EIS Investigation and Structural Characterization of Different Hot-Dipped Zinc-Based Coatings in 3.5% NaCl Solution

Corrosion behavior of hot-dipped zinc-based coatings (pure zinc, Zn–0.25%Al and Zn–5%Al) was studied through potentiodynamic polarization test and electrochemical impedance spectroscopy in 3.5% NaCl solution. Corrosion products were analysed by means of SEM, EDS and XRD. The results reveal that Zn–5%Al coating exhibited the highest corrosion resistance. The corrosion product layer formed on Zn–5%Al coating is more compact than the other two coatings. The β phase has two different influences on the corrosion behavior: the β phase can act as a galvanic cathode to accelerate corrosion and act as a corrosion barrier to hinder corrosion.