Corrosion of stainless steels AISI 304 and AISI 316 induced by sulfate reducing bacteria in anoxic groundwater

A laboratory system for studying the microbiological corrosion of stainless steel decommissioning waste from nuclear power plant was designed and developed. Understanding microbially induced corrosion (MIC) in deep bedrock is important for evaluating the long-term safety of radioactive waste disposal. In anoxic water, the overall corrosion rate of steel is low. Microorganisms however, may accelerate several types of corrosion. The groundwater at the radioactive waste repository depth contains up to 105 microbial cells mL-1 with considerable diversity. MIC of stainless steels AISI 304 and AISI 316 in natural anoxic groundwater containing enrichment of sulfate reducing bacteria (SRB) was studied over a one-year experimental period. Electrochemical techniques enabling real-time survey of corrosion, such as multi-electrode arrays sensors (MASS) and linear polarization resistance (LPR) were used to detect the differences in electrochemical behavior of two stainless steels. In addition, molecular biological methods were used to detect microbial biofilm formation on the stainless steel surfaces. The general corrosion rate for both studied stainless steel grades was very low, but localized corrosion was detected on AISI 316. The aim of this paper was to characterize the rate and mechanisms of corrosion in the presence of SRB. The results of this study can be used when evaluating the risks associated with MIC of metallic materials in underground storage of low and intermediate level nuclear waste. © 2017 by NACE International.