Electrodeposition of zinc–tin alloys from deep eutectic solvents based on choline chloride

Abstract

Here we describe the electrolytic deposition of Zn, Sn and Zn/Sn alloys from a solution of the metal chloride salts separately in urea and ethylene glycol/choline chloride based ionic liquids. We show that the deposition kinetics and thermodynamics differ from the aqueous processes and that qualitatively different phases, compositions and morphologies are obtained for the metal coatings in the different ionic liquid systems. We have quantified the electrochemical stripping responses using cyclic voltammetry together with compositional analysis using SEM/EDAX and X-ray diffraction. The differences in electrochemical responses are rationalised in terms of the speciation of both Zn and Sn chlorides in the ionic liquids that have been identified using FAB mass spectrometry. Also we demonstrate that composite metal coatings, e.g. containing Al2O3 particles, can be obtained from these liquid systems by virtue of the stable liquid suspensions. This novel feature of these liquids is a function of their relatively high viscosity.