Understanding the general and localized corrosion mechanisms of Cr-containing steels in supercritical CO2-saturated aqueous environments

Abstract

Effect of Cr content on corrosion of steel in static and dynamic supercritical CO2-saturated aqueous environments was investigated. The results showed that adding 3 wt% Cr aggravated general corrosion of the steel under static condition while inhibited the localized corrosion under dynamic condition, and 6.5Cr steel possessed the best general and localized corrosion resistance. The scale formation process on 3Cr steel contained two stages: the in-situ formation of initial amorphous Cr-rich layer consisted of Cr(OH)3 and FeCO3; the formation of outer FeCO3 crystalline layer as well as the transformation of initial amorphous layer to inner mixed layer, which consisted of amorphous FeCO3, Cr(OH)3 and a small number of crystalline FeCO3. The well localized corrosion resistance of Cr-containing steel attributed to the in-situ formation of initial amorphous Cr-rich layer.