Photoelectrochemical anticorrosion and self-cleaning effects of a TiO2 coating for type 304 stainless steel

We investigated the photoelectrochemical behavior of type 304 stainless steel (SUS 304) with TiO2 thin film coatings, applied by a spray pyrolysis technique, fur the purpose of cathodic photoprotection of the steel from corrosion. The photopotential of TiO2-coated SUS 304, was -350 mV vs. Ag/AgCl in an aerated aqueous solution containing 3 wt % NaCl (pH 7) under illumination with 10 mW cm(-2) ultraviolet (UV) light, which was more negative than the corrosion potential of the bare steel (-100 mV). The photopotential did not change in aqueous solutions containing from 0.01 to 5 wt % NaCl. No corrosion of TiO2-coated steel was observed at pH values greater than 3 in 3 wt % NaCl aqueous solution under UV illumination. TiO2 films with coverages greater than 30% achieved photoprotection ability at pH 6. When the UV light intensity was 3 mW cm(-2), that is, comparable with a typical daylight UV intensity in Tokyo, the photopotential of TiO2-coated SUS 304 was -220 mV in an aerated 3 wt % NaCl aqueous solution. In addition, the bleaching of methylene blue dye was confirmed on TiO2-coated SUS 304 under 1 mW cm(-2) UV illumination. pie conclude that TiO2 thin film-coated SUS 304 exhibits both a cathodic photoprotection effect against corrosion and the previously reported photocatalytic self-cleaning effect. (C) 2000 The Electrochemical Society. S0013-4651(00)06-050-X. All rights reserved.