镀锌钢板表面无机–有机复合无铬钝化膜

Chromium-free inorganic/organic composite passivation film on surface of galvanized steel

以磷钼酸盐溶液、水性丙烯酸改性环氧树脂、乙烯基三乙氧基硅烷(VS)和表面活性剂(SDS+OP-10)为A组分,水性改性胺固化剂(LJ810)为B组分,制备了无机–有机无铬复合钝化液。通过正交试验和单因素试验确定了A组分配方为:表面活性剂SDS 5 g/L+OP-10 15 g/L,有机硅烷偶联剂60 mL/L,水性丙烯酸改性环氧树脂乳液250mL/L,磷钼酸盐溶液100mL/L。以此无机–有机无铬复合钝化液对镀锌板进行钝化,采用扫描电镜和能谱分别分析了复合膜的表面形貌及元素组成。通过中性盐雾试验、醋酸铅点滴试验、Tafel极化曲线及交流阻抗研究,探讨了复合膜的耐腐蚀性能。结果表明,复合膜表面光滑平整,对镀锌板的附着力良好,72 h中性盐雾试验后的腐蚀率为3%,与铬酸盐钝化膜的耐蚀性相近。

A chromium-free inorganic/organic composite passivation solution was prepared with phosphomolybdate solution, waterborne acrylate-modified epoxy resin, vinyl- triethoxysilane （VS）, and surfactants （SDS ＋ OP-10） as component A and a water-based modified amine curing agent L J810 as component B. The formulation of component A was determined by orthogonal test and single-factor test as follows： surfactants SDS 5 g/L ＋ OP-10 15 g/L, organic silane coupling agent 60 mL/L, water-based acrylate-modified epoxy resin emulsion 250 mL/L, and phosphomolybdate solution 100 mL/L. The passivation was carried out on galvanized steel using the composite passivation solution. The surface morphology and elemental composition of the composite film obtained thereby were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively. The corrosion resistance of the composite filmwas examined by neutral salt spray （NSS） test, lead acetate dropping corrosion test, Tafel polarization curve measurement, and AC impedance spectroscopy. The results showed that the composite film features a level and smooth surface and good adhesion with galvanized steel. The corroded area is 3% for the composite film after 72-h NSS test, indicating that the composite film has comparable corrosion resistance to conventional chromate passivation film.