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采用正交试验法设计了以磷酸盐-高锰酸盐为基础的无铬转化工艺优化试验,讨论了工艺对转化膜厚度、耐蚀性能及形貌的影响。结果表明:当ZnSO4和NaF的浓度分别为5和1g/L,pH值为4时,转化膜耐蚀性能可提高8倍以上。转化液pH值对膜层厚度、形貌及耐蚀性能均影响显著,当pH过小时,膜层疏松易脱落,仅剩下内层转化膜,膜层较薄,耐蚀性能较差;当pH为4时,膜层厚度达到极大值,内、表膜层结合紧密,大幅改善转化膜的耐蚀性能;当pH值继续增大时,膜层致密,但内、外膜层结合力较差,耐蚀性能有小幅提高。
The optimum experiment of chromium-free conversion process based on phosphate-permanganate was designed by orthogonal test and the influence of process on the thickness, corrosion resistance and morphology of conversion coating was discussed. The results show that when the concentration of ZnSO4 and NaF are 5 and 1 g / L, respectively, the corrosion resistance of the conversion coating can be increased more than 8 times. The pH value of the conversion solution has a significant effect on the film thickness, morphology and corrosion resistance. When the pH is too small, the film loose easily fall off, leaving only the inner conversion film, thin film, corrosion resistance is poor; when When the pH value is 4, the film thickness reaches the maximum value, and the inner and outer film layers are tightly combined to greatly improve the corrosion resistance of the conversion film. When the pH value continues to increase, the film layer is dense, but the cohesion of the inner and outer film layers Poor, corrosion resistance increased slightly.