A study by electrochemical impedance spectroscopy and surface analysis of corrosion product layers formed during CO2 corrosion of low alloy steel

Abstract : In the following research, electrochemical and surface analysis techniques are used to define the main contributing factor to the protectiveness offered by a scale formed at high temperature and pH under CO 2 saturated conditions. At 80°C and pH 6.6, trace amounts of a magnetite (Fe 3 O 4) phase was identified at certain locations beneath a more dominant iron carbonate (FeCO 3) film. Furthermore, over time, the evolution of the corrosion product layer towards a very low porosity results in a "diffusion barrier" that is indicated by a positive shift in the open circuit potential and is considered key to corrosion protection.