Corrosion of Fe-2.25%Cr-1%Mo steels at 600-800°C in N 2/H 2O/H 2S atmospheres

Abstract

Fe-2.25%Cr-1%Mo alloys were corroded at 600, 700 and 800°C for up to 70 h in 1 atm of N 2/H 2O/H 2S-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 Cr 2S 3 to the FeCr 2S 4 spinel. The alloying elements of Cr and Mo sulfidized by the inwardly diffusing sulfur ions at the inner scale. Although FeCr 2S 4 can suppress sulfidation to a certain extent, the alloys corroded fast, owing to the formation of the nonstoichiometric FeS. © 2011 Published by Elsevier Ltd.