汽车用6061铝合金柠檬酸阳极氧化工艺的研究

对汽车用6061铝合金进行柠檬酸阳极氧化处理。研究发现:铝合金的阳极氧化过程伴随氧化膜的生成和溶解。适当升高氧化温度,有利于增加氧化膜的厚度和硬度。但氧化温度过高,会使得氧化膜的溶解速率加快。铝合金阳极氧化膜呈现典型的多孔结构。40℃下制备的氧化膜表面平整,具有优良的耐蚀性。当氧化温度高于40℃时,氧化膜表面的孔径增大,表面疏松,耐蚀性下降。

电流密度对建筑用6463铝合金柠檬酸阳极氧化膜性能的影响

在建筑用6463铝合金表面制备柠檬酸阳极氧化膜,并研究电流密度对阳极氧化膜的微观形貌、显微硬度和耐蚀性能的影响。结果表明:不同电流密度下获得的四种阳极氧化膜均呈现蜂窝状形貌,但性能存在一定差异。在一定范围内随着电流密度增加,阳极氧化膜的厚度呈现近似线性增加的趋势,孔隙率降低,致密性明显改善,显微硬度从125.4 HV增大到238.2 HV。但电流密度超过一定限度,阳极氧化膜的孔隙率升高,致密性变差,显微硬度减小到182.4 HV,耐腐蚀性能下降。电流密度为1.8 A/dm2时获得的阳极氧化膜厚度接近12μm,孔隙率为10.5%,该阳极氧化膜抵抗局部塑性变形的能力以及抑制腐蚀和阻挡腐蚀介质扩散的能力较强,因此表现出良好的性能。

铝合金柠檬酸-硫酸阳极氧化及性能研究

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。

Effect of citric acid on microstructure and electrochemical characteristics of high voltage anodized alumina film formed on etched Al Foils

Aluminum capacitor foils with a tunnel etch structure were reacted with boiling water and then anodized at 530 V in boric acid solution or boric acid＋citric acid mixed solution.The microstructure and crystallinity of the resulting anodized film were examined by TEM and XRD.The special capacitance,resistance and withstanding voltage of the film were explored with electrochemical impedance spectroscopy（EIS）,LCR meter and small-current charging.The results show that the high voltage anodized oxide film consists of an inner layer with high crystallinity and an outer layer with low crystallinity.However,the crystallinity of the film formed in boric acid＋citric acid mixed solution is higher than that of the film formed in only boric acid solution,leading to an increase in film＇s field strength and special capacitance.Meanwhile,there are more defects from phase transformation in the out layer of the film formed in boric acid＋citric acid mixed solution than in that of film formed in only boric acid solution,leading to a decrease in film＇s resistance and withstanding voltage.