Transpassivity mechanism of iron-chromium-molybdenum alloys studies by AC impedance, DC resistance and RRDE measurements

Martin Bojinov (Corresponding Author), Gunilla Fabricius, Timo Laitinen, Timo Saario

    Research output: Contribution to journalArticleScientificpeer-review

    47 Citations (Scopus)

    Abstract

    The transpassive dissolution of Fe-25%Cr, Fe-25%Cr-5%Mo and Fe-25%Cr-10%Mo alloys in 1 M H2SO4 was studied with a combination of electrochemical techniques—conventional and rotating ring-disk voltammetry, impedance spectroscopy and the d.c. resistance measurements with the contact electric resistance (CER) technique. Rotating ring-disk studies indicated that the amount of soluble CrVI released from the alloys in the transpassive region increases significantly with the Mo addition in the substrate. The electronic resistance of the anodic film was found to decrease as CrVI is released and to stabilise subsequently due to the formation of a secondary film depleted in Cr. Impedance spectra of the Fe-25%Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions. Mo addition was shown to have a catalytic effect on the transpassive dissolution of Cr. The experimental results were compared to a generalized model of the transpassivity of Fe–Cr alloys. 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. The transpassive dissolution reaction is assumed to be a two-stage process featuring a CrIV 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 as depending on the Mo content in the alloy.
    Original languageEnglish
    Pages (from-to)4331-4343
    Number of pages13
    JournalElectrochimica Acta
    Volume44
    Issue number24
    DOIs
    Publication statusPublished - 1999
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Molybdenum alloys
    Chromium alloys
    Dissolution
    Iron
    Electric contacts
    Film growth
    Voltammetry
    Surface charge
    Kinetic parameters
    Cations
    Positive ions
    Spectroscopy
    Semiconductor materials
    Defects
    Substrates

    Cite this

    Bojinov, Martin ; Fabricius, Gunilla ; Laitinen, Timo ; Saario, Timo. / Transpassivity mechanism of iron-chromium-molybdenum alloys studies by AC impedance, DC resistance and RRDE measurements. In: Electrochimica Acta. 1999 ; Vol. 44, No. 24. pp. 4331-4343.
    @article{47d4be00e1c34ecdae11d7bde2add5a8,
    title = "Transpassivity mechanism of iron-chromium-molybdenum alloys studies by AC impedance, DC resistance and RRDE measurements",
    abstract = "The transpassive dissolution of Fe-25{\%}Cr, Fe-25{\%}Cr-5{\%}Mo and Fe-25{\%}Cr-10{\%}Mo alloys in 1 M H2SO4 was studied with a combination of electrochemical techniques—conventional and rotating ring-disk voltammetry, impedance spectroscopy and the d.c. resistance measurements with the contact electric resistance (CER) technique. Rotating ring-disk studies indicated that the amount of soluble CrVI released from the alloys in the transpassive region increases significantly with the Mo addition in the substrate. The electronic resistance of the anodic film was found to decrease as CrVI is released and to stabilise subsequently due to the formation of a secondary film depleted in Cr. Impedance spectra of the Fe-25{\%}Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions. Mo addition was shown to have a catalytic effect on the transpassive dissolution of Cr. The experimental results were compared to a generalized model of the transpassivity of Fe–Cr alloys. 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. The transpassive dissolution reaction is assumed to be a two-stage process featuring a CrIV 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 as depending on the Mo content in the alloy.",
    author = "Martin Bojinov and Gunilla Fabricius and Timo Laitinen and Timo Saario",
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    year = "1999",
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    language = "English",
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    pages = "4331--4343",
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    Transpassivity mechanism of iron-chromium-molybdenum alloys studies by AC impedance, DC resistance and RRDE measurements. / Bojinov, Martin (Corresponding Author); Fabricius, Gunilla; Laitinen, Timo; Saario, Timo.

    In: Electrochimica Acta, Vol. 44, No. 24, 1999, p. 4331-4343.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Transpassivity mechanism of iron-chromium-molybdenum alloys studies by AC impedance, DC resistance and RRDE measurements

    AU - Bojinov, Martin

    AU - Fabricius, Gunilla

    AU - Laitinen, Timo

    AU - Saario, Timo

    N1 - Project code: V8SU00123

    PY - 1999

    Y1 - 1999

    N2 - The transpassive dissolution of Fe-25%Cr, Fe-25%Cr-5%Mo and Fe-25%Cr-10%Mo alloys in 1 M H2SO4 was studied with a combination of electrochemical techniques—conventional and rotating ring-disk voltammetry, impedance spectroscopy and the d.c. resistance measurements with the contact electric resistance (CER) technique. Rotating ring-disk studies indicated that the amount of soluble CrVI released from the alloys in the transpassive region increases significantly with the Mo addition in the substrate. The electronic resistance of the anodic film was found to decrease as CrVI is released and to stabilise subsequently due to the formation of a secondary film depleted in Cr. Impedance spectra of the Fe-25%Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions. Mo addition was shown to have a catalytic effect on the transpassive dissolution of Cr. The experimental results were compared to a generalized model of the transpassivity of Fe–Cr alloys. 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. The transpassive dissolution reaction is assumed to be a two-stage process featuring a CrIV 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 as depending on the Mo content in the alloy.

    AB - The transpassive dissolution of Fe-25%Cr, Fe-25%Cr-5%Mo and Fe-25%Cr-10%Mo alloys in 1 M H2SO4 was studied with a combination of electrochemical techniques—conventional and rotating ring-disk voltammetry, impedance spectroscopy and the d.c. resistance measurements with the contact electric resistance (CER) technique. Rotating ring-disk studies indicated that the amount of soluble CrVI released from the alloys in the transpassive region increases significantly with the Mo addition in the substrate. The electronic resistance of the anodic film was found to decrease as CrVI is released and to stabilise subsequently due to the formation of a secondary film depleted in Cr. Impedance spectra of the Fe-25%Cr alloy were found to include contributions from both the film growth and transpassive dissolution reactions. Mo addition was shown to have a catalytic effect on the transpassive dissolution of Cr. The experimental results were compared to a generalized model of the transpassivity of Fe–Cr alloys. 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. The transpassive dissolution reaction is assumed to be a two-stage process featuring a CrIV 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 as depending on the Mo content in the alloy.

    U2 - 10.1016/S0013-4686(99)00149-8

    DO - 10.1016/S0013-4686(99)00149-8

    M3 - Article

    VL - 44

    SP - 4331

    EP - 4343

    JO - Electrochimica Acta

    JF - Electrochimica Acta

    SN - 0013-4686

    IS - 24

    ER -