount of
material that can be used within two hours. Do not addthinner to attempt to compensate for thickened coatingsthat are beyond useful pot life. Mix the primer as follows:
a. Mix the pigmented component thoroughly toensure that the solids are completely dispersed. Use apaint shaker for approximately 10 minutes if possible. Ifa paint shaker is not available, use a clean metal orwooden paddle to stir the contents. After mixing, checkthe bottom of the container to ensure that all of thepigment is dispersed.
b. Pour the pigmented component into a clean,empty container. The empty container must be at leasttwo times the capacity of the pigmented component.
CAUTION
Only mix materials from the same manufacturer.Never mix materials from differentmanufacturers. Mix the two components in thevolume ratio specified by the manufacturer.Refer to the container label.
c. Pour the required amount of resin componentslowly into the container with the pigmented component.Stir thoroughly with a metal or wooden paddle. Toremain compliant with environmental regulations, donot add thinner to this material unless specificallyrequired by the manufacturer’s instructions.
A-10.2.4. Spray Application. After the primer isthoroughly stirred, strain the material through adisposable paint strainer to remove coarse particles.Prior to spraying, allow the mixed primer to stand forapproximately 30 minutes. This induction period isnecessary to allow components to partially react. Spraythe mixed primer in accordance with paragraph A-8.
A-10.2.5. Brush or Roller Application. For brush orroller application, strain the primer and allow it to standfor 30 minutes as per paragraph A-10.2.4. Apply theprimer uniformly to the surface in one coat (refer toparagraph A-8.5).
A-10.2.6. Touch-Up Pen Application. For convenienttouch-up of small areas, MIL-PRF-23377 Epoxy Primeris available in touch-up pens. Refer to paragraph A-9.1.
A-10.2.7. Aerosol Application. For convenient touch-upof small areas less than two square feet, MIL-PRF-23377Epoxy Primer is available in aerosol containers. Referto paragraphs A-9.2 and A-9.3.
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A-10.2.8. Film Thickness. The total dry film thickness ofprimer shall be 0.6 to 0.9 mils (0.0006 to 0.0009 inch)which is slightly more than a mist coat. After the coatinghas dried, the substrate should be barely visible throughthe film. Dry film thickness can be estimated using a wetfilm thickness gage (refer to paragraph A-5.7). Dry filmthickness will be approximately 50 percent of the wetfilm thickness. Primer thickness shall be doubled if notopcoat is to be applied.
A-10.2.9. Drying Time. Tack-free drying time ofMIL-PRF-23377 primer depends upon the temperature,but is generally between 30 minutes and 2 hours.Tack-free means that the coating can be touched lightlywith the fingertip without noticeable tackiness. Do notapply topcoat until the primer is tack-free. At this stageof drying, the primer is not completely cured and can beeasily marred. MIL-PRF-23377 primer will dry hard inapproximately 8 hours at 70°F, which means the coatingis fairly durable and can be handled. The primer driesmore slowly at lower temperatures. Topcoat is generallyapplied within 24 hours after primer application.
A-10.2.9.1. If the primer has dried for over 24 hours butnot longer than 7 days, proceed as follows:
a. Clean the surface by wiping with clean cheeseclothdampened with an approved solvent (see paragraphA-7.4).
b. Apply a thin (mist) coat of MIL-PRF-23377 epoxyprimer.
c. Allow primer to dry tack-free and then apply thespecified topcoat.
A-10.2.9.2. If the primer has dried longer than 7 days,it must be lightly scuff sanded prior to proceeding withparagraph A-10.2.9.1, to ensure proper adhesion.
A-10.3. EPOXY WATERBORNE PRIMER(MIL-PRF-85582).
A-10.3.1. Description. MIL-PRF-85582 is a VOCcompliant (340 g/l maximum) waterborne epoxy primerwith corrosion inhibitors. This specification covers twotypes and three classes of materials. Type I, Class C1or C2, is the standard yellow or light green primer usedprimarily in high gloss paint systems and on interiorcomponents and surfaces. Type II, Class C1 or C2, isthe dark green, low infrared reflective primer used intactical paint schemes or exterior surfaces. Each type isavailable in three classes: Class C1 (barium chromatebased corrosion inhibitor), Class C2 (strontium chromate
based corrosion inhibitor), and Class N (non-chromatebased corrosion inhibitor). Class N materials, especiallyType I, may be a variety of colors, such as white, tan,blue, black, or bright green. They will not have the samecoloration as Type I, Class C1 or C2 materials. Consultspecific maintenance instructions for guidance on theselection of primers for each weapons system. ClassC1 shall be selected when no class is specified. ClassN shall not be substituted for Class C1 or C2 unlessauthorization for its use is given by the engineeringauthority for the system or item to which the primercoating is to be applied. These primers can be appliedto properly treated metal surfaces and to cured, scuffsanded primers and topcoats. They dry to durable,chemical resistant films and offer excellent protectionagainst corrosion, particularly when coupled with acompatible topcoat.
A-10.3.2. Material Compatibility. MIL-PRF-85582 epoxywaterborne primer is generally interchangeable withMIL-PRF-23377 epoxy high solids primer for mostapplications. Since MIL-PRF-85582 primer containswater, to prevent possible corrosion it shall not be usedfor wet installations (refer to paragraph A-4.8) or fordirect application to bare steel (e.g. landing gearcomponents).
A-10.3.3. Temperature Requirements. Ensure thetemperature for each primer component is between60°F and 90°F before mixing and application. Surfacetemperature of the area to be coated must be between55°F and 95°F. Do not apply this material if the ambienttemperature is below 55°F.
A-10.3.4. Material Preparation. MIL-PRF-85582 primeris supplied as a two component kit. The two componentsmust be mixed together in the proper proportions priorto use. Distilled or deionized water is also required inmost cases as an additional component. One componentcontains the pigment within an epoxy vehicle, while theother component contains the clear resin solution. Thesecomponents are packaged separately and have excellentstorage stability. Once mixed, however, the twocomponents undergo a chemical reaction to achieveproper film characteristics. Over a few hours, the coatingwill gel regardless of whether or not it is exposed to air.Pot life is a measure of the length of time a catalyzedcoating remains useful for application. In general, thepot life of epoxy waterborne primer is 4 hours. Duringhot or humid conditions, the pot life will decrease. Onlymix the amount of material that can be used within twohours. Do not add thinner or water to attempt tocompensate for thickened coatings that are beyonduseful pot life. Mix the primer as follows:
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a. Consult manufacturer’s instructions printed onthe container label for proper mixing procedures. Ifdistilled or deionized water is specified, do not add tapwater. Tap water will have an adverse affect on filmproperties. Only add the specified amount of water. Donot add excess water.
CAUTION
Only mix materials from the same manufacturer.Never mix materials from differentmanufacturers. Mix the two components in thevolume ratio specified by the manufacturer.Refer to the container label.
b. Following manufacturer’s instructions, mix thecomponents as necessary to ensure that solids arecompletely dispersed. If using a paint shaker, do notexceed manufacturer’s specified agitation time sinceexcessive shaking can cause the coating to gelprematurely. If no shake time is specified, agitate thematerial for 10 minutes maximum. If a paint shaker isnot available, use a clean metal or wooden paddle to stirthe contents. After mixing, check the bottom of thecontainer to ensure that all solids are dispersed.
A-10.3.5. Spray Application. After the primer is mixedper manufacturer’s instructions, strain the materialthrough a disposable paint strainer to remove coarseparticles. No induction time is necessary prior to sprayingthis primer. Spray the mixed primer in accordance withparagraph A-8.
A-10.3.6. Brush or Roller Application. For brush orroller application, strain the primer and apply it uniformlyto the surface in one coat (refer to paragraph A-8.5).
A-10.3.7. Touch-Up Pen Application. For convenienttouch-up of small areas, MIL-PRF-85582 EpoxyWaterborne Primer is available in touch-up pens. Referto paragraph A-9.1.
A-10.3.8. Aerosol Application. For convenient touch-upof small areas, MIL-PRF-85582 Epoxy WaterbornePrimer is available in aerosol containers. Refer toparagraph A-9.3.
A-10.3.9. Film Thickness. The total dry film thickness ofthe sprayed primer shall be 0.6 to 0.9 mils (0.0006 to0.0009 inch) which is slightly more than a mist coat.After the coating has dried, the substrate should bebarely visible through the film. Dry film thickness can beestimated using a wet film thickness gage (refer toparagraph A-5.7). Dry fi lm thickness will be
approximately 50 percent of the wet film thickness.Primer thickness shall be doubled if no topcoat is to beapplied.
A-10.3.10. Drying Time. Tack-free drying time ofMIL-PRF-85582 primer depends upon temperature andhumidity, but is generally 1 to 2 hours. At 70°F and 50%relative humidity, the primer will be tack-free in 1 hour.Tack-free means that the coating can be touched lightlywith the fingertip without noticeable tackiness. Do notapply topcoat until the primer is tack-free. At this stageof drying, the primer is not completely cured and can beeasily marred. MIL-PRF-85582 primer will dry hard inapproximately 6 hours at 70°F, which means the coatingis fairly durable and can be handled. The primer driesmore slowly at lower temperatures and higher humidity.Topcoat is generally applied within 24 hours after primerapplication.
A-10.3.10.1. If the primer has dried for over 24 hoursbut not longer than 7 days, proceed as follows:
a. Clean the surface by wiping with clean cheeseclothdampened with an approved solvent (see paragraphA-7.4).
b. Apply a thin (mist) coat of MIL-PRF-85582 epoxyprimer.
c. Allow primer to dry tack-free and then apply thespecified topcoat.
A-10.3.10.2. If the primer has dried longer than 7 days,it must be lightly scuff sanded prior to proceeding withparagraph A-10.3.10.1, to ensure proper adhesion.
A-10.4. POLYURETHANE, ELASTOMERIC, HIGHSOLIDS PRIMER (TT-P-2760).
A-10.4.1. Description. TT-P-2760 is a VOC compliant(340 g/l maximum) flexible polyurethane primer withcorrosion inhibitors. This material is designed for usewherever high flexibility is required. This specificationcovers two types and two classes of materials. Type I isthe standard primer used primarily with high gloss paintsystems. Type I primer is the natural color of thecorrosion inhibiting pigments used. Type II is the darkgreen, low infrared reflective primer used with tacticalpaint schemes. Each type is available in two classes:Class C (strontium chromate based corrosion inhibitor)and Class N (non-chromate based corrosion inhibitor).Consult specific maintenance instructions for guidanceon the selection of primers for each weapons system.Class C shall be selected when no class is specified.
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Class N shall not be substituted for Class C unlessauthorization for its use is given by the engineeringauthority for the system or item to which the primercoating is to be applied. These primers can be appliedto properly treated metal surfaces and to cured, scuffsanded primers and topcoats. They dry to flexible,chemical resistant films and are usually coupled withMIL-PRF-85285 Polyurethane Topcoat.
A-10.4.2. Temperature Requirements. Ensure thetemperature for each primer component is between60°F and 90°F before mixing and application. Surfacetemperature of the area to be coated must be between60°F and 90°F. Do not apply this material if the ambienttemperature is below 60°F.
A-10.4.3. Material Preparation. TT-P-2760 primer issupplied as a two component kit. The two componentsmust be mixed together in the proper proportions priorto use. One component contains the pigment within avehicle, while the other component contains the clearresin solution. These components are packagedseparately and have excellent storage stability. Oncemixed, however, the two components undergo achemical reaction to achieve proper film characteristics.Over a few hours, the coating will gel regardless ofwhether or not it is exposed to air. Pot life is a measureof the length of time a catalyzed coating remains usefulfor application. In general, the pot life of this primer is 4hours. During hot or humid conditions, the pot life willdecrease. Only mix the amount of material that can beused within two hours. Do not add thinner to attempt tocompensate for thickened coatings that are beyonduseful pot life. Mix the primer as follows:
a. Following manufacturer’s instructions, mix thepigmented component as necessary to ensure thatsolids are completely dispersed. If using a paint shaker,agitate the material for approximately 10 minutes. If apaint shaker is not available, use a clean metal orwooden paddle to stir the contents. After mixing, checkthe bottom of the container to ensure that all solids aredispersed.
b. Pour the pigmented component into a clean,empty container. The empty container must be at leasttwo times the capacity of the pigmented component.
CAUTION
Only mix materials from the same manufacturer.Never mix materials from differentmanufacturers. Mix the two components in thevolume ratio specified by the manufacturer.Refer to the container label.
c. Pour the required amount of clear resin componentslowly into the container with the pigmented component.Stir thoroughly with a metal or wooden paddle. Toremain compliant with environmental regulations, donot add thinner to this material unless specificallyrequired per manufacturer’s instructions.
A-10.4.4. Spray Application. After the primer is mixedper manufacturer’s instructions, strain the materialthrough a disposable paint strainer to remove coarseparticles. No induction time is necessary prior to sprayingthis primer. Spray the mixed primer in one wet crosscoat in accordance with paragraph A-8.
A-10.4.5. Brush or Roller Application. For brush orroller application, strain the primer and apply it uniformlyto the surface in one coat (refer to paragraph A-8.5).
A-10.4.6. Film Thickness. The total dry film thickness ofprimer shall be 1.5 to 2.0 mils (0.0015 to 0.0020 inch).After the coating has dried, the substrate will not bevisible through the film. Dry film thickness can beestimated using a wet film thickness gage (refer toparagraph A-5.7). Dry fi lm thickness will beapproximately 50 percent of the wet film thickness.
A-10.4.7. Drying Time. Tack-free drying time ofTT-P-2760 primer depends upon temperature andhumidity, but will generally be within 5 hours. Tack-freemeans that the coating can be touched lightly with thefingertip without noticeable tackiness. Do not applytopcoat until the primer is tack-free. TT-P-2760 primerwill be dry hard in approximately 8 hours at 70°F, whichmeans the coating is fairly durable and can be handled.The primer dries more slowly at lower temperatures.Topcoat is generally applied between primer tack-freetime and 24 hours after primer application.
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A-10.4.7.1. If the primer has dried for over 24 hours butnot longer than 7 days, proceed as follows:
a. Clean the surface by wiping with clean cheeseclothdampened with an approved solvent (see paragraphA-7.4).
b. Apply a thin (mist) coat of TT-P-2760 primer.
c. Allow primer to dry tack-free and then apply thespecified topcoat.
A-10.4.7.2. If the primer has dried longer than 7 days,it must be lightly scuff sanded prior to proceeding withparagraph A-10.4.7.1, to ensure proper adhesion.
