The Electrodeposition Of Zn-Ni-nanoTiO₂ Composite Coating

In order to strengthen the corrosion resistance of metal,the industry tend to cover thesubstrate surface with the coating.For the improvement of Zn-Ni alloy coating quality,the DC electrodeposition,the PC electrodeposition and the PR electrodeposition are used to prepare Zn-Ni alloy coatings.The dependence of the bath or electrodeposition parameters and the quality of Zn-Ni alloy coating is summarized mainly from the appearance,morphology,the content of Ni.Zn-Ni-TiO₂ nano composite coatings from PR electrodeposition take advantage of insoluble solid particle property and photovoltaic cathodic protection of TiO₂ nanoparticles to further perfect thequality and performance of the coating.About DC electrodeposition of Zn-Ni alloy coating,current density,working temperature and pH value mainly affect the relative size of grain nucleation rate and growth rate,the diffusion of particles in the bath and the formation of Zn（OH）2.The concentration of the main salt ions and the bath mainly affect the concentration of metal ions near by the cathode and the competitivereduction of Zn2+and Ni2+.About PC electrodeposition of Zn-Ni alloy coating,duty ratio,frequency could change turn-on and turn-off time of pulse current and the peak current density,whose main role is to perfect the morphology of the coating.About PR electrodeposition of Zn-Ni alloy coating,the reverse current density,duty ratio and the number of forward and backward pulses adjust mainly the reverse anodic dissolution toperfect the morphology of the coating.About Zn-Ni-TiO₂ nanocomposite coating prepared by PR electrodeposition,the introduction of TiO₂ nanoparticles have an influence on the morphology and composition of coatings.The increase of size and concentration of TiO₂ nanoparticlescould increase the content of TiO₂ nanoparticles and decrease the grain size in the composite coating.The thickness of（PR Zn-Ni-TiO₂）,（PC Zn-Ni）,（PR Zn-Ni）,（DC Zn-Ni）reduce gradually.And the corrosion resistance of（PR Zn-Ni）,（PC Zn-Ni）,（DC Zn-Ni）reduce gradually.But the corrosion resistance of（PR Zn-Ni-TiO₂）is not good enough.