Power Washing and Overcoating is Effective and Much Less Expensive than Sandblasting and
Completely Repainting a Bridgeby
Wayne Senick, Technical Director
and
Craig Ballinger, P.E.
Termarust Technologies
Abrasive Blasted High Pressure Water Cleaned
Advantages of Abrasive Blasting and High Pressure Water Cleaning
Abrasive Blasting• Removal Of Lead based
paint• Prepare surface for zinc
based coating• Cosmetics
HPWC• Effectively cleans structure
critical crevice corroded connections
• Cost effectively removes Non Visible contaminants
• Provides a stable substrate for over coating
• Potential for at least 50% project cost savings
1 yr old 3 coat zinc epoxy 1 yr old 3 coat zinc epoxy urethane over pack rusturethane over pack rust
These Crevice corroded connections were not washed before coating to remove the active salts, not chemically
treated to neutralize the active corrosion causing chemistries and were then sealed - which created an oxygen
concentration cell and failure occurred
Crevice Corroded Connection Washed before Abrasive Blasting and Coating
• to remove the active salts• chemically treated with
HR CSA penetrant to neutralize the active corrosion causing chemistries
• sealed up with a top coat based on HR CSA* neutralization chemistry
• Coating failure has not occur in 18 years
*HR CSA (High Ratio Co-Polymerized Calcium Sulfonate)
Crevice Corroded connections treated with an HR CSA* corrosion control coating on the High Level Bridge Edmonton, Alberta,
Canada after 18 years the crevice corrosion has been stopped
Pack rust and Crevice corrosion can overstress structural connections
This structure has coating failure in the joints and connections, caused by severe crevice corrosion and
pack rust, but the coating on the flat surfaces is relatively intact
Typical Recycling Equipment and Negative Air Containment used in Abrasive Blasting
and Lead Removal Operations
Grit recycling unit and air mover with bag house
Two complete negative air grit recycling systems with air compressors hooked in a train to be towed
down the bridge as the containment moved
Two example of negative air containments
Water Collection, Containment and Surface Preparation Equipment for HPWC Lead
Removal Project
Shrink wrapped water tight ultra-light water collection containment
Movable flow thru tap system to contain paint chips and liquid water
3-5500 PSI HPWC Units and Injector for Soluble Salt Remover
7000 PSI 6 Gallon per minute hot Water HPWC Unit with salt remover injector
Complete Water Recycling and Filtration System on 100,000 square foot Bridge
Project
Fresh and filtered water storage Pressure pumps to supply head pressure of 15 PSI for wash pumps
Settling Tank, Skimmer and Feed Pumps for Filter System
Water passes thru 5 and 1 micron particle filters before going to storage for re use
Typical High Pressure Water Cleaning Surface Preparation Sequence with Adhesion Testing
and Testing for Non–Visible Contaminants
Removal of black oxides by hand or power tool cleaning
High Pressure Water Cleaning using 5000 PSI, zero degree rotating tip, a 4
inch stand off distance
Adhesion Testing using a Hydraulic Pull-off tester, 300 PSI minimum for over coating, 300 hundred tests per 100,000 sq ft. Photo
courtesy Ministry Transport Ontario
Testing for Non Visible Contaminants before coating application
Where are the costs• Removal of lead based coatings by abrasive blasting and ultra
high pressure water jetting micronizes the lead dust which makes it breathable and absorbable by plants.
• The containment for abrasive blasting is heavier and more expensive to construct because of the weight of the abrasive and the need for negative air pressure to facilitate environmental protection
• The surface needs to be washed to mitigate salts and the water must be collected. The washing step must be done, the water must be removed, and containment dried before blasting can take place
• The equipment required to contain, abrasive blast, collect and recycle the abrasive is much more expensive to buy and operate than a high pressure water cleaning system.
Adhesion of Remaining Substrate• If stressed by HPWC (High Pressure Water Cleaning) at a minimum
5000 PSI with a zero degree rotating tip at a maximum 4 inch stand off distance specified, adhesion testing in the field has shown that this surface preparation method consistently will produce adhesion values over 300 PSI for the remaining coating.
• The owner should specify a minimum adhesion value no less than 300 PSI and adhesion testing must be done before coating is applied.
