铝合金柠檬酸-硫酸阳极氧化及性能研究

Anodic Oxidation of Aluminum Alloy with Citric Acid-Sulfuric Acid and Its Properties

以2024铝合金做基体进行柠檬酸-硫酸阳极氧化,研究了电压对柠檬酸阳极氧化膜的微观形貌、成分、厚度、显微硬度和耐腐蚀性的影响,并分析了柠檬酸在阳极氧化中的作用机理。结果表明:添加柠檬酸使电解液对阳极氧化膜的腐蚀溶解作用减弱,提高了成膜效率并且有利于阳极氧化膜较均匀溶解,从而提高致密度和性能。随着电压升高(8~22 V),柠檬酸阳极氧化膜的孔洞尺寸增大且结构有所改变,致密度、厚度和显微硬度都呈先增加后降低的趋势,耐腐蚀性能先逐步提高而后下降,但电压对柠檬酸阳极氧化膜成分影响不大。电压18 V制备的柠檬酸阳极氧化膜厚度达15.0μm且孔隙率仅为9.4%,承受外加载荷的能力较强,同时能有效阻止腐蚀进一步发展,因此具有更高的显微硬度(192.4 HV)和良好的耐腐蚀性能,其低频阻抗值达到20.6 kΩ·cm^(2),腐蚀失重仅为0.85 mg/cm^(2)。该柠檬酸阳极氧化膜的致密度和性能明显好于相同电压下制备的硫酸阳极氧化膜。

Anodic oxidation of 2024 aluminum alloy with citric acid-sulfuric acid was carried out,the effects of voltage on the microstructure,components,thickness,microhardness and corrosion resistance of the anodic oxide films were studied,and the action mechanism of citric acid in anodic oxidation was also analyzed.The results showed that the addition of citric acid weakened the corrosion and dissolution of anodic oxidation film in the electrolyte,which improved the film-formation efficiency and was conducive to the uniform dissolution of anodic oxidation film,thus improved its compactness and properties.With the increase of voltage from 8 V to 22 V,the pore size of citric acid anodic oxidation film increased and the structure of pores changed.Moreover,the compactness,thickness and microhardness increased first and then decreased,and the corrosion resistance improved gradually and then weakened.However,voltage had little effect on the components of citric acid anodic oxidation film.The citric acid anodic oxidation film obtained at 18 V had the maximum thickness about 15.0μm and the lowest porosity of 9.4%and its ability to bear external load was strong and could effectively prevent further development of corrosion.Therefore,it exhibited higher microhardness(192.4 HV)and good corrosion resistance,the low frequency impedance reached 20.6 kΩ·cm^(2)and the corrosion weight loss was only 0.85 mg/cm^(2).The compactness and properties of the citric acid anodic oxidation film were obviously better than that of the sulfuric acid anodic oxidation film obtained at the same voltage.