On the electrodeposition of nickel–zinc alloys from a eutectic-based ionic liquid

The electrodeposition behavior of Ni–Zn alloys upon Cu was investigated in a choline chloride–urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl–urea IL) bath containing 0.1 M NiCl2 and 0.4 M ZnCl2. Cyclic voltammetry reveals that the more noble metal, Ni, deposits preferentially to Zn. Ni–Zn co-deposition was achieved via deposition of Zn upon deposited Ni, at potentials more negative than that of Ni deposition, resulting in a Zn content always less than 50 at.%. Chronoamperometric investigations combined with SEM reveal the nucleation mechanism changes from three-dimensional progressive to instantaneous, followed diffusion-limited growth during Zn-codeposition. The Ni content of electrodeposits could be controlled by deposition potential and current density. Ni–Zn deposits were solid solutions, and deposits containing Ni > ∼87 at.% display best corrosion resistance due to a dense and crack-free structure.