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.