Dynamics of microbial communities on the corrosion behavior of steel in freshwater environment

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.