Effect of Ca²⁺ Concentration on Protection Properties of X65 Steel Corrosion Scale

The effect of Ca2+ on the electrochemical protection of X65 pipeline steel was studied by the way of adding Ca2+ to the simulated solution.The corrosion rate and grain size were measured and SEM was used to get the micromorphology of the corrosion scales.The electrochemical impedance spectroscopy (EIS) and polarization curves were used to investigate the corrosion scales formed in different Ca2+ concentration.The results showed that Ca2+ could adhere to the matrix and accelerate corrosion rate.The corrosion scales in anodic region could restrain Fe2+ diffusing and improve anodic potential,and raise Ecorr.Ca2+ did not change the corrosion mechanism.When Ca2+ concentration increased,Warburg impedance appeared in the fitting circuit,and the electrochemical reaction was controlled by diffusion.