The n-type semiconductor SrTiO
3 was coated on the hot-dip zinc coated steel (Z18). Different from the sacrificial zinc coating, the coating acted as a stable photo-anode to offer non-sacrificial catholic protection to substrate steel. With ZnO formed on the galvanized steel by anodizing in 0.1M NaOH aqueous solution, a good photoeffect was found. With the sol-gel derived SrTiO
3 additionally coated on ZnO, the photoeffect was further improved. The open-circuit potential was maintained less noble even after stopping illumination for the coating with intermediate Fe-doped SrTiO
3 layer, SrTiO
3/Fe-SrTiO
3/ZnO/Z18. Moreover, photodecomposition that appeared for ZnO-coated galvanized steel could be prevented by the SrTiO
3 coating. The couples of SrTiO
3//Fe (Fe coupled with SrTiO
3/Fe-SrTiO
3/ZnO/Z18) and Zn//Fe (Fe coupled with Z18) were developed as ACM (atmospheric corrosion monitor) sensors to evaluate the corrosion behavior of galvanized steel with and without SrTiO
3 coating in atmosphere. For the SrTiO
3//Fe sensor, an anodic output was detected in the dark to show dissolution of Fe electrode, while it changed to cathodic one upon illumination. The cathodic value was larger than that of Zn//Fe sensor under certain conditions of lower amount of deposited sea salt and lower relative humidities, where substrate steel could be protected from rusting with the non-sacrificial coating.
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