Electroplating Amorphous Ni-mo-p-nano-zro <sub> 2 </ Sub> Composite Coatings

In this paper, the author proposed a solution by combining zirconium dioxide nano-particles with the conventional electroplating technology, intending to prepare a coating with high corrosion resistance, better micro-hardness and wear resistance both in room temperature or high temperature. The proposed technology has solved the problems of keeping the dispersity and stability of nano-particles deconcentrating in electroplating solutions. The research develops methods of preparing composite coatings containing nano-particles, investigating the appearance, microstructure, micro-hardness, corrosion resistance and wear resistance of the composite coatings. We also discuss the strengthening mechanism of zirconium dioxide nano-particles roughly. The focal points of the research have been listed as following:In order to obtain the optimized solution, orthogonal experiment have been applied in this research. According to the date of the electrochemical experiment, we receive the amorphous Ni-Mo-P coating, which has the excellent corrosion resistance.A new composite method, named chemical-ball milling method, is obtained to deconcentrate effectively the zirconium dioxide nano-particles within plating solution. Comparing with the other methods, such as supersonic method and chemical method, much more nano-particles are in nanometer scale in the composite solution after prepared by chemical-ball milling method. And the nano-particles can suspend steadily as longer as four hours. Furthermore, the proportion of nano-particles is much higher in the coating prepared by chemical- ball milling method. The surface of the composite coating is even, compact and smooth. Therefore, the chemical-ball milling method is a prospective method to prepare nano-particles composite solutions in the future.The morphology of composite coatings is observed. Compared with Ni-Mo-P coatings, the structure of composite coatings is smaller and compacter, and the cross-section has no flaw such as crack and hole, etc. The composite coating is combined tightly with matrix carbon steel.Electrochemical experiments show that, the corrosion resistance of composite coatings is superior to amorphous Ni-Mo-P coatings during in 5%NaCl solution and 0.5mol/L H₂SO₄ solution. The reason is that the structure of the composite coatings are strengthened and the contact area of composite coatings and corrosive is minished by dispersed nano-particles.