Electrodeposition of high Co content nanocrystalline Zn–Co alloys from a choline chloride-based ionic liquid

•A non-anomalous codeposition process of Zn–Co alloys was observed in ChCl–urea IL.•High Co content Zn–Co alloy was deposited from high Co2+ concentration ChCl–urea IL.•The high Co content Zn–Co deposit was dense, homogenous and nanocrystallized.

Zinc–cobalt (Zn–Co) alloys were electrodeposited from a choline chloride-based ionic liquid containing ZnCl2 and different concentration of CoCl2. It was found that the Co content in deposits increased with the increase of the concentration of Co2+ in the plating bath and the codeposition of Zn–Co alloy was a non-anomalous type, i.e. more noble metal Co depositing preferentially with respect to the less noble one Zn. Structural and composition analysis revealed that the concentration of Co2+ strongly affected the morphology and chemical content, as well as the phase structure of Zn–Co alloys. A high Co content (over 60 wt.%), dense, homogenous and nanocrystallized Zn–Co alloy was deposited from plating bath containing higher concentration of Co2+.