Materials Division RemarksNAVSEA 05P2
TALK OUTLINE
• NAVSEA Mission Priorities
• Some Recent Materials Challenges Relevant to Corrosion Control
• Unique Solutions/Common Enablers
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksMission Priorities
Focus Areas:
• Improving Ship Maintenance: • Improving Material Selection, Design for Corrosion Control, Paint Materials,
Paint Application, Cathodic Protection – Lessons Learned Into Shipbuilding and Repair Specifications
• Enable Fleet Sailor – Train & Assist (CCAT, other)
• Commonality • Universal Requirements (NSI 009-32, “Gen Specs”)
• Workforce Excellence and Judiciousness• “Knee in the Curve” – We could deliver a nearly corrosion-free ship, but could
not afford it
• Risk, Consequence, and Cost – Proper balance requires hard-core engineering
• Challenge Every Requirement• ERM, CWP, Specification Cost Reduction, Spec Deep Dives, Affordability
Initiatives
• SSRAC, TWH/PM Negotiation on Shipbuilding Specs
Key Enablers: People and Teamwork, Innovation, Contracting, MetricsDistribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
Aluminum Cracking
• Advantages of Aluminum– Low weight to strength ratio– Ease of forming– General corrosion resistance
• Disadvantages of aluminum– Historically Navy experience is from steel – Elastic modulus is 1/3 that of steel– Toughness is less than steel– Cracks grow quickly and at lower stresses– Fatigue limits does not exist for aluminum– Aluminum welding has some special considerations– Anodic to most alloys leading to galvanic corrosion– Structural fire protection covers virtually all interior aluminum
making inspection difficult and expensiveDistribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Aluminum Cracking – 5xxx Alloy
• Highest as-welded strength of aluminum alloys; alloy strength increases with magnesium content.
• Relatively good corrosion resistance in seawater.• Moderate loss (~20%) of material strength when
welded.• Alloys with greater than 3% Mg will sensitize based on
temper, time, temperature and microstructure.
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Aluminum Cracking - Corrosion Fatigue vs Fatigue• Data on corrosion fatigue behavior of aluminum has knowledge gaps that need to be filled. Examples include friction stir welding and extrusions
• Solution: The effect of corrosion fatigue on some aluminum features has not be adequately studied, leaving risk in Fleet.
Fatigue curves for 5083
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Aluminum Cracking – Sensitization
• Sensitization makes the material susceptible to stress corrosion cracking.• Sensitization of 5XXX aluminum is the development of a continuous network of magnesium-aluminum (Mg 2Al3) precipitate
(beta phase)along the grain boundaries. • Driven by magnesium content, temperature, and strongly affected by material microstructure.
Solutions:• Sensitization Resistant temper – H128• Paint (LSA, active corrosion inhibitors)• Desensitization heat treatment• New detection tools• DoS probe• In-situ metallography • Ultrasonic Peening
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Aluminum Cracking – Thick Section Lamellar Cracking
• Possibly an SCC component due to large grains from non-uniform through-thickness work
• Solution: • Clad Weld of Exposed Grains
• H128 Temper?
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Aluminum Cracking – Design and Repairs
Bonded aluminum doubler
Composite patch
Compression bolts
Weld repair with UIT
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Water Jet Tunnel Corrosion - Solutions
Sacrificial Anode System
Impressed Current Cathodic Protection
Navy Approved Coating System
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Stern Tube Corrosion
Problem:
• Aluminum stern tube and flange coupled to SS shaft
• Strategy to electrically isolate the materials not advisable
• No paint to reduce cathode surface area or protect
• No cathodic protection
Solutions:
Proper Coatings Selection and Application
• Cathodic Protection in Preparation for Coatings Failure
• Due to the lack of bearing and shaft seal face surface area, solution was to cut “Top Hats” into the tunnel and install sacrificial anodes.
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksRecent Materials Challenges
(continued)
Seawater Discharge
Root Cause: Improper isolation techniques
Solutions: • Proper Isolation• Bi-metallic material
separation, increased resistance in galvanic couple
• Utilization of waster piece
Distribution Statement A: Approved for release. Distribution is unlimited.
Composite Deck Drains:
• Problem: Fasteners corrode in Cu-based drain so they could not be easily removed for cleaning.
• Solution: Make drain insert from composite with twist lock and install SS fasteners permanently. Finger holes provided to remove and service without tools.
• Evaluation on USS PELELIU (LHA 5) validated performance for SS/CVN
• Needed to re-test?
Materials Division RemarksRecent Materials Challenges
(continued)
Distribution Statement A: Approved for release. Distribution is unlimited.
Composite Deck Drains (continued):
• Problem: Fasteners corrode in Cu-based drain so they could not be easily removed for cleaning.
• Solution: Make drain insert from composite with twist lock and install SS fasteners permanently. Finger holes provided to remove and service without tools.
• Evaluation on USS PELELIU (LHA 5) validated performance for SS/CVN
• Needed to re-test – Grade A Shock
• PCOE investment in implementing in Surface Fleet.
Deck drain mounted in shock test machine
Materials Division RemarksRecent Materials Challenges
(continued)
Distribution Statement A: Approved for release. Distribution is unlimited.
Materials Division RemarksUnique Solutions/Common Enablers
Solutions Vary• Barrier Coatings
• Sacrificial Coatings
• Materials Selection (H128 Temper)
• Low Solar Absorption Paint
• Desensitization heat treatment
• New detection tools
• DoS probe
• In-situ metallography
• Ultrasonic Peening
• Clad Weld of Exposed Grains
• Electrical Isolation
• Sacrificial CP
• ICCP
• Waster/Inspection Pieces
• Composites
• Many Others
Common Enablers • People and Teamwork
(MegaRust)• Innovation
• Contracting• Metrics
Distribution Statement A: Approved for release. Distribution is unlimited.
