The transport of ions and electrons through microscopically inhomogeneous passive films: Breakdown implications

Fromhold, A. T.; Noh, S. J.

doi:10.1016/0010-938x(89)90033-4

Cited by 8 publications

(11 citation statements)

References 7 publications

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“…It is a consequence that as our calculations evolved, we reached the percolation limit, which is one of many results which we have found to be intriguing. There is no overlap between the models employed in other calculations 25,26 and the model employed in our calculations, 10,24 and essentially no overlap in the results which have been obtained.…”

Section: Nature Of Proposed Models For Passivity Breakdown-thoughmentioning

confidence: 44%

“…Some of our calculations involving concentration gradients have already been presented. 10,24 Comparison with related models.-Leiva et al 25,26 have focused on the problem of electronic current by simulating percolation processes for electrochemical systems. The model evaluated numerically involves electron transfer within the layer as taking place between individual electronic states randomly located in position, these states presumably due to defects or impurities in the film.…”

Section: Nature Of Proposed Models For Passivity Breakdown-thoughmentioning

confidence: 99%

“…In the present series of numerical studies, we focus on the conductivity 10 of the passive layer, and determine the way the conductivity is changed by the introduction of point defects such as vacancies, interstitials, and impurities, and by extended defects such as dislocations and grain boundaries. We simulate the effects of point and extended defects by recognizing that on a microscopic scale the motion of the current-carrying species in an insulator-type layer is limited by activation energy barriers associated with the saddle-point energies in a multidimensional potential energy diagram, and that any point defect or extended defect in the layer will result in an attendant modification in the array of normal activation energy barriers.…”

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confidence: 99%

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Transport of Ions and Electrons Through Microscopically Inhomogeneous Passive Films

Fromhold

Noh

2003

J. Electrochem. Soc.

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Computations to elucidate the effects of microscopic nonuniformity on current flow in passive layers are extended to explore predictions in the bond percolation limit. Whereas the dependence of the leakage current on the percentage of low barriers ͑e.g., those promoted by Cl Ϫ in the passive layer͒ was found to be nearly exponential for relatively small differences in the activation energy barrier heights, the functional dependence is observed to be more complex for larger differences, manifesting a critical transition from a relatively nonconducting state to a state of sharply increasing conductivity as the percentage of lower activation barriers increases beyond the bond percolation threshold. This degrading of the insulating properties of the passive layer is postulated to constitute the condition needed for the chemical breakdown of passivity. This interpretation leads in turn to a mechanism for the experimentally noted delay in the time required before the occurrence of the relatively sudden and catastrophic breakdown of passivity after the addition of aggressive ions to the solution, the so-called induction time being that time required for the field-driven diffusion of aggressive ions to reach the critical concentration required for bond percolation.

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Section: Nature Of Proposed Models For Passivity Breakdown-thoughmentioning

confidence: 44%

Section: Nature Of Proposed Models For Passivity Breakdown-thoughmentioning

confidence: 99%

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confidence: 99%

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Transport of Ions and Electrons Through Microscopically Inhomogeneous Passive Films

Fromhold

Noh

2003

J. Electrochem. Soc.

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“…As such, it may promote a localized breakdown of the passive film formed on the alloy at low potentials ( Figure 7 ). Chlorine anions adsorb onto the passive film and penetrate the scale through grain boundaries and other structural defects [ 53 ]. The grain boundary diffusion of Cl − is several orders of magnitude higher compared to the bulk diffusion.…”

Section: Resultsmentioning

confidence: 99%

Microstructure and Corrosion Behavior of Sn–Zn Alloys

et al. 2022

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In the present work, the microstructure, phase constitution, and corrosion behavior of binary Sn–xZn alloys (x = 5, 9 and 15 wt.%) were investigated. The alloys were prepared by induction melting of Sn and Zn lumps in argon. After melting, the alloys were solidified to form cast cylinders. The Sn–9Zn alloy had a eutectic microstructure. The Sn–5Zn and Sn–15Zn alloys were composed of dendritic (Sn) or (Zn) and eutectic. The corrosion behavior of the Sn–Zn alloys was studied in aqueous HCl (1 wt.%) and NaCl (3.5 wt.%) solutions at room temperature. Corrosion potentials and corrosion rates in HCl were significantly higher compared to NaCl. The corrosion of the binary Sn–Zn alloys was found to take place by a galvanic mechanism. The chemical composition of the corrosion products formed on the Sn–Zn alloys changed with the Zn weight fraction. Alloys with a higher concentration of Zn (Sn–9Zn, Sn–15Zn) formed corrosion products rich in Zn. The Zn-rich corrosion products were prone to spallation. The corrosion rate in the HCl solution decreased with decreasing weight fraction of Zn. The Sn–5Zn alloy had the lowest corrosion rate. The corrosion resistance in HCl could be considerably improved by reducing the proportion of zinc in Sn–Zn alloys.

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“…Corrosion testing has demonstrated that the MWF is very corrosion resistant under repositoryrelevant conditions. The stability of most reactive metals is due to the formation of an adherent protective surface oxide scale [6,7]. Similarly, the durability of the MWF is attributed to protective oxide films that form over the steel and intermetallic phases.…”

Section: Introductionmentioning

confidence: 99%

Transmission electron microscopy analysis of corroded metal waste forms.

Dietz¹

2005

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The transport of ions and electrons through microscopically inhomogeneous passive films: Breakdown implications

Cited by 8 publications

References 7 publications

Transport of Ions and Electrons Through Microscopically Inhomogeneous Passive Films

Transport of Ions and Electrons Through Microscopically Inhomogeneous Passive Films

Microstructure and Corrosion Behavior of Sn–Zn Alloys

Transmission electron microscopy analysis of corroded metal waste forms.

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