Corrosion resistance of Cr2O3-Al2O3 ceramics by molten sodium sulphate–vanadium pentoxide

This report describes an investigation of the hot corrosion resistance of Cr2O3-Al2O3 ceramics in V2O5-Na2SO4 molten salt. Adding Cr2O3 to Al2O3 improves the hot corrosion resistance of Al2O3 ceramics, and thickness of the damage zone depends on the sintering temperature and the Cr2O3 content. Corrosion of the Cr2O3-Al2O3 ceramics is caused by the formation of a liquid of the dissolved Na2O-V2O5-(Al,Cr)2O3 system and by dissolution of the Cr2O3-Al2O3 ceramics into this liquid. The corrosion rate of the Cr2O3-Al2O3 ceramics becomes smaller than that of the Al2O3 ceramics because dissolution rate of grains into the liquid phase occurring in grain boundaries decreases, compared with the Al2O3 ceramics. If the sintering temperature is elevated, grain growth would occur to enhance the corrosion resistance of the ceramics.