镁合金AZ91D无铬磷化膜的形貌及其耐蚀性能

Morphology and Corrosion Resistance of Chrome-free Phosphate Film for AZ91D Magnesium Alloy

以磷酸盐、植酸为主要成分,通过化学沉积的方法在镁合金AZ91D表面获得了无铬磷化膜。经SEM分析表明,膜层存在均匀微裂纹,膜厚为6～10μm;中性盐雾试验,磷化样品72h未见腐蚀现象;电化学极化曲线测试,磷化后镁合金的Ecorr比未处理的正移150mV,Jcorr降低了3个数量级,分析结果进一步证实,磷化膜有效地提高了镁合金AZ91D的耐蚀性能。

A chrome-free phosphate film was prepared on the AZ91D magnesium alloy surface via chemical deposition method.The morphology of surface and interface was examined using scanning electron microscopy（SEM）.The results show that a uniform phosphate film with thickness of 6～10 μm and some micro-cracks can be prepared.The film hardly ethibited corrosion phenomenon for 72 h in the neutral salt spray test（NSS）.The potentiodynamic polarization curves prove that the Ecorr of the alloy with the film was shifted positively by 150 mV（vs.SCE）,the Jcorr was decreased at least by three orders compared with that of the bare substrate.The results confirm that the film possesses good corrosion resistance.