A-10.5.1.1. MIL-PRF-85285 Type I, PolyurethaneCoating is a VOC compliant (420 g/l maximum) topcoat.This specification covers three types of materials. Type Iis intended for aircraft use. Type II is intended for use onground support equipment (GSE) and is not for use onaircraft surfaces. Type III is a low VOC (50 g/l) coatingintended for use on both aircraft and GSE. Type III shallnot be substituted for Type I or Type II withoutauthorization from the aircraft engineering authority.Type I material is available in gloss, semigloss, and flat(lusterless) colors. It is intended for use over properlyapplied primers conforming to MIL-PRF-23377,MIL-PRF-85582, or TT-P-2760. The resulting paintsystem is durable, flexible, weather resistant, corrosionresistant, and chemical resistant.
A-10.5.1.2. Self-Priming Topcoat, TT-P-2756, is nolonger approved for use on Navy aircraft or equipment.
A-10.5.2. Safety Requirements for PolyurethaneCoatings Containing Free Isocyanates. Somepolyurethane coatings used on Navy and Marine Corpsaircraft, such as MIL-PRF-85285, require specialhandling during mixing, application, and curing to avoidexposure to free isocyanate vapors. Adequate ventilationand approved respiratory protection are mandatory.Polyurethane coatings generally present no specialhealth hazards when cured (dried), however,isocyanates are an integral part of the polyurethanereaction and can be released while the coating is stillwet. Isocyanate vapors, even in very smallconcentrations, can produce significant irritation of theskin, eyes, and respiratory tract and may also induce
allergic sensitization of personnel. Specific details areprovided in OPNAVINST 5100.23.
A-10.5.2.1. Sensitization. Isocyanate sensitization ischaracterized by bronchial constriction, causing difficultyin breathing, dry cough, and shortness of breath.Individual susceptibility appears to be a controllingfactor. Once sensitized, many personnel cannot tolerateeven minimal subsequent exposure to isocyanates,and must thereafter avoid work areas where suchexposure could occur. In addition, solvents employedwith polyurethane coatings tend to increase the rate ofabsorption and severity of the physiological effect.
A-10.5.2.2. Medical Examinations. All personnelassigned duties involving the mixing and application ofpolyurethane coatings that contain free isocyanatesshall receive a baseline medical examination followingthe guidance of the current edition of theNAVENVIRHLTHCEN Medical Surveillance ProceduresManual to include the protocols for mixed solvents andisocyanates. Periodic medical examinations are requiredif the results of the industrial hygiene survey recommendthem.
A-10.5.2.3. Protective Clothing. Protective clothinglisted shall not be substituted without specific approvalby the local industrial hygienist. Personnel applyingpolyurethane coating that contains free isocyanatesshall wear gloves (MIL-G-12223 or meeting OSHArequirements), chemical or splash-proof goggles,coveralls (A-A-55196 or MIL-C-2202) and respiratoryprotection as specified by the local Industrial Hygieneactivity. When this polyurethane coating is applied inconfined spaces (i.e., intake ducts), contact the localIndustrial Hygiene activity for guidance on properrespiratory protection. Consult OPNAVINST 5100.23for further information.
NOTE
Personnel wearing respirators are required toreceive initial and annual fit testing.
A-10.5.2.4. Unprotected Personnel. The hangar areashall be cordoned off during paint application to preventexposure to unprotected personnel. Safe distances forunprotected personnel, as determined by the localIndustrial Hygiene activity, must be maintained at alltimes.
A-10.5.2.5. Facility Requirements. Polyurethanepainting operations employing free isocyanates shallbe conducted in an area which has received a workplace
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evaluation by the local Industrial Hygiene activity. Thisarea shall be sufficiently isolated to prevent exposure tounprotected personnel, as described above.Intermediate maintenance activity production-type spraypainting operations or squadron paint touch-upoperations employing paint spray equipment shall beconducted only in well ventilated areas approved by thelocal Industrial Hygiene activity and in accordance withpertinent environmental regulations. Routine IndustrialHygiene evaluations must be obtained by contactingthe Occupational Health Office or Medical Clinic. Eachfacility will maintain a hard copy of the initial and periodicindustrial hygiene evaluation. Refer to OPNAVINST5100.23 for frequency of Industrial Hygiene Evaluations/Surveys.
A-10.5.3. Temperature and Humidity Requirements.Extreme temperature and humidity conditions willadversely affect film-forming properties of polyurethanetopcoats. Ensure the temperature for each coatingcomponent is between 60°F and 90°F before mixingand application. Surface temperature of the area to becoated must be between 60°F and 90°F. For bestresults, apply this material only when the ambienttemperature is between 60°F and 90°F, and relativehumidity is between 30 and 75 percent. Temperatureand relative humidity can be obtained using a slingpsychrometer (Volume IV). If applied when temperatureor humidity is low, the coating will not properly cure. Ifapplied when temperature or humidity is high, thecoating will dry too fast and exhibit pinholes,microblisters, or hazing in gloss films, and gloss variation(streaking) in lusterless films.
A-10.5.4. Material Preparation. MIL-PRF-85285 topcoatis supplied as a two component kit. The two componentsmust be mixed together in the proper proportions priorto use. One component contains the pigment within apolyurethane vehicle, while the other componentcontains the clear resin solution. These componentsare packaged separately and have excellent storagestability. Once mixed, however, the two componentsundergo a chemical reaction to achieve proper filmcharacteristics. Over a few hours, the coating will geland harden regardless of whether or not it is exposed toair. Pot life is a measure of the length of time a catalyzedcoating remains useful for application. In general, thepot life of polyurethane topcoat is 4 hours. During hot orhumid conditions, the pot life will decrease. Only mix theamount of material that can be used within two hours.Do not add thinner to attempt to compensate forthickened coatings that are beyond useful pot life. Mixthe topcoat as follows:
a. Mix the pigmented component thoroughly toensure that the solids are completely dispersed. Use apaint shaker for approximately 10 minutes if possible. Ifa paint shaker is not available, use a clean metal orwooden paddle to stir the contents. After mixing, checkthe bottom of the container to ensure that all of thepigment is dispersed.
b. Pour the pigmented component into a clean,empty container. The empty container must be at leasttwo times the capacity of the pigmented component.
CAUTION
Only mix materials from the same manufacturer.Never mix materials from differentmanufacturers. Mix the two components in thevolume ratio specified by the manufacturer.Refer to the container label.
c. Pour the required amount of clear resin componentslowly into the container with the pigmented component.Stir thoroughly with a metal or wooden paddle. Toremain compliant with environmental regulations, donot add thinner to this material unless specificallyrequired per manufacturer’s instructions.
A-10.5.5. Spray Application. After the topcoat isthoroughly stirred, strain the material through adisposable paint strainer to remove coarse particles.After mixing and straining, the material is ready forapplication. No induction time is required. Spray themixed topcoat in accordance with paragraph A-8. Twocoats are necessary to achieve adequate film thickness.The first coat shall be a light (mist) coat. Allow the firstcoat to set for 30 to 60 minutes before applying thesecond coat to permit solvent evaporation. The secondcoat shall be a full wet coat to achieve the desired filmthickness (refer to paragraph A-10.5.9). ApplyMIL-PRF-85285 topcoat within 24 hours of primerapplication.
A-10.5.5.1. If the primer has been allowed to dry longerthan 24 hours but not more than 7 days, proceed asfollows:
a. Clean the surface by wiping with clean cheeseclothdampened with an approved solvent (see paragraphA-7.4).
b. Apply a thin (mist) coat of MIL-PRF-23377 orMIL-PRF-85582 epoxy primer.
c. Allow primer to dry tack-free and then apply thespecified topcoat.
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A-10.5.5.2. If the primer has dried longer than 7 days,it must be lightly scuff sanded prior to proceeding withparagraph A-10.5.5.1, to ensure proper adhesion.
A-10.5.6. Brush or Roller Application. For brush orroller application, strain the topcoat per paragraphA-10.5.5. Apply one uniform coat to the surface (refer toparagraph A-8.5) and allow it to dry tack-free beforeapplying an additional coat (if needed) to achieve thedesired thickness.
A-10.5.7. Touch-Up Pen Application. For convenienttouch-up of small areas, MIL-PRF-85285 PolyurethaneCoating is available in touch-up pens. Refer to paragraphA-9.1.
A-10.5.8. Aerosol Application. For convenient touch-upof small areas less than two square feet, MIL-PRF-85285Polyurethane Coating is available in aerosol containers.Refer to paragraphs A-9.2 and A-9.3.
A-10.5.9. Film Thickness. The total dry film thickness ofMIL-PRF-85285 topcoat shall be 1.7 to 2.3 mils (0.0017to 0.0023 inches). Dry film thickness can be estimatedusing a wet film thickness gage (refer to paragraphA-5.7). Dry film thickness will be approximately 50percent of the wet film thickness.
A-10.5.10. Drying Time. Tack-free drying time ofMIL-PRF-85285 topcoat depends upon the temperature,but is approximately 4 hours at 70°F. Tack-free meansthat the coating can be touched lightly with the fingertipwithout noticeable tackiness. At this stage of drying, thecoating is not completely cured and can be easilymarred. The topcoat will dry hard in approximately 12hours at 70°F, which means the coating is fairly durableand can be handled. The coating dries more slowly atlower temperatures. Complete coating system curerequires approximately 7 days. In general, the aircraftshall be handled and taxied as little as possible duringthe first week after painting of exterior surfaces.
A-10.6. EPOXY HIGH SOLIDS COATING(MIL-PRF-22750).
A-10.6.1. Description. MIL-PRF-22750 epoxy topcoatis a VOC compliant (340 g/l maximum) high solidscoating suitable as an alternate touch-up material whenpolyurethane topcoats are not available or cannot beused. This topcoat has excellent chemical resistance,however, it is not as flexible as polyurethane topcoatand will chalk when exposed to sunlight. Exact colormatching of epoxy topcoat to polyurethane topcoat isusually poor and is aggravated by the tendency of
epoxy topcoat to chalk. MIL-PRF-22750 epoxy topcoatcan be applied over primers conforming toMIL-PRF-23377, MIL-PRF-85582, and TT-P-2760.
A-10.6.2. Temperature Requirements. Ensure thetemperature for each coating component is between60°F and 90°F before mixing and application. Surfacetemperature of the area to be coated must be between50°F and 95°F. Do not apply this material if the ambienttemperature is below 50°F.
A-10.6.3. Material Preparation. MIL-PRF-22750 topcoatis supplied as a two component kit. The two componentsmust be mixed together in the proper proportions priorto use. One component contains the pigment within anepoxy vehicle, while the other component contains theclear resin solution. These components are packagedseparately and have excellent storage stability. Oncemixed, however, the two components undergo achemical reaction to achieve proper film characteristics.Over a few hours, the coating will gel and hardenregardless of whether or not it is exposed to air. Pot lifeis a measure of the length of time a catalyzed coatingremains useful for application. In general, the pot life ofepoxy topcoat is 4 hours. During hot or humid conditions,the pot life will decrease. Only mix the amount ofmaterial that can be used within two hours. Do not addthinner to attempt to compensate for thickened coatingsthat are beyond useful pot life. Mix the topcoat asfollows:
a. Mix the pigmented component thoroughly toensure that the solids are completely dispersed. Use apaint shaker for approximately 10 minutes if possible. Ifa paint shaker is not available, use a clean metal orwooden paddle to stir the contents. After mixing, checkthe bottom of the container to ensure that all of thepigment is dispersed.
b. Pour the pigmented component into a clean,empty container. The empty container must be at leasttwo times the capacity of the pigmented component.
CAUTION
Only mix materials from the same manufacturer.Never mix materials from differentmanufacturers. Mix the two components in thevolume ratio specified by the manufacturer.Refer to the container label.
c. Pour the required amount of clear resin componentslowly into the container with the pigmented component.Stir thoroughly with a metal or wooden paddle. To
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remain compliant with environmental regulations, donot add thinner to this material unless specificallyrequired per manufacturer’s instructions.
A-10.6.4. Spray Application. After the epoxy topcoat isthoroughly stirred, strain the material through adisposable paint strainer to remove coarse particles.Prior to spraying, allow the mixed topcoat to stand forapproximately 30 minutes. This induction period isnecessary to allow components to partially react. Spraythe mixed topcoat in accordance with paragraph A-8. Toachieve the desired film thickness, two coats are usuallyrequired. The first coat shall be a light (mist) coat. Allowthe first coat to set for 30 to 60 minutes before applyingthe second coat to permit solvent evaporation. Thesecond coat shall be a full wet coat to achieve thedesired film thickness. Refer to paragraph A-10.6.6.Apply the epoxy topcoat within 24 hours of primerapplication.
A-10.6.4.1. If the primer has been allowed to dry longerthan 24 hours but not more than 7 days, proceed asfollows:
a. Clean the surface by wiping with clean cheeseclothdampened with an approved solvent (see paragraphA-7.4).
b. Apply a thin (mist) coat of MIL-PRF-23377 orMIL-PRF-85582 epoxy primer.
c. Allow primer to dry tack-free and then apply theepoxy topcoat.
A-10.6.4.2. If the primer has dried longer than 7 days,it must be lightly scuff sanded prior to proceeding withparagraph A-10.6.4.1, to ensure proper adhesion.
A-10.6.5. Brush or Roller Application. For brush orroller application, strain the epoxy topcoat and allow itto stand for 30 minutes as per paragraph A-10.6.4.Apply one uniform coat to the surface (refer to paragraphA-8.5) and allow it to dry tack-free before applying anadditional coat to achieve the desired film thickness.
A-10.6.6. Film Thickness. The total dry film thickness ofepoxy topcoat shall be 1.7 to 2.3 mils (0.0017 to 0.0023inch). Dry film thickness can be estimated using a wetfilm thickness gage (refer to paragraph A-5.7). Dry filmthickness will be approximately 50 percent of the wetfilm thickness.
A-10.6.7. Drying Time. Tack-free drying time ofMIL-PRF-22750 topcoat depends upon the temperature,
but is generally between 2 and 6 hours. At 70°F, thematerial will be tack-free in less than 5 hours. Tack-freemeans that the coating can be touched lightly with thefingertip without noticeable tackiness. At this stage ofdrying, the coating is not completely cured and can beeasily marred. MIL-PRF-22750 Epoxy Topcoat will dryhard in approximately 8 hours at 70°F, which means thecoating is fairly durable and can be handled. Epoxytopcoat dries more slowly at lower temperatures.
A-10.7. AIRCRAFT TOUCH-UP COATING(MIL-PRF-81352 TYPE I).
