Synergistic Effect of Brightener and Solution Temperature on the Electrodeposition Behavior of Zn–Ni Alloy from Alkaline Zincate Solution

Abstract

Zn-Ni alloys were electrodeposited on a Cu electrode at 10-5 000 A•m − 2 , 5 × 10 4 C•m − 2 , 293 K, 313 K, 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 alloys was investigated. The transition current density at which the deposition behavior shifted from normal to anomalous one decreased with IME at 293 K, but did not change regardless of IME addition at 313 K 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 K and 333 K, the suppression effect decreased on the Zn deposition but was maintained on the Ni deposition. Therefore, Ni content in deposits significantly decreased with IME as the temperature increased. The current efficiency of Zn deposition significantly decreased with IME at 293 K, with a small degree of decrease at 313 K and 333 K. The C content in deposits was the highest at 293 K and decreased with increasing solution temperature, indicating that the adsorption ability of IME on the cathode decreases with the increasing temperature. As a result, the suppression effect of IME on the Zn deposition decreases with the increasing temperature. The gloss of deposited films was the highest at 293 K, attributed to the IME adsorption ability being large at 293 K and deposited films with fine crystals becoming smooth.

Concentration Influence of Complexing Agent on Electrodeposited Zn-Ni Alloy

“…For ease of visibility, the current density is presented as a function of potential on a logarithmic scale. The equilibrium potential of Zn E eq Zn is −1.27 V with pure Zn depositing at room temperature [17]. The Zn polarization curve rose at approximately −1.0 V, which is nobler than E eq Zn , suggesting underpotential deposition of Zn.…”

“…Conversely, alkaline electrolytes operate at low current density and provide uniform Ni distribution with a higher content than that produced by acid baths. Alkaline solutions, including cyanide and zincate, yield higher throwing power than their counterparts [15][16][17]. While cyanide solution shows high toxicity in the environment, zincate is an eco-friendly candidate.…”

Corrosion Resistance of Zn–Ni Alloy Films Electroplated in Alkaline Zincate Solutions Containing a Brightener

“…Therefore, the authors selected the epichlorohydrin and imidazole (IME) reaction product as a brightener, which is reported to have a gloss effect on Zn-Ni alloy-plated films obtained from zincate solutions. [30][31][32][33] The effect of the brightener added to the electrolysis solution on the corrosion resistance of Zn-Ni alloy-plated films was investigated. In this study, the surface of the obtained Zn-Ni alloy-plated films was corrosion treated in a NaCl aqueous solution which is a representative corrosion environment containing Cl − ions.…”