High temperature corrosion of pure Fe, Cr and Fe–Cr binary alloys in O2 containing trace KCl vapour at 750 °C

Pure Fe, Cr and Fe–Cr binary alloys were corroded in O2 containing 298 ppm KCl vapour at 750 °C. The corrosion kinetics were determined, and the microstructure and the composition of oxide scales were examined. During corrosion process, KCl vapour reacted with the formed oxide scales and generated Cl2 gas. As Cl2 gas introduced the active oxidation, a multilayer oxide scales consisted of an outmost Fe2O3 layer and an inner Cr2O3 layer formed on the Fe–Cr alloys with lower Cr concentration. In the case of Fe–60Cr or Fe–80Cr alloys, monolayer Cr2O3 formed as the healing oxidation process. However, multilayer Cr2O3 formed on pure Cr.