Abstract
Zn–Ni alloys were electrodeposited on a Cu electrode at 10–5000 A·m−2, 5 × 104 C·m−2, and 293, 313 and 333 K in unagitated zincate solutions containing the reaction product of epichlorohydrin and imidazole (IME) as a brightener. The synergistic effect of IEM and solution temperature on the deposition behavior of Zn–Ni alloy was investigated. The transition current density, at which the deposition behavior shifted from the normal type to anomalous ones, decreased with IME at 293 K, but didn’t change regardless of IME addition at 313 and 333 K. The suppression effect of IME on the Zn and Ni depositions during alloy deposition was observed at 293 K, while at 313 and 333 K, the suppression effect was decreased on the Zn deposition but was maintained on the Ni deposition. Therefore, Ni content in deposits significantly decreased with IME as temperature increased. The current efficiency for Zn deposition significantly decreased with IME at 293 K, while the degree of decrease was small at 313 and 333 K. The content of C in deposits was highest at 293 K, and decreased with increasing solution temperature, indicating that the adsorption ability of IME on the cathode decreases with increasing temperature. As a result, the suppression effect of IME on the Zn deposition seems to decrease with increasing temperature. The gloss of deposited films was highest at 293 K. This is attributed to adsorption ability of IME being large at 293 K and deposited films with fine crystals becoming smooth.
