Oxidation of a novel CeO2-dispersion-strengthened chromium coating in simulated coal-combustion gases

A novel CeO2-dispersion-strengthened chromium coating was developed by chromizing a Ni-CeO2 composite film, which was prior deposited on a mild steel by co-electrodeposition of Ni with CeO2 particles from a nickel sulfate bath. For comparison two CeO2-free chromium coatings were also prepared by chromizing on the mild steel with and without prior Ni-plating. The oxidation performances of these coatings were investigated at −850 °C in simulated coal-combustion gases, which were N2 + 5 vol.% O2 base gas and the gas containing 1000 vppm SO2 or/and 20 vol.% H2O. There were several observations: (1) the mass gain of all chromium coatings was mainly from the contribution of oxidation induced by oxygen in these gases, (2) SO2 accelerated the oxidation of the CeO2-free chromium coatings, but did not have a significant effect on the oxidation of the CeO2-dispersed chromium coating, and (3) water vapor greatly increased the oxidation of the CeO2-free chromium coatings by causing the evaporation of Cr from the growing chromia scale, however, its effect on the oxidation of the CeO2-dispersed chromium coating was not significant.