Effect of Chloride Ion Concentration on Corrosion of Q235 Steel in Sulfate-Reducing Bacteria Containing Solution

The sedimentary water in crude oil storage tanks contains a large amount of chloride ions and microorganisms, represented by sulfate-reducing bacteria(SRB), which is the main reason for the corrosion of tank bottom. In this paper, electrochemical impedance spectroscopy(EIS) and polarization curves were used to study the effect of different chloride ion concentration on the corrosion behavior of Q235 steel in sterile solution and that containing sulphate-reducing bacteria. The results showed that the chloride ion concentration had a significant effect on the corrosion behavior of Q235 steel in SRB containing solution. With the increase of the concentration lower than 20 g.L-1, the current density of Q235 steel in SRB solution was greater than that of the sterile solution for the synergistic effect of chloride ion and SRB, and the corrosion potential shifted negatively, indicating that the microorganisms promoted the corrosion of Q235 steel. When the chloride ion concentration exceeded 20 g.L-1, the corrosion rate of Q235 steel decreased with the increase of the concentration. The self-corrosion current density was much smaller than that in the sterile solution, and the corrosion potential shifted positively, revealing that the higher chloride concentration inhibited the growth of sulfate-reducing bacteria.