Mechanism for the Morphological Change from Trenching to Pitting around Intermetallic Particles in AA1050 Aluminum
Mechanism for the Morphological Change from Trenching to Pitting around Intermetallic Particles in AA1050 Aluminum
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AA1050 铝中金属间颗粒周围从沟槽到点蚀的形态变化机制
DOI：
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发表时间：
2019
影响因子：
3.9
通讯作者：
N. Hara
中科院分区：
文献类型：
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作者：
H. Kakinuma;I. Muto;Y. Oya;Yoshihiko Kyo;Y. Sugawara;N. Hara
通过开路电位测量和显微偏振测量研究了 AA1050 铝中金属间颗粒的沟槽和点蚀机理，并确定了 Al-Fe 和 Al-Fe-Si 两种金属间颗粒在此过程中所起的作用。在自然通气的 0.1 M NaCl 溶液中，仅在 Al-Fe-Si 颗粒周围观察到沟槽。在 AA1050 在自然通气的 0.1 M NaCl 中的阳极极化下，沟槽中出现了晶体凹坑。然而，在自然通气条件下，含有 0.1 M NaCl 的柠檬酸-柠檬酸盐缓冲液中既没有发生沟槽，也没有出现点蚀。沟槽被证实是由颗粒上的氧还原反应引起的局部碱化的结果。微尺度极化表明，在-0.9至-0.6 V范围内，Al-Fe-Si颗粒周围发生沟槽，而在-0.5 V以上则不会发生沟槽。当纯Al表面在pH 14时溶解在1 M NaCl中时，腐蚀形态与点蚀不同。当纯铝预浸在 1 M NaCl (pH 14) 中后浸入 pH 0.0 的 1 M NaCl 中时，会出现晶体凹坑。结论是局部pH值从碱性到酸性的变化引发了从沟槽到点蚀的形态变化。
The mechanism of trenching and pitting at intermetallic particles in AA1050 aluminum was investigated by open circuit potential measurements and microscopic polarization measurements, and the role played by the two types of intermetallic particles, Al-Fe and Al-Fe-Si, in this process was determined. Trenching was observed only around the Al-Fe-Si particles in the naturally aerated 0.1 M NaCl solution. Under the anodic polarization of AA1050 in naturally aerated 0.1 M NaCl, a crystallographic pit was initiated in the trench. However, neither trenching nor pitting occurred in the citric-citrate buffer with 0.1 M NaCl under naturally aerated conditions. Trenching was confirmed to be the result of the local alkalization induced by the oxygen reduction reaction on the particles. Micro-scale polarization showed that trenching occurred around the Al-Fe-Si particle from −0.9 to −0.6 V and did not occur above −0.5 V. While the surface of pure Al dissolved at pH 14 in 1 M NaCl, the corrosion morphology was different from pitting. Crystallographic pits occurred when the pure Al was immersed in 1 M NaCl at pH 0.0 after preimmersion in 1 M NaCl (pH 14). It was concluded that the change in local pH from alkaline to acidic triggers the morphological change from trenching to pitting.