Influence of Additives on Electrodeposition of Metals from Deep Eutectic Solvents

In metal electroplating processes, additives are normally added to the plating bath to improve the physical and mechanical properties of the coating such as brightness, roughness, thickness, hardness and resistance to corrosion. The effects of additives on the electrodeposition of metals from aqueous solution have been extensively investigated. However, very few studies have considered the effects of additives on the electrodeposition of metals from ionic liquids (deep eutectic solvents). This work has shown that ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA), sodium iodide (NaI), boric acid (BA) and 5,5-dimethylhydantoin (DMH) as additives can be used to modify the Cu deposit morphology obtained from a 1:2 ChCl: ethylene glycol-based liquid (Ethaline 200) on a mild steel substrate. It was found that NaI significantly influenced the morphology of the Cu deposit, achieving a bright and thick Cu deposition. The effects of nicotinic acid (NA), boric acid (BA) and benzoquinone (BQ) on Zn deposit morphology from Ethaline 200 were also shown, and for the first time a bright zinc coating has been achieved on a copper substrate when NA was used. The feasibility of Zn-Ni alloy deposition from Ethaline 200-based deep eutectic solvents has been investigated in the absence and presence of boric acid and sodium bromide. It was found for the first time that a successful bright Zn-Ni alloy coating from Ethaline 200 can be produced in the presence of boric acid and NaBr as additives. Moreover, the effects of current density, temperature and concentration of Zn species on electrodeposition of Zn-Ni alloy from Ethaline 200 in the presence of both boric acid and NaBr have been studied. The last part of this work was to look at the effects of methyl nicotinate (MN) on the electrodeposition of Al from 1-ethyl-3-methylimidazolium chloride/AlCl3 and 1-butyl-3-methylimidazolium/AlCl3 as classical ionic liquids, and (1.5:1) AlCl3:acetamide, (1.5:1) AlCl3:N-methylacetamide and (1.5:1) AlCl3:N,N-dimethylacetamide as deep eutectic solvents. A mirror Al coating has been achieved on a copper substrate from both conventional ionic liquids as a result of using methyl nicotinate as an additive. MN has improved the morphology of Al deposited from (1.5:1) AlCl3:acetamide-based liquids and, furthermore, MN has been used to refine the grain size of the Al coating achieved from (1.5:1) AlCl3:N,N-dimethylacetamide as a deep eutectic solvent.