| In this experiment, we prepare a Ni-Co-Al2O3 composite coating on copper surface by composite electro-deposition. We discuss the optimized technological parameter of Ni-Co-Al2O3 composite electro-deposition. We take advantage of the cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy to study the effect of ultrasonic on the electrochemistry behavior of composite electro-deposition. The devices of high temperature friction-abrasion testing machine, scanning electron microscope, chamber electric furnace and so on are used to study the effect of ultrasonic on composite coating’s surface topography, micro-hardness, corrosion resistance, high-temperature oxidation resistance and so on. We make use of the linear sweep voltammetry to analyze the major control step in the reaction process by calculating its activation energy. The results show:(1) The optimized technological parameter of the composite electro-deposition: current density 5A/dm2, nano-particle concentration 2g/L, cobalt concentration 3.5g/L, temperature of plating solution 60°?, pH 3.8, stirring rate 500r/min;(2) Under the same electro-deposition condition, the reaction of Ni-Co deposition in the ultrasonic relies on higher over-potential. The depolarization of ultrasonic makes it easier for the cathode to afford higher current density and improve the nucleation rate, refine the grains.(3) Ultrasonic makes a different to the coating’s hardness, corrosion resistance, high temperature oxidation resistance and so on. The surface properties of the composite deposition coating decreases with the increase of ultrasonic power. When the ultrasonic power reaches 160 W, the surface properties of the composite deposition coating reaches its optimum. The improvement of surface properties brought by ultrasonic results from the higher over-potential gained in ultrasonic, so that we can get homogeneous and compact coatings.(4) Ultrasonic contributes to reduce the activation energy of the reaction process. The Ni-Co-Al2O3 electro-deposition is controlled by both of diffusion process and electrochemistry reaction process. |
