Corrosion protection characteristics of doped magnetite layers on carbon steel surfaces in aqueous CO2 environments

Magnetite (Fe₃O₄) corrosion product surface layers can limit uniform corrosion rates of carbon steel in aqueous carbon dioxide (CO₂)-saturated environments. However, as Fe₃O₄ is a semiconductor, localised corrosion can proceed due to galvanic interaction between the Fe₃O₄ layers and bare steel. In this study, metal dopants were integrated into Fe₃O₄ layers to mitigate the effects of localised corrosion, whilst maintaining its protective barrier properties. Model Fe₃O₄ and metal-doped Fe₃O₄ layers were electrodeposited on carbon steel and immersed in a pH 5, 1 wt% sodium chloride (NaCl), CO₂-saturated, 50 °C solution. Under the conditions studied, the incorporation of magnesium into the Fe₃O₄ layer resulted in reduced localised corrosion when the 3D surface profiles of the underlying carbon steel were measured using white light interferometry.