Effects of cerium and manganese on corrosion of Fe-Cr and Fe-Cr-Ni alloys in Ar-20CO2 and Ar-20CO2-20H2O gases at 650 °C

Model alloys Fe-9Cr, Fe-20Cr and Fe-20Cr-20Ni (wt.%) with 0.1% Ce or 2% Mn were exposed to Ar-20CO2 and Ar-20CO2-20H2O gas mixtures at 650 °C. Ferritic alloys underwent breakaway oxidation in both gases. Manganese additions significantly improved the oxidation resistance of Fe-20Cr in dry but not wet CO2. Water vapour accelerated internal oxidation of Fe-(9, 20)Cr. Austenitic alloys were more protective during corrosion in wet CO2. Cerium/manganese improved Fe-20Cr-20Ni performance in dry but not wet CO2. Most alloys carburised beneath their scales in both gases. Breakaway resistance is discussed in terms of Wagner's criteria for selective chromia scaling.