Influence of Sulfate Reducing Bacteria Growth Process on Corrosion Behavior of X70 Steel

Sulfate reducing bacteria (SRB) were added in simulated sea water, and then the growth curve of SRB, the pH value and dissolved oxygen concentration of the simulated sea water were measured; the open circuit potential, polarization curve and electrochemical impedance spectrum of X70 steel in the simulated sea water with and without SRB were obtained by three-electrode system, and the influence of SRB growth process on the corrosion behavior of X70 steel was also analyzed. The results show that the growth of SRB went through three stages of exponential growth period (0-5 d) with the exponential increase of SRB amount, stable growth period (6-10 d) with the largest SRB amount and decline period (11-14 d) with the decrease of SRB amount. The pH value of the simulated sea water with SRB was between 6.19 and 7.18 and the dissolved oxygen concentration decreased with the extension of time. In the simulated sea water with SRB, the free corrosion current density of X70 steel increased gradually with the SRB amount increasing. The corrosion pits were more obvious on the sample surface in the simulated sea water with SRB and the diameter of corrosion pit increased with the increase of time.