热镀锌钢板水性聚氨酯复合钝化膜的制备及其耐蚀性能

Preparation of Water-Borne Polyurethane Composite Passivation Film on Galvanized Sheet and Evaluation of the Corrosion Resistance

为了进一步提高热镀锌钢板的耐蚀性能并消除其他方法的弊端,以水性聚氨酯(PU)为主成膜物质,添加硅烷偶联剂KH560、乳化蜡、含异氰酸酯基团的水性固化剂,并加入防锈剂乙酰丙酮氧钒和磷酸二氢镁配成复合钝化液,对热镀锌钢板钝化。采用正交试验优化了复合钝化液的组成,采用中性盐雾试验、电化学扫描等方法测试了最优钝化膜的耐蚀性能。结果表明:钝化液组成为12.0%PU,8.0%硅烷偶联剂,5.0%乳化蜡,1.2%磷酸二氢镁,0.3%乙酰丙酮氧钒,0.8%水性固化剂时,复合钝化膜96 h盐雾试验腐蚀面积<4%,自腐蚀电流密度是不含防锈剂有机钝化膜的0.017 6倍,耐蚀性明显优于单一有机钝化膜。

A compound chrome-free passivation solution for hot-dip galvanized steel sheet was formulated with water-borne polyurethane( denoted as PU) as the major film-forming substance while silane coupling agent KH560,emulsifying wax,water-borne curing agent containing isocyanate group,and antirust agent including vanadyl acetylacetonate and magnesium dihydrogen phosphate were added. The composition of the compound passivation solution was optimized based on orthogonal test,while the corrosion resistance of the passivation film obtained from the passivation solution with the optimal composition was evaluated by neutral salt-spray test and electrochemical scanning method. Results indicated that the composite passivation film prepared from the passivation solution containing 12. 0% PU( mass fraction; the same hereafter),8. 0%silane coupling agent,5. 0% emulsifying wax,1. 2% magnesium dihydrogen phosphate,0. 3% vanadyl acetylacetonate,and 0. 8%water-borne curing agent exhibited much better corrosion resis-tance than organic passivation film. Namely,its corrosion area was less than 4% after 96 h of salt-spray test,and its density was only 1. 76% as much as that of organic film.