Hydration of Passive Oxide Films on Aluminum

Bunker, Bruce C.; Nelson, Gerald C.; Zavadil, Kevin R.; Barbour, J. C.; Wall, F. D.; Sullivan, John P.; Windisch, Charles F.; Engelhardt, M.; Baer, Donald R.

doi:10.1021/jp013246e

Cited by 210 publications

(171 citation statements)

References 19 publications

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“…Using K = 10, E = 1 V/nm, and R = 150 nm, ρ e is found to be equivalent to approximately 0.007 % of the charge density due to O -2 ions. This small amount of charge may be accommodated by nonstoichiometry, especially since Al surface oxides in aqueous solutions contain appreciable quantities of hydrogen, at least some of which is in the form of mobile protons (21,22). Thus, mechanisms are likely available to adjust the space charge, in order to maintain the electric field distribution dictated by current continuity.…”

Section: Resultsmentioning

confidence: 99%

Model for the Steady-State Growth of Porous Anodic Alumina Films

Houser

Hebert

2007

ECS Trans.

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Simulations were developed for the distributions of electrical potential and incorporated anions in porous anodic alumina (PAA) films during steady-state growth. Predictions of a model for the potential distribution based on Laplace's equation were compared to those of the current continuity equation in conjunction with high-field conduction. It was found that Laplace's equation, which has been used previously in PAA models, resulted in strong violations of charge conservation, when the current density was evaluated using the high field conduction equation. Interface motion predicted by the current continuity equation was nearly uniform except near convex ridges on the metal-film interface. This model was extended to predict the distribution of anions in the film, since incorporated anions may provide suppression of conduction near the ridge. The spatial distribution of acid anions predicted by the model agreed with experimental observations. Simulations were developed for the distributions of electrical potential and incorporated anions in porous anodic alumina (PAA) films during steady-state growth. Predictions of a model for the potential distribution based on Laplace's equation were compared to those of the current continuity equation in conjunction with high-field conduction. It was found that Laplace's equation, which has been used previously in PAA models, resulted in strong violations of charge conservation, when the current density was evaluated using the high field conduction equation. Interface motion predicted by the current continuity equation was nearly uniform except near convex ridges on the metal-film interface. This model was extended to predict the distribution of anions in the film, since incorporated anions may provide suppression of conduction near the ridge. The spatial distribution of acid anions predicted by the model agreed with experimental observations.

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Section: Resultsmentioning

confidence: 99%

Model for the Steady-State Growth of Porous Anodic Alumina Films

Houser

Hebert

2007

ECS Trans.

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“…Furthermore, this study considered repassivation to be induced by the precipitation of essentially bulk oxide species in the critical pit solution chemistry. The inclusion of the thermodynamics and kinetics of surface oxide precipitation 83,84 to inform the framework would provide more accurate estimates of the repassivation process. Such estimates would also facilitate the mechanistic validation of competitive adsorption models to describe repassivation.…”

Section: Discussionmentioning

confidence: 99%

Evaluating the Critical Chemistry for Repassivation at the Corroding Surface Using Mass Transport Model-Based Artificial Pit Experiments

Srinivasan

Kelly

2016

J. Electrochem. Soc.

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One-dimensional mass transport model calculations were utilized to design experiments with stainless steel artificial pit electrodes to determine the critical concentration of cations at the corroding surface representing the transition between stable pitting and repassivation. Rapid polarization scans following salt film precipitation and consequent open circuit dilution to different surface concentrations permitted the evaluation of kinetics at various degrees of saturation. These experiments showed a distinct change in kinetics as the surface concentration decreased, thus identifying the critical pit chemistry for the onset of repassivation. Chemical modeling of oxide precipitation from solution permitted the investigation of oxide nucleation across varying surface concentration as a function of pH as the cause of repassivation. This analysis enabled the estimation of the pH at which the first oxide would precipitate in the critical pit solution chemistry, which when combined with cation hydrolysis calculations, resulted in the evaluation of the critical pH at the transition between pit stability and repassivation. A mixed potential theory-based analysis of these results was utilized to provide mechanistic support to the quantitative framework describing critical factors for pitting stability and repassivation.

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“…3 shows the depth profiles of negative secondary ions for a typical 99.99 % Al sample, showing the major spectral peaks from the oxide film (AlO, O), the metal (Al, Al 2 ) and the deuterium-containing species (D, AlD). The time of 25 s corresponds to the decay of the AlO peak to half its maximum value, and to a sharp decrease of slope of the Al 2 signal; both of these features mark the oxide-metal interface (14,15). D and AlD peaks were very low or absent in mass spectra of as-electropolished samples, but were present in those of foils treated in NaOD.…”

Section: Methodsmentioning

confidence: 99%

Injection of Hydrogen and Vacancy-Type Defects during Dissolution of Aluminum

Hebert¹,

Adhikari²,

Lee³

et al. 2006

ECS Trans.

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Formation of interfacial nanoscale voids in Al during room-temperature caustic corrosion was characterized by positron annihilation spectroscopy (PAS) and compared with measurements of deuterium absorption using secondary ion mass spectrometry (SIMS). The hypothesis was investigated that voids are created from vacancy-hydrogen (Vac-H) defects introduced during corrosion. Evidence for both mobile and immobile forms of absorbed hydrogen was obtained, the latter present within distances of 50 nm from the metal-oxide interface, where voids were also found. During corrosion, the immobile hydrogen was found only during discrete 1-2 min intervals of time separated by periods of 1-2 min when it was not present. Model calculations suggested that this transient behavior is consistent with repeated nucleation and dissolution of clusters of Vac-H defects. Only some aspects of the time-dependence of the void concentration from PAS corresponded with that of absorbed hydrogen; the former is believed to be influenced by metallic impurities.

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Hydration of Passive Oxide Films on Aluminum

Cited by 210 publications

References 19 publications

Model for the Steady-State Growth of Porous Anodic Alumina Films

Model for the Steady-State Growth of Porous Anodic Alumina Films

Evaluating the Critical Chemistry for Repassivation at the Corroding Surface Using Mass Transport Model-Based Artificial Pit Experiments

Injection of Hydrogen and Vacancy-Type Defects during Dissolution of Aluminum

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