Corrosion of high-alloy stainless steels in the marine environment

High-alloyed stainless steels have been developed by increasing the amount of chromium up to 25 % and that of molybdenum up to 3.0 % in the stainless steels. They are widely applied in the sea-water environment where the most important corrosion types are crevice corrosion and galvanic corrosion possibly induced by microbial slime layer formation. In this study the microbial slime layer of the high-alloyed stainless steels is investigated by transmission electron microscope. The corrosion potential of the alloys is measured during the sea-water exposure. Based on the above experiments the corrosion potential of the alloys is predominantly increased by the adherent slime layer. The bacterial layer of the alloys consists of several microbial organisms and by-deposited metal-ions or metallic compounds.