Effect of CO on the corrosion behavior of 304 stainless steel in wet CO2 gas at 710°C

Abstract

The corrosion behavior of 304 stainless steel in wet CO₂ gas with or without CO and CO plus 400 ppmv SO₂ was investigated in this study. Corrosion kinetics was studied by thermogravimetric analysis at 710°C for 100 h under three gas conditions. After isothermal exposure, the corroded coupons were characterized in detail by X-ray diffraction, scanning electron microscopy, an electron probe microanalyzer, and transmission electron microscopy. CO addition to wet CO₂ resulted in lower oxygen partial pressure and lower oxide growth kinetics. It also suppressed iron-rich oxide nodule formation, as compared to the wet CO₂ gas environment. A Cr-depletion zone was observed underneath the oxide scale in the substrate, but no obvious internal carburization was observed in all three gas environments. A thin, protective oxide scale consisting of an outer layer of a Cr-rich spinel and an inner Cr-rich chromia layer was developed in CO-containing gas conditions, with or without SO₂. The effect of CO on oxidation and scale formation is discussed in comparison with that in wet CO₂ conditions.