SELF-HELP AT THE BERTH - EPOXY REPAIRS
Strafford Morss, Preservation Engineer
PROJECT COMPLETION REPORT
COOPERATIVE AGREEMENT CA 4000-9-9026
During 1995 and 1996, the Museum destroyer JOSEPH P. KENNEDY, JR. (DD-850) experienced approximately 36 holes in the vessel's shell plating, due to corrosion. The ship's staff was able to make temporary repairs each time; locating the leak, patching the hole, pumping out flooding water, and cleaning the affected space.
The initial preventive action was completion of repairs to, and activation of the ship's impressed current cathodic protection system. The total effectiveness of this action was questioned as impressed current systems are not effective at the water's edge and full effectiveness is achieved at and below four feet below the surface.
Inspection revealed that ice scraping against the hull of the vessel had removed the protective coating along the waterline (splash zone) leaving bare steel exposed to accelerated corrosion in the oxygen rich zone at and just below the waterline.
Further preventive action would require re-coating the bare steel to provide primary splash zone protection. A marine epoxy, manufactured by Belzona, was suggested as a solution. A 30 foot long X 2.5 foot high test section was applied in 1997. This application required heeling the ship about 7-8 degrees by flooding feed and fresh water tanks on the opposite side. This was done, but in the process significant tank leakage into the ship's interior was identified.
The project had three objectives:
The ship was first heeled to port to expose the 1997 demonstration project. Careful examination showed the demonstration project had performed as predicted and indicated that accomplishment of the proposed waterline belt application was practical and desirable.
Sandblasting the hull surface from just above the floatation waterline down to the water's edge, with the hull heeled over, revealed not only the expected corrosion at the waterline, but also extensive corrosion and pitting action over the exposed hull surface.
The hull was sandblasted to SSSP-10 standards (near white blast) and the Belzona 1121 applied by trowel. Where holes were noted in the plates (all 36 known penetrations were identified) a scrim was applied to provide re-inforcement for the 1121. The 1121 was applied in a continuous layer over the belt area.
Upon completion, Belzona 5811 was applied at a wet film thickness of 10 mils over the 1121 to provide a barrier coating and the correct color coat (black) for the vessel's boot top.
During the entire blasting operations other disturbing conditions were noted. Some hull doubler plates, applied during the 1986-87 dry docking, had penetrated and many seal welds along the edges of the doubler plates had been attacked and destroyed. Water was now between original hull plate and doublers that had been installed to protect the hull. In those cases none of the protective systems used to protect the underwater body are effective. The noted problem continued beneath the water's edge where corrective actions could not be addressed.
Conclusions - Water line belt
1. Corrosion Mechanisms.
2. Conclusion and Evaluation.
Repair of Feed and Fresh Water Tanks
Kennedy has four fresh and four feed water tanks. These tanks are built into the side of the vessel on the two Fire Rooms (B-1 and B-3). There are two tanks on each side of each fire room. The tanks use the vessel's shell plate as a boundary and extend into the fire rooms. They are relatively wide at the top, deep, and have a very narrow bottom (about a foot wide).
Six of the eight tanks were noted as leaking. Most of the leaks were at the bottom both in the plates and in the welds where considerable rust and debris had lodged over the years. At the time of the report KENNEDY had been out of service 27 years, half of her physical age, with little or no maintenance done on the tanks in that period.
Belzona repairs involved entering the tank, working in very tight areas, cleaning the wasted areas to clean (non-wasted steel) and applying both the scrim and Belzona 1121 to affect the repair. After product cure, the acceptance criteria was fill the tank and have no leaks.
The Belzona repair technique had been chosen due to the success of the waterline belt repair and the fear that welding might result in burning off existing exterior coatings in an affected area.
Conclusion and Evaluation
The physical conditions encountered, especially at or near the bottom of the tanks, rendered the application of Belzona moderately successful. After the first application, nearly all the tanks still leaked, although less. The contractor returned, made a second application. Two tanks still leaked. Red Hand Epoxy was applied by a second contractor which corrected the remaining leaks.
Two tanks had physically split near their tops, B-11W and B-13W. The openings were judged to be too large for epoxy repairs. The steel repairs were made and were satisfactory. As in any repair, access to the area requiring repair is very important. The access to the steel repair areas was as easy as the access to the epoxy repair areas was difficult.
One reason for choosing the epoxy repair was the fear of damaging exterior underwater coatings by burn through. The tank repairs were accomplished simultaneously with other repairs required by the insurance surveyor before the vessel could proceed to sea undertow to participate in making a movie. Some of the repairs required burning out and replacing the ends of five longitudinal stringers. Upon completion of that work, there was no evidence of coating burn through on the vessel's exterior. However, the fear of coating damage by burn through is a valid concern.
