| Cu-Zn alloy could keep golden yellow face, reduce the price of gold as well as adjusts the conflict between price and ornament request, so it has extensively used as an ideal ornament material. At present, Cu-Zn alloy is electroplated mainly in cyanide electrolytes, but cyanide electrolyte is a poisonous substance and it could break down when contact with air during electroplating, it is harmful for the environment and operators. So researchers tried to find some harmless and steady non-cyanide imiting gold plating electrolyte, but these electrolyte are not as good as the cyanide electrolytes for some problems such as the color shade is not controlled, electroplating time is short and so on. So search for a composition could controlled, steady and environmentally friendly new technique of alloy preparation have got the attention from green electrochemistry for a long time.Five kinds of ionic liquids (the molar ratio of BMIC to ZnCl2 in the ionic liquids are 1:0.5,1:1,1:1.5,1:2,1:3) were synthesized in this paper. Their structures were characterized by the IR spectrum; the viscosity and conductivity of those ionic liquids were measured. The electrowindow of every ionic liquid was studied by cyclic voltammetry. The BMIC-2ZnCl2 ionic liquid containing CuCl were investigated by some eletrochemical measurements, including cyclic voltammetry, controlled potential coulometry, et al. Electrodeposition of Cu-Zn alloy was carried on low-carbon steel in a Lewis acidic BMIC-2ZnCl2 molten salt containing CuCl. The effect of some electrodeposition parameters such as, CuCl concentration, deposition potential, temperature and anode materials on the content of Cu in the deposits and the current efficiency were studied. The surface morphology and elemental analysis of the gold-imitation deposits obtained were examined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD), respectively. The potential application of electrodeposition of gold-imitation was analysised, the major research results are drawn as follows:(1) The viscosity of these ionic liquids increase with the mol% of the ZnCl2 increases in the ionic liquids, and its Inηand 1/T consistent with the Arrhenius equationκ=Ae-Ea/RT. The conductivity of these ionic liquids increase firstly then decrease with the mol% of the ZnCl2 increases in the ionic liquids, and with the content of CuCl raises in the BMIC-2ZnCl2 ionic liquids, the conductivity decrease firstly then increase, its lnκand l/T consistent with the Arrhenius equationκ=Ae-Ea/RT.(2) Three pairs of redox peaks obtained in the BMIC-2ZnCl2 molten salt containing CuCl, it was two redox peaks more than the pure BMIC-2ZnCl2, this lead to the conclusion that copper and zinc could be codeposited in this system.(3) The copper content in the Cu-Zn alloys increases and the current efficiency decrease as the CuCl concentration in the plating bath increases at the same deposition potential; the copper content in the Cu-Zn alloys increases and the current efficiency decreases firstly then increases as the voltage increases when the same concentration of CuCl contained; the copper content in the Cu-Zn alloys increases and the current efficiency increases firstly then decreases as the temperature increases when the concentration of CuCl and deposition potential remain unchanged; the copper content was higher and the current efficiency was lower when copper plates were used as anode materials and the copper content was lower and the current efficiency was higher when zinc plates were used as anode materials, the copper content and the current efficiency were between them when a copper plate and a znic plate were used as anode materials.(4) It was found that the composition of Cu-Zn alloy could be controlled at the potential from-0.15V to-0.1V from the 0.1mol·L-1 to 0.4mol·L-1 CuCl containing plating bath at 70℃to 80℃.(5) At the same applied concentration(0.2mol·L-1), Tiny, well-distributed particles and yellow layer was obtained at lower voltage and temperature (-0.15V, 70℃), it was the best surface morphology of electrodeposition layer. In contrast, gathered and bad-distributed particles were obtained at higher applied voltage and temperature (-0.1V,80℃).The study of using BMIC-2ZnCl2 ionic liquids as electrolyte during the Cu-Zn alloy electrodeposition in this paper not only provides a kind of environment friendly and could be recycled potential non-cyanide system for the deposition of Cu-Zn alloy, but more important, the conditions of alloy composition could be controlled were obtained, all of this provide certain scientific basis for choosing and controlling electrolyte of gold-imitation electroplating. |
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