Measurement of thickness and porosity of oxide films on iron and aluminium

Lorking, K. F.

doi:10.1002/jctb.5010101104

Cited by 5 publications

(4 citation statements)

References 9 publications

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“…Results are shown in Table I with the a-c resistance values of the solution and double layers being calculated from Eq. [4] after correcting for the external series capacitor. Although the total solution resistance might include a small, term for the a-c resistance of a very thin oxide film on the platinum specimen, it is not believed that this is a significant portion of the total resistance of the platinum cell.…”

Section: Influence Of Chromate Solution On Accuracy Os Film Resistanc...mentioning

confidence: 99%

“…At 100,000 and 1,000,000 cps, Rp for the electrode plus solution must be calculated from Eq. [4] and the resistance of the solution from Table I subtracted to give accurate a-c resistance values for the film.…”

Section: Influence Of Chromate Solution On Accuracy Os Film Resistanc...mentioning

confidence: 99%

“…6 by the use of Eq. [4]. The total a-c resistance of the oxide film plus solution was then corrected by subtracting the a-c resistance of the solution and double layers at 100,000 cps from Table I.…”

Section: Probable Defect Structure Of Aluminum Oxide Filmsmentioning

confidence: 99%

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The Distribution of A-C Resistance in Oxide Films on Aluminum

Heine

Pryor

1963

J. Electrochem. Soc.

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Films of 7 A1203 produced by anodizing superpurity aluminum at 20v in neutral ammonium tartrate are thinned uniformly when placed in sodium chromate solution of pH range 7-9. During film thinning the metal remains passive and the inherent specific resistance of the film substance is not modified by the dissolution process. Uniform thinning can continue from an initial film thickness of around 240A down to the passive film thickness 20-25A. Measurement of capacitanCe and dielectric loss at frequencies of 1000 to 100,000 cps during thinning has permitted determination of the variation of electronic and ionic resistivity throughout the majority of the thickness of the alumina films. Corrections for a-c resistance of the solution have been found to be unnecessary at 1000 cps but mandatory at 100,000 cps in order to obtain accurate results. The films possess a region of low electronic resistivity up to 60-80A from the oxide-metal interface. At greater thickness, electronic resistivity is constant. Ionic resistivity is only constant across a central region of the film around 100A thick. Nearer to the oxide solution interface, the ionic resistivity falls gradually and then rises sharply in the outer 20A of the film. A defect model is advanced to account for this resistivity distribution.

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Section: Influence Of Chromate Solution On Accuracy Os Film Resistanc...mentioning

confidence: 99%

Section: Influence Of Chromate Solution On Accuracy Os Film Resistanc...mentioning

confidence: 99%

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The Distribution of A-C Resistance in Oxide Films on Aluminum

Heine

Pryor

1963

J. Electrochem. Soc.

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“…However, these techniques are unable to be applied in situ (during the growth of porous film), and, thus, can neither prove nor contradict the assumptions of the models if the morphology of the AAO barrier layer changes after the end of anodizing. 18,19 As AAO is a dielectric material that separates aluminium from electrolyte during anodizing, it can be studied by electrochemical impedance spectroscopy (EIS), which has been widely used for ex situ studies of both barrier 20,21 and porous 22,23 AAO films. However, the published data on in situ measurements in acidic electrolytes are scarce.…”

mentioning

confidence: 99%

Probing Barrier Oxide Layer of Porous Anodic Alumina by In Situ Electrochemical Impedance Spectroscopy

Leontiev

Napolskii

2021

J. Electrochem. Soc.

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Electrochemical impedance spectroscopy (EIS) is a unique tool for both ex situ and in situ studies of the barrier layer thickness of anodic aluminium oxide (AAO). Here EIS is applied to study porous AAO formed by anodizing of high-purity Al foils in 0.3 M sulphuric acid and 0.3 M oxalic acid electrolytes. It is shown that in the high-frequency range, in situ EIS spectra coincide with the ex situ ones. Thus, the thickness of the barrier layer at the pore bases does not change after the end of the anodic polarization. The barrier layer thickness (h) is governed by the anodizing potential (U) according to the equation h = 1.03(2) nm·V−1·U + 2.2(3) nm. Features of the current transients observed during potentiostatic anodizing are discussed. It has been proved that a local maximum of current at the initial stage of anodizing corresponds to the maximum of the aluminium electroactive surface area arising due to the rearrangement of pores.

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