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无论哪种类型的局部腐蚀电池,在它们的阴极和“闭塞”阳极之间总有一个电位差。本文作者从理论上分析了上述电位差的一个重要组成部份—扩散电位差—的产生和它的本质,模拟局部腐蚀电池在结构上的一些主要特征,设计了可用于测量扩散电位差的实验装置,研究了铁与10~(-3)NNaCl溶液构成的局部腐蚀体系的扩散电位差。结果表明,随着局部腐蚀的逐渐发展,“闭塞”阳极液中FeCl_2浓度逐渐增加,它与本底溶液之间的扩散电位差与FeCl_2浓度(N)的对数呈线性关系。在20℃时,其斜率为+32mV,和根据Planck-Henderson方程式计算的理论值完全一致。结果证明,在局部腐蚀电池阴、阳极之间的扩散电位差是所有有关离子的淌度的差或扩散系数的差所引起的非平衡电位差。
Regardless of the type of localized corrosion cell, there is always a potential difference between their cathodes and the “occluded” anode. The author of this paper theoretically analyzes the generation of an important component of the potential difference described above - diffused potential difference - and its essence. It simulates some key structural features of the locally etched cell and designs an experiment that can be used to measure the diffusion potential difference The diffusion potential difference of localized corrosion system composed of iron and 10 ~ (-3) NNaCl solution was studied. The results show that with the gradual development of local corrosion, the concentration of FeCl_2 in the “occluded” anolyte gradually increases, and the diffusion potential difference between it and the background solution has a linear relationship with the logarithm of FeCl 2 concentration (N). At 20 ° C, its slope is +32 mV, which is exactly the same as the theoretical value calculated according to the Planck-Henderson equation. The results demonstrate that the diffusion potential difference between the anodic and cathodic layers in a locally etched cell is the unbalance potential difference caused by the difference in the mobility of all the involved ions or the difference in diffusion coefficient.