EFFECT OF CERIUM SALT AND SILANE TREATMENTS ON CORROSION RESSISTENCE OF HOT-DIP GALVANIZED STEEL

A silane film was prepared on the hot-dip galvanized (HDG) steel sheets after treated in 20 g/L Ce(NO3)3·6H2O solution.The corrosion resistance was assessed by polarization curves and nevatral salt spray(NSS) tests.The films were characterized by AES.The single cerium salt conversion film or silane film could improve the corrosion resistance of zinc coating.However,the double-layer film obtained from the two-step treatment could markedly restrain the anodic and cathodic reactions in the corrosion process and result in the optimal corrosion resistance.AES analysis revealed that the double-layer film was formed on the surface,which mainly consisted of an inside Ce-rich cerium conversion film and an outside homogeneous silane film.