Surface Modification of Iron for Corrosion Protection: Kinetics of Anodic Film Formation and Electroreduction

The surface modification of Armco (R) iron for corrosion protection was performed by using the formation of the passive oxide film as well as the surface treatment by an ionic liquid. The band structure model was employed to explain the kinetics of oxide film growth and reduction in terms of point defects diffusivity. Low values of the diffusion coefficient and the concentration of anion vacancies as well as the high charge transfer resistance values point to high protecting properties of the passive oxide film in the wide potential range. Protection efficiency of the spontaneously formed oxide film at the open circuit potential (E-OCP) was markedly enhanced by adsorption of 1-butyl-3-methylimidazolium ([C(4)MIm](+)) cations on a negatively charged iron surface. The nature and the chemical composition of the surface oxide film on iron in the dependence of the formation potential were studied by X-ray photoelectron spectroscopy (XPS). XPS results showed a clear lowering of the iron valence through the oxide film until metallic iron.