镁锂合金无铬转化膜的制备工艺研究

Preparation of Conversion Coating with Cr free on Mg-Li Alloy

利用无铬化学转化技术来提高Mg-10Li-1Zn合金的抗腐蚀性能。采用磷酸盐-高锰酸盐转化液,在合金表面形成一层均匀的化学转化膜。用正交试验优选了转化液组分含量、温度及时间等工艺参数,并进一步分析了该无铬转化膜的显微结构。结果表明,此转化膜的最佳工艺条件是KH2PO4为50g/L,KMnO4为40g/L,成膜温度为55℃,成膜时间为20min。EDX测试结果显示,该转化膜主要由P、Mn、K、Mg和O元素构成。动电位极化曲线结果表明,与传统的铬酸盐转化膜相比,该磷酸盐-高锰酸盐转化膜能够对Mg-10Li-1Zn合金提供更好的腐蚀防护。

The chemical conversion coating was homogeneously created on the surface of Mg-10Li-1Zn alloy in a phosphate-permanganate solution.Some processing variables,including chemical composition content,temperature and time of the conversion solution,were optimized by orthogonal testing to obtain a desirable constituents and processing.Moreover,the microstructure and chemical composition of conversion coating with Cr free were described.Hydraulic-potential polarization curves show that the phosphate-permanganate conversion coating exhibits better corrosion-resistantance on Mg-10Li-1Zn alloy compared with conventional chromate conversion coating.