Dynamic evolution of corrosion products and their influence on carbon steel corrosion in supercritical CO₂

The successful implementation of carbon capture and storage depends on mitigating CO₂-induced pipeline corrosion. This study simulates supercritical CO₂ corrosion of carbon steel under extreme saturated water conditions, comparing corrosion mechanisms in atmospheric, low, and supercritical CO₂ environments using weight loss and electrochemical methods. The results show that the corrosion rate in the supercritical environment is 0.396 ± 0.017 mm/y, which is much higher than that in the atmospheric environment (0.226 ± 0.011 mm/y) and slightly higher than that in the low pressure environment (0.317 ± 0.013 mm/y). However, the electrochemical impedance data show that the resistance of the corrosion product layer formed in the supercritical environment in the later stage of corrosion to electric charge is 2439.53 Ω·cm², which is 5 times that in the low pressure environment and 31 times that in the atmospheric pressure environment. This shows that the supercritical corrosion product layer structure is denser and has a stronger protective effect on the carbon steel in the later stage of corrosion. The corrosion resistance in the supercritical CO₂ is controlled by the deposition of corrosion products, forming a double-layer structure. In-situ electrochemical data show that the resistance of the corrosion layer after corrosion for 192 h is 91 times that of corrosion for 6 h (26.66 Ω·cm²). Combined with TEM and other experiments, it is found that this is mainly due to the change of relative supersaturation driving the formation of amorphous and crystalline layers, which affects the overall corrosion protection of the material.