A-10.7.1. Description. MIL-PRF-81352 Type I is a VOCcompliant (340 g/l maximum) acrylic lacquer coatingthat can be used for application of temporary markings/MODEX. Lacquer coatings dry by solvent evaporation.These coatings are easily applied; however, they arenot very durable and are not resistant to operationalfluids and some cleaning compounds. For application ofmarkings, lacquer is generally applied over clean, lightlyscuff sanded topcoats. In areas where lacquer is notpermitted, use MIL-PRF-85285 Type I polyurethanetopcoat or MIL-PRF-22750 epoxy topcoat. Lacquercoatings do not provide sufficient durability for use as atouch-up material for conventional coatings.
A-10.7.2. Material Preparation. MIL-PRF-81352 Type Iacrylic lacquer is available in quart, gallon, and aerosol(pint) containers. Quarts and gallons should bethoroughly mixed, using a paint shaker if possible, tocompletely disperse the solids. Refer to manufacturer’sinstructions for obtaining the appropriate spray viscosity.
A-10.7.3. Spray Application. Dry film thickness oflacquer shall be 1.5 to 2.0 mils (0.0015 to 0.0020 inches),which can be obtained by applying two wet coats. Allowapproximately 15 minutes dry time between coats. Theunderlying paint coating should not be visible throughthe dried film. These coatings will dry hard within twohours.
A-10.7.4. Brush and Roller Application. Application oflacquer by brush or roller is not recommended but canbe used when spray application is not permitted.
A-10.8. SPECIALTY COATINGS. Many aircraft requirethe use of specialty coatings for operational or functionalrequirements beyond the scope of standard primer/topcoat paint systems. Specialty coatings include RainErosion Resistant Coating, Teflon Filled Anti-chafeCoating, Electrically Conductive Coating, Non-slipWalkway Coating, and Heat Resistant Coating. Refer tospecific maintenance instructions for coating
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requirements applicable to individual weapons systems.Some of the more common specialty coatings aredescribed below.
A-10.8.1. Rain Erosion Resistant Coatings(AMS-C-83231 and MIL-PRF-85322). Antistatic rainerosion resistant coatings are two component, roomtemperature curing polyurethane elastomer coatings.They are designed to protect fiber-reinforced plasticsurfaces (e.g. radomes, antennas, and leading edges)from rain impact at high speed while preventing staticcharge buildup. Many of these materials consist ofpolyurethane resins and, therefore, may pose healthrisks due to isocyanates. As stated in paragraph A-10.5.2,free isocyanate vapors, even in very smallconcentrations, can produce significant irritation of theskin, eyes, and respiratory tract and may also induceallergic sensitization of personnel. Personnel usingthese materials shall consult OPNAVINST 5100.23 forspecific details. Refer to specific maintenanceinstructions for information concerning the selectionand use of rain erosion resistant coatings. Consultmanufacturer’s data supplied with the material for safety,mixing, and application instructions.
A-10.8.2. Anti-Chafe Coatings. Anti-chafe polyurethanetopcoats are primarily used on surfaces where lowfriction and abrasion, impact, and chemical resistanceare required to reduce chafing and wear. Examples ofthese areas are slats, flap tracks, interference areas,and exit door areas. They are generally proprietarymaterials that often contain additives such aspolytetrafluoroethylene (PTFE or Teflon). These coatingsare available in several colors, including common graycolors used with tactical paint schemes. They are usuallysupplied as two component kits that must be mixedtogether in the proper proportions prior to use. Also,anti-chafe topcoats are designed to be applied over aprimer to provide maximum performance. Refer tospecific maintenance instructions for informationconcerning the selection and use of anti-chafe coatings.Consult manufacturer’s data supplied with the materialfor safety, mixing, and application instructions.
A-10.8.3. Black Conductive Coating (P/N: 8-B-6). Thismaterial is used as a protective coating onfiber-reinforced plastic parts, such as radomes andhelicopter rotor blades, to provide erosion protectionand dissipate static electricity. Refer to specific
maintenance instructions for information concerningthe selection and use of black conductive coatings.Consult manufacturer’s data supplied with the materialfor safety, mixing, and application instructions.
A-10.8.4. Non-Slip Walkway Coating (A-A-59166).Walkway coatings contain grit (e.g. pumice, aluminumoxide) to provide a nonskid surface for improved footingon specific aircraft surfaces. Examples of these areasare leading edge extensions (LEX) and upper walkwaysurfaces. This polyurethane topcoat is supplied as asingle component material and is available in two types:Type I has a smooth texture; Type II has a rough, grittytexture. Both types are usually applied by brush or rollerand are available in a variety of colors, including manyof the common gray colors used with tactical paintschemes. Refer to specific maintenance instructionmanuals for information concerning the selection anduse of non-slip walkway coatings. Consultmanufacturer's data supplied with the material for safety,mixing, and application instructions.
A-10.8.5. Heat Resistant Coating (TT-P-28 Type I).This is a VOC compliant (250 g/l maximum) aluminumpigmented coating resistant to temperatures up to1200°F. It is generally used on steel surfaces exposedto temperatures in excess of the tolerance of standardpaint systems. It is supplied as a single component andcan be applied by brush or spray. After application,allow the coating to air dry for 30 minutes followed bybaking at 400°F (204°C) for one hour. If baking is notpossible after air drying, the coating may be curedduring component use at elevated temperature. Referto specific maintenance instructions for informationconcerning the use of heat resistant coating. Consultmanufacturer's data supplied with the material for safetyand application instructions.
A-10.8.6. Decals. Traditional painted stencils tend towear off due to weather and flight wear. The use of vinyldecals instead of painted stencils has severaladvantages: elimination of hazardous air pollutants(HAPS) and hazardous waste, less frequent application,and reduced labor requirements. Decals should not beused in areas regularly exposed to temperatures above150°F. Comply with MIL-STD-2161 requirements forcolor and location of decals. Consult manufacturer'sdata supplied with the material for safety and applicationinstructions.
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A-11. SCOPE. This section discusses aircraft andengine cleaning. For corrosion charts of the specificaircraft, refer to the applicable maintenance instructionmanual (MIMs), or contact the Fleet Support Team(FST) for the aircraft.
A-12. AIRCRAFT CLEANING. Cleaning compoundsand materials which appear only in Appendix B(Supplemental Requirements for Army Aircraft) are notauthorized for cleaning Navy aircraft. See Chapter 2 fordetailed information on aircraft cleaning proceduresand authorized materials and equipment.
A-13. EQUIPMENT FOR ENGINE CLEANING.
A-13.1. JET ENGINE CORROSION CONTROL CART.The corrosion control cart, P/N 65A102-J1-1, is designedfor cleaning and rinsing the compressor section ofturbine engines. It is a trailer mounted, self containedmobile unit designed for shipboard use and shorebased operations (see Figure A-18). The cart consistsof a 33 gallon capacity solution tank and a work platformarea on top of the solution tank. There is a water supply
APPENDIX ASUPPLEMENTAL REQUIREMENTS FOR NAVY AIRCRAFT
SECTION II. AIRCRAFT AND ENGINE CLEANING
Figure A-18. Jet Engine Corrosion Control Cart
hose and applicator storage area on the right hand side.Two air cylinders are mounted on the left hand side tosupply the air pressure needed to discharge the watersolution from the solution tank. The instruction plate andschematic diagram are mounted on the left hand side toprovide information about operating the unit. The33 gallon capacity solution tank is divided into twoseparate compartments: a 7 gallon preservativecompartment at the front end of the unit and the 26 gallonwater compartment at the rear end of the unit. On top ofeach compartment is a filler opening and at the bottomof each compartment is a plug for drainage purposes.The operational instructions of the cart are listed inNAVAIR 19-20D-1 (Jet Engine Corrosion Control Cart).Washing with MIL-PRF-85704 (Gas Path Cleaner) shallbe performed as follows:
a. Fill the 7 gallon forward tank with 1 gallon ofMIL-PRF-85704 Type II and 4 gallons of fresh water, orwith 5 gallons of MIL-PRF-85704 Type II RTU (readyto use). Then fill the 26 gallon aft tank with fresh water.
b. Prepare the aircraft for turbine engine washing inaccordance with the applicable maintenancerequirements.
c. Spray the cleaning solution or fresh water asrequired (see Table 2-1 for additional information).
A-13.2. CORROSION CONTROL SPRAY UNIT,TRAILER MOUNTED. The spray unit,P/N 76E04000-30A, stores and controls the delivery ofwater, preservative oil, and cleaning solutions to thecompressor section of turbofan, turbojet, and turboshaftengines. It is a self contained sprayer mounted on atowable trailer (see Figure A-19). The spray unit consistsof a 200 gallon water tank and a 10 gallon oil/cleaningsolution tank. Compressed air from the compressorassembly pressurizes the tanks for delivery of fluids.The solution tank is a reservoir for storage of preservativeor cleaning solutions. Fresh water from the water tankis usually used during corrosion control for rinsing. The4:1 mixer assembly mixes four parts water to one partchemical in the solution tank. The unit can also supplycompressed air directly to the aircraft being serviced.The unit is secured to an aluminum chassis mounted ona four wheel running gear. Operating instructions forthe unit are listed in NAVAIR 19-20D-2 (CorrosionControl Spray Unit).
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Figure A-19. Corrosion Control Spray Unit
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APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
B-1. SCOPE. This appendix consists of eight sections.Section I deals with aircraft finish coating. Section IIdescribes frequency of cleaning. Section III coverschemical corrosion removal and pre-paint treatment ofaluminum alloys. Section IV encompasses the treatmentof specific areas. Section V contains decontamination
procedures for salt water and microbiological growthcontamination. Section VI details the identification ofmetals. Section VII contains procedures for plastic mediablasting. Section VIII lists a table of consumablematerials.
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B-2. PAINTING AND TOUCH-UP OF ARMYAIRCRAFT, CHEMICAL AGENT RESISTANTCOATING FINISH.
B-2.1. U.S. Army personnel will adhere to the DetailSpecification, MIL-DTL-53072, Chemical AgentResistant Coating (CARC) System ApplicationProcedures and Quality Control Inspection whenperforming painting or finish touch-up tasks on aircrafthaving CARC finish.
B-2.2. This document covers the general requirementsfor application and inspection of the chemical agentresistant coating (CARC) system used on tactical militaryequipment. It is intended for use as a guide in selectionof the appropriate materials and procedures, and as asupplement to information available in cleaning, pre-treating, and coating specifications. The document alsoincludes information on touch-up/repair, health andsafety guidelines, environmental restrictions, nationalstock numbers (NSN) for CARC and CARC-relatedmaterials, and application equipment and techniques.
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION I. AIRCRAFT FINISH COATING
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B-3. FREQUENCY OF CLEANING. The frequency ofcleaning of army aircraft shall be 30 days, with thefollowing exceptions, unless aircraft are stationed withintwo miles of salt water. Extended or low level operationsover salt water require daily fresh water rinsing. Cleaningprocedures and materials shall be in accordance withChapter 2 of this manual with the addition of the followingArmy approved exterior aircraft cleaners for helicopters:Hurrisafe 8015 and Hurrisafe 8065. Hurrisafe 8015 isapproved as substitute for MIL-PRF-85570 Type II
cleaner for cleaning exterior surfaces that are painted.Dilute Hurrisafe 8015 with water in the same equivalentparts ratio as the MIL-PRF-85570 Type II cleaner isdiluted per Chapter 2, Table 2-2, Exterior Surfaces,Painted Surfaces, for light to heavy soils. Hurrisafe8065 is to be used for moderate to heavy soils asdefined by Chapter 2, Table 2-2, Exterior Surfaces,Painted, and requires no dilution. See Section VIII forordering information.
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION II. CLEANING
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B-4. CHEMICAL CORROSION REMOVAL ANDPREPAINT TREATMENT OF ALUMINUM ALLOYS.
WARNING
Wear acid-resistant gloves, chemical or splashproof goggles, protective mask, and protectiveclothing when working with acidic compounds.If acid accidentally contacts the skin or eyes,flush off immediately with clean water. Reportto the medical facility if eyes are affected or ifskin is burned.
Magnesium surfaces should be protected andsubsequently treated as prescribed in Chapter 5of this manual.
CAUTION
Corrosion removal compound (SAE AMS 1640)is for use on aluminum alloys only and shall notbe used on or rinsed over magnesium. It shallbe used on aircraft only when required to removecorrosion as a pre-paint treatment and shall notbe used solely for the purpose of enhancing theappearance of the aircraft or equipment. Theuse of this compound under the premise ofgeneral corrosion removal is also prohibited.When this compound is accidentally splashedor spilled, remove immediately by rinsing withwater or wiping with a wet rag. Keep a wet ragon hand at all times for the removal of spills orsplashes.
When working with any acidic solution forcorrosion removal, keep the solution confinedto the area being treated. The acidic solutionshall be kept away from operating mechanisms,magnesium alloys, and steel parts, especiallysteel screws and fasteners in stressed panels(e.g. wing).
B-4.1. MASKING. All parts and assemblies, especiallycadmium plate items and hinges susceptible to damageby the acidic compound, shall be masked and/orprotected. Mask all openings leading to the primarystructure and any other openings which might allow thesolution (uncontrolled) to get into the aircraft or equipmentinterior. Specific examples of extremely critical areas onmost aircraft are the landing gears, engines, main
framing and support members of the landing gears,engines, elevons, elevators, rudder, and wings andwing stubs. Masking can be accomplished by usingwaterproof barrier paper (MIL-PRF-131 Class 1) andmasking tape (AMS-T-21595 Type I).
B-4.2. CLEANING. Surfaces should be thoroughly cleanbefore application of the corrosion removal compound(see Chapter 2). For pitted or heavily corroded areasthe compound will be more effective if applied warm(140°F (60°C) maximum) followed by vigorous agitationwith a nonmetallic acid-resistant brush (H-B-643) or analuminum oxide abrasive nylon mat (A-A-58054). Theapplication of the remover on the heavily corrodedareas may have to be repeated several times tocompletely remove the corrosion. When using the acidremover, be sure to allow a sufficient dwell time (12 to15 minutes) before rinsing.
B-4.3. INSPECTION. After each application, examinethe pits and/or corroded area with a 10 power magnifyingglass to determine if another application is required.Corrosion still on the area will appear as a powderycrust slightly different in color from the uncorroded basemetal. Darkening of the area due to shadows andreaction from the acid remover should not be considered.
B-4.4. CORROSION REMOVAL COMPOUND(SAE AMS 1640).
