The role of Ca2+ ions on Ca/Fe carbonate products on X65 carbon steel in CO2 corrosion environments at 80 and 150 °C

The role of Ca2+ ions on the corrosion behaviour of carbon steel in CO2-corrosion environments was evaluated at 80 degrees C and 150 degrees C. In the presence of Ca2+ ions there was a more significant effect on the general corrosion rate at the lower temperature of 80 degrees C where the protection afforded by the corrosion product layer was reduced. The extent of localised/pitting corrosion increased through the addition of Ca2+ ions indicating that Ca2+ plays a role in promoting localised corrosion. XRD based calculations, along with focused ion beam EDX-line scans confirmed that the mixed Ca/Fe carbonates precipitated with concentration gradients across their thicknesses.