Role of amino acids on electrodeposition and characterisation of zinc from alkaline zincate solutions

Amino acid-based addition agents have been employed in an alkaline zincate plating electrolyte to modify corrosion resistance, crystal size, surface morphology, and adhesion of deposits. These addition agents such as guanine, histidine and glutamic acid are recommended in zincate solution to improve the corrosion resistance, crystal size and adhesion of the deposits. The XRD pattern obtained for electrodeposited zinc from such baths shows a polycrystalline hexagonal close-packed (hcp) structure. The crystal size was calculated using the Scherrer formula. A uniform and pore-free surface was observed under scanning electron microphotography (SEM) analysis. The corrosion resistance behaviour of the zinc deposits was analysed by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Histidine appears to show most promise in enhancing corrosion resistance and grain refining.