Water vapour effects on corrosion of Fe-Cr and Fe-Cr-Ni alloys containing cerium and manganese in CO2 gas at 818 °C

Model alloys Fe-9Cr, Fe-20Cr and Fe-20Cr-20Ni (wt.%) with 0.1% Ce or 2% Mn were exposed to Ar-20CO2-20H2O gas at 818 °C, and the results compared with those of reaction with Ar-20CO2. Water vapour accelerated the corrosion of all Fe-9Cr alloys, and hastened the onset of breakaway oxidation for Fe-20Cr and Fe-20Cr-20Ni. Manganese additions prevented breakaway of the ferritic alloy, and retarded it for the austenitic, but cerium had no effect. All alloys except Mn-bearing variants were simultaneously carburised. Beneficial effects of manganese on high chromium content alloys are discussed in terms of scale phase constitutions.