Mechanism of corrosion inhibition of AA2024 by rare-earth compounds.
Mechanism of corrosion inhibition of AA2024 by rare-earth compounds.
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DOI：
10.1021/jp0560664
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发表时间：
2006-02
期刊：
影响因子：
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通讯作者：
K. Yasakau;M. Zheludkevich;S. Lamaka;M. Ferreira
中科院分区：
文献类型：
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作者：
K. Yasakau;M. Zheludkevich;S. Lamaka;M. Ferreira
本文详细介绍了稀土缓蚀剂Ce和La对广泛应用的2024-T3铝合金在氯化物介质中的腐蚀防护机理。用扫描开尔文探针力显微镜(SKPFM)、原位原子力显微镜和扫描电子显微镜结合能谱分析了腐蚀过程。高分辨率和现场技术的使用使人们对腐蚀过程的物理化学细节和机理有了深刻的了解。首次证明了SKPFM在不同缓蚀剂作用机理分析中的适用性。所研究的缓蚀剂对局部腐蚀过程有足够的抑制作用，特别是在金属间化合物S相颗粒周围形成点蚀的情况下。Ce(3+)和La(3+)在腐蚀防护中的主要作用是在S相夹杂物表面形成氢氧化物沉积物，缓冲了局部pH的升高，加速了金属间化合物的脱合金化。生成的氢氧化物沉淀物还可以起到扩散屏障的作用，阻碍活跃区的腐蚀过程。与硝酸镧相比，硝酸铈具有更高的缓蚀效率。在Ce的情况下，由于各自的氢氧化物的溶解度较低，获得了较高的效果。在热力学分析的基础上，提出了详细的腐蚀过程及其缓蚀机理。
The mechanism of corrosion protection of the widely used 2024-T3 aluminum alloy by cerium and lanthanum inhibitors in chloride media is described in detail in the present work. The corrosion process was investigated by means of scanning Kelvin probe force microscopy (SKPFM), in situ atomic force microscopy, and scanning electron microscopy coupled with energy dispersive spectroscopy. Employment of the high-resolution and in situ techniques results in a deep understanding of the details of the physical chemistry and mechanisms of the corrosion processes. The applicability of the SKPFM for mechanistic analysis of the effect of different corrosion inhibitors is demonstrated for the first time. The inhibitors under study show sufficient hindering of the localized corrosion processes especially in the case of pitting formation located around the intermetallic S-phase particles. The main role of Ce(3+) and La(3+) in the corrosion protection is formation of hydroxide deposits on S-phase inclusions buffering the local increase of pH, which is responsible for the acceleration of the intermetallics dealloying. The formed hydroxide precipitates can also act as a diffusion barrier hindering the corrosion processes in active zones. Cerium nitrate exhibits higher inhibition efficiency in comparison with lanthanum nitrate. The higher effect in the case of cerium is obtained due to lower solubility of the respective hydroxide. A detailed mechanism of the corrosion process and its inhibition is proposed based on thermodynamic analysis.