• The number of adhesion tests should be written into the specification. For example: a minimum of 300 tests per 100,000 square feet or whatever the engineer deems necessary based on the condition of the existing prepared substrate
• Field experience has shown a hydraulic pull off tester meeting ASTM D4541delivered the most consistent results
Test Site Photos and Adhesion Test Log Sheets
Site 24, Photo IM000824, 825 PSI
Site 33, Photo IM00833, 450 PSI
Test Site Photos and Adhesion Test Log Sheets
Site 163, Photo IM001000, 720 PSI
Site 179, Photo IM001022, 340 PSI
Cost Savings Case Histories Rail Bridge 260,000 square feet
• Total removal of lead based coating system
• Negative air containment• Collection, recycling or
disposal of abrasive• Standard 3 coat zinc
epoxy urethane coating• Bid price 7.6 million• No warranty provided
• High pressure water cleaning and over coating
• Collecting the lead paint and recycling the water
• High performance single coat HR CSA coating system
• Bid price $4.3 million• 5 year warranty
including crevice corroded joints and connections
Cost Saving including a 5 year warranty = $3.3 million
Contractors Actual Cost Savings Analysis as Proposed to Owner
Abrasive Blasting - 3 Coat Zinc System vs High Pressure Water Cleaning - HR CSA Coating System
• Specified Air and dust impenetrable enclosure
• Alternative Flow through tarps will trap paint chips and liquid water Cost saving
• Specified Mechanical ventilation system to protect workers sufficient to achieve a negative air environment within the enclosure
• Alternative Not required – no lead dust generated Cost saving
• Specified Exhaust ventilation system to provide filtration of the exhaust air
• Alternative Not required – no lead dust generated Cost saving
• Specified Weekly instrument testing to verify airflow and negative pressure inside containment
• Alternative Not required – no pressurized containment Cost saving
• Specified Air lock entry wall
• Alternative Not required – no lead dust to contain Cost saving
Cost Savings “Continued”• Specified
Cleaning and securing of containment at the end of workday• Alternative
Not required – no lead dust to blow around Cost saving
• Specified Daily assessment of visual emissions
• Alternative Not required - no lead dust generated Cost saving
• Specified Full time or part time high volume ambient air monitoring
• Alternative Not required – no lead dust generated Cost saving
• Specified Packaging, storage, transportation, and disposal of waste generated by the project
• Alternative Reduction of generated solid waste, approximately 1300 tons. in addition, no waste solvent, paint cans or catalyzed paint to dispose of Cost saving
Cost Savings “Continued”• Specified – coating system
Stripe coat zinc1st layer zinc2nd layer epoxy3rd layer 2k urethane
• Alternative Penetration for joints and connectionsCaulk coat + spot primePlus 1 layer wet on wet, instead of threeSeparate coats with curing time Cost saving
• Specified Caulking
• AlternativeSealing of joints included in coating operation Cost saving
• Specified – surface preparationSSPC-SP10 near white blasting andSSPC-SP7 brush-off blasting
• Alternative Not required Cost saving
• SpecifiedMeasure the surface profile of blast cleaned surfaces
• Alternative Not required – coating not profile sensitive Cost saving
Cost Savings “Continued”• Specified
Specified time restriction between cleaning and painting• Alternative
Not required – flash rust not an issue Cost saving
• SpecifiedContainment during coating application
• Alternative Containment not required for purpose of environmental protection or for a safe working environment. As coating is not hazardous, will contain overspray with flow through tarps. Cost saving
• Specified – recoat timeApply each coat after previous coat has been allowed to dry
• Alternative All successive coats can be applied wet on wet Cost saving
• Specified – caulkingCaulking shall be applied to crevices not sealed, after the application of the second intermediate layer.Manufacturer’s note – Caulking must be allowed to cure for 5 – 8 days at 23ºC and 50% R.H.
