Effect of Ca2+ on CO2 corrosion properties of X65 pipeline steel

The effect of Ca2+ on CO2 corrosion to X65 pipeline steel was investigated in the simulated stratum water of an oil field containing different concentrations of Ca2+. It is found that Ca2+ can enhance the corrosion rate, especially in the Ca2+ concentration from 256 to 512 mg/L, which can be attributed to the growing grain size and loosing structure of corrosion scales with increasing Ca2+ concentration. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) investigations reveal that a complex carbonate (Fe, Ca)CO3 forms at high Ca2+ concentration due to the gradual replacement of Fe2+ in FeCO3 by Ca2+.