Effect of One Sulfate-Reducing Bacterium SRB-Z Isolated from Pearl River on the Corrosion Behavior of Q235 Carbon Steel

Sulfate-reducing bacteria (SRB) have long been reported to participate in metal corrosion processes in anoxic environments. However, existing theories still need enrichment by identifying more corrosive microorganisms and exploring more plausible microbiologically-influenced corrosion pathways. In this study, a strain SRB-Z was isolated from the Pearl River in Guangzhou, and its effect and mechanisms on corrosion of Q235 carbon steel were examined. The biofilms, corrosion products, pits, and corrosion electrochemistry were characterized by SEM, XPS, CLSM, EDS, white light interferometer 3D profilometry, and electrochemical analysis, respectively. The results of this study indicate that SRB-Z could cause serious pitting of Q235 carbon steel. The maximum pit depth reached 54 mu m after immersion corrosion for 7 days. Strain SRB-Z promoted the cathodic reaction rate of Q235. The relative analyses revealed that pitting corrosion occurred because of galvanic corrosion caused by the formation of an FeS-SRB/Fe galvanic couple under the synergistic effect of the SRB-Z biofilm and its metabolite (H2S) on the Q235 coupon surfaces.