Effects of high current density on the characteristics of zinc films electroplated in ethaline electrolyte

Abstract

Zinc coatings on Cu substrates were successfully electroplated from choline chloride (ChCl) with ethylene glycol (EG) based deep eutectic solvent with the current density varied from 10 to 40 mA cm−2 in air atmosphere at a temperature of 343 K. The effects of current density on the microstructure and corrosion performance were investigated in this paper. Smooth zinc coatings were obtained at the current density of 10 mA cm−2 with a current efficiency of over 90 %. With the increase in current density, there was a declining trend in the current efficiency and the surface quality of zinc coatings. Although there was no diffusion layer between the coating and substrates, all the zinc coatings still bonded well with the copper substrates. Compared with the smooth zinc coating electroplated at 10 mA cm−2, the zinc coating obtained at 40 mA cm−2 exhibited a better corrosion resistance in 3.5 wt.% NaCl aqueous solution due to the dense packing of the large number of flake zinc grains.