2024铝合金混合酸阳极氧化

2024 Aluminum Alloy Anodic Oxidation in Mixed Acid

目的在混合酸溶液中,对2024铝合金进行不同条件下的阳极氧化,并制备氧化膜,研究比较氧化膜厚度、表面形貌和耐腐蚀性等的不同。方法 2024铝合金在硫酸-磺基水杨酸-乳酸体系中进行阳极氧化,改变氧化时间(20~60 min)与氧化电流密度(2.5~4.5 A/dm^2),观察氧化膜的表面形貌、显微硬度、厚度、晶体结构以及耐蚀性的变化。结果每次实验的氧化时间为40 min不变,改变电流密度得到一系列阳极氧化膜,当电流密度为3.0 A/dm^2,自腐蚀电位最正,接近0.0 V时膜层的耐蚀性最好。若继续增加电流密度,则自腐蚀电位会负向移动。当电流密度为4.5 A/dm^2时,自腐蚀电位最负,为-1.1 V。保持电流密度为2.5 A/cm^2不变,改变氧化时间,得到一系列阳极氧化膜,当氧化时间达到50 min时,氧化膜的耐腐蚀性最好,自腐蚀电位为-0.6 V。XRD分析表明,氧化膜由γ-Al2O3和α-Al2O3组成。氧化膜的显微硬度和厚度会随着电流密度及时间的增加而增大,氧化膜硬度、厚度最大分别为372.3HV、6.8μm。结论当阳极氧化电流密度为3.0 A/d、氧化时间为50 min时,膜层的耐蚀性最好。

The work aims to study difference in anodized film thickness, surface morphology, corrosion resistance, etc. by anodizing 2024 aluminium alloy in mixed acid solution and preparing anodized films. The 2024 aluminium alloy was anodized in sulfuric acid - sulfosalieylic acid - lactic acid system. Changes in surface morphology, microhardness, thickness, crystal structure and corrosion resistance were observed by changing oxidation time （20-60 min） and oxidation current density （2.5-4.5 A/dm2）. A series of anodized film was obtained by maintaining the oxidation time at 40 min and changing current density. The self-corrosion potential was the most positive and close to 0.0 V when current density was 3.0 A/dm2. The corrosion potential decreased as the current density increased. The corrosion potential was the most negative （-1.1 V） when the current density was 4.5 A/dm2. A series of anodized film was obtained by maintaining current density at 2.5 A/dm2 and changing oxidization time. The corrosion resistance was the best and the self-corrosion resistance was -0.6 V when the oxidization time reached 50 min. The XRD analysis showed that the anodized films were composed of γ-Al2O3 and α-Al2O3. The microhardness and thickness of the anodized films increased as the current density and oxidization time increased. The anodized layers exhibit the best corrosion resistance provided with the current density of 3.0 A/dm2 and oxidation time of 50 min.