1. Materials Division Remarks NAVSEA 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.

2. Materials Division Remarks Mission 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 , “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, Metrics
Distribution Statement A: Approved for release. Distribution is unlimited.

3. Materials Division Remarks Recent 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 expensive
Distribution Statement A: Approved for release. Distribution is unlimited.

4. Materials Division Remarks Recent 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.

5. Materials Division Remarks Recent 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.

6. Materials Division Remarks Recent 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 (Mg2Al3) 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.

7. Materials Division Remarks Recent 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.

8. Materials Division Remarks Recent Materials Challenges (continued)
Aluminum Cracking – Design and Repairs
Composite patch
Bonded aluminum doubler
Weld repair with UIT
Compression bolts
Distribution Statement A: Approved for release. Distribution is unlimited.

9. Materials Division Remarks Recent 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.

10. Materials Division Remarks Recent 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.

11. Materials Division Remarks Recent 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.

12. Materials Division Remarks Recent Materials Challenges (continued)
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?
Distribution Statement A: Approved for release. Distribution is unlimited.

13. Materials Division Remarks Recent Materials Challenges (continued)
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
Distribution Statement A: Approved for release. Distribution is unlimited.

14. Materials Division Remarks Unique Solutions/Common Enablers
Solutions Vary
Barrier Coatings
Ultrasonic Peening
Sacrificial Coatings
Clad Weld of Exposed Grains
Materials Selection (H128 Temper)
Electrical Isolation
Low Solar Absorption Paint
Sacrificial CP
Desensitization heat treatment
ICCP
New detection tools
Waster/Inspection Pieces
DoS probe
Composites
In-situ metallography
Many Others
Common Enablers
Contracting
People and Teamwork (MegaRust)
Metrics
Innovation
Distribution Statement A: Approved for release. Distribution is unlimited.