Electroformed Nickel Copper Alloy Process And Mechanism

The theory, development and application of electroform technology as well as the factors of electroform Ni-Cu alloy were reviewed in this paper.Ni-Cu alloy electroform film is more ancorrsive, more intensity and harder than pure nickel film. Recently, there are many studies on nanocrystalline Ni-Cu alloy and multilayer Ni-Cu alloy films, but hardly having the process of electroforming Ni-Cu alloy that has been reported in the domestic and internatioanal literature.In this paper, the films of Ni-Cu alloy were successfully electrodeposited on the aluminium alloy substrate from sulfate--sodium citrate solution. The ingredient of electrolyte, the function and content of the ingredient were studied. The component of Ni-Cu film is analyzed by chemistry titration method, particularly the influence of the electrolyte component, current density and pH value on Ni-Cu film were studied. By doing conditional experiment, the influence of the process parameters such as current density and temperature on the rigidity of electroforming layer as well as the electrodepositing speed was. studied. At last, Ni-Cu alloy electrodeposited was studied by the method of the electrochemsitry testing. The results are as follows:Ni-Cu film is successfully electrodeposited on the aluminium substrate from sulfate--sodium citrate solution, by Hull Cell tests and beening observed the appearance of Ni-Cu film, we chose proper electrolyte component and their content, the best electrolyte formula is showed as follows:NiSO4.6H2O 100g/L, CuSO4.7H2O 10g/L, C6H5Na3O7.2H2O 70g/L, H3BO3 30g/L, NaCl 8g/L.The electrodepositing speed rose with the increase of current density, increased and then declined with the increase of temperature, it reached maximum value at 55℃。The rigidity of the plating layer rose with the increase of current density and the temperature.The factors of the component of the Ni-Cu alloy layer is current density, pH value, content of the ingredient and additive of the electrolyte. Cu content of the layer rose with the increase of current density and pH value. When Ni2+concentration was invariable, Cu content of the layer rose with the increase of Cu2+concentration. When the complexation between Ni2+of the electrolyte and sodium citrate partly and excessively, Ni content of the layer was declined sharply, from 87.62%to 42.33%. Besides, the function of every additive on the alloy layer is different:butynediol and saccharin can accelerate the precipitation of the copper, while gelatin could restrain precipitation of the copper.Corrosion resistance of Ni-Cu alloy was influenced by Cu content, their corrosion resistance rose with the increase of Cu content. As to different thickness, the layer was thicker, the corrosion resistance was better.The results of the study on polarization curve testing showed:the complexation between citrate ion and Ni2+,Cu2+could move to the potential negative direction, the increace of CUSO4.7H2O concentration moves to the potential positive direction. The study on Ni,Cu,Ni-Cu alloy electrodepositing showed that the electrodepoditing speed of Ni-Cu alloy is faster than that of Ni or Cu, for the cathode polarization curve of Ni-Cu alloy is positive to that of Ni or Cu.By studying the influences of every process paraments on Ni-Cu alloy electrodepoditing, the best process parameters we chose is showed as follows:current density is 2.5-3.5A/dm2, temperature is 45-55℃, pH value is 4.5. And we added butynediol, saccharin and gelatin as additive to the electrolyte, so as to obtain the best surface appears.