Initial events during the passivation of rapidly dissolving aluminum surfaces
- Iowa State Univ., Ames, IA (United States). Dept. of Chemical Engineering
The early stages of oxide film passivation of corroding surfaces in aluminum etch tunnels and pits were investigated. Passivation was initiated by step reductions in applied current. A mathematical model for passivation was used to predict experimentally measured potential transients during the first millisecond after the current step. the experimental transients had a characteristic potential undershoot at about 70 [mu]s after the current step; according to the model, the undershoot was directly related to the partial coverage of the corroding surface with an oxide layer. The time and extent of the undershoot were in quantitative agreement with the theoretical predictions, suggesting that the fractional actively dissolving area in the pit at these times is a linear function of potential and adjusts rapidly to changes of the potential. This reconfiguration of the active area occurs at times when the extent of passive film formation is still small. A chemical mechanism for passivation which is consistent with the model is one in which the fractional active area is controlled by the coverage of specifically adsorbed chloride ions. Agreement between experimental and predicted potential transients was also observed at room temperature, where no tunnels are found, but only corrosion pits with irregular shapes.
- OSTI ID:
- 7006594
- Journal Information:
- Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 141:6; ISSN JESOAN; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360105* -- Metals & Alloys-- Corrosion & Erosion
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
COATINGS
DATA
ELEMENTS
EXPERIMENTAL DATA
INFORMATION
KINETICS
MATHEMATICAL MODELS
METALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PASSIVATION
PROTECTIVE COATINGS
REACTION KINETICS