The corrosion resistance mechanisms of the Cr-coated SiC in molten Na2SO4 salt: strengthened boundaries and protective scales

Abstract The corrosion resistance of pressureless-sintered silicon carbide (SiC) plates in the molten Na2SO4 salt was greatly enhanced by their surfaces coated with magnetron-sputtered chromium (Cr) coatings. The Cr-coated SiC plates remained good structural integrity in the 1000 °C molten Na2SO4 salt for >20 h, in contrast to the uncoated ones that completely crushed into pieces after 4 h. The corrosion-resistance mechanisms mainly depend on the strengthened boundaries by formation of the Cr-C and Cr-Si compounds to avoid the preferred corrosion of boundaries, and the barrier effect of the Cr2O3/Cr/Cr-Si-C protective scale.