Mechanism of protective film formation during CO₂ corrosion of X65 pipeline steel

Electrochemical techniques, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to study the corrosion behaviors of X65 steel in static solution with carbon dioxide (CO₂) at 65℃. The results show that iron carbonate (FeCO₃) deposits on the steel surface as a corrosion product scale. This iron carbonate scale acts as a barrier to CO₂ corrosion, and can reduce the general corrosion rate. The protection ability of the scale is closely related to the scale morphological characteristics.