Preparation of porous TiO2/ZnO composite film and its photocathodic protection properties for 304 stainless steel

TiO2/ZnO composite films with porous structure were prepared on the 304 stainless steel (304SS) by the sol-gel method and heating treatment. The crystalline phase and morphology of as-prepared TiO2/ZnO composite films were characterized systematically by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible (UV-vis) spectroscopy, respectively. The influences of Ti/Zn molar ratio and the annealing temperature on the photoelectric property of the samples have been investigated and their photocathodic protection performances for 304 stainless steel under dark and UV conditions have also been evaluated in 3.0% NaCl solution by the electrochemical measurements. The results indicate that porous TiO2/ZnO composite film has a great enhancement of the light absorption and photoelectric property under UV illumination. This can be ascribed to the mutual effect of TiO2/ZnO heterojunctions and the porous structures in the composite films, which provide a better photogenerated cathodic protection for 304SS.