We report field and experimental growth of microbially induced corrosion (MIC) at high temperature in the condenser of a geothermal electric power unit. Four chambers containing polished and disinfected 304L stainless steel tubes were exposed to the condenser environment during 2, 4, 6, and 8 months respectively. In the condenser the temperatures range from 150° C at the inlet and about 40° C in the cooler areas. The tubes developed pitting where Desulfotomaculum nigrificaris, and Desulfotomaculum acetoxidans colonies were clearly identified by biochemical tests. Also, some indications were observed of the presence of genus Desulfovibrio and genus Thermodesulfobacterium. The characteristics of pitting were studied employing SEM-EDS techniques and optical microscopy.
Keywords: Geothermal, Microbially Induced Corrosion (MIC), Desulfofomaculurn nigrificans, D. acetoxidans, Sulfate-Reducing Bacteria (SRB), corrosion chamber, 304L stainless steel. Geothermal Electric Unit.