Ce含量对Al在3.5%NaCl溶液中腐蚀行为影响的研究

Effect of Ce on Corrosion Behaviors of Aluminum in 3.5% NaCl Solution

稀土元素及其含量对铝合金耐腐蚀性能的影响及其机制是铝合金开发利用的重要研究课题,采用高频熔炼方法制备Al1-xCex(x=0,0.2%,2.0%(原子分数))合金,通过X射线衍射、金相分析、电化学测试、扫描电镜和能谱等分别对制备的Al1-xCex合金的结构、动电位线性扫描极化曲线、浸泡与电化学腐蚀前后表面形貌的变化进行了研究;对Al1-xCex在3.5%NaCl溶液中耐腐蚀性能与铈含量的关系进行了系统的分析。结果表明:由于Cl-离子的存在,铝在3.5%NaCl溶液中发生点蚀破坏;稀土Ce的加入能够细化晶粒,改善合金微观结构,减弱Cl-离子对点蚀的影响;Ce元素在腐蚀表面层富集,有利于形成连续钝化膜,提高合金在NaCl溶液中的耐蚀能力;微量稀土Ce(0.2%)的加入使合金的自腐蚀电位升高,腐蚀电流密度降低,耐腐蚀性能改善明显;但随着Ce含量的增加,即含量高于铈在铝中的溶解度后,铝与铈将形成金属间化合物,基底与金属间化合物相界面的存在使合金的耐腐蚀性能有所降低,Ce含量为0.2%合金的耐腐蚀性能比Ce含量为2.0%的合金要好。所有合金腐蚀后的主要产物为Al2O3。

The effect and mechanism of rare earth elements on the corrosion-resistance of aluminum alloys was an important topic of development of aluminum alloys. Al1-xCex（ x = 0, 0.2%, 2.0% （ atom fraction） ） alloys were prepared by high-frequency melting method. The structure of alloys, potentiodynamic linear polarization cure, the changes of the surface morphology by immersing and electrochemical corrosion processing were investigated by X-ray diffraction, metallurgical microscope, electrochemical analysis, scanning electron microscopy and EDS. The influence of Ce content to the corrosion resistance of aluminum in 3.5% NaCl solution was systematically analyzed. The results indicated that pitting corrosion occurred for Al1-xCex in 3.5% NaCl solution due to the presence of Cl-. The addition of Ce in aluminum refined the microstructure of the alloy, and weakened the impact of Cl-. Ce aggregated in the surface of alloys during corrosion, which was beneficial to the formation of a continuous passive film, and the corrosion resistance of aluminum alloys was improved. The corrosion resistance was improved with minor addition of Ce （0.2%）, which increased corrosion potential and decreased corrosion current. The corrosion resistance of Al99.8Ce0.2 was better than that of Al998. 0 Ce2.0 due to the existence of interface between the aluminum and intermetallic compound formed when the content of Ce was larger than the solution limit of Ce in A1. Al2O3 was the mainly corrosion products for the considered alloys.