AZ91D镁合金表面无氟微弧氧化膜的制备与表征

Preparation of Micro-Arc Oxidation Coating on AZ91D Magnesium Alloy and Evaluation of Corrosion Resistance of the Coating

目前,常用的硅酸盐镁合金微弧氧化液成分复杂且含F离子,对环境不利。以Na2Si O3-Na OH为电解质溶液,通过恒压在AZ91D镁合金表面制备了无氟微弧氧化膜。采用扫描电镜、能谱仪、X射线衍射仪及电化学测试对膜层表面的形貌、元素组成、相结构及耐蚀性等进行了表征分析。结果表明:氧化膜层表面微观多孔,膜厚约78μm,膜层由Mg,Al,Si和O 4种元素组成,不含F元素,物相主要为Mg O和Mg Si O3相;微弧氧化膜具有良好的耐蚀性能,与基体相比,自腐蚀电位变化较小,但腐蚀电流密度下降了近2个数量级。

Na_2SiO_3-NaOH solution was adopted as the electrolyte to prepare F-free micro-arc oxidation coating on AZ91 D Mg alloy substrate by constant voltage micro-arc oxidation.The surface morphology,element composition,phase structure and corrosion resistance of the as-prepared micro-arc oxidation coating were analyzed with a scanning electron microscope,an energy dispersive spectrometer,an X-ray diffractometer,and an electrochemical test rig.Results indicated that the as-prepared oxide coating was porous and had a thickness of about 78 μm;and it mainly consisted of Mg,Al,Si and O elements,with MgO and MgSiO_3 as the major species.Besides,as compared with the Mg alloy substrate,the micro- arc oxidation coating exhibited good corrosion resistance.Namely,although the corrosion potential of the micro- arc oxidation coating remained nearly unchanged as compared with that of the Mg alloy,its corrosion current density was reduced by a magnitude of nearly2 orders.