Corrosion behavior of an alumina forming austenitic steel exposed to supercritical carbon dioxide

Microstructure characterization of corrosion behavior of an alumina forming austenitic (AFA) steel exposed to supercritical carbon dioxide was conducted at 450-650 °C and 20 MPa. At low temperature and short exposure times, the oxidation kinetics were parabolic and the oxide scales were mainly composed of protective and continuous Al2O3 and (Cr, Mn)-rich oxide layers. As the temperature and exposure time increased, the AFA steel gradually suffered breakaway oxidation and its oxide scales showed a multilayer structure mainly composed of Fe3O4, (Cr, Fe)3O4, NiFe/FeCr2O4/Cr2O3/Al2O3, FeCr2O4/Al2O3, and NiFe/Cr2O3/Al2O3, in sequence. The corrosion mechanism based on the microstructure evolution is discussed in detail.