Investigating the corrosion of API-X100 pipeline steel in aerated carbonate solutions by electrochemical methods

This paper explores some key electrochemical aspects associated to the corrosion of API-X100 steel in aerated carbonate solutions. Investigated by polarization and electrochemical impedance spectroscopy tests, the corrosion rates and potentials, the cathodic reactions, and passivation are studied from the perspectives of carbonate content and temperature. The corrosion rates, more sensitive to temperature, were between 12 and 18 μA cm^-2, and the corrosion potentials decreased with carbonate content and increased with temperature. And reported for the first time, bicarbonate, which resulted from the CO₃^2-/H₂O equilibrium, contributed to the cathodic reactions, and in a manner more significant with carbonate content. The passive films showed evidence that they became more compact with carbonate content, and so with did the lower charge transfer resistance.