A synergistic effect of dissolved oxygen, HCO3-, and Cl- on the electrochemical corrosion behavior of X70 pipeline steel in the oilfield soil environment

The pipeline corrosion phenomenon in the Liaohe oilfield has become severe in recent years, and X70 steel has been extensively employed as a high-strength pipeline material in this oilfield. Therefore, in this study, the electrochemical corrosion of X70 steel in the simulated Liaohe oilfield soil solution was investigated under the combined action of dissolved oxygen (DO), HCO3-, and Cl-. The corrosion behavior of X70 steel was examined by both the orthogonal test and the fitting analysis. It was found that DO, HCO3-, and Cl- had profound influences on the corrosion behavior of X70 steel. When concentrations of HCO3-, and Cl- were stable in the solution, both current corrosion density and corrosion rate gradually increased with the increasing DO concentration. When concentrations of DO and Cl- were constant, the current corrosion density also increased with the increasing HCO3- concentration. When concentrations of DO and HCO3- were constant, the current corrosion density decreased significantly with the decreasing Cl- concentration. In the soil solution, the corrosive effect of Cl- ions were found to be the least among all three factors, whereas HCO3- ions had the greatest influence on the corrosion behavior of X70 steel.