A Comparison of Biotic and Inorganic Sulphide Films on Alloy 400

Distribution, tenacity and chemical composition of sulphide films produced by bacteria within biofilms were compared with those produced by waterborne inorganic sulphides. Attempts were made to differentiate corrosion mechanisms of alloy 400 (70Ni-3OCu) exposed to seawater in the presence or absence of sulphate-reducing bacteria (SRB). Experiments were conducted in an anaerobic environment in the presence of inorganic sulphide and sulphate-reducing bacteria (SRB) either freely corroding or coupled to an external cathode (alloy 400) exposed to air. Sulphur concentration in the films increased in the presence of SRB as well as when samples were coupled to an external cathode. Bacteria encrusted with corrosion products and integrated into the sulphide film were only observed in the presence of SRB in addition to coupling with an external cathode. [This is an unrefereed preprint].