Fundamental aspects of the corrosion of N80 steel in a formation water system under high CO partial pressure at 100 °C.

The corrosion behavior of N80 carbon steel in a simulated formation water system saturated with CO under high pressure at 100 °C was investigated. The effect of the CO partial pressure on the electrochemical behavior and surface morphologies of the N80 carbon steel was analyzed by electrochemical methods and surface analysis, combined with a series of thermodynamic calculations of the potential of anodic/cathodic reactions. While an increase in the CO partial pressure did not alter the corrosion mechanism of the N80 steel, it resulted in higher concentrations of H and HCO ions, thereby significantly enhancing the rate of the cathodic reactions. The precipitation rate of FeCO increased with the CO partial pressure, with small and fine grains nucleating and growing on the steel surface with poor protectiveness.