Microarc oxidation coating fabricated on AZ91D Mg alloy in an optimized dual electrolyte  

用优化的双电解液制备AZ91D镁合金微弧氧化膜(英文)

作　　者：王淑艳[1,2] 夏永平[1] 

机构地区：[1]江苏科技大学材料科学与工程学院,镇江212003 [2]江苏科技大学江苏省先进焊接技术重点实验室,镇江212003

出　　处：《Transactions of Nonferrous Metals Society of China》2013年第2期412-419,共8页中国有色金属学报（英文版）

基　　金：Project (12504230006) supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China

摘　　要：Microarc oxidation （MAO） process was conducted on AZ91D magnesium alloy in an electrolyte composed of NazSiO3, NaAlO2, NaEB4O7, NaOH, C3H803 and C6H5Na307 by AC pulse electrical source. The surface and cross-sectional morphologies, film thickness, chemical composition and structure of the coatings were characterized by scanning electron microscopy（SEM）, layer thickness metry, energy disperse spectroscopy（EDS） and X-ray diffraction（XRD）. The corrosiofi resistances of the coatings in a 3.5% NaC1 neutral solution were evaluated by electrochemical impedance spectroscopy （EIS） and potentiodynamic polarization test. The results showed that an optimized electrolyte with a composition of 15 g/L NazSiO3, 9 g/L NaA102, 2 g/L NazB407, 3 g/L NaOH, 5 mL/L C3H803 and 7 g/LC,HsNa307 was developed by means of orthogonal experiment. The coating obtained in the optimized electrolyte had a dense structure and revealed a lower current density, decreased by two orders of magnitude as compared with the magnesium substrate. Meanwhile, the corrosive potentials of the coated samples increased nearly by 73 inV. EIS result showed that the corrosion resistance of the coating was mainly determined by the inner dense layer. The coating primarily contained elements Mg, Al, O and Si and XRD analyses indicated that the coating was mainly composed of MgO, Mg2SiO4 and MgAl204.在含有Na2SiO3、NaAlO2、Na2B4O7、NaOH、C3H8O3和C6H5Na3O7的电解液中,采用交流脉冲电源对AZ91D镁合金进行微弧氧化处理。利用SEM、膜层测厚仪、EDS和XRD分别研究膜层的表面和截面微观形貌、厚度、成分及相结构。利用交流阻抗和动电位极化曲线试验测量膜层在3.5%NaCl中性溶液中的耐蚀性能。结果表明,正交试验得到的双电解液成分为15g/LNa2SiO3、9g/LNaAlO2、2g/LNa2B4O7、3g/LNaOH、5mL/LC3H8O3和7g/LC6H5Na3O7。经过微弧氧化处理而得到的膜层较致密,其腐蚀电流密度较镁合金基体的降低了2个数量级,自腐蚀电位提高了近73mV。EIS结果认为膜层的耐蚀性取决于内部致密层。微弧氧化膜主要组成元素为Mg、Al、O和Si,主要组成相为MgO、Mg2SiO4和MgAl2O4。

关 键 词：magnesium alloy microarc oxidation dual electrolyte corrosion resistance 

分 类 号：TG174.4[金属学及工艺—金属表面处理]