Localized corrosion of 2205 DSS with Sigma phase under alternate immersion induced by Pseudomonas aeruginosa (C2026-00086)

Liyang Zhu, Dun Zhang, Tianlei Li, Linfeng Zan, Jiajia Wu

Duplex stainless steel (DSS) exhibits good mechanical properties and corrosion resistance in marine environment due to its ferrite (α) and austenite (γ) phases with a volume ratio of ca. 1. However, it is not immune completely to microbiologically influenced corrosion (MIC). Furthermore, the preferential corrosion sites of DSS in the presence of bacteria are still in controversy, which can be closely related to the difference in microstructure of metals and environments. In the present work, localized corrosion under the synergistic effect of alternate immersion and σ phase was investigated, and the mechanism was elaborated. The pitting corrosion was further accelerated by the synergistic effect of σ phase and alternate immersion. The distribution of pitting sites on coupons with σ phase under alternate immersion was changed from concentrating around σ phase on ones under full immersion. The pitting sites on coupons with σ phase under alternate immersion in biotic medium mainly concentrated at the α-γ phase boundaries, which might be closely related with Cr/Mo depletion at the phase boundaries and bigger proportion than that of the σ phase. Additionally, micro-galvanic corrosion between α and γ phase was inhibited by alternate immersion, resulting in absence of height differences between these two phases.