Corrosion performance of heat resistant alloys in Na2SO4–V2O5 molten salts

The corrosion resistant of three heat resistant alloys in molten vanadium pentoxide (V2O5), sodium sulfate (Na2SO4) and 80(mol%) V2O5–20Na2SO4 has been evaluated using the weight loss technique. Materials included Fe–25Cr–35Ni–0.45C, Fe–35Cr–45Ni with 0.12 and 0.45C alloys. Temperatures included 600, 700 and 800 °C for V2O5 and the 80V2O5–20Na2SO4 mixture, and 800, 900 and 1000 °C for Na2SO4. The tests were supplemented by detailed electronic microscopy and microanalysis studies. In all cases, the least resistant alloy was the Fe-25Cr–35Ni–0.45C one whereas the most resistant was the Fe–35Cr–45Ni–0.12C one. The results are discussed in terms of the acidic dissolution of the external protective Cr2O3, Al2O3 and SiO2 layers, by the salts and internal sulfidation.