镁锂合金表面锌锰磷化膜的制备与性能表征

Preparation and Characterization of Zn-Mn Phosphate Conversion Coatings on Mg-Li Alloy

摘要:

采用化学转化法在镁锂合金表面制备了外观深灰色、结构均匀致密、耐蚀性能良好的锌锰磷酸盐转化膜，并研究了磷化温度对磷化膜性能的影响。采用扫描电子显微镜(SEM)、能谱(EDS)仪、X射线光电子能谱(XPS)和X 射线衍射(XRD)仪对膜层的表面形貌、化学组成及结构进行了表征。采用动电位极化曲线、电化学交流阻抗（EIS）和腐蚀失重实验对磷化膜的耐蚀性进行了研究。结果表明，锌锰磷化膜主要由Zn、Zn3(PO4)2、MnHPO4、Mn3(PO4)2组成。锌锰磷酸化膜起到了保护镁锂合金的作用，提高了镁锂合金的耐蚀性，当磷化温度为45 ℃时，磷化膜的腐蚀电流密度最低，腐蚀速率最小，耐蚀性能最好

Abstract:

A dark gray, uniform and better corrosion resistant Zn-Mn based conversion coating on the Mg-Li alloy was prepared using the phosphate baths. The temperature of phosphate solution was discussed in this experiment. The surface morphology of the conversion coatings was observed by scanning electron microscopy (SEM), and the chemical composition and crystal structure were analyzed by X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The corrosion resistance of Mg-Li alloy and phosphate conversion coatings were investigated by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and a mass loss method. The results show that the Zn-Mn phosphate conversion coating is composed of Zn, Zn3(PO4)2, MnHPO4 and Mn3(PO4)2. The corrosion resistance of permanganate conversion coatings is improved greatly compared with that of Mg-Li alloy. When the temperature of phosphate solution is 45 oC, the phosphate conversion coating exhibits the smallest corrosion current density, the highest capacitance arc and minimum corrosion rate, so the conversion coating presents the best corrosion resistance behavior