The effect of sulphate-reducing bacteria biofilm on passivity and development of pitting on 2205 duplex stainless steel
By Weronika Dec and Micha? Mosia?ek and Robert P. Socha and Marzena Jaworska-Kik and Wojciech Simka and Joanna Michalska
Published in Electrochimica Acta
2016
Abstract
Results on biofilm formation and microbiologically influenced corrosion induced by pure D. desulfuricans strain on 2205 duplex stainless steel (DSS) are presented. Biofilm development stimulated by \DSM642\ standard strain was evaluated with reference to their metabolic activity and to the surface characterization including the structure and configuration of the biofilm. Electrochemical techniques (open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves) and X-ray photoelectron spectroscopy (XPS) were carried out to determine the effect of bacteria on the passivity and corrosion resistance of 2205 DSS. The electrochemical results showed that the \DSS\ corrosion resistance was affected in the presence of \DSM642\ biofilm. This statement was based on the significant decrease in the charge transfer resistance (R1) obtained from \EIS\ and the increase in the measured current densities obtained from potentiodynamic polarization curves. Although the breakdown potentials (Eb) were still high, \SEM\ observations revealed micropits as well as signs of crevice attack on the steel surface. Significant sulphidation of the passive film affected the nature of cathodic behaviour of steel and helped to impede micropit growth. \XPS\ analysis revealed the layered structure of the biofilm. Accumulation of sulphides and hydroxides was proved in the outermost layer, while the increasing contents of disulphides, organometallic and \CN\ bonds were detected along the biofilm thickness in the \XPS\ analysis.