CAUTION
When using corrosion removal compound onaluminum alloy surfaces, take particular care tokeep acid out of faying surfaces, butt joints,seams, and crevices.
When using the flap brush to remove corrosion,take action to control the particles or abrasivesthat break away and prevent them fromcontaminating systems or components. Prior toaccomplishing corrosion removal from severelypitted areas, check the component or itemagainst the applicable aircraft or overhaulmanual for authorized or allowable metalremoval limits.
B-4.4.1. The corrosion removal compound(SAE AMS 1640) material is basically intended for use
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION III. CORROSION REMOVAL AND SURFACE TREATMENT
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as a pretreatment prior to the application of a protectivecoating. However, it also can be used to remove corrosionproducts from aluminum alloy materials or items (e.g.,skins, stringer, ribs in wings, tubing, or ducts). The wipe-off technique is recommended for ducting, tubing,stringer, and similar parts, followed by a thoroughrinsing of the treated area with clean water. In cases ofsevere pitting, the chemical method of removal may beaided by hand agitating (lightly) the pits with a corrosionresistant steel wire (0.005 to 0.006 inch maximumdiameter of filament wire) brush (MIL-B-15319) or byagitating with a power driven nylon flap brush, Density 5,Type A, grade fine or very fine (3M Corp. or equal).
B-4.4.2. General Application Procedure.
a. Pre-clean surfaces in accordance with Chapter 2.
b. Survey or inspect equipment and determinearea(s) that should be treated with the corrosion removalcompound, using criteria cited in Chapter 3. Pittedsurfaces and/or aluminum surfaces with a powderymetallic residue which was not removed by cleaningshould be treated. If the aircraft is being prepared forcomplete painting or repainting, prepare all cleanedbare aluminum surfaces for treatment.
B-4.4.3. Mask Applicable Areas (see B-4.1.).
c. Set up application equipment, put on protectiveclothing, and prepare corrosion removal and prepaintsolution by diluting Type I material with an equal volumeof water before using. Mix the compound in wood,plastic, or plastic lined containers only. Follow themanufacturers mixing instructions.
NOTE
SAE AMS 1640 Type I corrosion removalsolution has a one year shelf life; therefore, itshall not be used after one year from the dateof manufacture. SAE AMS 1640 Type II materialshould be used within 90 days after dissolution.
d. Apply the corrosion removal solution by spray,mop, sponge, or brush. When applying a the solution onlarge surface areas, begin application on lower surfaceand work upward, with a circular motion, brushingenough to loosen the surface film. Allow the solution toremain on the surface for approximately 12 minutes,then rinse away with clean tap water. Chromateconversion coating (MIL-DTL-81706) shall be appliedimmediately thereafter. Refer to Chapter 5 for prepainttreatment application instructions.
NOTE
The final protective paint system or primer shallbe applied only on a completely dry surfacewithin 48 hours after applying the conversioncoating. A second conversion coating shall beapplied over the previous application if morethan 48 hours has elapsed since the firstconversion coating was applied.
B-5. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF MAGNESIUM ALLOYS.
WARNING
When preparing the chromic acid pickle solution,add chromium trioxide to water; do not addwater to chromium trioxide.
B-5.1. The chromic acid pickle solution described hereinmay be used to remove surface oxidation and lightcorrosion products from magnesium surfaces. It is notconsidered adequate where deep pitting or heavycorrosion has occurred, which require mechanicalmethods, nor is it satisfactory for removing sand or theeffects of blasting. The chemical method causes lessreduction in section thickness. This method shall not beused for parts containing copper based inserts unlessthe inserts are masked off. Excessive amounts of anions,such as chlorides, sulfates, and fluorides, must not beallowed to build up in the solution, as these anions tendto coat or etch the metal rather than clean the surface.
B-5.2. CHROMIC ACID PICKLE SOLUTION. Mix 24ounces of chromic acid and enough water to make onegallon in a container constructed from lead lined steel,stainless steel, or 1100 aluminum.
B-5.3. APPLICATION PROCEDURE.
a. Mask off nearby operating mechanisms, cracks,and plated steel to keep the solution from attackingthem.
b. Heat the solution to 190° to 202°F (88° to 94°C).The solution can be applied at room temperature for alonger reaction time, if desired.
c. Carefully apply the chromic acid solution to thecorroded area with an acid resistant brush (H-B-643).Allow the solution to remain on the surface forapproximately 15 minutes.
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d. Thoroughly rinse the solution from the surfacewith plenty of clean water.
e. Repeat the preceding sequence as necessaryuntil all corrosion products have been removed and themetal has a bright appearance.
f. Apply the chemical pretreatment and finalprotective finish recommended for the area.
B-5.4. PRE-TREATMENT PROCESSES (BRUSHAPPLICATION). Chemical pre-treatment, such as thechromic acid brush- on solution, provides a passivesurface layer with an inhibitive characteristic that resistscorrosive attack and also provides a bond for subsequentcoatings. Properly applied magnesium pre-treatmenttend to neutralize corrosion media in contact with thesurface. Numerous type treatments are available;however, for the purpose of this manual, the followingbrush-on treatment corresponding to Type VI ofSpecification AMS-M-3171 is given. The pre-treatmentshall be applied immediately after paint removal andwashing in order to prevent corrosion and surfacedeterioration.
B-5.4.1. Chromic Acid Brush-On Pretreatment. Thechromic acid brush-on pretreatment may be applied toall magnesium parts that require touchup. This treatmentis generally used in refinishing procedures or whenparts and assemblies are too large to be immersed. Thistreatment is less critical to apply than the other brush-on treatments, is relatively inexpensive, not as harmfulwhen trapped in faying surfaces and does not presentthe toxicity hazards of the other brush-on treatments.Ensure that all contaminants, grease, and oil are removedprior to the treatment process.
B-5.4.1.1. Preparation.
WARNING
When preparing the chromic acid brush-onpretreatment, add the chemicals to the water inthe order shown below, stirring the solutionvigorously, either mechanically or by agitation,for at least 15 minutes. Avoid skin contact orinhalation of acid fumes.
B-5.4.1.2. Add 1-1/3 ounces (37.8 grams) of technicalgrade chromic acid (A-A-55827) and one ounce (28.3grams) of calcium sulfate (CaSO4-2H20) to enough
water to make one gallon in a container constructedfrom stainless steel, aluminum, vinyl, polyethylene, orrubber. The operating temperature range is 70° to 90°F(21° to 32°C). After mixing, the pH of the solution shouldbe between 1.1 and 1.6. Adjust with acid if the pH isgreater than 1.6 and with water if the pH is less than 1.1.
B-5.4.1.3. Application Procedure.
a. Clean the surfaces to be treated (see B-4.2). Awater break test is recommended if the cleanliness ofthe surface is in doubt.
b. Apply the coating solution by brush, swab, or alow pressure, non-atomizing spray. Keep the receivingsurfaces wet throughout the treatment operation untilthe required or specified coating film is produced. Underoptimum conditions (i.e., at temperatures of 70°F (21°C)or above, and using fresh materials), the time requiredis usually one to five minutes; up to one to two minutesof treatment should produce a brassy film, and three tofive minutes should produce a dark brown coating.Under adverse conditions, and if the desired or specifiedfinish color is not produced in the specified time, thetreatment may have to be prolonged (up to 20 to 30minutes in some instances) until the proper finish isobtained. For good paint adhesion, a dark brown colorfree of powder is considered best. The color may varyin using different manufacturers materials.
NOTE
Too long an exposure to the brush-on solutionproduces coatings which will powder and impairadhesion of applied paint finish and films.
c. The coating should be closely observed duringthe treatment for color changes, rinsed with cold runningwater when the desired condition or color is reached,and air dried. The preparation and use of test panels,made of the same material and under the sameconditions, prior to starting the actual treating operationmay be used as an aid in determining the applicationtime required to produce the necessary coating. A goodcoating is uniform in color and density, adheres well,and is free of loose powder.
d. Apply wash primer (MIL-C-8514) to the treatedsurface as soon as practical after thorough drying.
e. Apply recommended final protective finish.
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B-5.5. PAINT SYSTEMS. Use paint systems which arerecommended for aluminum (see TM 55-1500-345-23). Treat touch-up of broken conversion films ormagnesium as described in paragraph B-5.6. prior tothe application of any paint system.
NOTE
The final protective paint system or primer shallbe applied on a completely dry surface andshall be applied within 48 hours after applicationof the AMS-M-3171 or chromic acid brush-onpretreatment. A second pretreatment coatingshall be applied over the previous if more than48 hours have elapsed since the previousapplication.
B-5.6. REPAIR OF MIL-M-45202 COATINGS. Somemagnesium parts in current aircraft have been originallyprotected by proprietary electrolytic processes. TheHAE process can be identified by the brown to mottledgray appearance of the unpainted surface. DOW 17coatings have a green to grayish-green color. Coatingsof the electrolytic type are thicker than those applied byimmersion or brushing. Electrolytic finishes cannot berestored in the field. When failure occurs, removecorrosion products, touch-up bare magnesium withchemical treatment solution (AMS-M-3171), and repaintthe part. Take care to minimize the removal of thesecoatings.
B-6. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF FERROUS METALS OTHER THANSTAINLESS STEEL.
WARNING
The phosphoric acid-type corrosion remover(MIL-C-10578 Type III) contains a strong acid.Protect hands, face, and eyes, wear protectiveclothing, and avoid prolonged inhalation ofvapors. Corrosion removing compound, sodiumhydroxide base (A-A-59261) is highly alkaline,and, therefore, harmful to the skin and eyes.Operators should wear rubber gloves, aprons,and chemical or splash proof goggles and useadequate ventilation when working with thismaterial.
CAUTION
Do not use the phosphoric acid-type corrosionremover (MIL-C-10578 Type III) if the dangerof trapping the material in crevices or recessesexists. Steel parts heat-treated above RockwellC40 (180,000 psi) tensile strength are subjectto hydrogen embrittlement; therefore, the useof the phosphoric acid-type corrosion remover(MIL-C-10578 Type III) is prohibited.
Do not use the sodium hydroxide base corrosionremoving compound (A-A-59261) to removecorrosion from aluminum alloys. Do not processdissimilar metals in the solution.
B-6.1. Chemical corrosion removal is recommendedfor use where there is no danger of the chemicalsbecoming, trapped in crevices or recesses. Chemicalrust remover is either acid or alkaline. The acid type(MIL-C-10578 Type III) is intended for removal of redrust and black oxide formations by either immersion orbrush application of the chemical. The alkali type(A-A-59261) is intended for removing red rust byimmersion treatment.
B-6.2. APPLICATION PROCEDURES.
B-6.2.1. Brush-On Method. Phosphoric acid-typecorrosion remover (MIL-C-10578 Type III) is used toremove rust and condition the metal surface prior topainting. Type III material should always be rinsed offwith water after application.
a. Protect adjacent components to prevent damageby scale, chips, corrosion products, or chemicals.
b. Remove any grease or soil by method outlines inChapter 2 of this manual.
c. Remove heavy rust by chipping and/or wirebrushing.
d. Add one part of the concentrated material asreceived to one part of water by volume, adding the acidto the water. Use acid resistant mixing tanks.
e. After proper dilution, apply the material to thecorroded area with brush or swab. Allow the material toremain long enough loosen the rust (usually two to 10minutes, depending on the degree of rusting).
f. Remove the by with hot water. The material mustbe completely rinsed from the part.
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g. If corrosion is still evident, repeat paragraphs e.and f.
h. Dry the part and immediately apply the protectivepaint or other corrosion preventive finish.
B-6.2.2. Immersion Method (Acid Type). Use inhibitedphosphoric acid-type rust remover (MIL-C-10578Type III) for small parts. Corrosion resistant steel tanksare preferred for the immersion treatment.
a. Remove grease and oil as outlined in Chapter 2of this manual.
b. Remove heavy rust by chipping and/or wirebrushing.
c. Mix the rust remover as described above.
d. Immerse the parts in the solution only long enoughto loosen the rust. For removal of heavy rust, thesolution can be heated to 140°F (60°C) maximum.Agitate the parts in the solution to further increase therate of rust removal.
e. Rinse in a continuously overflowing cold waterrinse tank, if water rinse tank is available, or spray withclean, preferably hot, water.
f. Dry the parts and immediately apply the finalprotective paint or other corrosion preventive finish.
B-6.2.3. Immersion Method (Alkali Type). Use an alkalitype corrosion remover for removing corrosion fromsmall parts with or without attendant paint, grease, orother surface coating. Corrosion removing compound,sodium hydroxide base (MIL-C-14460) is suitable forrust removal by simple immersion of the parts. Thecompound will also remove grease, paint, and rust fromthe parts, and may be used to clean copper and brassand strip phosphate coatings. In addition, rust can beremoved from critical or machined surfaces with thecompound without causing dimensional change of thepart.
g. Prepare alkaline rust remover in accordance withmanufacturers instructions as printed on the container.The usual concentration employed for Type I material isfive pounds per gallon of water. Carbon steel or corrosionresistant steel tanks may be used.
h. Immerse parts in the rust remover solution. Rustremoval time varies with the extent of the rust.Temperatures up to the boiling point of the solution maybe used to increase the rate of rust removal.
i. Rinse thoroughly in clean (preferably hot) water.
j. Dry thoroughly and immediately apply finalprotective finish or other corrosion preventive compound.
B-6.3. PAINT SYSTEMS. See TM 55-1500-345-23 forpaint systems applicable to aircraft in general. In addition,see the aircraft maintenance manuals overhaul manuals,or parts drawings for specific paint systems.
B-7. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF STAINLESS STEEL AND NICKELBASE ALLOYS.
CAUTION
Take care to protect surrounding unaffectedareas next to area being treated by avoidingleakage of chemicals into recesses orinaccessible area in order to prevent additionaldamage from corrosion attack.
The heat-treatable straight-chromium alloys,such as AISI Types 403, 410, and 420 aresusceptible to cracking when placed in picklingsolutions; therefore, corrosion removal bybrushing or grinding is recommended.
B-7.1. Chemical removal of corrosion is recommendedfor severely corroded areas where there is no danger ofthe chemicals becoming entrapped in recesses orstructural complexities or the possibility of damagingsurrounding metals and plating.
B-7.2. Corrosion removal procedure for installedcomponents which are not readily removable.
a. Protect adjacent unaffected areas not beingtreated to prevent additional corrosive attack. Wheninternal corrosion is evident, the components shall beremoved and processed through an overhaul facility inaccordance with the specific directives.
b. Protect nearby non-corrosion-resistant steelalloys, plated areas, copper-bronze alloys, aluminumalloys, braided flexible lines, and operating mechanismsto prevent the chemical treating solution from coming incontact with those areas.
c. Remove all loose corrosion by brushing withstainless steel wool or No. 400 carborundum paper.Remove loose particles by wiping with a clean clothdampened with approved compliant cleaning solvents.
