Anticorrosion of WO 3 -Modified TiO 2 Thin Film Prepared by Peroxo Sol-Gel Method

The aim of this study was to develop a method to\r\nprepare WO3-TiO2 film which has high anticorrosion\r\nproperty when it was coated on type 304 stainless steel. A series of WO3-modified\r\nTiO2 sols were synthesized by peroxo-sol gel method using TiCl4 and Na2WO4 as the starting materials. TiCl4 was converted to Ti(OH)4 gel. H2O2 and Na2WO4 were added in Ti(OH)4 solution and heated at 95°C. The WO3-TiO2 sol was transparent, in neutral (pH~7) solution, stable suspension without\r\nsurfactant, nano-crystallite and no annealing is needed after coating, and very\r\nstable for 2 years in stock. WO3-TiO2 sol was formed with\r\nanatase crystalline structure. These sols were characterized by XRD, TEM, and\r\nXPS. The sol was used to coat on stainless steel 304 by dip-coating. The WO3-TiO2 was anatase in structure as characterized by X-ray diffraction. There were no\r\nWO3 XRD peaks in the WO3-TiO2 sols, indicating\r\nthat WO3 particles were very small, possibly incorporating into TiO2 structure, providing the amount of WO3 was very small. The TiO2 particles were rhombus shape. WO3-TiO2 had smaller size\r\narea than pure TiO2. The SEM results showed that the film coated on\r\nthe glass substrate was very uniform. All films were nonporous and dense films.\r\nIts hardness reached 2 H after drying at 100°C, and reached 5 H after annealing\r\nat 400°C. The WO3-TiO2 film coated on 304 stainless steel\r\nhad better anticorrosion capability than the unmodified TiO2 film\r\nunder UV light illumination. The optimum weight ratio of TiO2: WO3 was 100:4.