Biocorrosion in a geothermal power plant

Hyperthermophilic archaebacteria (Thermoproteus neutrophilus) promoting the corrosion of type 316 stainless steel (SS) (UNS S31600) in vapor ducts of the Tejamaniles geothermal electric power plant in Los Azufres, Michoacan, Mexico, were isolated from condensed steam. Metallographic analysis and scanning electron microscopy were performed to determine the morphology of microbiological attack on the SS. Electrochemical corrosion tests showed that the bacteria induced corrosion on type 316 SS preferentially at grain boundaries. Large amounts of elemental sulfur and carbon were detected where the bacterial culture was located.