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d. In areas where there is no danger of liquid oxygenspillage, corrosion may be removed with phosphoricacid base rust remover (MIL-C-10578).
e. Thoroughly rinse all chemical corrosion removerfrom the area.
f. Allow the area to dry, then apply final protectivefinish or other corrosion preventive if required.
B-7.3. PICKLING FOR CORROSION REMOVAL.
WARNING
The scale loosening solution, the picklingsolution, and the passivating solution all containstrong acids. Observe the standard safetyprecautions for handling acids. Wear protectiveclothing, avoid inhaling fumes, provide adequateventilation, and always add acid to water.Hydrofluoric acid is exceptionally hazardous.
a. Mixtures of nitric acid (O-N-350) and hydrofluoricacid (MIL-A-24641) in water are recommended. Thecorrect percentage content of the two acids for a givencorrosion removal job shall be determined by testing.(See B-7.2.c). The nitric acid content may vary from 5 to50% and the hydrofluoric acid from 0.5 to 5%, both byvolume. Normally, an aqueous mixture containing 12 to15% nitric acid and 1% hydrofluoric acid is used toremove light scale or corrosion. The percentage ofhydrofluoric acid may be increased to remove heavierscale or corrosion. The more nitric acid present withrespect to hydrofluoric acid, the less rapid the corrosionor scale removal. Nitric acid acts to inhibit the action ofhydrofluoric acid. Rubber lined or Koroseal tanks maybe used to hold the solutions.
b. The pickling temperature may be adjusted fromroom temperature to 140°F (60°C). Higher temperaturesshall be avoided to reduce evaporation loss ofhydrofluoric acid. Temperatures below 120°F (49°C)should be used if intergranular attack is experienced inlocalized areas, such as weld zones. Type 300 seriesstainless steels may be used to manufacture steam
coils to heat the solution. The heating coils should beinstalled so that they are easily replaced since they willbe corroded by the solution.
c. Optimum pickling conditions (temperature, time,and acid concentration) shall be determined by exposureof test panels to all conditions of the cleaning cycle.Excessive etching or intergranular attack of the basemetal shall be avoided.
(1) Make test panels, 1 x 4 inches, of the samematerial as that of the compound being cleaned. Processthe test panels through the complete cleaning andpickling cycle.
(2) If etching, intergranular attack, or metal lossis excessive (i.e., would cause component to becondemned), or if cleaning is not complete, adjust theacid concentration, immersion time, or solutiontemperature until the desired result is obtained.Table B-1 shows the effect of the variables (acidconcentration, immersion time, and solutiontemperature) on the pickling action of the solution.
d. The following procedures are merely guidelinesfor acid pickling. Competent operators must establishspecific procedures by test as outlined in paragraph c.above. A scale loosening procedure is included for useonly if severe scale is encountered and it is desired toloosen the scale by chemical means. Normally, heavyscale may be removed by mechanical means prior toacid pickling. A passivating procedure is also includedand may be used following pickling. Solvent or vapordegreasing shall precede the following procedure:
(1) If necessary, remove severe scale by amechanical method.
(2) If necessary, loosen severe scale byimmersing parts in an 8-10% (by weight) solution ofsulfuric acid (A-A-55828) in water at 150° to 160°F (66°to 71°C) for approximately five minutes. Observe resultsand repeat if required. Scrub as required to removesludge.
Table B-1. Control of the Dissolving Action of Nitric-Hydrofluoric Acid Solution
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(3) Rinse parts quickly and thoroughly in clean,hot water.
(4) Transfer parts to the nitric-hydrofluoric acidpickling bath. A typical bath consists of 15% nitric acid(O-N-350), 2 to 3% hydrofluoric acid (MIL-A-24641),and 82 to 83% clean water, all by volume.
(5) Immerse parts for five to 15 minutes at atemperature of 60° to 140°F (16° to 60°C). Scrub oragitate as required.
NOTE
The required acid concentration, temperature,and time shall be determined by test prior tostarting pickling operations (see B-7.2.c). Newwelds should be mechanically vibrated duringthe pickling operations.
(6) Immediately rinse thoroughly in clean, hotwater.
(7) Transfer the parts to a passivating solutionfor treatment as follows:
(a) Immerse parts in an aqueous solutioncontaining 20 percent by volume nitric acid (O-N-350) atordinary room temperature for 30 minutes.
(b) Rinse in clean, hot water.
(c) Immerse parts for one hour in a hotaqueous solution (140° to 160°F (70° to 71°C)) containing5% sodium dichromate.
(d) Rinse thoroughly.
B-7.4. PAINT SYSTEMS. Stainless steel parts normallyare not painted. However, where extreme corrosiveconditions are encountered or where organic finishesare required for decorative purposes, finishing systemsmay be found in TM 55-1500-345-23, the overhaulmanuals, or on the parts drawings.
B-8. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF COPPER AND COPPER BASEALLOYS. Copper and copper alloys are relativelycorrosion resistant, and attack on such components willusually be limited to staining and tarnish. Generallysuch changes in surface conditions are not dangerous
and should ordinarily have no effect on the function ofthe part. Copper corrosion is evidenced by theaccumulation of colored products. Corrosion can beremoved from copper with phosphoric acid base rustremover (MIL-C-10578), provided that there is no dangerof trapping the acid in the crevices or recesses.
B-8.1. CORROSION REMOVAL FROM IMMOVABLEAREAS.
a. Protect adjacent components to prevent damageby chemical agents.
b. Remove grease or soil from the area to be treatedwith cleaner and/or solvent (see Chapter 2).
c. Remove corrosion with phosphoric acid base rustremover (MIL-C-10578).
d. Rinse the area thoroughly, dry, and apply finalprotective paint or other finish if required.
B-8.2. CORROSION REMOVAL FROM REMOVABLECOMPONENTS.
a. Components which can be disassembled can betreated in immersion tanks. The tanks should bemanufactured from or lined with stainless steel, lead,ceramic, glass, or acid resistant rubber. Immersionracks should be manufactured from stainless steel orMonel. The proper conditions (time, temperature, andacid concentration) for the process should be determinedby test, using panels of the same material which is to betreated.
b. Disassemble the component as necessary. Donot simultaneously process dissimilar metals in the acidbath.
c. Degrease parts by immersion, spray, or vaporcleaning.
d. Immerse parts in a solution containing 5 to 10%sulfuric acid (A-A-55828), by volume, in water; add theacid to the water, not the water to the acid. Maintainsolution between 60° and 120°F (15° and 49°C). Therequired temperature, immersion time, and acidconcentration shall be determined by test.
e. Rinse thoroughly.
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f. If a red stain appears on the parts following theabove treatment, remove the stain by immersing partsin a solution containing sulfuric acid (A-A-55828), 4-10%by volume, sodium dichromate, 4 -8 ounces per gallonof solution, and water, remainder.
g. Maintain the above solution at 60° to 120°F (15°to 49°C). The required temperature, immersion time,and acid concentration shall be determined by test.
h. Rinse thoroughly. This will remove any residualacid, which could cause staining of the metal surface.
i. Dry rapidly, preferably with hot air. Rapid dryingwill prevent water stains on the metal surface.
B-8.3. PAINT SYSTEMS. Normally copper and copperalloys are not painted. However, if paint is required fordecorative or other purposes the finishing systems arelisted in TM 55-1500-345-23, the aircraft maintenancemanuals, overhaul manuals, or parts drawings.
B-9. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF TITANIUM AND TITANIUM-BASEALLOYS.
CAUTION
Titanium is susceptible to hydrogenembrittlement in acid solutions; therefore, theacid pickle should be used only when othercorrosion removal methods are not adequate.Assign competent operators to monitor theprocess.
B-9.1. An acid pickle will remove most oxide coatingsfrom titanium, provided that the scale was formed attemperatures below 1000°F (540°C). Gray or blackoxides should be removed by a mechanical method,such as abrasive blasting, prior to the acid pickle toprevent pitting of the titanium.
a. If present, remove gray or black oxide bymechanical means.
b. Remove soil as outlined in Chapter 2.
WARNING
Hydrofluoric acid is extremely hazardous. Followall MSDS safety precautions and ensure use ofall required PPE.
NOTE
The required acid concentration and immersiontime shall be determined by test prior to thepickling operation.
c. Immerse parts in a solution normally containing20% nitric acid (O-N-350) and 3% hydrofluoric acid(MIL-A-24641) in water, by volume. Maintain the solutionat the normal room temperature. Allow the parts toremain in the solution only long enough to remove theoxide coats. Intermittent wiping with a brush or clothduring the pickling operation will facilitate oxide removalwith a minimum of pitting.
d. Rinse thoroughly in cold running water, air dry, ordry in air oven at 180° to 240°F (82° to 116°C).
e. Apply final protective finish, if required.
B-9.2. PAINT SYSTEMS. Titanium does not require apaint system for corrosion protection. Where organicfinishes are required for decorative or other purposes,finishing systems may be found in TM 55-1500-345-23,aircraft maintenance manuals, overhaul manuals, orparts drawings.
B-10. CHEMICAL CORROSION REMOVAL ANDTREATMENT OF PLATED AND PHOSPHATEDSURFACES. Chemical corrosion removal isrecommended for use where there is no danger of thechemicals becoming trapped in crevices or recesses.Acid-type chemical rust removers are recommended.The acid type is intended for removing red rust andother types of corrosion from the base metal by brushapplication of the chemical. The acid rust remover isintended for use following removal of heavy corrosionby mechanical means. The acid will remove anyremaining corrosion and condition the metal surface toimprove paint adhesion.
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B-10.1. TOUCH-UP OF CORRODED AREAS ONCADMIUM OR ZINC PLATED SURFACES. Cadmiumand zinc plate provide cathodic protection to theunderlying base metal. If, during normal use, the platedsurface is broken, the cadmium or zinc plate will beanodic to the base metal (usually steel or copper alloy):therefore, the plate will corrode and sacrificially protectthe base metal. Removal of corrosion from cadmium orzinc plated surfaces shall be limited to the removal ofthe corrosion products from the underlying base metal.Mechanical corrosion removal methods shall be used.
a. Protect adjacent components for scale, corrosionproducts, and chemical agents.
b. Clean the area with dry cleaning solvent(MIL-PRF-680 Type II) or other approved materials toremove grease or other soils (see Chapter 2).
c. Remove corrosion products from the base metalwith abrasive paper or abrasive nylon pad. Avoidremoving undamaged cadmium or zinc plate adjacentto the corroded area. Corrosion removal shall be limitedto the immediate area of the corrosion on the basemetal.
d. Remove any remaining corrosion and conditionthe metal surface with phosphoric acid base rust remover(MIL-C-10578). Allow the acid to contact the surfaceonly long enough to remove the corrosion.
e. Allow the area to dry, and immediately apply finalprotective paint or other corrosion preventive finish.
NOTE
The above procedures are intended only fortouchup of corroded areas on cadmium or zincplated surfaces. Where service temperaturespreclude the use of organic finishes or thethickness of the organic finish will impairoperation of the part, severely corroded partsmust be replaced. Where facilities are available,severely corroded cadmium plated parts maybe replated.
f. Small corroded areas can be brush plated inaccordance with instructions in Depot MaintenanceWork Requirements (DMWRs).
B-10.2. TOUCH-UP OF CORRODED AREAS ONPLATED PARTS (EXCEPT THOSE PLATED WITHCADMIUM OR ZINC). When a break occurs in thesurface of plates such as chromium, nickel, tin, orcopper, corrosion of the base metal will follow. Thecorrosion will normally be accelerated because theabove plates are cathodic to most base metals.
a. Protect adjacent components from scale,corrosion products, and chemical agents.
b. Clean the area to remove grease or other soil.
c. Remove heavy corrosion by mechanical means,such as wire brushing.
d. Remove any remaining corrosion and conditionthe metal surface with phosphoric acid base rust remover(MIL-G-10578). Allow the acid to contact the surfaceonly long enough to remove the corrosion.
e. Thoroughly rinse the acid from the surface withclean water.
f. Allow the area to dry and immediately apply finalprotective paint or other corrosion preventive finish.
B-10.3. PAINT SYSTEMS. Paint may be used to preventfurther corrosion on plated or phosphated surfaces,provided that the part does not operate at temperatureswhich preclude the use of organic finishes and that thefinish will not prevent the part from performing itsintended function. Organic finishes shall not be usedon: bearings or wearing surfaces of gears, cams, orslides; where an electrical conducting surface is required;where the reflective properties of the plates are essential,and, other areas where the finish will prevent the partfrom performing its intended function. Finishes consistentwith the requirements for corrosion protection of thebase metal should be used. Refer to TM 55 1500-345-23, the aircraft maintenance manuals, overhaul manuals,or parts drawings for specific paint systems.
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B-11. PURPOSE. This section covers preventive andcorrective procedures and materials for specific aircraftparts or areas.
B-12. CORROSION TREATMENT OF SPECIFICTYPE TUBING.
WARNING
Do not use Specification MIL-PRF-16173material on any oxygen line fittings. This materialcontains petroleum solvents which are notoxygen compatible. Explosion may occur ifoxygen contacts this material and the resultingmixture is subjected to sudden pressure orimpact. After installation, apply the exteriorpaint system to the exposed tubing, sleeve, andback portion of the B nut of these fittings.
B-12.1. No paint coating shall be applied to the interiorsurface of airspeed indicator tubing, oxygen tubing, orother plumbing lines. Interior and exterior surfaces ofother aluminum alloy tubing shall be treated withMIL-DTL-81706, except oxygen lines which shall betreated on external surfaces only. Tubing inmethylbromide or trifluorobromoethane fire extinguishingsystems shall be finished with baked resin coatingconforming to MIL-PRF-3043. The process shall be inaccordance with MIL-C-5056.
B-12.2. If possible, the interior surfaces of structuralaluminum alloy tubing shall be protected in accordancewith the general schedule for aircraft interior surfaces.The interior surfaces of structural aluminum alloy tubingsealed by welding need not be painted on land planes.On amphibian aircraft, however, the interior of suchmembers shall be coated with epoxy polyamide primer(MIL-PRF-23377) or corrosion preventive compound(MIL-C-11796 Class 3), applied through appropriatelydrilled holes when permitted by aircraft maintenancemanuals.
