MICROBIOLOGICALLY INFLUENCED CORROSION OF 316L SS BY MARINE BIOFILMS IN SEAWATER

The microbiologically influenced corrosion behaviors of marine microorganism on 316L SS were studied by the immersion experiments in the nature seawater using the open circuit potential(Eocp),electrochemical impedance spectroscopy(EIS),potentiodynamic anodic and cyclic polarization curves,scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS) methods.It was observed that marine biofilm was formed by microorganisms on the surface of stainless steel.It was confirmed that E(ocp) of 316L SS in nature seawater shifted in noble direction nearly 450 mV.However,in sterile seawater,E(ocp) was stable in experimental period.The presence of marine biofilms on the stainless steel played a role in inhibiting the initial corrosion according to the decrease in corrosion current densities obtained from the polarization curves,the increase of the polarization resistance(Rρ) obtained from EIS and the increase of the pitting cor rosion potential from the potentiodynamic polarization by the comparison test of 316L SS immersed in nature seawater and sterile seawater.It was suggested that marine biofilm and its metabolites improved the superficial anticorrosive properties of 316L SS by inhibiting the anodic dissolution behavior of stainless steel.