In the previous study, corrosion products were sampled from the bottom of a tank and analyzed with SEM-EDS and tested for the presence of MIC relevant microorganisms. Sulfur was detected with the SEM-EDS and microbiological analysis showed the presence of sulfur oxidizing bacteria (SOB) with qPCR, a molecular technique. It was concluded that MIC was the active corrosion mechanism and that SOB were introduced into the system during hydro-testing. The recommendation was to clean the tank and the entire pipe system with a biocide to stop the microbial activity.
However, some pieces of the puzzle didn’t fit. First, only uniform corrosion was present in the tank. In addition, the tank was flushed with nitrogen, so that there was no longer any oxygen present. It is possible that the detected sulfur oxidizing bacteria (SOB) were transported with the water into the system, but SOB require oxygen for their microbial activities. In addition, localized corrosion would be expected at MIC. Furthermore, sulfur was also part of the butane gas stored in the tank and probably not of microbial origin.
