Abstract The influence of electrolytic variables on the content of Zn, Ni and Pb in copper deposited cathodically from ammine solution has been investigated. Solutions spiked with zinc or nickel sulphate were studied using a rotating cylindrical titanium cathode and a lead anode. The nickel and zinc contents in the cathodic deposit increase with increasing current density and their concentration in the electrolyte. A rise in the rotation speed of the cathode increases the lead and nickel contents but diminishes the zinc content in the deposit. To explain these results an attempt has been made to schematically reconstruct polarisation diagrams for each metal. Direct potential measurements are subject to considerable experimental error in the system studied. Polarisation measurements performed on a simplified system were in good agreement with the hypothetical diagram.