Interactions of Desulfovibrio desulfuricans biofilm with 2205 duplex stainless steel – the role of microstructure

The paper presents the results on sulfate-reducing bacteria (SRB) induced corrosion of 2205 duplex stainless steel (DSS) in as-received and thermally aged conditions. Biofilm formation and damage process stimulated by DSM642 strain were analyzed with reference to its metabolic activity and to the surface characterization of structure and configuration of the biofilm. Electrochemical techniques were applied to monitor bacterial attachment to the steel surface and to determine the effect of bacteria on the passivity and corrosion resistance of 2205 DSS. Results demonstrated that MIC behavior was strongly affected by the microstructure and phase composition of the steel. Enhanced biofilm interactions were mainly limited to the austenitic phase, as well as primary (γ) and intergranular (γ₂) austenite was found to be more prone to bacterial attack. Thermal aging of 2205 DSS led to the enhanced bacterial attack. Thermally aged samples were characterized by quicker and more intensive biofouling. Pitting and crevice-type attacks were predominant on the thermally aged samples. It has been found that the presence of DSM642 biofilm changed the corrosion mechanism of 2205 DSS in 3.5% NaCl and the SRB-induced selective attack was evident even for the material in phase-balanced conditions.