Effects of CR content and pressure on corrosion behavior of steel in supercritical CO₂ environment

The influence of chromium content and pressure on the corrosion behavior of steel in a supercritical CO₂ environment was investigated using a high-temperature and high-pressure reactor. Gravimetric analysis, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and confocal laser scanning microscopy were employed to characterize the corrosion processes. The results indicate that an increase in chromium content leads to a reduction in the corrosion rate of steel under supercritical CO₂ conditions. Among the tested materials, N80 steel exhibited the highest corrosion rate, whereas 13Cr steel demonstrated the lowest. This behavior is attributed to the enhanced formation of a dense oxide film on the steel surface with higher chromium content, which effectively isolates the substrate from the corrosive medium and suppresses corrosion progression. With increasing pressure, the formation of corrosion products on chromium-containing steel typically initiates locally before spreading across the surface to form a continuous primary corrosion product layer. This layer subsequently evolves into a compact corrosion-resistant membrane that further impedes corrosive attack and lowers the corrosion rate. The corrosion product membrane formed on chromium-containing steel exhibits a dual-layer structure, where the outer layer consists of FeCO₃ and the inner layer comprises amorphous FeCO₃ and Cr (OH)₃.