复合表面改性及功能特性
(华南理工大学 机械与汽车工程学院 国家金属材料近净成形工程技术研究中心，广州 510640)
摘 要: 采用微弧氧化与有机镀膜技术对AZ31镁合金进行复合表面改性，分别对微弧氧化膜的形成过程及表面特征、微弧氧化膜表面有机镀膜过程、微弧氧化膜与复合膜的润湿性及耐腐蚀性进行研究。结果表明：镁合金经微弧氧化改性后，由于表面具有微纳多孔粗糙结构，同时具有较高的表面自由能和极性分量，与蒸馏水接触时存在较强的范德华力和毛细管吸附力，且对强极性水分子具有很强的相溶性，使其蒸馏水的静态接触角接近0°，表现为超亲水特性；而微弧氧化膜表面再经有机镀膜复合改性后，具有较低的表面自由能，对强极性水分子具有一定的排斥作用，使其静态接触角达到113.7°，表现为疏水特性；微弧氧化膜经有机镀膜表面改性后，耐腐蚀性能明显改善，疏水复合膜层在0.1 mol/L NaCl溶液中，与基体相比，其动电位极化腐蚀电流密度减小3个数量级，而电化学阻抗提高3个数量级，表现为类似纯电容行为。
关键字: 镁合金；微弧氧化；有机镀膜；复合表面改性；超亲水；疏水；耐腐蚀性
（National Engineering Research Center of Near-net-shape Forming for Metallic Materials,
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:A duplex surface modification method combined with micro-arc oxidation (MAO) and developed polymer plating was applied to AZ31 magnesium alloy. The growth and surface morphology of MAO-modified film, electrochemical reaction process during polymer plating on MAO-modified film surface, wettability and corrosion behaviors of MAO-modified film and duplex-modified film were researched. The results show that a superhydrophilic surface is fabricated after MAO modification and its contact angle (CA) of distilled water is almost 0, because Van der Waals force and capillary suction effect are relatively strong contacted with the distilled water when MAO-modified surface formed with micro- and nano-porous rough structures, moreover, MAO-modified film with high surface free energy and high polar component have very strong intermiscibility to strong-polar water molecules. However, the alteration from superhydrophilic to hydrophobic surface with contact angle of 113.7° is realized by duplex modification of polymer plating on MAO-modified film surface due to repelling interaction between the strong-polar water molecules and duplex-modified surface with low surface free energy. The corrosion resistance has been greatly improved by duplex modification of polymer plating on the MAO-modified film surface. Compared with bare magnesium alloy, the corrosion current density of hydrophobic duplex-modified film from potentiodynamic polarization decreases by three orders of magnitude, while the electrochemical impedance from electrochemical impedance spectroscopy increases by three orders of magnitude as the duplex-modified film presents similar to pure capacitance behavior in 0.1 mol/L NaCl solution.
Key words: magnesium alloy; micro-arc oxidation; polymer plating; duplex surface modification; superhydrophilic; hydrophobic; corrosion resistance
