In this work the mechanisms for initial growth and repassivation within cubic etch pits and etch tunnels were studied. Constant current and step current reduction experiments were performed to understand the current sources which supply the external current and the potential driving force for repassivation;During the first 35 ms of a constant current etch of 12.89 mA/cm[superscript]2, the potential transient goes through a maximum approximately 1.6 V above the open circuit potential. It was found that the external current was supplied by a capacitive charging current and a metal dissolution current. For samples which had been pretreated with HCl prior to the etch, it was found that the initial growth of the pits is due a currentless mechanism in parallel with the metal dissolution current density. In contrast, a sample which had not been pretreated gave evidence of electrochemical dissolution only. Vacancy condensation was discussed as a possible currentless mechanism;The results from the step current reduction experiments were used to determine the kinetics of metal dissolution and repassivation. A decrease in the surface over-potential relative to the repassivation potential is associated with an increase in the passivation velocity and a decrease in the metal dissolution current density within a pit. A mathematical model which predicted the potential transient after a step current reduction was developed. A mechanism involving competitive adsorption between specifically adsorbed chloride ions and oxygen, similar to that proposed by Kolotyrkin (1) and Uhlig and Bohni (2), was utilized in this investigation;A study of the pit and tunnel morphology was also used to study the potential driving force for repassivation. These observations gave evidence that nucleation induces the rapid passivation of small etch pits and the sidewalls of tunnels. A computer simulation which assumed that each pit and tunnel experienced the same potential driving force for repassivation was unable to predict the experimentally observed pit and tunnel morphology. Thus it was concluded that local potential changes accompanying pit nucleation are responsible for the rapid passivation that occurs. ftn (1) Ja. Kolotyrkin, J. Electrochem. Soc., 29, 363 (1989). (2) H. H. Uhlig and H. Bohni, J. Electrochem. Soc., 116, 906 (1969).
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机译：在这项工作中，研究了立方蚀刻坑和蚀刻隧道内初始生长和重新钝化的机理。进行恒定电流和阶跃电流减小实验以了解提供外部电流的电流源和用于重新钝化的潜在驱动力；在12.89 mA / cm [2]的恒定电流蚀刻的前35 ms中，潜在的瞬态最高经过开路电位约1.6V。发现外部电流由电容充电电流和金属溶解电流提供。对于在蚀刻之前已经用HCl预处理过的样品，发现凹坑的初始生长是由于无电流机制与金属溶解电流密度平行所致。相反，未预处理的样品仅给出电化学溶解的证据。讨论了空位凝结作为一种可能的无电流机理的方法；分步电流减少实验的结果用于确定金属溶解和再钝化的动力学。相对于再钝化电位的表面过电位的降低与钝化速度的增加和凹坑内金属溶解电流密度的降低有关。建立了预测阶跃电流减小后潜在瞬态的数学模型。与Kolotyrkin（1）和Uhlig and Bohni（2）提出的机制类似，涉及一种专门吸附的氯离子和氧之间竞争性吸附的机制;该研究还使用了坑和隧道的形态研究。重新钝化的潜在驱动力。这些观察结果提供了成核作用导致小的蚀刻坑和隧道侧壁快速钝化的证据。假设每个坑和隧道都经历相同的潜在钝化驱动力的计算机模拟无法预测实验观察到的坑和隧道的形态。因此得出结论，伴随凹坑成核的局部电势变化是造成快速钝化的原因。 ftn（1）Ja。 Kolotyrkin，J.Electrochem。 Soc。，29，363（1989）。 （2）H.H.Uhlig和H.Bohni，J.Electrochem。 Soc。，116，906（1969）。
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