Abstract
A range of duplex and austenitic stainless steels and high grade cobalt and nickel base alloys were immersed in natural sea water off the West Coast of Scotland for periods of up to 18 months. This paper assesses the effect of biofouling by microorganisms and macrospecies on the electrochemical corrosion response of each alloy and the corrosion mechanisms prevalent in these conditions. The comparative behaviour of the eight alloys studied is discussed. The limiting factor for performance in sea water has been shown to be crevice corrosion, but the cobalt base Ultimet alloy was unaffected by localised corrosion for periods of up to 18 months. Large differences in behaviour have been found between Stellite 6 and Ultimet in sea water, partially explained by the larger concentration of Mo in the Ultimet alloy.
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