Preparation And Performance Of NiP/TiO₂ Composite Film On Carbon Steel

Metal surface modification has been widely used as an anti-corrosion technology. Metal oxide thin films have attracted a great deal of attention in last decade with their unique chemical stability and good mechanical properties. In recent years, Titanium dioxide (TiO2) films have been widely used for several industrial applications such as a photo catalyst for degradation of environmental pollutants due to its non-toxic and stable properties at the normal pressure and temperature. In addition, Titanium dioxide (TiO2) thin films are one of the chemical-corrosion resistance and photo resist coatings in the solutions, and refractory oxide at high temperatures, so more and more titanium dioxide coatings have been used for protection against corrosion. Studies have been found that preparation of titanium dioxide thin films on metal surfaces, not only protected the substrate by isolating external media, also had the role of photo generated cathodic protection under ultraviolet(UV) or visible light illumination. So they further improve the corrosion resistance of the base metal.In this paper, NiP/TiO2 composite films have been coated on the carbon steel surface by anodic electro-deposition technique, with NiP coating as the transition layer to improve the adhesion of dioxide thin films to the substrate. Using EDS and XPS, components of the composite films were characterized; and the best pH of film-forming electroplate liquid was 2.25. The electrochemical process of film-forming was discussed by using linear sweep voltammetry (LSV) and cyclic sweep voltammetry (CV), the potential of film-forming process should maintain at around 0.3V. Scanning electron microscopy (SEM) results showed that NiP/TiO2 composite film is smoother than the NiP coating. The crystalline of the composite films was characterized by XRD. The crystal transition temperature of titanium dioxide powder obtained during film-forming process was obtained by differential thermal analysis (DTA), also the heat treatment temperature of the composite films was 400℃. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicated that NiP/TiO2 composite film has a better corrosion resistance than Ni P coating.This also combined photo-electrochemical methods to make some preliminary tests of photoelectric performance in this laboratory the first time. Optical absorption results indicated that TiO2 film showed a stronger absorption in the 450-650nm range. Photo-electrochemical measurement results showed that, TiO2 thin films not only separated external medium, but also could function effectively a photo-generated cathodic protection for metals under ultraviolet light, to further improved the corrosion resistance of metal matrix.