Atomic insights into the corrosion behavior of Fe-Cr alloys in supercritical CO2 environment

Abstract

In this work, the corrosion process of Fe-Cr alloys in flowing CO2 was simulated using molecular dynamics within an extended ReaxFF force field. The effects of Cr content, temperature variations, impurity gases and vacancy defects were discussed. The corrosion process was dominated by oxidation and carburization reactions, with the oxidation rate higher than carburization rate, resulting in the formation of a carbide layer within the central region between two oxide layers. The increase in Cr content tended to decelerate corrosion, while raising temperature aggravated the corrosion of Fe-Cr alloy. The presence of O2 and SO2 impurities was found to thicken the corrosion layer, in contrast to the effects of CO and H2O impurities. A notable finding highlighted the positive influence of 2% vacancy defects in enhancing the corrosion resistance of the Fe-Cr alloy. The Al2O3 coating achieved a good corrosion protection by inhibiting the dissociation of CO2.