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 semi-conductor, 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, 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.