An electrolyte for electrodeposition of hard gold based on choline chloride-urea ionic liquid

Hard gold has excellent physical and chemical properties, and is widely used in jewelry and the electronics industry. The deposition of hard gold has long been focused on cyanide-based aqueous electrolytes, which are highly toxic with relatively low electroplating efficiency due to the coreduction of hydrogen. Ionic liquids have recently been studied as a solvent for the electrodeposition of various metals. Herein, choline chloride-urea ionic liquid was used as the solvent with 5,5-dimethylhydantoin as the complexing agent and Co2+ was added to produce cobalt-hardened gold deposits. The addition of Co2+ promoted grain size refinement and improved the hardness of deposits. With 62.5 mg/L Co2+ present in the electrolyte, the coating showed a high degree of hardness (2.3 GPa) and relatively good corrosion resistance.