CO₂ Corrosion of Iron and Steel in Oil and Gas Production

Abstract

CO₂ corrosion phenomena are characterized by a high corro sion rate even under weak acid conditions and cause specific corrosion figures such as ringworm, wormhole and mesa corrosion. The former is due to the catholic reaction and the latter are due to the properties of the corrosion product. In addition to analyses of previous research, CO₂ corrosion of pure iron was investigated. The activation energy of CO₂ corrosion of pure iron at P_CO2=3MPa was very similar to that of the hydration reaction of CO₂. Although the cathodic reaction is a superposition of the diffusion controlled reduction of H⁺ ion and direct reduction of H₂CO₃, the latter was the main reaction at high P_CO2, 1.1-3MPa and/or at high temperature 313-353K. CO₂ corrosion can be categorized into three types depending upon the temperature, and is closely related to the properties of the corrosion product film caused by formation of FeCO₃. The effect of the environmental conditions and metallurgical fact ors on CO₂ corrosion behavior, specifically both structure and constituents of corrosion products, were investigated. The applicability of the de Waard-Milliams equation, which is utilized for engineering purposes to predict the corrosion rate of carbon steel, was investigated experimentally and theoretically. Anti-CO₂ corrosion tubular materials and their properties are discussed.