目的 通过不同成膜温度下转化膜上的微裂纹宽度和面积的统计以及电化学测试，研究成膜温度对镁合金磷酸盐转化膜微裂纹形成及耐蚀性的影响。方法 采用扫描电子显微镜观察不同成膜温度所得转化膜的微裂纹形貌，使用Image-pro-plus软件测量转化膜的微裂纹宽度和面积。采用极化曲线和电化学阻抗研究转化膜的耐蚀性。结果 微裂纹统计结果表明，成膜温度为50 ℃时，所得转化膜的微裂纹宽度和面积最小，分别为2.68 μm和1067 μm2；而30 ℃所得的转化膜的微裂纹宽度和面积最大，分别为3.14 μm和1391 μm2；70 ℃所得的转化膜的微裂纹宽度和面积分别为2.74 μm和1170 μm2。电化学测试表明，成膜温度为50 ℃时，转化膜的自腐蚀电流最小，Jcorr=20.3 μA/cm2，且交流阻抗图谱中的容抗弧半径最大。结论 随着成膜温度的升高，转化膜中的微裂纹变窄并减少，但温度更高时，转化膜上的微裂纹略有变宽增多。当成膜温度为50 ℃时，转化膜上的微裂纹较少且窄，转化膜的耐蚀性最好。

The work aims to study the effect of film-forming temperature on the microcracks and corrosion resistance of phosphate conversion films on magnesium alloy based on statistics of size and area of microcracks on the surface of conversion films at different film-shaping temperatures and electrochemical test. Morphology of microcracks obtained at different temperatures was observed by scanning electron microscopy (SEM). Width and area of microcracks on the surface of conversion films were measured by Image-pro-plus software, and corrosion resistance of the conversion films was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Statistical results showed that the microcrack width and area of the conversion film prepared at 50 ℃ were the minimum, 2.68 μm and 1067 μm2, respectively; for the conversion film prepared at 30 ℃, the maximum, 3.14 μm and 1391 μm2, respectively; for the conversion film prepared at 70 ℃, 2.74 μm and 1170 μm2, respectively. The electrochemical test indicated that self-corrosion current of the conversion film prepared at 50 ℃ was the minimum, Jcorr=20.3 μA/cm2, and radius of capacitance arc in the electrochemical impedance spectroscopy was the maximum. Microcracks narrow down and decrease with the increase of film-forming temperature. However, the microcracks broaden and increase at higher temperature. At the film-forming temperature of 50 ℃, the micro cracks are the least and narrowest and are provided with the best corrosion resistance.