Corrosion of austenitic and ferritic-martensitic steels exposed to supercritical carbon dioxide

► Oxidation is the primary corrosion phenomenon for the steels exposed to S-CO 2. ► The austenitic steels showed significantly better corrosion resistance than the ferritic-martensitic steels. ► Alloying elements (e.g., Mo and Al) showed distinct effects on oxidation behavior. Supercritical carbon dioxide (S-CO 2) is a potential coolant for advanced nuclear reactors. The corrosion behavior of austenitic steels (alloys 800H and AL-6XN) and ferritic-martensitic (FM) steels (F91 and HCM12A) exposed to S-CO 2 at 650 °C and 20.7 MPa is presented in this work. Oxidation was identified as the primary corrosion phenomenon. Alloy 800H had oxidation resistance superior to AL-6XN. The FM steels were less corrosion resistant than the austenitic steels, which developed thick oxide scales that tended to exfoliate. Detailed microstructure characterization suggests the effect of alloying elements such as Al, Mo, Cr, and Ni on the oxidation of the steels.