The effect of additives on zinc electrodeposition from deep eutectic solvents

► The effect of additives on the morphology of electrodeposited zinc is demonstrated. ► Two ionic liquids were used for the study. ► The additives brighten the deposit due to double layer changes ► Ethylene diamine and ammonia are the most effective additives. The electrodeposition of metals using ionic liquids has received considerable attention during the last ten years. Recent developments have taken these novel electrolytes from laboratory to commercial scale. One of the factors limiting the development into practical plating systems is the understanding of how brighteners function. In this study we describe the addition of three polar additives and their effect upon the nucleation mechanism of zinc and the resultant morphology. It is shown that the structure of the zinc deposits is controlled by double layer properties and it is proposed that the brightening effect of ethylene diamine and ammonia are caused by their ability to inhibit the adsorption of chloride at the electrode surface. The deposition of most metals using ionic liquids results in apparently amorphous deposits, which tend to be actually nano-crystalline. The additives used in this study produce macro-crystalline deposits, which resemble those obtained from aqueous solutions.