B-12.3. The interior surfaces of structural magnesiumalloy tubing shall be painted in accordance with thegeneral schedule for aircraft interior magnesiumsurfaces. Interior surfaces of sealed structuralmagnesium tubing shall be coated with epoxy polyamide
primer (MIL-PRF-23377) or corrosion preventivecompound (MIL-C-11796 Class 3), applied throughappropriately drilled holes when permitted by aircraftmaintenance manuals.
B-12.4. The interior and exterior surfaces of copperalloy, corrosion resistant alloy (stainless steel), andheat resistant alloy tubing need not be painted exceptas required for protection against dissimilar metalcontact.
B-12.5. The interior of structural carbon steel tubularassemblies not closed by welding shall be finished inthe same manner as exterior surfaces as possible.Assemblies completely closed by welding or to whichapplication of primer is not practicable or not effective,such as crimped-end tubing not closed by welding ortubing heat treated after assembly, shall be treated afterassembly, (and heat treatment, if performed) with hotlinseed oil (ASTM D260) in lieu of the zinc chromateprimer coats. The liquid shall be applied by forcing it intothe hollow member under pressure through holes drilledtherein or by immersing the part in a bath of the liquid.For a large structure, interconnecting holes may bedrilled between various members in order that the liquidwill circulate. The presence of the hot material in eachmember may be checked by noting the increase intemperature of the member. Parts that are immersedshall be manipulated to ensure that no airpockets areformed, and the parts shall remain in the bath until allbubbling has ceased. The members shall be thoroughlydrained after treatment, and all exterior surfaces shallbe wiped free of oil. All access holes drilled in themembers shall be closed with cadmium plated self-tapping screws or equivalent. Solder shall not be usedto close the holes.
B-12.6. Aluminum tubing which is normally exposed tothe combined direct action of climatic elements eitherduring flight or on the ground shall be protected with thecomplete exterior paint system. Climatic elementsinclude humidity extremes, rain, hail, snow, sleet, salt-laden air, industrial atmospheres, windblown sand, anddust. Tubing in areas such as wheel wells and theirfairings, speed-brakes, wing flaps, and unshelteredtubing at missile sites is categorized as exposed tubing.
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION IV. TREATMENT OF SPECIFIC AREAS
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a. Clean tubing in accordance with paragraphB-4.4.1.
b. Condition surface by the method outlined inB-4.4.1.
c. Apply chromate conversion coating(MIL-DTL-81706) to the interior and exterior surfaces;treat only the exterior surfaces of oxygen lines.
NOTE
Apply only the conversion coating if toleranceswill not allow the application of the primer coat.Take precautions to exclude primer from internaltubing areas.
d. For permanent installations, apply two coats ofepoxy polyamide primer (MIL-PRF-23377) and twocoats of paint. (See TM 55-1500-345-23 for typical paintsystems). The chromate conversion coating and primershall be applied over the entire external surface of thetubing including under the sleeve. After fabrication andprior to installation, the complete exterior paint systemshall be applied to all lines and fittings. Coating damagedduring installation shall be retouched. Fittings that areinaccessible for inspection and refinishing as may berequired in service or are so oriented that fluid cancollect on or behind the fittings shall have exposedsurfaces between parts sealed with a corrosion inhibitivesealing and coating compound (MIL-PRF-81733). Aftersealing, the seals and the surfaces adjacent to themshall receive the prescribed paint finish.
NOTE
Where double flares are used, such as in oxygensystems, the ends must be capped, and paintmust be applied after the flaring operation toprevent coating the inside face of the flare(sealing surface) which mates with the seat ofthe fitting. To prevent contamination, end fittingsshall not be painted until after installation on theaircraft.
e. Paint coating shall be omitted for a distance ofone inch from each fitting of lines which are known torequire periodic removal in service. After installation,apply MIL-PRF-81309 Type II water displacing corrosionpreventive compound with a small brush to the unpaintedportion of the tubing, the exposed part of the sleeve, andthe back portion of the B nut. Do not apply to fittingthreads. Allow to dry for a period of at least one hour andthen coat the same area with MIL-PRF-16173 Grade 4corrosion preventive compound.
NOTE
Use dry cleaning solvent (MIL-PRF-680) toremove the preservative coatings from fittingsinstalled on painted tubing.
B-12.7. Often corrosion occurs on or near sleeves usedunder fittings on tubing. When corrosion is encounteredand/or tubing is replaced, determine what type sleeve(type metal and/or plate) is installed.
B-12.8. Stainless steel tubing which is normally exposedto the direct action of climatic elements may also requirean organic finish for corrosion protection. Austeniticstainless steels are particularly susceptible to pittingand/or stress corrosion cracking when exposed tocombinations of salt-laden air and dust particles (metallicor nonmetallic) or other materials which can causeconcentration cells to form on the stainless steel surface,Where severe deteriorating conditions cause frequentreplacement of stainless steel tubing, the tubing shallbe protected as follows:
a. Remove all foreign soils, oils, and grease by handcleaning.
b. Remove corrosion products (see Chapter 4 andparagraph B-7.).
c. Wipe down immediately before painting with anapproved solvent cleaner.
d. Apply wash (DOD-P-15328).
e. Apply two coats of epoxy polyamide primer(MIL-PRF-23377).
f. Where appearance is a consideration as analternate to paragraph e., apply one coat of primerfollowed by a topcoat of the exterior coating being usedin the surrounding area. Ensure that primer and topcoatare compatible (see TM 55-1500-345-23).
B-12.9. Cadmium plate may deteriorate under exposureto certain chemicals, abrasion, or environmentalconditions. Until such time as the tubing can be replacedor replated, the following method of touchup will beused:
a. Clean the tubing thoroughly.
b. Mechanically remove the deteriorated cadmiumand/or corrosion.
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c. Wipe thoroughly with an approved solvent cleaner.
d. Apply wash (DOD-P-15328).
e. Apply two coats of epoxy MIL-DTL-53022(corrosion inhibitor, lead and chromate free).
f. As an alternate to paragraph e., apply one coat ofprimer followed by a topcoat to match surrounding area.Ensure that the primer and topcoat are compatible (seeTM 55-1500 345-23).
B-13. CORROSION REMOVAL FROM THIN METAL.When corrosion and stains are to be removed fromairframe structure skins thinner than 0.0625 inch and anabrasive method of removal is required, the followingprocedure applies:
a. Prepare pumice paste by mixing pumice powder(SS-P-821) and water to form a slurry. Use a clean, softcloth such as cheesecloth to apply the paste to the stainand rub gently.
CAUTION
Do not allow metallic or corrosion particles tobuild up on the polishing area or polishing tool(cloth or grit paper) during polishing. Damageto the metal may result.
b. When pumice has dried to a white powder, wipeoff with clean, dry, soft cloth. If corrosion products stillexist (stubborn stains), use number 600 grit, wet or dry,abrasive paper and water to remove the remainingcorrosion. Wipe clean with clean, dry, soft cloth.
B-14. CORROSION AND PAINT REMOVAL FROMMETAL COMPONENTS REMOVED FROMAIRCRAFT. Metal components removed from aircraft(except control surfaces, precision components, andclose tolerance fittings) and taken to repair shops forroutine rework may be cleaned free of paint and corrosionby abrasive blasting. See Chapter 4 and the specificalloy sections for detailed information.
B-15. AIR INTAKE DUCTS-JET AIRCRAFT. Air intakeducts are fabricated from materials (usually 5000 seriesaluminum) which have high corrosion resistance. Certaincomponents of these ducts may be cast aluminum ormagnesium. Coating of these castings and frequentcleaning of the duct is usually sufficient to precludeattack by corrosion. Aircraft performing low level missions
or take-off and landings over salt water or in highlysaline atmospheres may need the ducts painted toreduce corrosion attack. Such a requirement must bedetermined by the operating activity. A polyurethanepaint system as outlined in TM 55-1500-345-23 isrecommended.
NOTE
When the history of an aircraft reveals ductcracking and rivet shear, a coating is notdesirable. Painting of such ducts will makedetection of failures difficult, and oftenimpossible, without removal of the paint.
B-16. CLOSELY COILED SPRINGS. Springs that areclosely coiled, preventing the application of plating tointernal surfaces, shall receive two coats ofMIL-DTL-53022 (corrosion inhibitor, lead and chromatefree) or MIL-PRF-23377.
NOTE
These requirements do not apply to springsmade of corrosion resistant steel or berylliumcopper, or to springs in oil or hydraulic fluids.
B-17. CORROSION TREATMENT OF STEELCABLES.
a. Inspect cable for damage in accordance withTM 1-1500-204-23-1, paragraph 9-12e, and appropriateaircraft manuals.
b. Move surface controls of the particular cable tothe extremities to reveal the cable in the pulley contact,fairlead area, or drum. If the surface of the cable iscorroded, relieve cable tension and carefully force thecable open by reverse twisting and visually inspect theinterior.
c. Corrosion on the interior strands of the cableconstitutes failure, and the cable must be replaced. If nointernal corrosion is detected, remove loose externalrust and corrosion with a clean, dry, coarse-weave ragor fiber brush.
d. After thorough cleaning, apply MIL-PRF-16173Grade 1 corrosion preventive compound sparingly. Donot apply the material so thick that it will interfere withthe operation of cables at fairleads, pulleys or groovedbellcrank areas.
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B-18. GENERAL. This section describesdecontamination procedures to be followed after it hasbeen determined that a fuel system is contaminatedwith salt water or microbiological growth. It is extremelyimportant that fuel system decontamination proceduresbe initiated as soon as possible following evidence ofcontamination, particularly if salt water contaminated,because serious corrosion damage to metalliccomponents can begin within a few hours. Defueling,depuddling and purging are required as part ofdecontamination of the fuel system. Defueling shall bedone in accordance with instructions contained in theapplicable aircraft maintenance manual.
B-18.1. COMPONENTS REQUIRING SPECIALTREATMENT. Components such as cork floats, wiringbundles, braided hose covering and capacitance typefuel quantity indicators may require special treatmentswhich include removal and soaking in a hot cleaningsolution followed by scrubbing to remove residual saltdeposits and/or microbiological growth. When ultrasoniccleaning equipment is available, cleaning time can beshortened considerably.
B-18.2. WATER EMULSION CLEANINGCOMPOUNDS. Water emulsion cleaning compoundsare specified to assist in cleaning grossly contaminatedsystems. Since residues from these cleaning compoundsprovide food for microorganisms leading tomicrobiological growth, it is essential that thoroughfresh water rinsing follow their use.
B-19. SALT WATER CONTAMINATION. Salt watercontamination of the aircraft fuel system does notnecessarily result in immediate engine fuel systemcontamination. Therefore, fuel samples shall be obtainedfrom the engine fuel system beginning with main filtersand working downstream until the extent of salt waterpenetration into the fuel system can be established. Ifthere is no evidence of salt water in the engine fuelsystem, the system shall be disconnected and/or blankedoff to prevent possible contamination during fuel celland aircraft plumbing system decontamination.
B-19.1. DECONTAMINATION PROCEDURES.
WARNING
Sodium dichromate crystals (A-A-59123) aretoxic to the skin and eyes. Chemical or splashproof goggles, rubber gloves (MIL-G-12223),coveralls (MIL-C-2202), and a respirator(GGGM-125/1) shall be worn when handlingthese crystals.
CAUTION
To prevent possible damage to fuel systemnonmetallic components, the solutiontemperature shall not exceed 120°F (49°C).
Do not allow sodium dichromate solution to dryout on any metallic surface during treatment.
Ensure that cellulose sponges are in goodcondition (i.e., not coming apart or shredding)when used inside a fuel cell or tank. Also, toprevent a fire hazard, cellulose sponges andcheesecloth used for cleaning fuel cells ortanks shall be disposed of in accordance withlocal safety instructions.
B-19.2. To decontaminate the fuel system, proceed asfollows:
a. While the fuel system is still assembled, defuelaircraft and drain remaining fuel using low point drains.Include draining the engine fuel systems, if contaminated.
b. Prepare an inhibitor solution by adding 35 to 40pounds of sodium dichromate crystals (A-A-59123) toeach 50 gallons of fresh water. To improve flushingability, use warm water (100° to 120°F (38° to 49°C)), ifavailable. The inhibitor solution will dissolve and removemost of the residual salts, thus providing temporarycorrosion protection for metallic components.
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION V. DECONTAMINATION PROCEDURES FOR SALT WATER ANDMICROBIOLOGICAL GROWTH CONTAMINATION
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c. To treat systems by flushing, remove tank or cellaccess plates and removable components, asnecessary, to provide maximum access to contaminatedareas. Using a pump (5100-254B) and rubber hose,pump and circulate the sodium dichromate solutionthroughout the tanks and cells, keeping all surfaces wetfor at least 30 minutes. Allow tanks and cells to drain intoreceptacles during this operation.
d. As soon as treatment by flushing is completed,drain all inhibitor solution from system. Immediatelybegin rinsing with fresh water and continue rinsing untilrinse water is clear or has only a slight orange tint.
NOTE
Fuel system components contaminated withsalt water that cannot be thoroughly inspected"in place" for corrosion damage shall be removedand disassembled sufficiently to establishinternal conditions and for damage correction.For metering devices and other items, removeand flush with fresh water, drain, dry, andpreserve internally with water displacing,corrosion preventive compound (MIL-PRF-81309 Type II Class 1), tag with thenotation "CONTAMINATED INTERNALLYWITH SEA WATER", and forward to thedesignated maintenance facility for rework.
e. As soon as possible after flushing and inhibitingtreatment, open all cells and tanks by removing accessplates, probes, pumps, fittings, etc., for maximum visualinspection of interior areas.
f. Remove residual fuel and sodium dichromatesolution using an explosion-proof vacuum cleaner orcellulose sponges (A-A-2073) and cheesecloth(CCC-C-440). For cells which are impossible to enter,use an explosion-proof vacuum cleaner or attach thecellulose sponge or cheesecloth to a wooden handle forreaching remote areas.
g. Inspect fuel cells for corrosion and evidence ofmicrobiological growth. Treat corrosion in accordancewith Chapter 6. If microbiological growth is found proceedto and comply with paragraph 2-4c of TM 1-1500-204-23-3.
h. Test fuel system for leaks as outlined in paragraph2-5g of TM 1-1500-204-23-3.
B-20. MICROBIOLOGICAL GROWTH CONTAMINA-TION OF FUEL CELLS.
WARNING
Solutions containing isopropyl alcohol(TT-I-735) are flammable and shall be drainedinto safety containers and disposed of inaccordance with local safety instructions.
