Abstract:Two additives of ethylene diamine tetraacetic acid (EDTA) and ammonium chloride (NH₄Cl) were separately used in the electrodeposition of Zn-Ni alloy films from a deep eutectic solvent. The effects of these two additives on electrodeposition behavior, composition, morphology, and corrosion performance of the Zn-Ni alloys were investigated. The electrodeposition behaviors of Zn-Ni alloy revealed by the cyclic voltammetry show that the addition of EDTA to the Zn-Ni electrolyte enhances the Zn incorporation into the alloy film while the addition of NH₄Cl produces an opposite effect by suppressing Zn incorporation into the film. With an increase of EDTA concentration in the electrolyte, the Zn content of the Zn-Ni films increases, while the grain size of the deposits and the current efficiency of the plating process decrease. The increase of NH₄Cl concentration in the electrolyte would significantly refine the grain size of the electrodeposited Zn-Ni films, reduce the Zn content and increase the cathodic current efficiency. The corrosion testing indicates that the barrier corrosion resistances of Zn-Ni films electrodeposited from NH₄Cl containing electrolytes are superior to those electrodeposited from EDTA-containing electrolytes, which in turn are superior to those electrodeposited from additive-free electrolytes.

Key words: additive; EDTA; NH₄Cl; deep eutectic solvent; corrosion resistance