The obvious final conclusion is that there is not universal repair method. Access, materials drive the technique used. Usually a combination of methods will provide a better result than one. The Belzona application on the wind/water belt appears very successful. The tank application was difficult for any method. In the areas where the hull doublers have been penetrated, or the seal welds failed, we are currently relying on the mild steel (A-36) doubler plates electrolytically sacrificing themselves to protect the already thinned high tensile steel shell plate. This is not totally comforting.
2005 Additional Conclusions
The Belzona belt was completed on DD-850 in October 1998, and the application of International Red Hand epoxy filler to Battleship MASSACHUSETTS was completed in March 1999.
In Spring 2005, preparing for the annual Navy Inspection, the following was noted. On MASSACHUSETTS port quarter at the floatation waterline, approximately one square foot of Red Hand epoxy had disbonded and broken off half above and half below the waterline, exposing bare steel. At the same time it was noted that some edges of the port side Belzona belt had started to break their bonds to KENNEDY's hull above the water's edge.
The epoxies appear to have a substantially larger coefficient of expansion for thermal changes than the steel hulls. In both cases the epoxies are used crossing the waterline. Except when ice has formed, or is present adding possible abrasion to the equation, below the waterline temperature change is slow and varies from about 32°F to 75°F during the year. Above the waterline the temperature gradient is much steeper, the maximum temperature much higher, and substantial temperature swings take place every day. Both products had substantial overcoating that protected them from the degrading effects of direct ultra-violet radiation.
The postulated failure mechanism included substantial, and repeated, thermal cycling above the waterline as the epoxies expanded and contracted at a greater rate than the steel resulting in the fracture of some of the chemically-induced mechanical bonds between the products and the surface profile of the steel substrate.
On KENNEDY this can be monitored over time with some spot patching. On MASSACHUSETTS repairs had to be made using Hycote 151, an epoxy that could cure underwater. Repairs were made by a Hycote-licensed applicator, and cost approximately $13,000.
The waterline failures were not unexpected and will require monitoring. The addition of Hycote 151 to the maintenance arsenal is a great improvement, although even the manufacturer recognized it as a temporary repair. The product is greatly improved over what was tried on TEXAS during 1987.
Below the waterline there is no reason to believe the epoxies are not doing their job and doing it well. While at TEXAS in 1987 and 1988, conversations with several tankship owners indicated that some of their ships had Red Hand patches dating back to the 1960s, and that the patches were only removed, not easily, when the Coast Guard wished to inspect the steel beneath.
NATIONAL PARK SERVICE
PROJECT PRODUCT SPECIFICATIONS
WATER LINE BELT, 810 feet by 2.5 feet
1. Belzona 1121, Super XL-Metal
A two component paste grade system based on a silicon steel alloy blended with high molecular weight reactive polymers and ogolimers (modified epoxide resins). Product is used to build up wasted metal, fill pits, etc. To fill through holes, a special scrim is first used to provide a matrix upon which the 1121 may be applied. Application is by trowel to thicknesses as necessary to build up and fare hull steel plate to original thickness (5/16 inch).
Cured color is gray; water line boot topping color should be black in this area.
2. Belzona 5811, High Performance barrier coating.
A two component system applied by brush or spray for protection o f metallic surfaces from aqueous solutions. Product is a modified epoxide resin. Color is black. Application is at 10 mils Wet Film Thickness. An additional advantage is that 5811 has been subject to a Cathodic Disbondment Test, ASTM G8, and has appeared to pass, according to Belzona furnished documentation. The test results are desirable as KENNEDY 's underwater hull is protected by impressed current cathodic protection.
INTERIOR FRESH AND FEED WATER TANK REPAIRS
3. Belzona 1121, Super XL-Metal
A two component paste grade system based on a silicon steel alloy blended with high molecular weight reactive polymers and ogolimers (modified epoxide resins). Product is used to build up wasted metal, fill pits, etc. To fill through holes, a special scrim is first used to provide a matrix upon which the 1121 may be applied. Application is by trowel to thicknesses as necessary to build up the steel of fresh and feed water tanks as necessary.
Cured color is gray. As the water tanks are located in interior spaces, final color is not critical. As with any epoxy, upon cure the surface may be roughed up by sanding and color coats applied to match the interior spaces.
MATERIAL SAFETY DATA SHEETS (MSDS)
Product Specification Sheets and MSDS's for Belzona 5811 and 1121 are enclosed. The products appear normal for epoxies as skin sensitizers with hazardous thermal decomposition products at elevated temperatures.