Electrochemistry of CO2 corrosion of mild steel: Effect of CO2 on iron dissolution reaction

The kinetics of the iron dissolution reaction was investigated in CO2-saturated acidic sodium chloride solutions. While the effect of CO2 on the iron dissolution reaction during corrosion process has received little attention in the existing literature, the experimental polarization curves obtained in the present study on X65 mild steel suggest that CO2 and/or its related carbonate species are directly involved in the metal dissolution reaction. The presence of CO2 was found to significantly influence the kinetics and the mechanism of the iron dissolution reaction at partial pressures as low as 1 bar. The higher corrosion rates observed in CO2-saturated brines as compared to strong acid solutions at the same pH could possibly be explained by the effect of CO2 on the kinetics of the anodic reaction.