Effects of silty sand and pH on the formation of corrosion film and corrosion behaviour of low-Cr steel in the CO₂ environment

Abstract

The effects of silty sand and pH on the corrosion characteristics of 1Cr steel were investigated. The results revealed that silty sand changed the nucleation behaviour of FeCO 3 crystal from homogeneous nucleation to heterogeneous nucleation through increasing the critical supersaturation of FeCO 3 . The compactness and protection of corrosion film were improved by silty sand. The amorphous FeCO 3 content decreased as the pH increased in the CO 2 environment with silty sand, while the Cr(OH) 3 content increased. The critical pH for the good corrosion resistance of 1Cr steel was 4.5. The amorphous FeCO 3 dominated the protective properties of corrosion film when the pH was lower than the critical pH, whereas the Cr(OH) 3 was predominant when the pH was higher than the critical pH. Therefore, the corrosion resistance of 1Cr steel was reduced and then enhanced with increasing pH under silty sand condition.