热镀锌钢板无铬钝化膜的改性及其耐蚀性能

Modification of Chromium-Free Passivation Coating on Hot-Dip Galvanized Steel and Corrosion Resistance of the Passivation Coating

以丙烯酸树脂作主成膜剂,钼酸、磷酸盐作缓蚀剂,再加入经铝溶胶改性的硅烷偶联剂,通过交联反应在镀锌板表面形成无铬钝化膜。利用红外光谱、中性盐雾试验、电化学交流阻抗和极化曲线对镀锌板表面钝化膜特征进行了表征。结果表明:铝溶胶改性硅烷在钝化膜中形成了Si-O-Al键;改性后的无铬钝化膜更加致密,耐腐蚀性能更高。

Chromium-free passivation fluid for hot-dip galvanized steel was formulated by using acrylic resin as the major film-forming agent,molybdate and phosphate as the corrosion inhibitors,and silane modified by alumina sol as the coupling agent.Cr-free passivation coating was prepared on the surface of the hot-dip galvanized steel via crosslinking reaction.The chemical feature of as-prepared Cr-free passivation coating was analyzed by means of Fourier transfer infrared spectrometry,and its corrosion resistance was examined using neutral salt-spray test as well as electrochemical impedance spectroscopy and polarization curve measurement.Results indicate that the silane coupling agent modified by alumina sol can form Si-O-Al bond in as-prepared Cr-free passivation coating,resulting in improved compactness and corrosion resistance of the passivation coating.