Electrodeposits of zinc from a chloride bath without organic additives had (0002) preferred orientation at low current density and (1120) at high current density. In the presence of additives, however, the (0002) plane of preferred orientation diminished and changed to random deposits of (1010), (1011) and (1120) planes. The relative surface energy of the crystal plane and the mechanism of adsorption inhibition could explain the results of the preferred orientation to some extent. Since the crystal growth on the (0002) axis of preferred orientation was inhibited by the dominative adsorption of additives onto the plane that has the highest value for surface energy, other axes of orientation can be developed. Carbon derived from additives was codeposited to a maximum of 1wt.%, and the lattice constant for the c-axis decreased slightly but clearly with the increase in the codeposition percentage, whereas exhibited no change in the a-axis. The hardness of the deposits from the bath without additives was about 40HV 0.01. Deposits from those with additives rose to about 100HV which was ascribed to the deformation from a slight shrinkage in the direction of the c-axis.
A new nickel electroplating bath called a “Nickel citrate bath” uses citric acid in place of boric acid. In order to clarify its properties, a Hull cell test and measurements of current efficiency and pH titration curves were performed. The results were compared with those obtained from a Watts bath. The citric acid in a Nickel citrate bath consists of various ratios of citrate ion and nickel-citrate complexes forming complex equilibrium at various pH levels. A Nickel citrate bath with a concentration of citric acid above 0.06M has a good appearance, current efficiency, and pH buffering action for the bath. The results were almost the same as those obtained with a Watts bath under the same conditions. This result is attributed to interaction of nickel-citrate complexes at the electrode surface in the Nickel citrate bath.