SRB and methanogens in corrosion of steel in anaerobic water

During the operation, maintenance and decommissioning of nuclear power plants contaminated waste is produced. This waste is disposed of in underground repository 60-100 meters below the ground surface. The metallic waste consists mostly of carbon steel and stainless steel. A long-term field exposure show high corrosion rates, general corrosion up to 29 ?m a-1 and localized corrosion even higher. Corrosion rates this high are possible if microbes are present and produce corrosive products or alter the local microenvironment to corrosion favoring. The bacterial and archaeal composition of biofilm formed on the surface of carbon steel was studied using 16S rRNA gene targeting pyro-sequencing followed by phylogenetic analyses of microbial community. The functional potential of microbial communities in biofilm was studied by functional gene targeting quantitative PCR. The corrosion rate was analyzed with weigh loss measurements and the deposits on the surfaces were analyzed with SEM/EDS. Our results demonstrate that the bacterial diversity on the surface of carbon steel and their functionality is vast. Our results suggest that the role of methanogenic archaea in corrosive biofilm, in addition to sulphate reducing bacteria, could be greater than previously suspected in these nutrient poor conditions.