Corrosion of 2205 duplex stainless steel in chloride medium containing sulfate-reducing bacteria
P.J. Antony a,∗ , Shobhana Chongdar b , Pradeep Kumar b ,R. Raman a
Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay, Powai 400076, Mumbai, India b Naval Materials Research Laboratory, Addl. Ambernath421 506, Mumbai, India Received 1 May 2006; received in revised form 18 November 2006; accepted 18 November 2006 Available online 12 December 2006
Abstract Sulfate-reducing bacteria (SRB) playsigniﬁcant role in the corrosion of stainless steels exposed to marine and soil environment. Sulfate reduction by bacterial species results in the production of H2 S, which can signiﬁcantly inﬂuence theanodic and cathodic processes and ultimately enhances the corrosion of materials. In the present study, 2205 type duplex stainless steel (DSS) coupons in solution-annealed condition were exposed tochloride medium containing SRB species, Desulfovibrio desulfuricans, for 40 days and examined by microscopy. Etching of the duplex structure, pitting as well as crevice attack were noticed. Similarresults were obtained by microscopic studies with coupons exposed for 14 days in medium containing SRB followed by anodic polarization. SEM studies, of crevices observed after anodic polarization,indicated that the attack was initiated at the grain boundaries and slowly encroached into austenite grains. The initiation of attack was also evident from AFM studies of coupon exposed under freely corrodingconditions for 7 days. ESCA studies reveal that under anaerobic conditions of SRB growth sulﬁdation of passive ﬁlm occurs. The modiﬁed passive ﬁlm found to depolarize the cathodic reactions. Thenature and mechanism of SRB attack on DSS and possibility of detection at early stages were discussed. © 2006 Elsevier Ltd. All rights reserved.
Keywords: Duplex stainless steels; Sulfate-reducing...