1. Naval Sea Systems Command and National Surface Treatment Center Rudder Coating Failures on Navy Ships SSPC October 2003 © 2003 Innovative Productivity, Inc. All Rights Reserved.

2. Outline Problem Definition Lab Testing Attempted Solutions; Ship Tests Summary Conclusion

3. The Problem

4. Problem Definition Rudder coating failure--12-18 months Causes not completely understood Fails to support docking cycle High Cost – Recoating rudders, struts, etc. costs $25K to $100K+ per ship – Sole source of supply

5. Number of Ships Affected Severe coating failures: – ARLEIGH BURKE (DDG 51) class 39 ships commissioned (10 under construction or planned) Moderate coating failures: – TICONDEROGA (CG 47) class 27 ships – SPRUANCE (DD 963) class 19 ships

6. Ship Areas Affected

7. Areas Affected (DDG 51 Class) Rudders: 700 sq ft/ship Stools: 466 sq ft/ship Palms:67 sq ft/ship Struts:229 sq ft/ship Barrels:136 sq ft/ship Total surface area affected = 1598 sq ft

8. Problem is Unique to USN Navy generally looks to industry for solutions – Similar commercial application – No marine driver in this case Commercial fleets not experiencing – Transit speeds – Maneuvers – Ship Design – Shorter docking interval Foreign Military not experiencing

9. Possible Causes and Mechanisms Possible causes – Ship design – Coating selection (unsuitable materials) Likely mechanisms: – Flow-induced corrosion – Cathodic disbondment – Erosion – Cavitation/Surface Turbulence – A combination of the above

10. Lab Testing Ocean City Research (OCRC) 1986 Tested fourteen coating systems Tests included: – Cavitation – Cathodic Disbondment – Seawater Permeability – Seawater Immersion

11. Lab Testing (cont.) OCRC Testing 1988 16 new coatings tested (cavitation only) Issues – Cathodic disbondment – Cavitation

12. Lab Testing (cont.) OCRC 1989 - 1990 Additional cavitation tests completed Test protocol included – Total coating system thickness – Per coat thickness – Primer used – Conditions similar to previous tests, plus influence of cathodic protection

13. OCRC Tests Findings 1990 Damage modes – Damage at cavitation inducement point – Disbondment at coating scribe – Coatings resisted either cavitation or disbondment, but not both 3M Company’s EC-2216 coating system determined to be most promising

14. 3M EC-2216 Tested by OCRC from 1986 to 1990 Tested in seawater flow channel Better cavitation resistance than MIL-DTL- 24441 More disbondment than MIL-DTL-24441 Selected as baseline system Only coating system specified in NAVSEA STD ITEM 009-32 for repair to cavitation-prone areas Marginal performance in service

15. Penn State Applied Research Laboratory (ARL) Testing 1996 ARL tested cavitation properties – 1.5 inch cavitation tunnel – 115 knots for 20 hours Tested 17 coating products – Test designed to assess metal loss due to cavitation – Test conditions were not designed to match actual rudder operating conditions One of two coatings that showed promise was an elasto-ceramic polymer paste

16. Shipboard Trials 1997 Elasto-ceramic polymer coating (paste grade material) applied to DDG-60 rudders prior to sail-away – Inspected during Post-Shakedown Availability – Improvement over previous coating system Also applied to DDG-68 rudders

17. Shipboard Trials (cont.) 1998 Polymer Tile surface treatment (applied via adhesively attached tiles) tested on DDG-78 – Applied with no prior test data or history – Tiles delaminated; replaced with elasto- ceramic paste during PSA

18. Shipboard Trials (cont.) 1999 HVOF tungsten-carbide coating tested on DDG-80 – Initially promising; significant damage at PSA – Replaced with elasto-ceramic polymer paste coating system

19. Shipboard Trials (cont.) Ultra thick elasto-ceramic polymer coating formulation tested on DDG-82 – Ultra thick (250 mils) patch applied to 30 sq ft of the outboard side of the stbd rudder in the area of highest stress – Basic elasto-ceramic paste formulation (60-90 mils) applied to rudders – Showed little damage during dry-dock inspection (22 months service)

20. Summary of Coating Systems and Test Applications

21. Polyurea Coating System Polyurea coating system (NSWCCD) No previous test data available Ship tested in: – USS UNDERWOOD (FFG 36) – USS BULKELEY (DDG 84) – USS LEYTE GULF (CG 55)

