Corrosion behaviors of steels under supercritical CO2 conditions

Carbon dioxide (CO2) corrosion at low partial pressure has been widely recognized, but research on supercritical CO2 (SC CO2) corrosion is very limited. By far, investigations on steel corrosion under SC CO2 conditions have mainly focused on the corrosion rate, structure, morphology, and composition of the corrosion scales as well as the electrochemical behaviors. It was found in aqueous SC CO2 environment, that the corrosion rate of carbon steel was very high, and even stainless steels (13Cr and high-alloy CrNi steels) were subjected to some corrosion. Inhibitor could reduce the corrosion rate of carbon steels and stainless steels, but none of the tested inhibitors could reduce the corrosion rate of carbon steel to an acceptable value. Impurities such as O-2, SO2, and NO2 and their mixtures in SC CO2 increased the corrosion rate of carbon steel. However, the existing studies so far were very limited on the corrosion mechanism of steels in SC CO2 conditions. Thus, this paper first reviews the finding on the corrosion behaviors of steels under SC CO2 conditions, points out the shortcomings in the present investigations and finally looks forward to the research prospects on SC CO2 corrosion.