Abstract

The research aims to investigate the formation of corrosion products and corrosion resistance mechanism of 3Cr+0.5Mo steel after the exposure in CO2-enriched NaCl solutions at temperatures of 90 and 180 °C. The results indicate that at 90 °C, the corrosion rates of the steel increase as the chloride ion concentrations increase from free to 1.0 mol/L. Conversely, at 180 °C, the relationship between Cl− concentrations and the corrosion rates follows a distinct pattern. The combined effect of Mo alloying and higher Cl− concentrations plays a critical role in producing sufficient Fe2+ ions for the precipitation of nano-sized FeCO3 crystals in the initial corrosion stage, leading to enhanced corrosion resistance. This approach may present a new strategy for enhancing the corrosion resistance of steels. In contrast, the low-Cr steel is not suitable for low-temperature and high Cl− concentration environments due to the selective degradation of inner Cr-enriched films by Cl−.