Photoelectrochemical Anticorrosion and Self-Cleaning Effects of a TiO[sub 2] Coating for Type 304 Stainless Steel

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Abstract
We investigated the photoelectrochemical behavior of type 304 stainless steel (SUS 304) with TiO2TiO2 thin film coatings, applied by a spray pyrolysis technique, for the purpose of cathodic photoprotection of the steel from corrosion. The photopotential of TiO2TiO2 -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 TiO2TiO2 -coated steel was observed at pH values greater than 3 in 3 wt % NaCl aqueous solution under UV illumination. TiO2TiO2 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 TiO2TiO2 -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 TiO2TiO2 -coated SUS 304 under 1 mW cm−2 UV illumination. We conclude that TiO2TiO2 thin film-coated SUS 304 exhibits both a cathodic photoprotection effect against corrosion and the previously reported photocatalytic self-cleaning effect. © 2000 The Electrochemical Society. All rights reserved.