Preparation And Properties Of The Composite Coating Of Nano-TiO₂/Ni-P Alloy On Magnesium Alloy

Magnesium alloy has already been used wider and wider. Its protection technology has become a hard task and a hotspot. In this thesis the composite electrolyte with nanoparticles is prepared by adding TiO₂ particles and surfactant into the Ni-P alloy electrolyte of magnesium alloy under the effect of ultrasonic wave vibration. Four factors of the content of nanoparticles in the electrolyte, the content of surfactant in the electrolyte, pH value and temperature of the electrolyte which affect the performance of composite coatings are optimized in the orthogonal experiments. Influences of reductant, stabilizer, complexing agrent pH value and temperature on deposition rate are studied, and the effects of various surfactants, bath content of surfactants, temperature and bath content of nano particles on the hardness of the coating are also investigated. An optimum technique has been obtained.The performances of composite coatings are also compared with those of the Ni-P alloy coatings. The results indicate that both of the coatings combine very well with the substrate, and the microhardness and wear resistance of nanocomposite coatings are higher than those of Ni-P alloy coatings. Therefore it can be deduced that nanoparticles can strengthen the coatings. The corrosion resistances of both the composite coating and the alloy coating are much higher than that of the substrate magnesium alloy. Dynamic potential scanning and the erosion resistances in various erosive mediums show that nano composite coating can promote the corrosion resistance of the Ni-P alloy coating. No bubbling, corrugation, abscission and cracking are found through bending and filing tests on the composite coatings, so the bonding state is very well between the coatings and the substrate.