薄型无铬有机复合涂层钢板耐蚀性的研究

Corrosion Resistance of Chromate-Free Thin Organic Composite Coatings on Hot Dipped Galvanized Steel Sheet

在热镀锌钢板上分别制备了纳米硅溶胶／改性水溶性丙烯酸树脂复合涂层（AC-Si）、钼酸盐＋胶态SiO2系钝化膜＋AC-Si薄膜复合涂层（AB-2）、钼酸盐＋钛（IV）盐＋胶态SiO2系钝化膜＋AC-Si薄膜复合涂层（AB-6）等3种无铬有机复合涂层，并通过中性盐雾试验和电化学测试技术对复合涂层钢板的腐蚀、电化学行为和防蚀机理进行了探讨。结果表明，与AC-Si和AB-2复合涂层相比，厚度为4～5μm的AB-6复合涂层表现出良好的防护效果，使镀锌板的耐蚀性能提高了10倍，其抗白锈能力达48h。究其原因，主要是由于AB-6复合涂层高分子膜的屏障作用、SiO2沉淀膜的缓蚀作用及TiO2粒子的阻化作用和掺杂作用所致。

Novel chromate-free organic composite coatings(marked as AC-Si,AB-2 and AB-6),comprised of molybdate passive film and modified water-soluble acrylic resin,were prepared on the surface of hot-dipped galvanized steel sheet(HDG).With the aid of the neutral salt-spray and electrochemical measurements,the corrosion and electrochemical behavior and anti-corrosion mechanisms of the composite coatings were explored.The results showed that as compared with AC-Si composite coating(water-soluble acrylic resin coating modified with nano-silica)and AB-2 composite coating(composed of molybdate,colloid silica-containing passive film,and water-soluble a-crylic resin coating modified with nano-silica),the AB-6 composite coating(composed of molybdate,Ti(IV)salt,colloid silica-containing passive film,and water-soluble acrylic resin coating modified with nano-silica)with a thickness of 4-5 μm showed the best protection to the hot-dipped galvanized steel sheet.Namely,the corrosion-resistance of the HDG coated with the AB-6 coating was increased by a factor of 10 as compared with that of uncoated HDG,and this composite coating was able to prevent the HDG steel sheet from white rust within a period of 48 s.It was supposed that the excellent corrosion resistance of the AB-6 composite coating could be attributed to the barrier effect of the organic film,the corrosion mitigation effect of the SiO2 deposited film,and the blocking and doping effects of TiO2 particles.