The importance of using hydrogen evolution inhibitor during the Zn and Zn-Mn electrodeposition from ethaline

Cyclic voltammetry was used for the characterization of zinc electrodeposition on steel from ethaline deep eutectic solution (1:2 choline chloride:ethylene glycol). The influence of 4-hydroxy-benzaldehyde (HBA) as an additive was analyzed. It was shown that hydrogen evolution is inhibited in the presence of HBA and further significantly retarded upon addition of Zn2+ to the solution containing HBA. The cathodic peak for Zn2+ reduction in this type of ionic liquid (ethaline+HBA+Zn2+) resembles the zinc reduction in aqueous solution. The corrosion resistance of Zn coatings deposited at different current densities was evaluated by electrochemical methods, i.e., polarization measurements and electrochemical impedance spectroscopy in 3 % NaCl solution. The possibility of Zn–Mn alloy deposition from ethaline deep eutectic solvent was investigated for the first time. In addition, the corrosion stability of these alloy coatings was analyzed and compared to the stability of bare Zn coatings. It was shown that the optimum deposition current density for both Zn and Zn–Mn coatings with increased corrosion stability from ethaline + HBA electrolyte is 5 mA cm˗2.