Mg-9Gd-3Y镁合金PEO-EPD复合膜层组织结构与耐蚀性研究

为了提高镁合金的耐蚀性,本文利用扫描电镜分析了Mg-9Gd-3Y(GW93)镁稀土合金表面等离子电解氧化陶瓷层、等离子电解氧化-电泳复合膜层和电泳膜层的表面与纵截面形貌组织,利用傅立叶红外光谱仪(FT-IR)分析了电泳膜层有机官能团类型,用电化学测试手段和盐雾试验方法测试了该合金不同处理膜层的耐蚀性,讨论了电泳电压和固体粉料分数对等离子电解氧化-电泳复合膜层厚度、成膜速率和耐蚀性的影响.研究结果表明,随着电压、固体份的升高,等离子电解氧化-电泳复合涂层厚度和成膜速率呈增大趋势,腐蚀速率随着电压升高呈先减小后增大的趋势,随着固体份的增加呈降低趋势.电泳电压为70V,固体份为19%时,在等离子电解氧化膜层上生成陶瓷层与有机化合物层结合紧密的等离子电解氧化-电泳复合膜层,腐蚀电流密度比等离子电解氧化膜层降低两个数量级,自腐蚀电位正移200mV,耐蚀性提高近13倍.

Microstructure and Corrosion Resistance of PEO-EPD Composite Film on Mg-9Gd-3Y Magnesium Alloy

The samples of Mg-9Gd-3Y（GW93） Mg alloy were coated with plasma electrolytic oxidation （PEO） ,electrophoretic deposition （EPD） and PEO-EPD processes respectively .Varius coating surface and cross-section morphologies ,organic functional structure and the corresponded corrosion resistance were studied using scanning electron microscopy （SEM ） ,Fourier transform infrared spectrometer , electrochemical and salt spray tests .The effect of voltage and solids fraction in electrodeposition solution on the thickness ,forming rate and corrosion resistance of PEO-EPD composite coating was discussed and compared with those of PEO and EPD only .The results showed that thickness and film forming rate of PEO-EPD composite coating increased with the increase of voltage and solids ,the corrosion rate increased first ,then decreased with the increase of voltage ;however ,the corrosion rate is decreased with the increase of solids .The PEO-EPD composite film consists of ceramic zone ,which formed during PEO process ,and the organic compound zone ,which formed by EPD process .The organic compound zone is bonded closely with the PEO zone in the optimum EPD condition of voltage 70 V ,solids fraction 19% . Compared with PEO coating only ,the corrosion current density of composite coating significantly decreased by two orders of magnitude ,the corrosion potential moved positively more than 200 mV ,and the corrosion resistance improved up to 13 times .