Preparation And Anti-corrosion Study Of TiO₂ Film

Modification on metal surface has been one of newly important techniques to resist corrosion. Metal oxides had gained people's recognition because of their specific chemical stability. TiO₂ modified films have good stability in acid and base solution, and it also shows light-resistant property. Therefore, people have an increasing interest in TiO₂ film which can improve the anti-corrosion performance of steel. Among all of the preparation methods of TiO₂ film, electrodeposition method is an importance wet chemical method.There are many merits when ceramic film was electrodeposited on the metal substrate: the procedure was proceeded in a low temperature electrolyte, and homogeneous ceramic film can be prepared on substrate with complex shape and porosity surface, at the same time, the investment of equipment and the cost of production are less.The combination of TiO₂ film and 301 stainless steel was poor and film's porosity was relatively high by electrochemical process directly, so it can not be prepared by this method directly. In order to improve the binding force between the TiO₂ film and 301 stainless steel and significantly reduce porosity on the surface of TiO₂ film, a special heat treatment method and optimally technological conditions are needed.In the experiment, TiO₂ films were prepared by cathodic electrodeposition method and anodic electrodeposition method, at the same time, high temperature sintering and hydrothermal treatment was adopted. The problem of the recombination between substrate and modified films, which was caused by heat treatment, was successfully solved. While TiO₂ films was electrodeposited on the surface of 301 stainless steel, there are mainly 3 factors influencing the quality of films: technological improvement of the electrolyte's preparation method, such as the dissolution of the electrolyte, the election of organic solvent, the instable electrolyte and selection of a complexing agent, etc.; technological optimization of electrodepositing TiO₂ films, such as the electrolyte's concentration, current density, electrodeposition time, etc.; technological modification of heat treatment, such as the election of heat-treated methods and the time of thermal retardation. The composition and structure of TiO₂ deposit were characterized by X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA), and Fourier transform infrared spectroscopy (FTIR). The XRD characterization result of TiC>2 deposits showed that they have different crystal conversion at higher temperature. TG-DTA analyzing result illustrates the dehydration procedure, FTIR analysis characterized the transformation procedure of functional groups of electrolyte precursor with the increasing temperature.TiO₂ films were prepared on the surface of stainless steel in accordance with optimized technology. Electrochemical corrosion behavior of TiO₂ film was measured in the solution of Cl^- ionic and H⁺ ionic corroding media by using open circuit potential (OCP) technique, Tafel technique, cyclic voltammetry (CV) technique, linear sweep voltammetry (LSV) technique, and AC impedance technique. The anti-corrosion mechanics of TiO₂ film was preliminarily discussed.The experimental results of electrochemical corrosion test illustrated that the TiO₂ film which was electroplating 20 min (current density of 5 mA/cm²) on the surface of 301 stainless steel and finally hyrothermal-treated about 10 min has the best anti-corrosion performance.