CORROSION OF STAINLESS STEELS EXPOSED TO SEAWATER CONTAINING SULFATE-REDUCING BACTERIA

Abstract. Sulfate-reducing bacteria (SRB) play significant role in the corrosion of stainless steels exposed to marine environment in several industrial plants especially in the extraction and processing oil and gas industry. Sulfate reduction by bacterial species results in the production of sulfide and, depending of the pH, hydrogen sulfide, which can significantly enhances the corrosion of several types of steels. In the present study, samples of two types of stainless steel, namely the austenitic AISI type 304 and the superduplex UMS S32750, were immersed in seawater containing Desulfovibrio vulgaris ssp vulgaris DP4 collected from Brazilian oil fields and identified by sequencing aps reductase gene. The samples were examined using optical microscopy, the aqueous solution was chemically characterized, and the corrosivity of the sterile medium was evaluated using electrochemical tests. The results obtained indicated that the superduplex stainless steel present a higher resistance to corrosion in a severe media containing chlorides and SRB compared to common austenitic stainless steel AISI typ