Comparison of the high-temperature chloride-induced corrosion between duplex steel and Ni based alloy in presence of H2S

Duplex steel 1.4462 and Ni-based alloy Centralloy ET45 micro were tested in HCl- and H2S-containing atmospheres at 680 °C for 24, 72 and 240 h. Corroded samples were investigated by metallography, SEM/EDX and XRD. Corrosion products on the surface consisted of Cr2O3 and chromium sulfides. Beneath this surface layer, iron and chromium chloride were found. A depletion of iron was observed due to formation of volatile iron chloride. Both materials displayed a selective attack of the existing phases. The ferrite phase of the Duplex steel was attacked, while the Ni-based alloy showed the selective attack of chromium carbides.