THE INFLUENCE OF THE MEDIA ON THE CORROSION OF MILD-STEEL BY DESULFOVIBRIO-DESULFURICANS BACTERIA - AN ELECTROCHEMICAL STUDY

Electrochemical studies and weight loss measurements on the biocorrosi on of mild steel in the presence and absence of sulphate reducing bact eria (SRB) grown either in lactate/sulphate and or in lactate/nitrate aqueous media, have been performed. Tafel analysis of the quasi-steady state polarisation curves gave the corrosion current densities, j(cor r), of 20 and 30 mu A cm(-2) for mild steel samples in the SRB culture in lactate/sulphate and lactate/nitrate media, respectively. In the a bsence of SRB the corresponding values of j(corr) were 19 and 9 mu A c m(-2), respectively. Corrosion current densities given by the linear p olarisation resistance method were very close to the ones given by Taf el analysis. A comparison of the corrosion rates obtained either from electrochemical or from weight loss data is given for all the media un der study. Open circuit potential and redox potentials measured over t wo days showed great differences for the lactate/sulphate and lactate/ nitrate growth media. Scanning electron microscopy (SEM) observations resulted in good correlation with open circuit potential data. (C) 199 7 Elsevier Science Ltd.