硅溶胶在镁合金阳极氧化反应中的成膜作用

Behavior of silica sol during the anodizing process of magnesium alloy

采用溶胶化学与电化学相结合的新型表面处理方法——将自制的硅溶胶添加到电解质溶液中进行阳极氧化.以AZ91D镁合金及镁锂合金为研究基材,研究体系分别为硅酸钠和氢氧化钠溶液,通过对不同溶胶添加量下的溶液电导率、反应击穿电压、氧化膜层厚度及微观形貌、膜层表面成分及XRD结果分析,来探讨溶胶粒子在成膜过程中的作用.结果表明:溶胶粒子的加入增大了阳极表面的电阻,使得反应的击穿电压升高,从而导致了膜层厚度增加;同时硅溶胶粒子参与了阳极氧化反应,其在高温高压的条件下与MgO生成了Mg2SiO4.

Anodic films were prepared on AZ91 D magnesium alloy and Mg-Li alloy separately in 150 g/L NaOH and 1.0 mol/L Na2SiOz with varied silica sol addition. The conductivity of the solution and the surface morphologies of the anodic films were characterized by conductivity instrument （DDS-307） and scanning electron microscopy （SEM）. The solution＇s conductivity would become small with the silica sol addition. The energy dispersion spectrometry （ EDS）, the thickness and the X-ray diffraction （XRD） of the films were also investigated. Results show that the thickness of the anodic film increases linearly with the addition of silica sol in both solutions and mainly depends on the anodizing break voltage which is affected by the solution＇s conductivity and the resistance of the magnesium/solution interface. The sol particles take part in the anodizing reaction process. The silica sol reacts with MgO and the product is Mg2SiO4.