An electrochemical study of iron carbonate layers formed on carbon steel during corrosion in elevated pressure CO2 environments.

Iron carbonate (FeCO 3) layers influence the electrochemical properties of carbon steel during aqueous corrosion in carbon dioxide–saturated environments. In this study, electrochemical measurements conducted in an autoclave at 80°C and 5 barg are combined with cross-sectional imaging to elucidate interfacial properties of X65 carbon steel at key stages of FeCO 3 layer development. The effects of evolving system chemistry are also considered by variation of the X65 surface area to solution volume (A/V) ratio. FeCO 3 reduces general corrosion rates through a combination of active site blocking and restriction of mass transport, with resultant layer properties dependent on the A/V ratio. • Area to Volume Ratio significantly affects FeCO 3 corrosion product layer properties. • In-situ electrochemical techniques employed at 80°C, 5.5 pCO 2 and initial pH 3.7. • Four key stages in FeCO 3 corrosion product layer development on carbon steel. • Substrate protection provided by active site blocking and mass transport restriction through thick but porous FeCO 3 layer. [ABSTRACT FROM AUTHOR]