THE INFLUENCE OF THE CULTURE MEDIA ON THE STEEL CORROSION INDUCED BY Desulfovibrio vulgaris subsp. Oxamicus: AN ELECTROCHEMICAL NOISE STUDY

摘要

The corrosion processes induced by Desulfovibrio vulgaris subsp. Oxamicus (DSM192 DSM192T) on carbon steel growing in lactate/sulfate and in lactateitrate media were analyzed through the use of electrochemical noise technique. Like some other sulfate-reducing bacteria, this Desulfovibrio species was able to reduce nitrate and produced ammonia in the absence of sulfate Sterile control of lactate/sulfate culture medium without bacteria did not show any significant change in localization index (LI) evolution. However, the sterile control of lactateitrate culture medium showed the occurrence of a localized corrosion process during the first 100 h. The corrosion patterns induced in the presence of the Desulfovibrio strain were significantly influenced by the composition of the culture medium. The corrosion process observed in lactate/sulfate medium was initially mixed and then became localized. On the other hand, LI indicated three well defined corrosion processes in lactateitrate medium: a localized corrosion process (0 h - 250 h), a mixed corrosion process (254 h – 430 h) and a uniform corrosion process from 435 h to the end of the experiment. The values of LI, that indicated localized corrosion, were higher in lactate/sulfate medium compared with those obtained in lactateitrate medium. The time series analysis showed the occurrence of pitting on steel only when Desulfovibrio vulgaris subsp. Oxamicus was cultivated in lactate/sulfate medium.