Preparation Of Zn-Ni-TiO₂ Composite Coatings And Studying On Their Photoelectric Effect

The photovoltaic cathodic protection of TiO₂ has attracted wide spread attention.Its application has become a hot study spot.Zinc-nickel alloy coating is a new kind of excellent protective coating,which fit harsh industrial atmosphere and harsh marine environment.The effect of additives on zinc-nickel alloy electroplating was studied in the paper.The best additives formulas were determined.To obtain high hardness,high corrosion resistance of a new type of Zn-Ni-TiO₂ nano-composite coating,TiO₂ particles were added in the bath.The photoelectric effect of TiO₂ was also discussed.Through the potentiodynamic polarization curve measurement,optical microscope, SEM,E-probe and so on,the effect of additives on the electroplating bath and macro-morp hology,morphology,roughness,thickness,polarization resistance of the coatings which obtained by orthogonal were analyzed.The effect of additives on zinc-nickel alloy electroplating was studied in the experiment.The results showed that urotropine as the first type brightener can half-level up the coatings;vanillin as the second brightener and leveling agent have leveling effect and can level up the coatings;sodium hydroxide is the first type brightener and the stress relieving additive;second ethylhexyl sulfate as the surfactant play the role to prevent the pinhole.The best additives formulas were determined through orthogonal experiments.The result confirmed that the coatings which contain 13%nickel were bright,uniform,and have a better corrosion resistance.Through the potentiodynamic polarization curve measurement,optical microscope,SE M,E-probe and so on,the amount of TiO₂,the addition of dispersant,the current density, temperature and stirring speed effect on the apparent coating morphology,morphology, roughness,thickness,hardness,polarization resistance was studied in the paper.The Zn-Ni-TiO₂ nano-composite coatings'optimum conditions were determined through orthogonal experiments.The mechanism was studied after adding TiO₂ particles.Due to the addition of TiO₂ particles,the abnormal codeposition mechanism of zinc-nickel alloy was changed,so that nickel which had positive potential prior deposited.The coatings had more nickel,so the coatings were dark.Through the E-t curve,galvanic current,polarization resistance and AC impedance, Zn-Ni-TiO₂ nano-composite coatings were tested in 5%NaCl solution under light and dark state.The results showed that the coatings had photoelectric effect in the UV light.And they had the similar photocatalytic properties compared with the TiO₂ film.The photovoltaic current protected the coatings by the analysis of its mechanism.