Atomic force microscopy study of microbiologically influenced corrosion ofmild steel

The anaerobic corrosion of mild steel in seawater was studied by atomic for ce microscopy (AFM). In the presence of sulfate reducing bacteria (SRB), co rrosion was intensified and accelerated. A biofilm consists of heterogeneou s microbial cells and extracellular polymeric substance with interstitial v oids was observed on the surface of mild steel coupons. The greatest damage of steel occurred beneath the biofilm, in the form of pitting corrosion. T he corrosion of steel can be quantified through section and bearing analyse s. The depth of pits increased linearly with time whereas the volume of pit s increased as t(2.83), the 2.83 power of time. Compared with a control exp eriment without SRB, the depth of pitting corrosion is about one order of m agnitude higher. Weight loss estimates from AFM images are about one order of magnitude smaller than actual weight loss experimental results. The prob lems of AFM quantification of corrosion rate at extended stage of corrosion are discussed. (C) 1999 The Electrochemical Society. S0013-4651(99)01-006- X. All rights reserved.