An approach to improve corrosion resistance in electro-galvanized Zn-Al composite coating by induced passivity

In the current work, zinc and zinc-aluminum nano-composite was electro-galvanized onto mild steel at specified current densities from a sulfate bath. The incorporation of aluminum was found to enhance the corrosion resistance (0.0008 to 0.0003 mm/yr) as well as passivity of the deposits as compared to pure zinc deposition. Hence, attempts were made to analyze the effect of aluminum addition on the passive film and its protective nature by using several techniques including SEM, XRD, Mott-Schottky (MS), Electrochemical Impedance Spectroscopy. The results proved that the films were of protective nature and are of n-type semiconductor properties with adequate defect densities/charge carriers.