Effect of preferential growth of Shewanella oneidensis MR-1 on microbial corrosion of constituent phases of 2205 duplex stainless steel

Understanding selective growth of electroactive bacteria on surface of constituent phases (ferrite/ austenite) of 2205 DSS is required for mitigating microbiologically influenced corrosion (MIC). In this study, the preferential attachment of bacteria and its impact on corrosion of single phase were investigated under anaerobic condition using Shewanella oneidensis MR-1. Single-ferrite phase was more susceptible to biofilm formation compared with single-austenite phase. Atomic force microscope (AFM) revealed that the surface of ferrite phase coupon was fully covered with S. oneidensis MR-1 biofilm whereas few S. oneidensis MR-1 cells were observed on the surface of austenite phase. After 14 d of incubation, the maximum biofilm thicknesses on 2205 DSS, ferrite and austenite phase were 15.5 ± 1.0 µm, 13.8 ± 3.2 µm, and 10.2 ± 0.8 µm, respectively. S. oneidensis MR-1 accelerated the pitting corrosion of materials. The maximum pits depth on single ferrite and austenite phase in sterile medium (3.2 µm vs 2.2 µm with mean values 2.5 µm vs 1.7 µm) were relatively small than those in biotic medium (6.0 µm vs 4.5 µm with mean values 4.5 µm vs 3.8 µm). Synergistic effects of Cr and Ni enhanced the stability of passive film on austenite phase.