The stability of the passive state of iron-chromium alloys in sulphuric acid solution

Martin Bojinov, Iva Betova, Gunilla Fabricius, Timo Laitinen (Corresponding Author), R. Raicheff, Timo Saario

    Research output: Contribution to journalArticleScientificpeer-review

    77 Citations (Scopus)

    Abstract

    The passivation and the transpassive dissolution of Fe–Cr alloys (12% and 25% Cr) was studied with a combination of electrochemical techniques—conventional and rotating ring–disk voltammetry, impedance spectroscopy and the contact electric resistance (CER) technique developed to measure the dc resistance of surface films. Rotating ring–disk studies indicated that both soluble Cr (VI) and Fe (III) are released from the alloys in the transpassive region. The electronic resistance of the transpassive anodic film was found to decrease as Cr (VI) is released from the outermost layers adjacent to the interface and to increase subsequently due to the formation of a Fe (III) rich secondary passive film. Impedance spectra of the Fe–25% Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions, whereas the corresponding spectra of the Fe–12% Cr alloy reflected mainly the contribution of the film. On the basis of the experimental results, a generalized model of the transpassivity of Fe–Cr alloys is proposed. The model represents the anodic film as a highly doped n-type semiconductor–insulator–p-type semiconductor (n–i–p) structure. Injection of negative defects at the film/solution interface results in their accumulation as a negative surface charge. It alters the non-stationary film growth rate controlled by the transport of positive defects (oxygen vacancies). The transpassive dissolution reaction is assumed to be a two-stage process featuring a Cr (IV) intermediate. The relaxation of the Fe fraction in the outermost cation layer of the film is taken into account as well. Fitting of the experimental data on the basis of equations derived for the steady state and impedance response enable the determination of the kinetic parameters of transpassive dissolution.
    Original languageEnglish
    Pages (from-to)1557-1584
    Number of pages28
    JournalCorrosion Science
    Volume41
    Issue number8
    DOIs
    Publication statusPublished - 1999
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Chromium Alloys
    Chromium alloys
    Iron alloys
    Acids
    Dissolution
    Film growth
    Electric contacts
    Defects
    Oxygen vacancies
    Voltammetry
    Surface charge
    Kinetic parameters
    Passivation
    Cations
    Positive ions
    Spectroscopy
    Semiconductor materials

    Cite this

    Bojinov, Martin ; Betova, Iva ; Fabricius, Gunilla ; Laitinen, Timo ; Raicheff, R. ; Saario, Timo. / The stability of the passive state of iron-chromium alloys in sulphuric acid solution. In: Corrosion Science. 1999 ; Vol. 41, No. 8. pp. 1557-1584.
    @article{6b1fb1cb7c824d6e9c45f0a0338fd344,
    title = "The stability of the passive state of iron-chromium alloys in sulphuric acid solution",
    abstract = "The passivation and the transpassive dissolution of Fe–Cr alloys (12{\%} and 25{\%} Cr) was studied with a combination of electrochemical techniques—conventional and rotating ring–disk voltammetry, impedance spectroscopy and the contact electric resistance (CER) technique developed to measure the dc resistance of surface films. Rotating ring–disk studies indicated that both soluble Cr (VI) and Fe (III) are released from the alloys in the transpassive region. The electronic resistance of the transpassive anodic film was found to decrease as Cr (VI) is released from the outermost layers adjacent to the interface and to increase subsequently due to the formation of a Fe (III) rich secondary passive film. Impedance spectra of the Fe–25{\%} Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions, whereas the corresponding spectra of the Fe–12{\%} Cr alloy reflected mainly the contribution of the film. On the basis of the experimental results, a generalized model of the transpassivity of Fe–Cr alloys is proposed. The model represents the anodic film as a highly doped n-type semiconductor–insulator–p-type semiconductor (n–i–p) structure. Injection of negative defects at the film/solution interface results in their accumulation as a negative surface charge. It alters the non-stationary film growth rate controlled by the transport of positive defects (oxygen vacancies). The transpassive dissolution reaction is assumed to be a two-stage process featuring a Cr (IV) intermediate. The relaxation of the Fe fraction in the outermost cation layer of the film is taken into account as well. Fitting of the experimental data on the basis of equations derived for the steady state and impedance response enable the determination of the kinetic parameters of transpassive dissolution.",
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    The stability of the passive state of iron-chromium alloys in sulphuric acid solution. / Bojinov, Martin; Betova, Iva; Fabricius, Gunilla; Laitinen, Timo (Corresponding Author); Raicheff, R.; Saario, Timo.

