2198和5A90铝锂合金脉冲阳极氧化膜制备及耐蚀性

在18%(质量分数,下同)H_2SO_4+5%C_2H_2O_4水溶液中,采用脉冲(PC)电流对2198和5A90两种铝锂合金进行阳极氧化处理。用扫描电子显微镜(SEM)观察铝锂合金阳极氧化膜表面和截面形貌;用能谱仪(EDS)对其成分进行面扫描和线扫描;用动电位极曲线检测氧化膜在3.5%NaCl水溶液中的耐蚀性。结果表明:2198和5A90铝锂合金阳极氧化膜主要由Al的氧化物组成;2198合金氧化膜表面存在细小颗粒,厚度约为150μm;5A90合金氧化膜表面存在微孔,为后续封孔处理提供结构条件,厚度约为180μm;用脉冲方法在两种铝锂合金表面生成的较厚阳极氧化膜具有较高的耐蚀性。

Preparation and Corrosion Resistance of Pulse-Current Anodic Oxidation Films of 2198 and 5A90 Al-Li Alloys

Anodic oxidation processes of 2198 and 5A90 Al-Li alloys were carried out with pulse-current (PC) in the mixture of acid solution of 18%(mass fraction,the same below)H2SO4+5%C2H2O4 at room temperature.Surface and cross-sectional morphologies and composition distributions of anodic oxidation films were observed and determined by scanning electron microscope equipped with energy disperse spectroscopy (SEM/EDS).The corrosion resistances of these films were assessed by means of 10%NaOH aqueous solution dropping test and potentiodynamic polarization plot in 3.5% NaCl solution.The results show that the oxidation films of 2198 and 5A90 Al-Li alloys are mainly composed of Al oxides.For 2198 Al-Li alloy,fine and small particles evenly distribute in the oxidation film;and the film thickness is about 150 μm.For 5A90 Al-Li alloy,micro-pores existing in the film can provide better structure for later sealing;and the film thickness is nearly 180 μm.The larger thickness oxidation films of both two kinds of alloys prepared by pulse current anodic oxidation treatment have superior corrosion resistance in 3.5%NaCl solution.