ELECTROCHEMICAL STUDIES OF ZINC-NICKEL CODEPOSITION IN CHLORIDE BATHS

The electrodeposition of Zn-Ni alloys from a chloride bath with differ ent Ni2+/Zn2+ ratios was studied. The bath had the composition 2 mol d m(-3) KCl, 1 mol dm(-3) NH4Cl, 0.5 mol dm(-3) H3BO3, 0.5 mol dm(-3) Zn Cl2, 0.25-1.25 mol dm(-3) NiCl2 . 6H(2)O. The cathodic polarization du ring electrodeposition and the alloy composition were greatly influenc ed by the ratios Ni2+/Zn2+ in the bath and are related to both the pH and temperature of the solutions used for electrodeposition. Under the examined conditions, the electrodeposition of the alloys was of the a nomalous type. X-ray diffraction studies revealed that the alloys cons isted of the gamma phase (Ni5Zn21) or of a mixture of the two phases d elta (Ni3Zn22) and gamma. Cyclic voltammetry enabled a convenient esti mation of phase compositions. Smooth and semi-bright layers with a rat her uniform nickel content are obtained using additives containing the phenolic derivative and an amine compound.