CAUTION
To prevent possible damage to fuel systemnonmetallic components, the solutiontemperature shall not exceed 120°F (49°C).
a. Defuel aircraft in accordance with instructionscontained in the applicable maintenance manual.
b. Remove capacitance type fuel quantity indicatorprobes, internal plumbing, valves, electrical wiring, floatswitches, etc., as necessary to gain access to all areaswhere salt water or microbiological growth may havecollected, or where hidden corrosive attack may haveoccurred. Except for fuel quantity indicator probes (whichshall always be removed and cleaned), the extent offurther component removal shall be determined by theevidenced need for a more in-depth inspection of acomponent.
c. Make up a water emulsion cleaning solution byadding one part by volume of MIL-PRF-85704 Type Icleaning compound to nine parts of fresh water.
d. For electrical wiring, fuel quantity indicator probes,fittings, plumbing lines, and any intricate componentsthat cannot be effectively cleaned with the water emulsioncleaning solution and scrubbing with a hog bristle brush(H-B-420), immerse in water emulsion cleaning solutionfor approximately one to three hours. If possible, thesolution should be heated and maintained atapproximately 120°F (49°C).
e. When all residues have been loosened, rinsethoroughly with water until items are clean. Drain as wellas possible, rotating items to get complete draining.Place items in drying ovens maintained at 120°F (49°C)maximum for 12 hours. If ovens are not available dry byimmersing items in undiluted isopropyl alcohol (TT-I-735)for approximately one minute and blow dry with cleancompressed air at a pressure of no more than 10 psi.Install new fuel quantity probes if these cleaning
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procedures prove to be ineffective when processedprobes are tested electrically in accordance withapplicable maintenance instruction manuals.
NOTE
When cleaning bladder and self-sealing cells,look for evidence of cell liner porosity,deterioration, punctures, tears, etc., which mayallow salt water, sodium dichromate solution orfuel to leak from the fuel cell into the airframecavity and cavity liners. If leaks are suspected,inspect airframe cavity liners and cavities whenthe cell is removed for repair or replacement. Ifauthorized repair does not require removal,disassemble and loosen cell sufficiently toexamine for liquid entrapment and corrosiondamage. If cavity liner or cavity is wet, removeresidual fuel/water using an explosion-proofvacuum cleaner, cellulose sponges (A-A-2073),and cheesecloth (CCC-C-440). Treat corrosionin accordance with Chapter 6.
f. Clean fuel cells or tanks by scrubbingcontaminated areas with water emulsion cleaningsolution (see paragraph B-20.c.). Efficient scrub brushesmay be prepared by trimming bristles of paint brushes(H-B-420) to approximately one half the normal length.Brushes may be attached to wooden handles for reachingremote areas. Thoroughly scrub all interior areas untilall residues have been loosened.
g. Ensuring that lower sections of fuel cells andtanks are open to permit free drainage, thoroughly flushand rinse interior of fuel cells with fresh (warm water, ifavailable) to remove all foreign matter and cleaningcompound residues. Continue rinsing until all evidenceof cleaning compound is removed or until dischargewater is clear.
h. To assist in cleaning, flush fuel cells with a mixtureof one part isopropyl alcohol (TT-I-735) and one part tapwater. A pump (5100-254B) and extension hose may beused to apply the water/alcohol solution.
i. Flush the hidden area with the 50% water/alcoholsolution. Remove residual water/alcohol solution withan explosion-proof vacuum cleaner, cellulose sponges(A-A-2073) and cheesecloth (CCC-C-440). To facilitatedrainage of hidden or inaccessible areas formed bybulkheads, baffles, stiffeners, etc., alter attitude of aircraftby inflating and deflating gear struts or by using jacks inaccordance with applicable maintenance instructionsmanuals.
j. Remove all visible traces of water: alcohol solutionby passing warm (120°F (49°C) maximum), dry airthrough fuel cells for approximately eight to 12 hours.This can be accomplished by closing a cell except fortwo openings: one for entry and one for exit of hot air.The entry and exit openings should be as far apart aspossible. The exit opening should be large enough toallow water and alcohol vapors to readily escape andprevent pressure buildup in fuel cells. When possible,during the last part of the drying operation, close off theexit opening and direct the drying air through the installedfuel boost and transfer pump ports to ensure adequatedrying of these parts.
k. After drying, inspect fuel cells and tanks forevidence of salt crystals or remaining sodium dichromate.Remove any such residues by swabbing with spongesdampened with the 50% water: alcohol solution. Unlessthe deposits are so extensive that reflushing with wateris needed, it will not be necessary to perform additionalforced air drying.
l. Inspect for corrosion and treat all corroded areasin accordance with Chapter 6.
m. For integral type fuel cells, inspect the conditionof sealants. Repair or replace, as necessary, all sealantcoatings in accordance with paragraph 2-5f ofTM 1-1500-204-23-3.
n. Functionally check all electrical equipment inaccordance with applicable maintenance instructionsmanuals before installation.
o. As soon as possible after cleaning, drying, andany replacing of sealant, reassemble fuel system andchange all fuel filters and fuel aircraft to normal operatingcapacity in accordance with applicable maintenanceinstructions manuals. After fueling wait a minimum offour hours and then take fuel samples from the low pointdrains.
p. Test fuel system for leaks in accordance withparagraph 2-5g of TM 1-1500-204-23-3.
q. A test flight or maintenance operational check inaccordance with applicable aircraft maintenancemanuals shall be performed following the performedmaintenance.
r. Inspect fuel storage tanks and trucks for possiblesources of fungus and/or water contamination.
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s. To avoid future fungus contamination, use onlymilitary specification turbine fuel, which contains abiocidal agent (MIL-DTL-85470), or add this agentaccording to accepted commercial methods noted onthe biocidal container when refueling with non-militaryfuel.
B-21. REMOVAL OF MICROBIOLOGICALGROWTHS.
WARNING
Open all circuit breakers associated with batterypower (refer to applicable maintenancemanuals) prior to application of isopropyl alcohol(TT-I-735). Do not use synthetic wiping clothswith flammable solvents such as isopropylalcohol. Observe personal precautionary andprotective measures. Use chemical or splashproof goggles and rubber gloves when workingwith tri-basic sodium phosphate (O-S-642).When solution is splashed into eyes,immediately flush thoroughly with water andreport to dispensary.
CAUTION
The use of strong tri-basic sodium phosphate(O-S-642) is not recommended for removingpaint from wood surfaces, since the solution willattack the fibers, causing swelling anddiscoloration.
B-21.1. Fungus growth such as mildew and mold occuron organic materials (plastic and oil), and on organiccoatings (paints) or deposits on the surface of inorganic(metal and concrete) materials, particularly in damp,warm climates.
B-21.2. MICROBIOLOGICAL GROWTH ONPLASTICS. Since the term plastics includes compoundsof different chemical compositions varying widely inchemical and physical properties, one type of plasticmay be cleaned by a method which may be destructiveto another type of plastic. In general, organic solvents,including petroleum solvents such as dry cleaning solventand mineral spirits paint thinner, should not be used toclean plastics or allowed to come in contact with plastics.Plastics are cleaned by wiping with a lint-free cloth orsponge moistened with clean water or a solution of two
ounces by weight of detergent (P-D-410) per gallon ofwater. Plastics are polished by rubbing with groundabrasive technical pumice (SS-P-821). Other cleaningmethods can be used for certain types of plastics.
B-21.2.1. Acrylate and Methacrylate Resin Plastics(Plexiglas). These plastics are cleaned by washing witha solution containing one ounce of general purposedetergent (MIL-D-16791) in one gallon of water. Wipearea with a flannel cloth.
B-21.2.2. Plastic Electrical Insulation. Clean plasticelectrical insulation by wiping with a lint-free cloth orsponge moistened with isopropyl alcohol TT-I-735).
B-21.3. PAINTED AND UNPAINTED METALSURFACES.
B-21.3.1. Fungus Growth. Fungus growth is removedfrom painted and unpainted metal surfaces by scrubbingwith a solution of two ounces by weight of detergent(P-D-410) per gallon of water. When fungus cannot beremoved from unpainted surfaces by scrubbing withdetergent, mechanical removal is recommended inaccordance with Chapter 4 of this manual.
B-21.3.2. Mildew. Mildew may be produced by fungusgrowing on organic matter adhering to a soft paint filmor on the paint oil itself. Remove mildew by scrubbingwith a water solution of tribasic sodium phosphate(O-S-642).
a. A strong phosphate solution (three pounds per 10gallons of water) is most effective, but the solutionshould be applied to small areas of the surface at a time,rinsed off immediately with clean water, and dried witha wiping cloth. When allowed to remain on the paintedsurface for several minutes, the solution will loosen thepaint and may attack the wood fibers.
b. Scrubbing the surface with a mild phosphatesolution (21⁄2 ounces by weight per 10 gallons of water)will not loosen the paint and is less effective in removingthe mildew. Rinse the surface thoroughly to removeresidue.
c. To prevent recurrence of mildew, the old paintsystem should be removed in accordance withTM 55-1500-345-23.
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B-22. GENERAL. The metal identification kit (FSN6630-831-5932) shall be used to determine the types ofmetal(s) used in the construction of aircraft. The use ofthis kit employs two methods of identification: (a) primaryclassification of metals; and (b) chemical spot analysis.See Table B-2.
NOTE
Before proceeding with test, remove paint (ifpresent) from a one inch square area with clothsoaked in an approved compliant solventcleaner.
B-23. PRIMARY CLASSIFICATION.
a. For a preliminary identification, compare metalstrips in the kit with unknown metal on aircraft.
b. Place a magnet on the metal surface. Magneticattraction classifies the base metal as a ferrous magneticmaterial (i.e., iron or steel).
B-24. CHEMICAL SPOT ANALYSIS. Chemical testsare used to identify a base metal and/or plating. If thebase metal is plated and its identification is desired, theplating must be mechanically removed by abrasionbefore tests are made. Surrounding surface treatmentsof the metal will not interfere with these tests.
B-25. TESTING PROCEDURES FOR TYPES OFSURFACE TREATMENT.
B-25.1. PHOSPHATE TREATMENT. To confirm thepresence of a phosphate treatment on steel, zinc,cadmium, or aluminum, place a drop of 20% nitric acidsolution on the surface and follow this with two drops ofammonium molybdate solution. If the metal surface hashad a phosphate treatment, a yellow precipitate willform.
B-25.2. CHROMATE TREATMENT. Surface chromatetreatments on zinc, cadmium, aluminum, or magnesiumare highly colored and are indicative of the applicationof these treatments. A bleached chromate treatmentmay have been applied, however, and then coated withlacquer to mask any residual iridescence for the sake ofappearance. If so, visual detection of the chromate is
impossible. To test for this lacquer, proceed as directedin the following paragraph.
B-25.2.1. Test for Lacquer. Place a drop ofconcentrated sulfuric acid on the surface. If lacquer ispresent, the spot will rapidly turn brown with noeffervescence. If lacquer is not present, the spot will notturn brown. If the metal is zinc, there will be a rapideffervescence; if cadmium, there will be no reaction.
B-25.2.2. Test for Chromate Film on Zinc Chromium.Place a drop of 5% aqueous solution of lead acetate onthe surface. If the metal has been treated, the surfacewill show no discoloration for 10 seconds. If there is nosurface treatment, an immediate dark spot will appear.
NOTE
A bleached chromate treatment is not approvedbecause the bleaching process lowers corrosionresistance of metal.
B-26. CONTENTS OF METAL IDENTIFICATION KIT.This kit consists of metal strips (1.0 x 6.0 x 0.063 cubicinches) to be used for visual comparison and practice,and reagents to be used for performing a chemical spotanalysis. Conduct the following test procedures:
NOTE
Where tests have been conducted, it will benecessary to remove the test chemical,neutralize the surface, and apply the originalpaint coating. Where plating has been removed,recoat with two coats of epoxy primer(MIL-PRF-23377).
B-26.1. IRON AND STEEL. Place a drop of 10%hydrochloric acid on the metal surface. The acid will notnoticeably react on iron or steel. Place a drop of sodiumsulfide over the drop of hydrochloric acid. This willcause a black ring to form around a white precipitate. Toconfirm this test, a drop of 20% nitric acid on iron or steelwill cause a black spot, and a drop of sodium sulfideover the nitric acid will cause a black precipitate. If thesteel or iron has been bonderized, the spot will appearas a black ring around a white spot in both tests. This isnot a test for bonderizing process.
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
B-26.2. CHROMIUM. Place a drop of 10% hydrochloricacid on the metal surface, followed by a drop ofconcentrated sulfuric acid. If the plating is chromium,the solution will turn green within one to two minutes.
B-26.3. ZINC. Place a drop of 10% hydrochloric acid onthe metal. If the metal is zinc, reaction will be rapid. Adrop of sodium sulfide over the hydrochloric acid willcause a white precipitate. To confirm this test, a drop of20% nitric acid also will cause a rapid reaction, and theaddition of sodium sulfide will form a white precipitate.
B-26.4. CADMIUM. Place a drop of 10% hydrochloricacid on the metal. If the plating is cadmium, there will beno noticeable reaction. The addition of a drop of sodiumsulfide over the drop of acid; however, will cause ayellow ring to form around a white precipitate. Toconfirm this test a drop of 20% nitric acid will react withthe metal but there will be no color change. A drop ofsodium sulfide over the drop of acid will cause a yellowprecipitate.
B-26.5. TIN. The hydrochloric acid-sodium sulfide testwill have the same reaction on tin as on cadmium. If themetal is tin, a drop of 20% nitric acid on the surface willcause a rapid reaction and a black spot to form. Whena drop of sodium sulfide is added to the acid, the resultis a black precipitate.
B-26.6. SILVER. Place a drop of 20% nitric acid on thesurface and let it react for 10 seconds. Then add a dropof 10% hydrochloric acid. If the metal is silver, there willbe an immediate formation of a white precipitate.
B-26.7. NICKEL. Place a drop of dimethylglyoximesolution on the metal and follow it with a drop ofammonium hydroxide. The result will be pink-redcoloration. Both the 10% hydrochloric acid-sodiumsulfide and the 20% nitric acid-sodium sulfide tests willcause a black ring around a white precipitate.
B-26.8. MAGNESIUM. A drop of 10% hydrochloric acidon magnesium will cause a violent reaction and a blackspot to form. To confirm that the metal is magnesium,place a drop of 10% sodium hydroxide on the surface.There should be no reaction.
B-26.9. ALUMINUM. Unlike its reaction on magnesium,10% hydrochloric acid will have no noticeable reactionon aluminum. A spot of 10% solution of sodium hydroxide(caustic soda) on the surface, however, will cause arapid reaction.