    In: Corrosion Science, Vol. 41, No. 8, 1999, p. 1557-1584.

    Research output: Contribution to journalArticleScientificpeer-review

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    T1 - The stability of the passive state of iron-chromium alloys in sulphuric acid solution

    AU - Bojinov, Martin

    AU - Betova, Iva

    AU - Fabricius, Gunilla

    AU - Laitinen, Timo

    AU - Raicheff, R.

    AU - Saario, Timo

    N1 - Project code: V8SU00123

    PY - 1999

    Y1 - 1999

    N2 - The passivation and the transpassive dissolution of Fe–Cr alloys (12% and 25% Cr) was studied with a combination of electrochemical techniques—conventional and rotating ring–disk voltammetry, impedance spectroscopy and the contact electric resistance (CER) technique developed to measure the dc resistance of surface films. Rotating ring–disk studies indicated that both soluble Cr (VI) and Fe (III) are released from the alloys in the transpassive region. The electronic resistance of the transpassive anodic film was found to decrease as Cr (VI) is released from the outermost layers adjacent to the interface and to increase subsequently due to the formation of a Fe (III) rich secondary passive film. Impedance spectra of the Fe–25% Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions, whereas the corresponding spectra of the Fe–12% Cr alloy reflected mainly the contribution of the film. On the basis of the experimental results, a generalized model of the transpassivity of Fe–Cr alloys is proposed. The model represents the anodic film as a highly doped n-type semiconductor–insulator–p-type semiconductor (n–i–p) structure. Injection of negative defects at the film/solution interface results in their accumulation as a negative surface charge. It alters the non-stationary film growth rate controlled by the transport of positive defects (oxygen vacancies). The transpassive dissolution reaction is assumed to be a two-stage process featuring a Cr (IV) intermediate. The relaxation of the Fe fraction in the outermost cation layer of the film is taken into account as well. Fitting of the experimental data on the basis of equations derived for the steady state and impedance response enable the determination of the kinetic parameters of transpassive dissolution.

    AB - The passivation and the transpassive dissolution of Fe–Cr alloys (12% and 25% Cr) was studied with a combination of electrochemical techniques—conventional and rotating ring–disk voltammetry, impedance spectroscopy and the contact electric resistance (CER) technique developed to measure the dc resistance of surface films. Rotating ring–disk studies indicated that both soluble Cr (VI) and Fe (III) are released from the alloys in the transpassive region. The electronic resistance of the transpassive anodic film was found to decrease as Cr (VI) is released from the outermost layers adjacent to the interface and to increase subsequently due to the formation of a Fe (III) rich secondary passive film. Impedance spectra of the Fe–25% Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions, whereas the corresponding spectra of the Fe–12% Cr alloy reflected mainly the contribution of the film. On the basis of the experimental results, a generalized model of the transpassivity of Fe–Cr alloys is proposed. The model represents the anodic film as a highly doped n-type semiconductor–insulator–p-type semiconductor (n–i–p) structure. Injection of negative defects at the film/solution interface results in their accumulation as a negative surface charge. It alters the non-stationary film growth rate controlled by the transport of positive defects (oxygen vacancies). The transpassive dissolution reaction is assumed to be a two-stage process featuring a Cr (IV) intermediate. The relaxation of the Fe fraction in the outermost cation layer of the film is taken into account as well. Fitting of the experimental data on the basis of equations derived for the steady state and impedance response enable the determination of the kinetic parameters of transpassive dissolution.

    U2 - 10.1016/S0010-938X(99)00003-7

    DO - 10.1016/S0010-938X(99)00003-7

    M3 - Article

    VL - 41

    SP - 1557

    EP - 1584

    JO - Corrosion Science

    JF - Corrosion Science

    SN - 0010-938X

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    ER -