22. Polyurea Ship Tests USS UNDERWOOD (FFG 36) – Improper application; failed USS BULKELEY (DDG 84) – Applied to twisted rudder, struts, props USS LEYTE GULF (CG 55) – Applied to both rudders Applied to SSPC-SP-10 surface

23. USS LEYTE GULF (CG 55) Inboard side of stbd rudder <1 year in service Anti-fouling paint peeling off 50% bare metal <2 years in service

24. Elasto Ceramic Polymer Paste Tested by ARL – Performed well under cavitating flow in fresh water Test application on DDG-60 rudders Specified for new construction (DDG- 68+) Conflicting performance reports Difficult to apply (60 mils +) Currently applied to 36 ships

25. Elasto-Ceramic Polymer Paste (cont.) Two component, 100% solids, “fluid consistency elasto-ceramic polymer composite” “…specifically formulated to surface and protect equipment subject to cavitation accelerated erosion/corrosion”

26. Elasto-Ceramic Paste / Polymer Tile Ship Test Tested on USS PORTER (DDG 78) in ‘97 – Elasto-ceramic polymer paste applied by troweling; 60+ mil thickness Failed in area of highest stress – Polymer tile system applied via adhesively attached tiles Tiles delaminated

27. Elasto-Ceramic Paste / Polymer Tile Ship Test (cont.) Polymer Tiles at PSAElasto-ceramic paste at PSA

28. Elasto Ceramic Paste / HVOF Ship Test Both systems tested on USS ROOSEVELT (DDG 80) in 1999 – HVOF tungsten carbide coating applied to 40 sq ft area of port rudder – Elasto-ceramic polymer paste applied to remainder of port rudder, entire starboard rudder

29. Elasto Ceramic Paste / HVOF Ship Test (cont.) Condition of rudders after ~1.5 years HVOF tungsten carbide (top) and elasto-ceramic paste (bottom) showed failure, corrosion of substrate

30. Ultra Thick Elasto-Ceramic Paste No laboratory testing Applied to various ships; mixed results Difficult to apply Unusually thick coating (250 mils) Used as barrier layer in high cavitation areas – Topcoated with basic elasto-ceramic paste formulation

31. Ultra Thick Elasto-Ceramic Paste (cont.) Two component, 100% solids “elasto-ceramic polymer composite” Expensive – Material cost – Application cost

32. Ultra Thick Elasto-Ceramic Paste Ship Test Tested on USS LASSEN (DDG 82) in 1999 – Ultra thick elasto-ceramic paste formulation ~30 sq ft on starboard rudder 250 mils Feathered at the edges – Basic formulation then applied to both rudders at 60 mils

33. Ultra Thick Elasto-Ceramic Paste Ship Test Condition of rudders after ~2 years Ultra thick formulation (top): little damage Basic formulation only (bottom): significantly more damage

34. Ultra Thick Elasto-Ceramic Paste Ship Test Condition of port rudder 2 years since last docking Repair procedure/coating system ineffective DDG-82 Sept 03 Drydocking

35. Twisted Rudder Developed by NSWCCD – Twisted to align with propeller wash – Designed to reduce cavitation on rudder Tested at NSWCCD’s Large Cavitation Channel (LCC) Ship tests on USS BULKELEY (DDG 84) – Rudders installed Feb 00 – Polyurea installed Feb 01

36. Twisted Rudder (cont.) Performance: – No cavitation < 29 knots Current rudder cavitates at 23 knots Coating requirements remain Twisted rudder in the LCC

37. Twisted Rudder Coating Ship Test Top: Loss of anti- corrosive primer and damage to substrate Bottom: Polyurea application to rudders and propellers

38. Twisted Rudder Coating Ship Test USS BULKELEY—Dec 02

41. Summary Multifaceted problem – But limited area; not tying ships to the pier – A costly annoyance (for now) ICCP System designed to protect up to 15% of underwater hull Inadequate laboratory testing No root cause analysis To date, the Navy has found no cost-effective solution to the rudder coatings failures

42. Conclusion No coating system currently approved or previously tested provides a viable, cost effective solution The Navy is still seeking a coating system that will last for at least one full docking cycle (6-8 years) Candidate coatings must allow application in a shipyard environment at a reasonable cost