EFFECT OF ORGANIC TOP COATING ON ANTICORROSION PERFORMANCE OF SINTERED Zn-Al COATING

Composite coating was prepared by adherence of the epoxy Al-rich coating on sintered Zn-Al coating,in order to improve the anticorrosion performance of Zn-Al coating in seawater.The adhesion of sintered Zn-Al coating and composite coating were tested by cross cut test.The two different coatings were observed by scanning electron microscope(SEM).The anticorrosion performances of the two different coatings were studied by means of immersion test in seawater and neutral salt spray test.The corrosion electrochemical behaviors of the two different coatings were studied by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results show that the composite coating is more compact than the Zn-Al coating.It exhibits better waterproof performance than the Zn-Al coating.The epoxy Al-rich coating could effectively prevent corrosive species attacking.The composite coating exhibits obviously better anticorrosion performance than the Zn-Al coating.A typical Warburg impedance character appears at the beginning of corrosion process of the composite coating;Al flakes of the epoxy coating dissolve and exert sacrificial anode effects with the penetration of erosive species.The organic top coating improves the application of Zn-Al coating in seawater.