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

•The addition of 1.83 wt.% Ca2+ at 80 °C led to the precipitation of thicker and less protective corrosion product layers consisting of FexCayCO3.•The addition of Ca2+ ions at 80 °C accelerated pit growth. Greater uniform corrosion rates were also observed, owing to the establishment of a less protective corrosion product layer.•The influence of Ca2+ ions was less substantial at 150 °C which establishes that mixed carbonates such as FexCayCO3 can be as protective as FeCO3 if precipitated under the right conditions.•The stoichiometry (x and y) of iron-calcium carbonate (FexCayCO3) corrosion products can exist with concentration gradients across their depths.