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Propeller shafts of AISI type 316 stainless steel (UNS S31600) on several ships suffered severe pitting within 12 days of launching. The corrosion occurred within the water-lubricated stern tubes in a pattern that outlined the bearing staves and the shaft packing seals. This suggested some form of crevice corrosion was involved. Rapid onset of pitting indicated the corrosion process was accelerated by stray current. Laboratory simulations of the environment reproduced corrosion observed on the shafts within the same time frame. A second set of experiments, in which the stray current flowing through a simulated shaft was measured, confirmed that crevice corrosion could be initiated within 3 days. A prototype instrument was designed and built to allow automatic measurement and storage of current flow and potential difference data from four experimental configurations. Experiments conducted with this instrument provided further evidence that corrosion on the propeller shafts had been initiated and promoted by stray current passing through the shafts. Existence of a crevice was not, by itself, sufficient to produce the observed attack within the same time frame. Experiments indicated an appropriate shaft grounding system would eliminate corrosion of the shafts on these ships.

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