Effect of silicon on corrosion of Fe-20Cr and Fe-20Cr-20Ni alloys in wet CO_2 with and without HCl at 650 °C

摘要

The effect of silicon on the corrosion of Fe-20Cr and Fe-20Cr-20Ni was investigated in N-2-10CO(2)-10H(2)O-(0.05 and 0.1 vol.% HCl) gas at 650 degrees C. Breakaway oxidation occurred for undoped alloys in all gases. The addition of Si (0.5 %) suppressed breakaway oxidation of both alloys in all gases by forming a thin protective oxide scale. In HCl-free gases, both Si-bearing alloys developed fine-grained chromia scales. In HCl gas, Si addition markedly improved alloy oxidation resistance by forming an amorphous (Cr, Si)O-x layer, fine-grained polycrystalline chromia, and a continuous SiO2 sublayer. The formation of this scale is discussed in terms of chloride volatilization and redeposition.