In a freshwater environment, accelerated corrosion of carbon and stainless steels is frequently observed. Here, an immersion study was conducted using nine types of steels in a freshwater pool for 22 mo. Accelerated corrosion was observed in carbon and Cr-containing steels and cast iron, whereas no visible corrosion was observed in stainless steels, even after 22 mo. Microbial community analysis showed that, in general corrosion, Fe(II)-oxidizing bacteria were enriched in the early corrosion phase, Fe(III)-reducing bacteria increased in the corrosion-developing phase, and sulfate-reducing bacteria were enriched in the corrosion products during the final corrosion phase. In contrast, in the 9% Cr steel with localized corrosion, the family Beggiatocaea bacteria were particularly enriched. These microbial community compositions also differed from those in the water and sediment samples. Therefore, microbial communities are drastically altered with the progression of corrosion, and iron-dependent microbial energy metabolism contributes to an environment that enables the enrichment of other microorganisms.
The presence and activities of microorganisms on metal surfaces can affect corrosion. Microbial communities after such corrosion incidents have been frequently analyzed, but little is known about the dynamics of microbial communities in biofilms on different types of stainless steels, such as austenitic, martensitic, and duplex stainless steels. Here, we conducted immersion experiments on 10 types of stainless steels in a freshwater environment, where microbiologically influenced corrosion was observed. During 22-month of immersion, severe localized corrosions were observed only on martensitic S40300 stainless steel. Microbial community analysis showed notable differences between non-corroded and corroded stainless steels. On the surfaces of non-corroded stainless steels, microbial communities were slowly altered and diversity decreased over time; in particular, relative abundance of Nitrospira sp. notably increased. Whereas microbial communities in corrosion products on corroded stainless steels showed low diversity; in particular, the family Beggiatoaceae bacteria, iron-oxidizing bacteria, and Candidatus Tenderia sp. were enriched. Furthermore, sulfur enrichment during localized corrosion was observed. Since there was no enrichment of sulfate-reducing bacteria, the sulfur enrichment may be derived from the presence of family Beggiatoaceae bacteria with intracellular sulfur inclusion. Our results demonstrated slow and drastic changes in microbial communities on the healthy and corroded metal surfaces, respectively, and microbial communities on the healthy metal surfaces were not affected by the composition of the stainless steel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.