Abstract: Nano-sized TiO₂/Sb₂O₅ bilayer coatings were prepared on type 304 stainless steel substrate by solgel method. Surface morphology, structure and composition of the asprepared TiO₂/Sb₂O₅ coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscope (XPS). The performance of photoelectrochemical and photogenerated cathodic protection of the coatings was investigated using the electrochemical method. SEM results indicate that the coating surface is continuous, uniform and dense, XRD results show that the coating is of anatase TiO₂, XPS results indicate the outer and inner coatings are mainly composed of Ti, Sb, C and O elements. Moreover, the test results of the steady potential and polarization curves demonstrate that the nanosized TiO₂/Sb₂O₅ bilayer coating has worsen photoelectrochemical properties than the plain nanosized TiO₂ coating in 3% NaCl solution. Type 304 stainless steel coated with the bilayer coating can maintain cathodic protection for 4h in the dark after irradiation by UV illumination for 1h. In addition, a novel mechanism of the photogenerated cathodic protection for the bilayer coating is put forward.

Key words: nano-sized TiO₂, nano-sized Sb₂O₅, bilayer coating, photoelectrochemical, photocathodic protection, corrosion protection