Corrosion mechanism and oxide scale evolution of austenitic stainless steels in supercritical CO2

: Austenitic stainless steels are considered promising structural materials for advanced energy systems operating in supercritical CO 2 (S-CO 2 ) environments due to their favorable high-temperature mechanical and corrosion properties. However, the long-term stability of the protective oxide scales remains a key concern under prolonged exposure, particularly due to breakaway corrosion associated with Fe-rich oxide formation and carburization. This review provides a mechanism-oriented analysis of corrosion behavior in S-CO 2 , with a specific focus on the formation, evolution, and destabilization of oxide scales in austenitic stainless steels. By integrating thermodynamic considerations, diffusion kinetics, and experimental observations, the corrosion process is organized into sequential stages, ranging from initial protective scale formation to diffusion-controlled growth and eventual degradation. Particular emphasis is placed on the coupling between oxidation and carburization, as well as on distinguishing the onset mechanisms of oxide-scale destabilization from the result mechanisms. The interdependent effects of temperature, gas impurities, and alloying elements on oxide scale stability and carburization behavior are systematically analyzed. These insights aim to clarify key mechanistic controversies and provide guidance for improving long-term corrosion resistance and impurity management strategies in S-CO 2 systems.