Abstract
The effect of adding fresh nutrients to the growth of Sulfate-Reducing Bacteria (SRB), Desulfovibrio desulfuricans, in synthetic seawater was investigated by counting the planktonic cells in the solution. The corrosion of carbon steel exposed to mixed solution in the presence and absence of Desulfovibrio desulfuricans was characterized by Electrochemical Impedance Spectroscopy (EIS), linear polarization resistance (Rp) and open circuit potential (OCP) measurements. EIS spectra showed two time constants for the sterilized system of synthetic seawater and growth media. A high frequency constant is related to an outer layer due to the precipitates of chlorides, organic compound of the growth media and corrosion products. The constant at low frequency is a contribution of the metal dissolution reaction. The formation of biofilm by Desulfovibrio desulfuricans accelerates the corrosion rate and a diffusion controlled process appears as a result of sulfide-base iron corrosion products. The metal surface was examined by the Scanning Electron Microscopy (SEM) and the elemental composition of the corrosion products was estimated by X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Energy Dispersive Spectroscopy (EDS). Experimental result revealed a substantial decrease in the Rp values for the coupon in the solution provided with fresh growth media in the presence of Desulfovibrio desulfuricans.
