Preparation of nano TiO2-V2O5 composite coating and its functions in corrosion protection of metals

Abstract

Using sol-gel method and dip-coating process, TiO2 and sandwiched TiO2-V2O5 Composite films (TiO2 / TiO2,V2O5,/TiO2) have been used to coat the surface of 316L stainless steel. The morphology and structure of the films have been analyzed by AFM and XRD. The anticorrosion properties of the composite films have been studied under dark condition by electrochemical methods. The performance of photogenerated cathodic protection of the composite coatings has been measured in 0.5 mol center dot L-1 NaCl solution(pH=4.6) by combining photoelectrochemical system with corrosion electrochemical system under UV illumination. The results show a significant dual protective performance for the composite films. Under UV illumination the photo-generated cathodic protection is active, and after the UV light is shut off, it takes about 6 hours for the photogenerated potential to shift from -0.25 V to -0.14 V, which implies a possibility to remain a cathodic protection of metal even in the dark condition. Furthermore, under the dark condition the sandwiched TiO2/TiO2-V2O5/TiO2 composite coatings as excellent barrier layers are able to provide a protection for the 316L in a corrosive environment.