Corrosion behaviour of 16%Cr–4%Al and 16%Cr ODS ferritic steels under different metallurgical conditions in a supercritical water environment

The corrosion behaviour of 16%Cr and 16%Cr–4%Al ODS ferritic steels in different heat treatment conditions has been investigated in a supercritical water environment. The exposed coupons were analyzed using scanning electron microscopy (SEM), electron probe micro analysis (EPMA), Auger and X-ray diffraction analysis (XRD). It was found that the formation of oxides depends on the chemical composition and not on the metallurgical condition. The Al-free alloys formed a monolayer oxide film composed of (Cr, Fe)2O3. The Al-containing alloys formed an oxide film composed of an outer layer of hematite and magnetite and an inner layer of Al2O3. The oxidation mechanisms are discussed.