CTAB下真空搅拌制备车用AZ80合金阳极氧化膜腐蚀性能分析

Surface Anodic Oxidation of AZ80 Mg-Alloy in CTAB-Added Alkaline Silicate Solution

在氧化液中加入2 g/L十六烷基三甲基溴化铵(CTAB)的情况下测试了车用AZ80镁合金表面形成的阳极氧化膜特性,并分析CTAB和基体组织之间的具体反应机制以及极氧化膜腐蚀性能。研究结果表明:在加入CTAB的情况下,CTAB与部分分解产物会在孔洞附近与镁反应。添加CTAB之后,氧化膜孔隙率减小近50%,并且孔洞尺寸与数量发生降低。添加CTAB氧化膜内并未形成大尺寸孔洞,小孔数量也明显减少,形成了更加致密的氧化膜。相比较未添加CTAB,添加CTAB氧化膜厚度增大明显,可见CTAB有助于氧化膜的成长。发生火花放电时,熔融物获得了更强的流动能力,孔隙率与孔径尺寸都发生了减小。添加CTAB氧化膜获得了比未添加CTAB更高的自腐蚀电位,能够显著增强阳极氧化膜的耐蚀能力。在添加CTAB氧化膜内存在C4H6MgO4、MgO、Mg2SiO4多种成分。

The surfaces of AZ80 Mg-alloy,an important high-tech material,were modified by anodic oxidation in the alkaline silicate solution mixed with 2 g/L cetyltrimethylammonium bromide(CTAB).The microstructures and corrosion resistance of the coating were characterized with X-ray diffraction,scanning electron microscopy and electrochemical workstation.The results show that the CTAB-addition matters.For instance,the CTAB-addition decreased the surface porosity by 50%,improved the compactness by reducing the density and size of micro-pores,increased the thickness of oxides coatings,induced formation of quite a few compounds including C4H6MgO4,MgO,and Mg2SiO4,and significantly enhanced the corrosion resistance,because CTAB accounted for the much higher self-corrosion potential of the anodic oxides coating.Possible mechanisms responsible for the impact of CTAB-doping on the synthesis,oxidation and corrosion resistance of the oxide coatings were tentatively discussed in a thought provoking way.