High Temperature Corrosion Behaviors of 20G Steel, Hastelloy C22 Alloy and C22 Laser Coating under Reducing Atmosphere with H2S

Abstract

High-temperature corrosion behaviors of 20G steel, Hastelloy C22 alloy and C22 laser coating was evaluated by corrosion mass gain measurements at 450 °C. The corrosive atmosphere is 0.2 vol% H2S–0.1 vol% O2–N2, which simulated the severe high-temperature corrosion environment occurred under low-NOx combustion in pulverized-coal furnaces. Experimental results showed that the corrosion resistance of the C22 laser coating and the C22 alloy was obviously better than 20G steel. Furthermore, it should be noted that the C22 laser coating fabricated in this study displayed a higher corrosion resistance than the commercial C22 alloy although they had the same chemical composition. The severe pitting corrosion was observed in 20G steel with the corrosion products consisting of FeS2, Fe2O3 and Fe3O4. The C22 alloy and C22 laser coating exhibited the uniform corrosion and their main corrosion products were NiS2, CrS and a small amount of chromium and manganese oxides.