Electrochemical Co-Deposition of Metals Coating

   The present work has been mainly aimed to find a relationship between current densities of individual copper and zinc anodes with percentages of brass alloy plating in certain solutions .The influence of various variables on the individual plating of copper and zinc that would provide good plating on graphite bar (cathode) using copper and zinc as anodes has been investigated. The cathodic current efficiencies are also investigated under various values of temperature, time, cathodic current density, and concentrations of CuCN in copper bath and ZnO in zinc bath. The important factor in alloy deposition is the deposition potential determined by polarization processes occurring on cathode rather than the standard potential of the two metals as determined by the e.m.f series. The use of complex solutions (cyanide) is to bring the deposition potential of two different metals closer together than is possible in aqueous solution. The performance of cathodic current efficiency has been tested for four major factors that affect the plating process. These were temperature, , time of plating process, cathodic current density and concentration of CuCN in copper plating and ZnO in zinc plating. The results showed that the cathodic current efficiency increasing with increasing temperature, time of plating and concentration of both CuCN in copper bath and ZnO in zinc bath and decreases with increasing cathodic current density. An empirical equation expressing the relationship between copper current density(i)and zinc current density(iZn) with percentages of brass alloy(Cu%, Zn%) plating has been obtained as follows:
iCu/iZn =0.719735+0. 005395 *exp (0.082058*Cu%) -0.001086*exp (0.082123*Zn %) The conditions of equation above are bath temperature 500 C and 200RPM, in a solution of 17.5 g/l CuCN, 12.5 g/l ZnO, 38 g/l NaCN and 96.1 g/lNaOH.