Microbiologically Influenced Corrosion Behavior in Stainless Steels for Public Sewage Treatment Plants

A study was performed on the cases of corrosion regarded as microbiologically influenced corrosion (MIC), for stainless steel centrifuge, which had been used in the processes of sludge concentration and dehydration in public sewage treatment plants. Evaluation was made on chemical concentrations of the steels and macroscopic as well as microscopic features on the corrosion status. Most of the cases relate to cast stainless steel with two-phase microstructure similar to that of weld metal. A number of studies have been reported so far on the cases where MIC occurs on stainless steel in seawater and fresh water, but there have been very few reports on the cases of damage in sewage treatment plant. Further, almost no study described the corrosion of a material such as duplex stainless steel with highly corrosive property. It is known that MIC is very likely to occur on weld metal. As the causes of the corrosion, special attention is now focused on influence of oxidation and reduction in the environment and relation between two-phase microstructure and MIC such as galvanic effect of austenite phase and ferrite phase in stainless steel weld metal microstructure.