镁合金表面锌系磷化膜及硅酸盐封闭工艺与性能

为提高镁合金的耐蚀性能,在镁合金表面制备锌系磷化膜,并对磷化膜进行封闭。比较了未封闭磷化膜、浸油封闭磷化膜、铬酸盐封闭磷化膜和硅酸盐封闭磷化膜的表面形貌、元素组成、厚度和耐蚀性能,结果表明:浸油封闭、铬酸盐封闭和硅酸盐封闭对镁合金表面磷化膜的厚度基本没有影响,但封闭前后磷化膜的表面形貌和元素组成有所不同。Cr、Na和Si元素分别通过形成化学转化膜、胶体状膜或物理填充孔隙被引入封闭后磷化膜中。硅酸盐封闭磷化膜的致密性相对较好,使镁合金的耐蚀性能得到有效提高。在铬酸盐封闭逐渐被弃用的趋势下,效果较好并且低污染环保的硅酸盐封闭在磷化膜封闭中具有应用潜力。

Preparation and Properties of Zinc Phosphating Film with Silicate Sealing on Surface of Magnesium Alloy

In order to improve the corrosion resistance of magnesium alloy,zinc phosphating film was prepared on the surface of magnesium alloy,and then the phosphating film was sealed.The surface morphology,elemental composition,thickness and corrosion resistance of unsealed phosphating films,oil-immersed sealed phosphating film,chromate sealed phosphating film and silicate sealed phosphating film were investigated.The results showed that oil-immersed sealing,chromate sealing and silicate sealing have little effect on the thickness of phosphating film on surface of magnesium alloy,but the surface morphology and elemental composition of phosphating film were different before and after sealing.Cr,Na and Si elements were introduced into the sealed phosphating film by forming chemical conversion film,colloidal film or physically filled pore,respectively.The silicate sealed phosphating film has relatively good compactness,which can improve the corrosion resistance of magnesium alloy effectively.With the gradual abandonment of chromate sealing,silicate sealing which has the characteristics of good effect and low pollution and environmental protection has potential application in phosphating film sealing.