Corrosion of carbon steel under CO2 conditions: Effect of CaCO3 precipitation on the stability of the FeCO3 protective layer

This study investigates the effect of CaCO3 precipitation on the corrosion of 1Cr carbon steel covered by protective FeCO3 layer. Tests were conducted at atmospheric pressure in 1 wt.% NaCl solution saturated with CO2 at 80 degrees C. Three different concentrations of Ca2+ (100, 1,000 and 10,000 ppm by mass) were studied. Linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to investigate the electrochemical behavior. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were used to analyze the corrosion products. Results suggested the precipitation of CaCO3 led to an urtdersaturated solution with respect to FeCO3 followed by dissolution of the protective layer.