Corrosion of Fe-2.25Cr-lMo steels at 600-800°C in N2/H2O/H2S atmospheres

摘要

Fe-2.25%Cr-1%Mo alloys were corroded at 600, 700 and 800 °C for up to 70 h in 1 atm of N2/H2O/H2S-mixed gases. The base metal sulfidized to FeS. This at the outer scale formed by the outwardly diffusing Fe ions, whereas that at the inner scale formed by the inwardly diffusing sulfur ions. Some of FeS at the inner scale further reacted with Cr2S3 to the FeCr2S4 spinel. The alloying elements of Cr and Mo sulfidized by the inwardly diffusing sulfur ions at the inner scale. Although FeCr2S4 can suppress sulfidation to a certain extent, the alloys corroded fast, owing to the formation of the nonstoichiometric FeS.