Fundamental aspects of the corrosion of N80 steel in a formation water system under high CO2 partial pressure at 100°C

Abstract

The corrosion behavior of N80 carbon steel in a simulated formation water system saturated with CO2 under high pressure at 100 °C was investigated. The effect of the CO2 partial pressure on the electrochemical behavior and surface morphologies of the N80 carbon steel was analyzed by in situ electrochemical methods and surface analysis, combined with a series of thermodynamic calculations of the potential of anodic/cathodic reactions. While an increase in the CO2 partial pressure did not alter the corrosion mechanism of the N80 steel, it resulted in higher concentrations of H+ and HCO3- ions, thereby significantly enhancing the rate of the cathodic reactions. The precipitation rate of FeCO3 increased with the CO2 partial pressure, with small and fine grains nucleating and growing on the steel surface with poor protectiveness.