Effects of [HMIM]HSO4 and [OMIM]HSO4 on the electrodeposition of zinc from sulfate electrolytes

The effects of the organic additives 1-hexyl-3-methylimidazolium hydrogen sulfate ([HMIM]HSO4) and 1-octyl-3-methylimidazolium hydrogen sulfate ([OMIM]HSO4) on current efficiency (CE), power consumption (PC), polarization behavior of the cathode, deposit morphology, and crystallographic orientation during electrodeposition of zinc from acidic sulfate solution were investigated. The results were compared with those of a common industrial additive, gum arabic. Addition of these additives increases current efficiency, decreases power consumption, and improves the surface morphology at lower concentrations. Both the additives showed similar polarization behavior to gum arabic and the extent of polarization was in the order: gum arabic > [OMIM]HSO4 > [HMIM]HSO4. The nature of the electrode reactions was studied through measurements of Tafel slopes, transfer coefficients, and exchange current densities. Data obtained from X-ray diffractogram revealed that the presence of any of these additives did not change the structure of the electrodeposited zinc but affected the crystallographic orientation of the crystal planes.