A review of organic additives in zinc electrodeposition process (performance and evaluation)

This review provides an overview of some important studies and investigations performed on various organic additives in zinc electrodeposition process. Organic additives are widely used due to their special functions during the electrodeposition of zinc or its alloys. These additives are found to affect the growth and crystal building of deposits through their adsorption on the cathode surface. Most of these additives act as hydrogen inhibitors and crystal growth modifiers, so an appropriate addition is necessary for the formation of fine-grained, smooth, and compact deposits. The presence of metallic impurities in the industrial electrolytes cannot be neglected as well. Most of these impurities decrease the induction period associated with the zinc electrodeposition process resulting in deterioration of the zinc deposit quality and decrease of the cathodic current efficiency. Accordingly, some additives are used to reduce the detrimental effect of these impurities and to improve the operating performance. Although, glues and gelatins are the most known additives in industry but searching for better ones with good stability, high efficiency, low cost, and being environmentally acceptable is still continuing. Therefore, this review considers previous studies conducted on various organic additives from different groups such as: quaternary ammonium salts, polymers, surfactants, natural compounds, organic acids, and ionic liquids salts. This study emphasizes as well the employed electrochemical techniques in evaluating the performance of organic additives during the electrolytic extraction of zinc.