Corrosion behavior of B10 alloy exposed to seawater containing vibrio azureus, sulfate-reducing bacteria, and their mixture

With increasing attention paid to the security issues of onshore engineering structure, corrosion researches of copper alloy were focused on the influence of single bacteria, especially the anaerobic sulfate-reducing bacteria (SRB). However, a part of documents indicated that comprehensive influence of natural bacteria on the copper alloy does exist, and whether the influence of single bacteria could represent the real impact of natural complex bacteria is remaining unclear. Under this consideration, electrochemical measurements, incorporated with surface morphology and composition analysis, were employed to investigate the corrosion behavior of B10 alloy in seawater which was inoculated into Vibrio azureus, SRB and their mixed strains, respectively, in this work. The results showed that these marine micro-organisms could affect the corrosion process of B10 alloy in relatively different ways. Compared with the sterile condition, Vibrio azureus could inhabit the corrosion of B10 alloy to some extent by blocking cathodic oxygen reducing process, while SRB could significantly promote its corrosion by accelerating anodic dissolution of B10 alloy via hydrogen depolarization and forming loose and bulky corrosion products without complete protection. In the mixed microbial medium, SRB multiply rapidly in the local anaerobic environment created by the biological membrane of Vibrio azureus, their interacting changed the corrosive micro-environment on the surface of B10 alloy. The smaller and complicated corrosion products formed in the seawater containing mixed strains obviously performed better than that produced in the medium containing SRB only, giving rise to a significant increase in anodic polarization; at the same time, similar cathodic process was still occurred in the mixed culture. As a result, the corrosion current density of B10 alloy fell in between those detected in two single microbial media. For the practice engineering applications, therefore, the conclusions drawn from single microbe medium should be cautiously and carefully adopted as the criterion to evaluate corrosion behavior of B10 alloy in actual microbial environment. ©, 2014, Chinese Academy of Sciences. All right reserved.