Electron Microscope Study of Breakdown and Repair of Anodic Films on Aluminum

Zahavi, J.; Metzger, M.

doi:10.1149/1.2404027

Cited by 22 publications

(20 citation statements)

References 22 publications

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“…This provided a featureless or almost featureless surface which facilitated observation of B-R, B-P-R, or stable pitting events and of any possible associations with structural features of the substrate such as grain boundaries (1,2); it had been used earlier in examining the structure-related free-corrosion behavior of this material (6). HC104 electropolishing baths have also been used in several major studies of the classical pore structure (7,8).…”

Section: Methodsmentioning

confidence: 99%

Effect of Chloride on Growth of an Anodic Film

Zahavi

Metzger

1974

J. Electrochem. Soc.

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A1 was anodized in 2.4M H2SO4 at 5 mA/cm 2 and electronmicroscopic studies made of breakdown and formation of pits beneath the film after various surface treatments or after additions of up to 0.05M Cl-to the acid and selection of those specimens which had remained in the film-growth stage before stable pits grew. An electron-opacity technique was developed for studying film growth. Even in the absence of Cl-, there was a continued incidence of breakdown and a substantial time-dependent direct-dissolution current. With CI-, cell voltage tended to be lower. Film formation efficiency and geometrical structure were correlated directly with average cell voltage and not directly with C1-concentration. Cl-was interpreted as having only an indirect effect on film growth by stabilizing concurrent pit growth, wl~ch reduced the filmforming current. Possible modes of pitting beneath the film are discussed.In a recent paper (1), the authors presented electronmicroscopic evidence that during galvanostatic anodizing of aluminum in sulfuric acid many small breakdown-repair (B-R) or breakdown-pitting-repair (B-P-R) events occurred at the base of the film concurrently with porous film growth and that these events were not generally associated with substrate lattice defects or impurity clusters. As part of a program concerned with the mechanism of pit initiation, this was followed in the present work by studies of: (i) the possible influence of the surface preparation on the incidence of breakdown and (ii) the effects of C1-additions to the anodizing bath. The previous results and those of Part (i) directed attention not to the production by C1-of breakdown, which occurred in its absence, but to its reduction of the effectiveness of repair. This might be due to an effect of C1-on film growth rate or structure. Conditions favorable for examining this question were obtained by adjusting the C1-concentration in the bath to the highest level at which film growth would not be immediately short-circuited by growth of optically visible stable pits. Observations had been made identifying the transition in behavior with increasing C1-concentration (2).The surface treatment before anodizing was of concern specifically because with the perchloric acidethanoi electropolishing bath employed a residual film was known to be present after rinsing and this film presumably contained C1, which has been detected by Auger analysis on surfaces polished in this bath (3). Such surfaces have been reported to yield films of low ionic resistance after forming (4).The processes occurring in this system were such that the microtopographic features most accessible to observation were not those of growing pits but those of repair zones in the film and of the pore structure at various stages of growth. Comparisons were effectively made by examining the film after anodizing times at which it contained evidence of the previous occurrence of a high density of small (~0.1 ~m) B-P-R or B-R "events," and the nature of the geometry deduced is illustrated schematically ...

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Section: Methodsmentioning

confidence: 99%

Effect of Chloride on Growth of an Anodic Film

Zahavi

Metzger

1974

J. Electrochem. Soc.

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“…After anodising and oxide relaxation defects in films were observed by electron microscopy and related methods [1,[52][53][54][55], met in the literature occasionally as breakdown events participating in a breakdown and repair process [55], penetration paths or cracks traversing the whole thickness of grown film [1], active paths of suitable geometry or large spaces through which electrolyte anions move [53,56], etc. These defects can be well explained by recrystallisation of oxide and its shrinkage towards the o|e interface during anodising, its further shrinkage and as expected crack-like rupture locally in barrier layer, or throughout across it during oxide relaxation after anodising, in certain cases.…”

Section: Variability Of Oxide Structure Across the Film In The First mentioning

confidence: 99%

“…1, yields irregularities of nm scale [1,[52][53][54][55] and surface unevenness with local depressions dividing the surface into cell-like regions. The growth of denser nanocrystallites and rupture of intercrystalline oxide in the surface during substage AB contribute complementarily to the entire shrinkage of surface layer oxide which can thus justify the appearance of maximum in the surface density of such cell-like depressions at some t e.g.…”

Section: Variability Of Oxide Structure Across the Film In The First mentioning

confidence: 99%

The origin of nucleation and development of porous nanostructure of anodic alumina films

Patermarakis

2009

Journal of Electroanalytical Chemistry

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“…[22][23][24][25] In general, the breakdown was caused by localized selective dissolution with the presence of Cl − and/or other similar aggressive anions in the electrolyte, 22 the formation of minute cracks by the crystallization of the oxide 23 or by the mechanical stress induced during the oxidation. Such an increase in oxidation current meant that some structural variation oc- curred at the pore base during the prolonged oxidation.…”

Section: Resultsmentioning

confidence: 99%

Growth characteristics of oxide during prolonged anodization of aluminum in preparing ordered nanopore arrays

Leu

Hon

2004

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Ideally ordered 10 nm channel arrays grown by anodization of focused-ion-beam patterned aluminum Time and orientation dependence of ordering in anodized aluminum for self-organized magnetic arraysIn this study, one-step anodization was conducted on both mechanically polished and electropolished Al foils at different temperatures to examine their growth characteristics during prolonged anodization. Several unusual phenomena different from those reported previously were observed, especially for the preparation of ordered pore arrays on electropolished Al foils. First, under a constant voltage condition, a continuous increase of the oxidation current with fluctuation was observed in a prolonged period of anodization at high temperatures. Second, the ordered pore arrangement of the oxide initially obtained on the electropolished Al foil anodized at 25°C was found to become disordered after being anodized for 72 h. Third, the total film thickness increased in the beginning and decreased in the prolonged period when the anodization was conducted at a high temperature. Thus, it is concluded that a highly ordered pore configuration with a large aspect ratio could only be obtained on the electropolished substrate by anodizing for a moderate period of time at low temperatures.

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Electron Microscope Study of Breakdown and Repair of Anodic Films on Aluminum

Cited by 22 publications

References 22 publications

Effect of Chloride on Growth of an Anodic Film

Effect of Chloride on Growth of an Anodic Film

The origin of nucleation and development of porous nanostructure of anodic alumina films

Growth characteristics of oxide during prolonged anodization of aluminum in preparing ordered nanopore arrays

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