Biofilm formation and corrosion behaviour of 1010 carbon steel in SRB cultures by microscopic techniques and electrochemical impedance spectroscopy

Abstract

Biofilms cause various problems such as medical infections, fouling of water cooling system, product contamination, and microbiologically influenced corrosion (MIC)[1]. MIC accounts for as much as 20% of all forms of corrosion, amounting to billions of dollars in losses each year[2]. Among aerobic and anaerobic bacteria related to MIC, sulfate reducing bacteria (SRB) are most often blamed [3]. The ubiquity of these bacteria leads to a variety of impressive industrial, economic and ecological effects because of their proneness to generate large quantities of H2S. SRB are the main reason to cause the MIC by accelerating corrosion rate, inducing stress corrosion and pitting corrosion [4-6]. The aim of this study was to evaluate the corrosion associated with the formation of SRB biofilms on carbon steel surfaces. The bacterial strain used in the experiments was Desulfovibrio vulgaris cultured in Postgate´C. Carbon steel coupons of SAE 1010 were placed in the cultures for biofilm development during 1 and 7 days. Then, the coupons were extracted and bacterial adherence and biofilm formation were measured by viable bacteria counts, epifluorescence microscopy and by the crystal violet assay. Surface attack of carbon steel and biofilm morphology were analyzed by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Studies carried out allowed correlating the biofilm formation (Figure 1) with the different degree of attack suffered by the SAE 1010 carbon steel coupons. The impedance spectra (Figure 2) show that the charge transfer resistance increases with the time.