Evidence of coupling between film growth and metal dissolution in passivation processes

Martin Bojinov, Sandro Cattarin, Marco Musiani (Corresponding Author), Bernard Tribollet

Research output: Contribution to journalArticleScientificpeer-review

54 Citations (Scopus)

Abstract

In the anodisation of Nb in acidic fluoride solutions or warm aqueous alkali, and in that of Mo in concentrated phosphoric acid, impedance spectroscopy provides evidence that 3D film growth proceeds already during the active–passive transition. Indeed, linear potential dependences of both the inverse of the high-frequency capacitance and of the product of the high-frequency resistance times the steady-state current are observed already below the peak potential. Simultaneously, a pseudo-inductive loop at intermediate frequencies is detected in the impedance spectra. In the present paper, we propose a kinetic model for the interpretation of these data. The model assumes that the metal is covered with a non-stoichiometric oxide containing at least two oxidation states of the cation. The processes of oxidative dissolution of the lower valence cations and their transformation to cations of higher valence, leading to passivation, explain the shape of the I–E curve. These processes are limited by both charge transfer at the film–solution (F/S) interface and transport of cation vacancies through the film. Thickening of the oxide film is assumed to proceed simultaneously, and is limited by transport of oxygen vacancies accelerated by an interfacial charge of cation vacancies.
Original languageEnglish
Pages (from-to)4107-4117
JournalElectrochimica Acta
Volume48
Issue number28
DOIs
Publication statusPublished - 2003
MoE publication typeA1 Journal article-refereed

Fingerprint

Film growth
Passivation
Cations
Dissolution
Positive ions
Metals
Vacancies
Alkalies
Phosphoric acid
Oxygen vacancies
Fluorides
Oxides
Oxide films
Charge transfer
Capacitance
Spectroscopy
Oxidation
Kinetics

Keywords

  • anodic films
  • impedance
  • modelling
  • molybdenum
  • niobium
  • oxides

Cite this

Bojinov, Martin ; Cattarin, Sandro ; Musiani, Marco ; Tribollet, Bernard. / Evidence of coupling between film growth and metal dissolution in passivation processes. In: Electrochimica Acta. 2003 ; Vol. 48, No. 28. pp. 4107-4117.
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abstract = "In the anodisation of Nb in acidic fluoride solutions or warm aqueous alkali, and in that of Mo in concentrated phosphoric acid, impedance spectroscopy provides evidence that 3D film growth proceeds already during the active–passive transition. Indeed, linear potential dependences of both the inverse of the high-frequency capacitance and of the product of the high-frequency resistance times the steady-state current are observed already below the peak potential. Simultaneously, a pseudo-inductive loop at intermediate frequencies is detected in the impedance spectra. In the present paper, we propose a kinetic model for the interpretation of these data. The model assumes that the metal is covered with a non-stoichiometric oxide containing at least two oxidation states of the cation. The processes of oxidative dissolution of the lower valence cations and their transformation to cations of higher valence, leading to passivation, explain the shape of the I–E curve. These processes are limited by both charge transfer at the film–solution (F/S) interface and transport of cation vacancies through the film. Thickening of the oxide film is assumed to proceed simultaneously, and is limited by transport of oxygen vacancies accelerated by an interfacial charge of cation vacancies.",
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Evidence of coupling between film growth and metal dissolution in passivation processes. / Bojinov, Martin; Cattarin, Sandro; Musiani, Marco (Corresponding Author); Tribollet, Bernard.

In: Electrochimica Acta, Vol. 48, No. 28, 2003, p. 4107-4117.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Evidence of coupling between film growth and metal dissolution in passivation processes

AU - Bojinov, Martin

AU - Cattarin, Sandro

AU - Musiani, Marco

AU - Tribollet, Bernard

N1 - Project code: G3SU00219

PY - 2003

Y1 - 2003

N2 - In the anodisation of Nb in acidic fluoride solutions or warm aqueous alkali, and in that of Mo in concentrated phosphoric acid, impedance spectroscopy provides evidence that 3D film growth proceeds already during the active–passive transition. Indeed, linear potential dependences of both the inverse of the high-frequency capacitance and of the product of the high-frequency resistance times the steady-state current are observed already below the peak potential. Simultaneously, a pseudo-inductive loop at intermediate frequencies is detected in the impedance spectra. In the present paper, we propose a kinetic model for the interpretation of these data. The model assumes that the metal is covered with a non-stoichiometric oxide containing at least two oxidation states of the cation. The processes of oxidative dissolution of the lower valence cations and their transformation to cations of higher valence, leading to passivation, explain the shape of the I–E curve. These processes are limited by both charge transfer at the film–solution (F/S) interface and transport of cation vacancies through the film. Thickening of the oxide film is assumed to proceed simultaneously, and is limited by transport of oxygen vacancies accelerated by an interfacial charge of cation vacancies.

AB - In the anodisation of Nb in acidic fluoride solutions or warm aqueous alkali, and in that of Mo in concentrated phosphoric acid, impedance spectroscopy provides evidence that 3D film growth proceeds already during the active–passive transition. Indeed, linear potential dependences of both the inverse of the high-frequency capacitance and of the product of the high-frequency resistance times the steady-state current are observed already below the peak potential. Simultaneously, a pseudo-inductive loop at intermediate frequencies is detected in the impedance spectra. In the present paper, we propose a kinetic model for the interpretation of these data. The model assumes that the metal is covered with a non-stoichiometric oxide containing at least two oxidation states of the cation. The processes of oxidative dissolution of the lower valence cations and their transformation to cations of higher valence, leading to passivation, explain the shape of the I–E curve. These processes are limited by both charge transfer at the film–solution (F/S) interface and transport of cation vacancies through the film. Thickening of the oxide film is assumed to proceed simultaneously, and is limited by transport of oxygen vacancies accelerated by an interfacial charge of cation vacancies.

KW - anodic films

KW - impedance

KW - modelling

KW - molybdenum

KW - niobium

KW - oxides

U2 - 10.1016/S0013-4686(03)00578-4

DO - 10.1016/S0013-4686(03)00578-4

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JF - Electrochimica Acta

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