Abstract：The silicate conversion coating was prepared by immersing hot dip galvanized (HDG) steel in sodium silicate solution with a SiO2∶Na2O molar ratio of 1.00 or 3.50, respectively. The corrosion resistance of coatings was investigated by neutral salt spray (NSS) test, Tafel polarization and electrochemical impedance spectroscopy (EIS) measurement. NSS corrosion process of the coatings scratched by the edge of knife was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the superior corrosion resistance and self healing ability are obtained from the silicate coating pretreated in sodium silicate solution with higher SiO2∶Na2O molar ratio. During the corrosion process, silicate anions migrate from the coating to the scratch, on which a new passive coating composed of Zn, O and Si is formed and the corrosion is suppressed. Moreover, it is observed that by the atomic force microscopy (AFM), the silicate coatings obtained in the sodium silicate solution with molar ratio of 3.50 is more compact, which is favor of the migration of silicate anions. The detail of corrosion process of the scratches on silicate coatings is discussed.
袁美蓉, 卢锦堂, 孔纲, 车淳山. 热镀锌层上硅酸盐膜的耐蚀性和自愈性[J]. 材料工程, 2012, 0(6): 48-53.
YUAN Mei-rong, LU Jin-tang, KONG Gang, CHE Chun-shan. Corrosion Resistance and Self Healing Ability of Silicate Conversion Coatings on Hot Dip Galvanized Steels. Journal of Materials Engineering, 2012, 0(6): 48-53.
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