Influences Of Suphate-Reducing Bacteria On The Corrosion Behavior Of Carbon Steel

Testing for Sulphate-Reducing Bacteria (SRB) from four kinds of media was discussed. The numbers of each kind of SRB were counted by Most Probable Number estimate method. By using solid culture medium, SRB was purified and conserved at low temperature. The musculomyces of the Sulphate-Reducing Bacteria was identified with simple staining method and Gram's staining method. It was showed that the bacteria belong to G".By measuring the polarization curves and electrochemical impedance spectrum as well as the aid of microscope and scanning electron microscope, the correlation between bacterial numbers and corrosion behavior of carbon steel was studied. The influences of the ion of Fe2+ and oxygen on the growth of SRB were also investigated. The results showed that there're acidic substances during the process of metabolism of Sulphate-Reducing Bacteria. The corrosion potential decreased in the medium inoculated with bacteria. It is detected that the more the concentration of the bacteria, the more negative the corrosion potential. The slope of cathodic polarization curves measured in the medium inoculated with SRB is lower than the one obtained in the medium without bacteria, while the slope of anodic polarization curves is higher than it. It is concluded that the process of anodic polarization was repressed at the presence of Sulphate-Reducing Bacteria. There's some part of anodic polarization curves changed slowly in the medium of SRB. The results showed that the biofilm could restrain the development of the corrosion when the biofilm was compact on the surfaces of specimens. The diameters of Electrochemical Impedance Spectrum vary with the amount of SRB. When the double-electronic layer capacitance Cd decreased, the polarization resistance Rp increased, which indicated that the biofilm on the surfaces of carbon steel raised the reactive resistance in the medium with higher concentration of bacteria. On the contrary, in the medium inoculated with lower amount of SRB, the Cd is higher and the Rp is lower.