The National Shipbuilding Research Program 1985 Ship Production Symposium Volume 2 Paper No. 18: Overcoating of Inorganic Zinc Primers for Underwater Service
OCEAN CITY RESEARCH CORP ALEXANDRIA VA
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A study sponsored by MARAD under the National Shipbuilding Research Program was undertaken to determine whether overcoating of inorganic zinc primers for underwater service will result in accelerated blistering or disbondment of the topcoat. The study included 5 inorganic zinc primers -- 2 U.S.-manufactured preconstruction- type, 1 Japanese preconstruction type, and 2 full-coat type. Two different weathering periods were tested -- 7 days and 60 days. Three different topcoats were evaluated, including the Navy MIL-P-24441 system and two commercial epoxy coating systems. Coated test panels were subjected to three different tests to rank susceptibility to blistering 1 guiescent seawater immersion at a potential of -1.0 volt vs. SCE, 2 quiescent seawater immersion at 25 psi, 1500E, and 3 continuous seawater flow at 18 knots. Interim test results suggest that, for underwater service, overcoating of certain inorganic zinc primers may result in premature blistering or disbondment of the topcoat.
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