Hot corrosion behaviour and its mechanism of a new alumina-forming austenitic stainless steel in molten sodium sulphate

Hot corrosion behaviour and related mechanism of an alumina-forming austenitic (AFA) stainless steel at 1173 K in molten sodium sulphate were investigated. Compared with the Ni-based super-alloy K438, K417 and the commercial steel 316L, the current AFA steel exhibited a high hot-corrosion resistance with less internal sulphidation. It was found that a dense, continuous Al2O3 scale created at the early corrosion stage enabled formation of a compact Cr2O3 scale on it in the subsequent corrosion. Such dual layers effectively suppressed the sulphur penetration and protected the matrix from the hot corrosion.