为进一步提高镁合金表面磷化膜的耐蚀性, 在磷酸二氢铵和高锰酸钾组成的磷化液中加入酒石酸钾钠, 通过扫描电镜和能谱分析分别对磷化膜的表面形貌和组成元素进行观察和测试, 通过电化学阻抗谱和极化曲线对磷化膜的耐蚀性进行考察。结果表明, 酒石酸钾钠加入到磷化液中以后, 磷化膜表面的微裂纹数量明显减少, 表面更加平整、致密, 膜电阻和电荷转移阻力明显增大, 减少了腐蚀介质渗入到基体的通道, 增大了腐蚀性离子的迁移阻力。同时, 磷化膜中Mn、O和P等元素含量的增加, 磷化膜中含有更多镁的磷酸盐和锰的氧化物, 使磷化膜的耐蚀性进一步提高。

To improve the corrosion resistance of chrome free phosphating films on magnesium alloy, potassium sodium tartrate was added into the phosphate-permanganate solution. The morphology and chemical composition of the phosphating films were observed and tested by SEM and EDS respectively. The corrosion resistance was evaluated using electrochemical impedance spectroscopy (EIS) and polarization curves. The results show that the phosphating film obtained from the solution with potassium sodium tartrate was more compact and had less cracks, and higher film resistance and charge transfer resistance, and the corrosion paths were reduced. Moreover, the amounts of Mn, O and P in the phosphating film increased, and the concents of magnesium phosphate and manganese oxide in film were also higher, and thus the corrosion resistance of the phosphating film was improved.