| Plating protective coatings on steel substrate is a kind of important measures to prevent steel corrosion. Zinc as more lively and cheap metal, it has a large proportion in the application of traditional steel corrosion protection. Nickel metal has high hardness, low hydrogen brittleness and high corrosion resistance, so it’s widely used in various kinds of functional and decorative plating industry. Zinc-nickel alloy as a kind of zinc base ally, with the advantage of high corrosion resistance, low hydrogen brittleness and weldability, and it also plays a sacrificial anode cathodic protection for steel substrate. In this paper, with 45#steel as the base material, we prepared the zinc, nickel and zinc-nickel alloy deposited layers using electrochemical deposition, while investigating the effect of different plating conditions on the morphology of the plating layers by SEM (scanning electron microscope) and the effects of different conditions on the crystal structure of the plating layers by XRD (X-ray diffraction), and the effects of different conditions on the deposition layer corrosion resistance by Tafel polarization curves and AC impedance spectroscopy. Moreover, we study the effect of different process conditions on the zinc-nickel alloy deposited layer of zinc nickel content by EDS (Energy dispersive X-ray spectroscopy). From all the above, we acquired the optimum conditions for zinc, nickel and zinc-nickel alloy deposited layer.By acidic sulfate zinc system, zinc coatings were obtained by adding additives CTAB(hexadecyl trimethyl ammonium bromide) and BDA(benzylidene acetone). We discussed the effect of the additive, current density, pH and plating solution temperature on the zinc platings surface morphology, corrosion resistance and crystal structure. The results show that the surface morphology of the zinc coatings had obvious different between the coatings added additives with the coatings without additives. With the added additives, the orientation of the crystal plane was changed and the corrosion resistance of the coatings was enhanced. The morphology of the zinc coatings, crystal plane orientation and corrosion resistance performance were influenced by The cathodic current density, plating pH and solution temperature. The optimum conditions for electrodeposited zinc was that we add both CTAB and BDA, electrolyte temperature 30 ℃, current density of 20 mA/cm2, pH=4,.The nickel coatings was obtained by watt nickel plating liquid system. The effect of current density, electrolyte solution temperature and pH on the nickel coatings’s surface morphology, crystal plane orientation and corrosion resistance were discussed. The optimum conditions for plating nickel was that the current density was 50 mA/cm2, pH=4 and plating solution temperature was 50℃,.The zinc-nickel alloy was obtained by acidic chlorate plating system. The effect of zinc nickel ion concentration ratio, current density, electrolyte solution temperature and pH value on the zinc-nickel alloy coating’s surface morphology, crystal plane orientation and corrosion resistance were discussed. In the case of that the concentration of zinc and nickel was a constant, as the zinc nickel ion concentration ratio changed from 0.8 to 1.6, the content of nickel in zinc-nickel alloy decreased gradually. When the cathodic current density in the range of 10 mA/cm2 to 40 mA/cm2、 electrolyte solution pH value in the 2.6～5.0 scope changed, the change of the content of nickel in zinc-nickel alloy was not big. When the electrolyte solution temperature in the 20℃～50℃ scope changed, the change of the content of nickel in zinc-nickel alloy was big. The zinc nickel ion concentration ratio was 1.2, electrolyte solution temperature was 30℃、current density was 20 mA/cm2 and pH=4.2, which were the optimum conditions for electrodeposited zinc-nickel alloy. |
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