The corrosion and passivation of iron in the presence of halide ions in aqueous solution
The corrosion and passivation of iron in the presence of halide ions in aqueous solution
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DOI：
10.1016/s0010-938x(79)80113-4
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发表时间：
1980-04
影响因子：
8.3
通讯作者：
M. D. Castro;B. E. Wilde
中科院分区：
文献类型：
--
作者：
M. D. Castro;B. E. Wilde
使用固定电极和旋转电极研究了铁在卤化物溶液中的阳极溶解行为。对于固定电极，可以观察到主动溶解动力学，而对于旋转，则发生明显的主动/被动转变。在每种溶液中都观察到明显的点蚀电位(Ec)，E的值按I>Br>Cl>F的顺序增加。卤化物离子浓度和电极速度对Ec值没有任何影响，表明凹坑引发的动力学与传质效应无关。在比Ec更负的电位下进行阳极溶解时，注意到抑制作用，其程度取决于阴离子的原子半径。建议建立一个模型，其中涉及铁与电解质的三个电极反应：（1）主动溶解，涉及众所周知的 FeOH+(ads) 速率决定步骤。 (2) 高于钝化电位，金属表面与氢氧根离子的反应增加，由于 OH− 与表面的接触增强，以及旋转和扩散层变薄导致溶剂化质子的加速去除，从而导致钝化。 (3) 在点蚀电位下，金属与电吸附的卤化物离子的直接反应通过络合离子形成反应产生点蚀引发和生长，这在较低电极电位下是不可能的。
The anodic dissolution behaviour of iron in halide solutions has been studied with both stationary and rotating electrodes. With stationary electrodes active dissolution kinetics are observed, whereas with rotation a pronounced active/passive transition occurs. A distinct pitting potential (Ec) was noted in each solution, the value ofEcincreasing in the order I>Br>Cl>F. Halide ion concentration and electrode velocity did not have any effect on the value ofEc, indicating that the kinetics of pit initiation are independent of mass-transfer effects.During anodic dissolution at potentials more negative thanEc, an inhibiting effect was noted, the degree of which depended on the atomic radius of the anion. A model is suggested which involves three electrode reactions of iron with the electrolyte: (1) Active dissolution involving the well-known FeOH+(ads) rate-determining step. (2) Above the passivation potential, increased reaction of the metal surface with hydroxyl ions causes passivation due to the enhanced access of OH−to the surface and accelerated removal of solvated protons caused by rotation and a thinning of the diffusion layer. (3) At the pitting potential, direct reaction of the metal with electro-adsorbed halide ions produces pit initiation and growth by a complex ion formation reaction not possible at lower electrode potentials.