Corrosion of Fe-(9~37) wt.%Cr Alloys at 700-800 oC in (N2, H2O, H2S)-Mixed Gas

Abstract

Fe-(9, 19, 28, 37)wt.% Cr alloys were corroded at 700 and 800 oC for 70 h under 1 atm of N2, 1 atm of N2/3.2%H2O-mixed gas, and 1 atm of N2/3.1%H2O/2.42%H2S-mixed gas. The corrosion rate of Fe-9Cr alloy increased with the addition of H2O, and furthermore with the addition of H2S in N2 gas. Fe-9Cr alloy was always nonprotective. In contrast, Fe-(19, 28, 37) wt.%Cr alloys were protective in N2 and N2/H2O-mixed gas because of formation of the Cr2O3 layer. They were, however, nonprotective in N2/H2O/H2S-mixed gas because sulfidation dominated to form the outer FeS layer and the inner Cr2S3 layer containing some FeCr2S4.