On the novel approach of corrosion protection of carbon steel by TiO
2 coating under illumination, photoeffect of TiO
2/C-steel system is affected by the structural and electronic properties of the interfacial Ti-Fe oxide. In the present work, Ti-Fe oxide with a wide range of composition, from TiO
2 to α-Fe
2O
3, was prepared by sol-gel method. By studying the characteristics of the Ti-Fe oxides and their influences on the photoeffect of TiO
2/C-steel system, a multi-layer coating, expressed as from outer coating layer to substrate: TiO
2 (amorphous)/TiO
2 (anatase)/Ti-Fe oxide/α-Fe
2O
3/C-steel, was proposed for more effective photoelectrochemical cathodic protection of carbon steel. TiO
2 (anatase) layer without Fe contamination exhibits a good photoeffect and behaves like the source of photo-excited electrons. The inner α-Fe
2O
3 layer acts as both a barrier to retard the diffusion of Fe into TiO
2 and a way for the transfer of photo-excited electrons from the TiO
2 (anatase) coating to the substrate. The outer layer of amorphous TiO
2 inhibits the oxygen reduction and reduces the photopotential to a more less noble value. The intermediate layer of amorphous Ti-Fe oxide provides deep levels for Fe
2+/Fe
3+ redox couple, for which Fe
3+ is reduced to Fe
2+ by the photo-excited electrons under illumination. The state of Fe
2+ left after stopping illumination contributes to phenomenon that the electrode potential is maintained at considerably less noble value until all the Fe
2+ is re-oxidized by oxygen reduction.
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