Corrosion behaviors of steels under supercritical CO ₂ conditions

Abstract Carbon dioxide (CO 2 ) corrosion at low partial pressure has been widely recognized, but research on supercritical CO 2 (SC CO 2 ) corrosion is very limited. By far, investigations on steel corrosion under SC CO 2 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 CO 2 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 , SO 2 , and NO 2 and their mixtures in SC CO 2 increased the corrosion rate of carbon steel. However, the existing studies so far were very limited on the corrosion mechanism of steels in SC CO 2 conditions. Thus, this paper first reviews the finding on the corrosion behaviors of steels under SC CO 2 conditions, points out the shortcomings in the present investigations and finally looks forward to the research prospects on SC CO 2 corrosion.