Corrosion behavior of spangle on a batch hot-dip galvanized Zn-0.05Al-0.2Sb coating in 3.5 wt.% NaCl solution

The corrosion behavior of shiny and dull spangle on a batch hot-dip galvanized Zn-0.05Al-0.2Sb coating in an aerated 3.5 wt.% NaCl solution was evaluated by potentiodynamic polarization curves, electrochemical impedance spectroscopy and neutral salt spray test. Experimental results demonstrated that shiny spangle shows a better corrosion resistance than dull spangle. beta-Sb3Zn4 particles precipitated on the spangle surface motivate the cathodic activity and thereby increase the corrosion rate of spangle in NaCl solution. Finally, the degradation mechanism and the role of galvanic protection of spangle have been discussed by a proposed corrosion model.