• Alternative Caulk not required Cost saving
• SpecifiedWarranty 2 years or 5 years – separate price
• Alternative5 year warranty included Cost saving
Based on a cost saving of $3,000,000.00
3.5% 5.0% 7.5% 10.0%Year 1 $3,105,000.00 $3,150,000.00 $3,225,000.00 $3,300,000.00
Year 2 $3,213,675.00 $3,307,500.00 $3,466,875.00 $3,630,000.00
Year 3 $3,326,153.63 $3,472,875.00 $3,726,890.63 $3,993,000.00
Year 4 $3,442,569.00 $3,646,518.75 $4,006,407.42 $4,392,300.00
Year 5 $3,563,058.92 $3,828,844.69 $4,306,887.98 $4,831,530.00
Interest at end of warranty $563,059.00 $828,845.00 $1,306,888.00 $1,831,530.00 $1,831,530.00peroid
Interest Rates
Time Value of Money
Time Value of MoneyExample of one Owner’s use of the cost savings from HPWC are as follows:• Cost saving will be invested during the 5 year
warranty period ( shown on chart )• On going maintenance program will be
funded with earned interest • After the 5 year warranty period the saved
capital can now be used to fund another project
Case History Highway Bridge 100,000 square feet
• Total removal of lead based system
• Negative air containment• Collection, recycling or
disposal of abrasive• Standard 3 coat zinc
epoxy urethane coating• Bid price 3.5 million• No coating system
performance warranty available
• High pressure water cleaning and over coating
• Collecting the lead and recycling the water
• High performance single coat HR CSA coating system
• Bid price 1.2 million• 5 year warranty
including crevice corroded joints and connections
Cost Saving including a 5 year warranty 2.3 million dollars
Example SpecificationSurface Preparation
• SURFACE PREPARATION AND CLEANING:• High Pressure Water Cleaning - The structure (or the portions of it to be coated) are to be cleaned using a 7,000
psi 6 Gal/Min hot water HP WC (high-pressure water cleaning)– with a zero degree rotating tip (at a maximum of a 4” standoff distance) to a (SSPC –SP12 WJ4- NV2 ) to remove loose paint and loose rust (SSPC SP2 &SP3 hand or power tool cleaning maybe used in inaccessible areas or when water cleaning is not possible). In some cases after HP WC there are areas of tightly adhered black oxide which was not removed. This tightly adhered black oxide even though it meets the WJ4 standard (and the active corrosion under it) is highly contaminated with Chloride &/or Sulfates &/or Nitrates and if allowed to remain, will result in delamination of the black oxide substrate and the coating which has adhered to it and must be removed.
• Crevice Corroded Joints and Connections• When using a 7,000 psi 6 Gal/Min hot water HPWC (high-pressure water cleaning) with a zero degree rotating tip
(at a maximum of a “4” standoff distance) to a (SSPC –SP12 WJ4- NV2) The jet must be focused right on the crevice corroded joints and connections to flush them thoroughly. In addition to properly clean the joints and connections a soluble salt remover must be incorporated into the wash water. A minimum 100:1 solution of Chlor*Rid (manufactured by CHLOR*RID International. www.chlor-rid.com 1-800-442-3217 (USA) or 1-888-279-5497 (CDN) or equivalent is required to remove as much salt from the joint as possible. This is mandatory when preparing crevice corroded joints and connections for treatment with the HR CSA Penetrant/Sealer and HR CSA Primer/Topcoat System.
• NV (Non Visible Contaminants) When it is expected (and/or confirmed by testing) that the surface of the steel is
contaminated with soluble salts (Chlorides &/or Sulfates &/or Nitrates) – the HP WC (high pressure water cleaning) should be finished with or incorporated into the wash water initially a 100:1 solution of Chlor*Rid (manufactured by CHLOR*RID International. www.chlor-rid.com 1-800-442-3217 (USA) or 1-888-279-5497 (CDN) or equivalent to remove those salts. (Just washing with water is not adequate because the salts are chemically & polar attracted to steel) [For additional information on this topic please access chlor-rid’s website]
• DRYING: It is required that even if the joints and connections look dry - that they be blown dry with clean, DRY, oil free, high pressure ( 100 psi) compressed air.
Example SpecificationKey Points
• Testing to determine whether or not wash water is hazardous
• If water is hazardous - establish a collection and recycling or disposal system
• Collection of any hazardous material including paint chips
• Do adhesion test to verify surface preparation has been done correctly
• Do testing to determine non visible contaminants have been removed to acceptable levels
Conclusion• High Pressure Water Cleaning and a HR CSA coating
system is a cost effective alternative to Abrasive Blasting especially on structures with structure critical crevice corroded and pack rusted joints and connections
• In most cases washing is now specified for all painting projects for removal of non-visible contaminants
• The condition of the existing coating is not an issue as the HPWC surface preparation will remove any coating not suitable for over coating as proven by adhesion testing done in the field
• The cost saving can be used to fund other projects or invested to fund the long term maintenance of the structure especially for private owners and toll authorities.
