High-temperature corrosion of aluminized and chromized Fe-10.4% Cr steels in N-2/H2S/H2O-mixed gas

摘要

Fe-10.4Cr-0.8Mn-0.2Si-0.1C (at%) steel was either chromized or aluminized via pack cementation, and corroded at 800 degrees C for up to 100 h in 1 atm of (N-2/3.1% H2O/2.42%H2S)-mixed gas. The corrosion of the chromized coating resulted in the formation of an outer Cr2S3 and an inner Cr2O3 scale. Later, an FeS scale formed over the preformed Cr2S3/Cr2O3 scale. The corrosion of the aluminized coating led to the formation of the thin alpha-Al2O3 scale. At the later stage of corrosion, discrete nodules that consisted mostly of Al2O3 and Al2S3 formed locally. Aluminizing was more effective than chromizing in increasing the corrosion resistance of the steel, due mainly to the formation of alpha-Al2O3.