Evaluation of New Surface Preparation and Coating Repair Techniques in Ballast Tanks Interim Report (Three Year Results)
NATIONAL STEEL AND SHIPBUILDING CO SAN DIEGO CA
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Ship ballast tanks present special problems as concerns corrosion control. In addition, ballast tanks are one of the most costly areas in which to apply coatings in both new ship construction and ship maintenance. Being subjected to intermittent wet and dry cycles of aerated sea water places extreme demands on corrosion control methods. Harsh service environments are coupled with necessarily complex tank geometries, especially in Navy combatants where weight and hull designs dictate small, irregular tanks with difficult accessibility. The SP-3 Panel of SNAME recognized these problems and formulated a series of research and development projects to investigate alternate, cost effective corrosion control solutions. The first project began in 1980 and was entitled cathodic ProtectionPartial Coatings Verses Complete Coating in Tanks. A series of ballast tank mock ups were constructed which duplicate ballast tank geometries. The tanks were also large enough to allow access for surface preparation and installation of the various corrosion control methods. In 1988, the project was redirected to evaluate maintenance procedures and techniques. At that time the tanks had been under test for six years. Included in the new project were VOC compliant340 gramsliter, surface tolerant epoxies from two suppliers, reformulated MIL-P-24441 VOC compliant epoxy, and a technique common to the Japanese marine industry, namely the addition of zinc anode cathodic protection in lieu of complete coating removal and re-application. Two coating systems from the original project were still providing adequate protection and, therefore, left undisturbed.
- Coatings, Colorants and Finishes
- Marine Engineering