B-26.10. HEAT-TREATABLE AND NONHEAT-TREATABLE ALUMINUM ALLOYS. Place a drop of10% solution of sodium hydroxide (caustic soda) on themetal. Pure or nonheat-treatable aluminum will notdiscolor, but heat-treatable aluminum alloys will turnblack.
B-26.11. CLAD ALUMINUM ALLOYS. Clad alloysmust be tested on the unclad edge. A drop of 10%cadmium chloride solution on a clean unclad surface ofthe metal will produce a dark discoloration on 7076 and7178 aluminum alloys within two minutes. Nodiscoloration will appear on 2024 aluminum alloy withintwo minutes.
B-26.12. COPPER AND BRASS. If plating ispresent, remove it by abrasion with sandpaper.Determine whether the metal is copper or brass bynoting the typical brass or copper color. Similarlydetermine copper plating by its typical color.
B-26.13. STAINLESS STEEL (18-8). Mix 10 gramsof cupric chloride in 100 milliliters of hydrochloric acidand place one drop of the mixture on the metal. After twominutes, follow this with three or four drops of water,then dry the surface. If a brown spot appears, the metalis 18-8 stainless steel.
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APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
SECTION VII. PLASTIC MEDIA BLASTING (PMB) FOR ARMY AIRCRAFT COMPONENTS
B-27. PLASTIC MEDIA BLASTING (PMB) FORARMY AIRCRAFT COMPONENTS.
B-27.1. SCOPE. The purpose of this section is toestablish the requirements and controls for the PMBprocess for use at intermediate and depot levelmaintenance of Army aircraft components of rotarywing aircraft.
B-27.1.1. Application.
a. This section provides the requirements andprocedures for removing organic coatings (paints,primers, or lacquers); surface cleaning and removal oflight surface corrosion and carbon deposits; removal ofsealants and adhesives; and assist in removal of any ofthese after chemical soaking, from parts and componentsof aircraft using PMB techniques.
b. PMB is authorized only for parts and componentswhere PMB is specified by the applicable aircraftcomponent Depot Maintenance Work Requirement(DMWR) or Technical Manual (TM). Comply with anyadditional processing instructions required by theseauthorizing documents. The applicable technical datashall be used when additional processing, such asetching to remove metal flow, flushing, solvent cleaning,stripping, etc., is used in conjunction with the PMBprocessing.
c. Request for processing Flight Safety Parts (FSP)with internal oil, grease, air, or other fluid passages, willbe coordinated and approved via official writtencorrespondence by the AMCOM Aviation and MissileResearch Development Engineering Center (AMRDEC)before authorizing PMB.
d. For purposes of this section, PMB shall be usedon metal surfaces and the following composite surfacesonly: fiberglass, carbon fiber, boron and graphite/epoxy,and Kevlar. Proper masking shall be in place whereother types of surfaces are present.
B-27.1.2. Limitations. The PMB shall not be authorizedfor the following surfaces:
a. Engineering plastics and glass that must remainclear.
b. Elastomeric rubber surfaces.
c. Cadmium plated parts and other plated orcontaminated parts where the PMB may generateairborne hazards controlled by safety, health, orenvironmental regulations.
d. Parts made of Beryllium Copper.
e. Bearings and assemblies with exposed seals andgaskets unless these can be properly masked and postexamination reveals zero intrusion of media in active orlube wetted surfaces.
f. Teflon lined surfaces and small threaded holesand inserts.
B-27.1.3. Classification.
B-27.1.3.1. Critical Parts. Parts with Internal air orfluid flow passages, or FSP where any portion of thePMB is considered a Critical Inspection Point.
B-27.1.3.2. Soft Metal Parts. Parts made of Aluminumor Magnesium Alloy.
B-27.1.3.3. Ferrous Parts. Parts made of FerrousAlloy.
B-27.1.3.4. Titanium Parts. Parts made of TitaniumAlloy.
B-27.1.3.5. Non-metal Parts. Non-metal parts orsurfaces approved for PMB.
B-27.2. DOCUMENT CONFLICTS. In event of conflictbetween the requirements of this section and theapplicable aircraft component DMWR or TM, the aircraftcomponent DMWR or TM shall take precedence. Therequirements of this section shall take precedence overany other specifications or standards referenced herein.
B-27.3. MATERIAL REQUIREMENTS.
B-27.3.1. The plastic media type used for the PMBprocess shall be in accordance with MIL-P-85891Type V, 20-40 particle size. Optional media and particlesize is not authorized unless approved by the aircraftcomponent DMWR or TM.
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B-27.3.2. Media used on ferrous alloys shall not beused on parts made of aluminum, magnesium, ortitanium.
B-27.3.3. Media having a high density level of 200 partsper million (ppm) or more of any type of contaminationcan cause mechanical damage. Purge and dispose ofcontaminated media.
CAUTION
PMB with heavily contaminated media maypermanently damage substrate surfaces.
B-27.4. EQUIPMENT REQUIREMENTS.
B-27.4.1. General.
a. PMB equipment used to remove organic coatingsfrom aircraft components shall be a direct pressure feedabrasive blasting unit capable of propelling a controlledand continuous stream of plastic media from 15-40 psiand 0-500 pound per hour media flow. The equipmentshall be equipped with setting indicators and regulationdevices. A blast cabinet (glove box) or walk-in typefacility may be used.
b. Siphon fed abrasive blasting equipment shall notbe used for plastic media blasting.
c. PMB equipment shall have a recovery system,consisting of a cyclone separator, a rotary airlock, amagnetic particle separator, and a screen separator.The recovery system shall be capable of producingmedia cleanliness levels as described in B-27.4.1.f.Alternate recovery system configurations requireengineering approval prior to use.
d. The blast cabinet or walk-in facility shall havelighting capable of producing a minimum of 55 footcandles illumination at the work surface. Portable lightingmay be used to eliminate shadows at the work surface.All lighting shall meet the requirements of the NationalElectric Code for Class II Division 1 locations (dustignition proof). Reference Army Regulation 11-27.
e. Nozzles shall be venturi type, 1⁄4 to 1⁄2 inch indiameter, constructed of a material with an abrasiveresistant characteristic of tungsten carbide or better.
f. PMB equipment shall be capable of maintainingacceptable levels of media size per MIL-P-85891 andcleanliness of 200 parts per million or less of heavyparticle contamination.
g. Compressed air supply to the PMB equipmentshall be dry and filtered, 60% maximum relative humidity.Dedicated source is recommended.
h. Preventative maintenance shall be in accordancewith the manufacturer's recommendations, includingallowable nozzle ID wear. Annual PM program for thePMB equipment shall include replacing worn nozzles,lines, and valves; recalibrating pressure and flow gageson the equipment; and re-certification for full capabilityfor the intended PMB operation.
i. Equipment certification shall include calibrationof air pressure gages, verification of pressure at nozzleexit, and flow rate.
j. Re-certification shall be required of any equipmentthat was repaired or is deemed responsible for failure toproduce consistent results, including supply air, operator,or media deficiencies, prior to returning to production.
k. There shall be sufficient PMB units to support thePMB operations so that processing Ferrous Alloys,Titanium, Magnesium, Thorium, etc., are each done intheir own dedicated separate units (designed for thatpurpose), different from the units used for all other work.If this is not feasible, the media shall be completelypurged when switching between these differentprocesses.
B-27.4.2. Glove Box Cabinet Type Equipment. GloveBox Cabinets shall be specifically designed for use withplastic media meeting the general requirements above.All aircraft component parts shall be processed usingthe Glove Box Cabinets unless the equipment is notcapable or the part will not properly fit inside the cabinet.
B-27.4.3. Walk-In Facility. This processing isauthorized when the part or component exceeds thesize limitations of the Glove Box Cabinet. The Walk-InFacility (open blasting), in addition to the generalrequirements, shall meet the requirements ofOSHA 29CFR1910.9:
a. Ventilation. A minimum cross-draft ventilationrate of 75 cubic feet/minute per square foot of open facearea shall be provided.
b. Dust Collector. The dust collector system shall becapable of removing 99.97% of the particles 0.3 (threetenths) micron or greater in size from re-circulationsystems.
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c. Dust Monitor. The dust monitor equipment shallbe capable of continuously monitoring explosiveconditions of air in the facility.
d. Safety. Walk-in room operator safety equipmentshall include a carbon monoxide monitor, respiratoryequipment, blast hood and hearing protection. Safetyequipment shall be as specified by the cognizant Safetyand Industrial Hygiene Department.
e. Maintenance. The Walk-In Facility shall beoperated and maintained in accordance with theequipment manufacturer's instruction manual.
B-27.5. PMB PROCESS.
B-27.5.1. General Requirements.
B-27.5.1.1. The PMB blast shall be kept moving in aneven sweeping motion and not allowed to dwell overone spot while maintaining stand off distance andnozzle angle.
B-27.5.1.2. The PMB operator shall stop the processimmediately when any abnormality in the process isobserved or damage to the substrate is noticed.Sometimes the coating scheme may be different thanexpected, media characteristics may change, airpressure may fluctuate, etc. The anomaly shall becorrected or appropriate changes made beforeproceeding.
B-27.5.1.3. An operating procedure or processingsheet shall be developed for each part and shall includethe following:
a. P/N, substrate (including plating), andidentification of film to be removed (indicate limitations).
b. Part preparation, including cleaning and masking.
c. Media type, specification.
d. Air pressure.
e. Flow rate.
f. Stand off distance.
g. Angle of impingement.
h. Maximum dwell time.
i. Post processing cleaning, inspection, flow.
j. Special instructions.
NOTE
The aircraft component DMWR or TM mayexclude certain parameters as stated above,as required.
B-27.5.1.4. The air pressure selected for removal oforganic coatings shall be within 25-40 psig, unlessotherwise specified in the aircraft component DMWR orTM.
B-27.5.1.5. The air pressures selected for generalcleaning and removal of oxides and carbon depositsshall be within 15-25 psig, unless otherwise specified inaircraft component DMWR or TM.
B-27.5.1.6. The angle of impingement shall be within45-90 degrees, unless otherwise specified in aircraftcomponent DMWR or TM.
B-27.5.1.7. The minimum stand off distance of nozzleto work place shall be 2 inches unless otherwise specifiedin aircraft component DMWR or TM.
B-27.5.1.8. Metal parts with wall thickness less than0.032 inch shall not be PMB processed.
B-27.5.1.9. Parts and components must be free of oil,grease, dirt, or other contamination, and shall be airdried prior to PMB blasting.
B-27.5.1.10. Masking of aircraft component parts shallbe as required in order to protect sensitive areas, areasthat do not require PMB, or that require a different PMBprocess, and to avoid media intrusion in internalpassages or bearing surfaces. The following maskingmethods are acceptable as required.
a. Tape, impact resistant, 3M 500, BT 100, orequivalent.
b. Plugs, oversize, tapered, made from Neoprenerubber are recommended.
c. Bags.
d. Fixtures and covers.
e. BER mating parts.
f. Molds.
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B-27.5.1.11. Masking used shall be made to adequatelywithstand the blasting force, prevent media intrusion,and protect from mechanical damage. The effectivenessof the masking shall be verified by visual and fiber opticinspection before approving initial production.
B-27.5.2. Critical Parts.
B-27.5.2.1. All parts with internal air or fluid passagesor areas that may entrap PMB media that could remainentrapped until assembly and/or cause crosscontamination of other subsequent processing of theend item, will be masked to prevent media intrusion.
B-27.5.2.2. Thoroughly clean excess PMB media fromthe parts by vacuuming or blowing with dry/filteredcompressed air before removing the masking. Thenvacuum or blow air through the internal passages toremove any entrapped media.
B-27.5.2.3. Flush with solvent or detergent as requiredby the applicable aircraft component DMWR or TM toclear internal passages.
B-27.5.2.4. FSP with Critical Inspection Points shallbe Fiber Optic inspected after PMB, cleaning, andflushing, and evidence of the inspection shall bemaintained on file.
B-27.5.3. Soft Metal Parts.
B-27.5.3.1. Unless otherwise specified in the aircraftcomponent DMWR or TM, aluminum and magnesiumparts shall only be stripped to the primer layer appliedto the anodized or chemical surface treatment. Theymay exhibit a haze of primer after stripping.
B-27.5.3.2. Magnesium parts coated with Rock Hard®resin coating or MIL-R-3043 resin coatings shall bestripped only to the resin coatings if subsequent penetrantinspection is required.
B-27.5.3.3. If the chemical conversion coating,anodize, or resin coating has been completely removedexposing the bare metal substrate, etching to removeflowed metal shall be required after PMB and beforeNDI. Refer to applicable aircraft component DMWR orTM for etching chemicals and process. The chemical
conversion coating, anodize, or resin coating shall bere-applied before re-painting.
B-27.5.4. Titanium Parts. Titanium parts may bestripped to bare metal. Any chemical conversion coatingsor soft metal platings removed shall be re-applied.
B-27.5.5. Ferrous Parts. Ferrous alloy parts may bestripped to bare metal if these are not cadmium plated.Any chemical conversion coatings or soft metal platingsremoved shall be re-applied.
B-27.5.6. Non-Metal Parts.
B-27.5.6.1. Non-metal surfaces may be stripped tothe primer layer. The lowest effective air pressuresetting should be used to avoid damaging the surface.
B-27.5.6.2. A rough haze or exposed fibers isunacceptable.
B-27.5.7. Post Processing.
B-27.5.7.1. All parts blasted by PMB shall bethoroughly cleaned by blowing with dry/filtered air orvacuuming. If masking was applied, masking shall notbe removed prior to blowing with air. Other mediacleaning methods, such as ultrasonic cleaning or solventflushing, may be used as per the applicable aircraftcomponent DMWR or TM.
B-27.5.7.2. After removing the masking, clean thepart per the applicable aircraft component DMWR or TMto remove lingering PMB media and masking residue.
B-27.5.7.3. Parts susceptible to corrosion that havebeen stripped to bare metal shall be coated with acorrosion preventive compound if subsequentprocessing is delayed.
B-27.6. TRAINING AND CERTIFICATIONREQUIREMENTS. Personnel performing andsupervising media blasting of organic coatings fromaircraft component surfaces shall complete a trainingprogram leading to certification. An AMCOM authorizedsource shall be used for the initial training andcertification. Operators shall be re-certified every twoyears.
B-33
NAVAIR 01-1A-509-2TM 1-1500-344-23-2
15 April 2009
APPENDIX BSUPPLEMENTAL REQUIREMENTS FOR ARMY AIRCRAFT
