The formation of FeCO3 and Fe3O4 on carbon steel and their protective capabilities against CO2 corrosion at elevated temperature and pressure

This study investigates the corrosion performance of X65 carbon steel at elevated temperatures (up to 250 °C) and CO2 partial pressures (up to 28.5 bar pCO2). A detailed appraisal of how the corrosion products can protect against general and localised corrosion is presented. The morphology and chemical composition of corrosion products were determined using various microscopic and spectroscopic techniques, with localised corrosion rates being determined by surface profilometry. An increase in temperature or reduction in CO2 partial pressure favours the formation of a protective magnetite layer. It is thermodynamically more stable and more protective than iron carbonate in these conditions.