Effect of Pb on the electrodeposition behavior of Zn-Ni alloy

The effect of Pb in the bath on the electrodeposition behavior of Zn-Ni alloys in sulfate type baths was investigated for the hydroxide suppression mechanism. In the presence of Pb in the bath, the transition current density where codeposition behavior changes from normal type to anomalous type was increased. This increase can be explained by the following two factors, one is the current density which is equal to reduction rate from Pb²⁺ ion to Pb as metal, another is the increase of apparent current density because of rough deposits on the electrode surface. The Ni content in deposits increased in the region II where anomalous type codeposition occurred with high current efficiency. This phenomenon appears to have been caused by the metal Pb electrodeposition continuously supplying activation sites for electrodeposition of Ni, which is not blocked in Zn hydroxides, thus accelerating the rate of electrodeposition of Ni, compared to that of Zn.