Influence of molybdenum on the conduction mechanism in passive films on iron-chromium alloys in sulphuric acid solution

Martin Bojinov (Corresponding Author), Gunilla Fabricius, Timo Laitinen, Kari Mäkelä, Timo Saario, Göran Sundholm

    Research output: Contribution to journalArticleScientificpeer-review

    46 Citations (Scopus)

    Abstract

    This paper describes an extension of the mixed-conduction model to predict quantitatively the electrochemical behaviour and transport properties of anodic films on pure Cr, Fe–Cr alloys and Fe–Cr–Mo alloys in 1 M sulphuric acid solution. The anodic films on Fe–Cr–Mo alloys (12 and 25% Cr; 0, 5 and 10% Mo) were studied using rotating ring-disk voltammetry, impedance spectroscopy and resistance measurements. The addition of Mo to the Fe–Cr alloys was found to decrease the resistance of the film both in the passive and transpassive region. During the re-activation of the Fe–12%Cr–x%Mo alloys at negative potentials, soluble products were found to be released at a higher potential than during the re-activation of the Fe–12%Cr alloy. Re-activation proceeds to a lesser extent for the Fe–25%Cr alloy, and was not observed for the Fe–25%Cr–x%Mo alloys. The addition of Mo was also found to lead to a marked increase of the transpassive dissolution rate of the alloys. The impedance spectroscopic results indicated that the addition of Mo increases the rate of the interfacial generation of positive defects and especially annihilation of negative defects. The present extension of the mixed-conduction model for anodic passive films was found to describe quantitatively the resistance and impedance spectroscopic data for Fe–25%Cr and Fe–25%Cr–10%Mo alloy, as well as earlier data on pure Cr. The same kinetic model can be used to describe the behaviour of the films on all these materials. It is thus most likely that a Cr-oxide-based film is formed which determines the behaviour of the Fe–25%Cr and Fe–25%Cr–10%Mo alloys as well.
    Original languageEnglish
    Pages (from-to)1339-1358
    Number of pages20
    JournalElectrochimica Acta
    Volume46
    Issue number9
    DOIs
    Publication statusPublished - 2001
    MoE publication typeA1 Journal article-refereed

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    Chromium Alloys
    Chromium alloys
    Molybdenum
    Iron alloys
    Acids
    Chemical activation
    Defects
    Voltammetry
    Transport properties
    Oxides

    Cite this

    Bojinov, Martin ; Fabricius, Gunilla ; Laitinen, Timo ; Mäkelä, Kari ; Saario, Timo ; Sundholm, Göran. / Influence of molybdenum on the conduction mechanism in passive films on iron-chromium alloys in sulphuric acid solution. In: Electrochimica Acta. 2001 ; Vol. 46, No. 9. pp. 1339-1358.
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    title = "Influence of molybdenum on the conduction mechanism in passive films on iron-chromium alloys in sulphuric acid solution",
    abstract = "This paper describes an extension of the mixed-conduction model to predict quantitatively the electrochemical behaviour and transport properties of anodic films on pure Cr, Fe–Cr alloys and Fe–Cr–Mo alloys in 1 M sulphuric acid solution. The anodic films on Fe–Cr–Mo alloys (12 and 25{\%} Cr; 0, 5 and 10{\%} Mo) were studied using rotating ring-disk voltammetry, impedance spectroscopy and resistance measurements. The addition of Mo to the Fe–Cr alloys was found to decrease the resistance of the film both in the passive and transpassive region. During the re-activation of the Fe–12{\%}Cr–x{\%}Mo alloys at negative potentials, soluble products were found to be released at a higher potential than during the re-activation of the Fe–12{\%}Cr alloy. Re-activation proceeds to a lesser extent for the Fe–25{\%}Cr alloy, and was not observed for the Fe–25{\%}Cr–x{\%}Mo alloys. The addition of Mo was also found to lead to a marked increase of the transpassive dissolution rate of the alloys. The impedance spectroscopic results indicated that the addition of Mo increases the rate of the interfacial generation of positive defects and especially annihilation of negative defects. The present extension of the mixed-conduction model for anodic passive films was found to describe quantitatively the resistance and impedance spectroscopic data for Fe–25{\%}Cr and Fe–25{\%}Cr–10{\%}Mo alloy, as well as earlier data on pure Cr. The same kinetic model can be used to describe the behaviour of the films on all these materials. It is thus most likely that a Cr-oxide-based film is formed which determines the behaviour of the Fe–25{\%}Cr and Fe–25{\%}Cr–10{\%}Mo alloys as well.",
    author = "Martin Bojinov and Gunilla Fabricius and Timo Laitinen and Kari M{\"a}kel{\"a} and Timo Saario and G{\"o}ran Sundholm",
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    year = "2001",
    doi = "10.1016/S0013-4686(00)00713-1",
    language = "English",
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    Influence of molybdenum on the conduction mechanism in passive films on iron-chromium alloys in sulphuric acid solution. / Bojinov, Martin (Corresponding Author); Fabricius, Gunilla; Laitinen, Timo; Mäkelä, Kari; Saario, Timo; Sundholm, Göran.

    In: Electrochimica Acta, Vol. 46, No. 9, 2001, p. 1339-1358.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Influence of molybdenum on the conduction mechanism in passive films on iron-chromium alloys in sulphuric acid solution

    AU - Bojinov, Martin

    AU - Fabricius, Gunilla

    AU - Laitinen, Timo

    AU - Mäkelä, Kari

    AU - Saario, Timo

    AU - Sundholm, Göran

    N1 - Project code: V9SU00119

    PY - 2001

    Y1 - 2001

    N2 - This paper describes an extension of the mixed-conduction model to predict quantitatively the electrochemical behaviour and transport properties of anodic films on pure Cr, Fe–Cr alloys and Fe–Cr–Mo alloys in 1 M sulphuric acid solution. The anodic films on Fe–Cr–Mo alloys (12 and 25% Cr; 0, 5 and 10% Mo) were studied using rotating ring-disk voltammetry, impedance spectroscopy and resistance measurements. The addition of Mo to the Fe–Cr alloys was found to decrease the resistance of the film both in the passive and transpassive region. During the re-activation of the Fe–12%Cr–x%Mo alloys at negative potentials, soluble products were found to be released at a higher potential than during the re-activation of the Fe–12%Cr alloy. Re-activation proceeds to a lesser extent for the Fe–25%Cr alloy, and was not observed for the Fe–25%Cr–x%Mo alloys. The addition of Mo was also found to lead to a marked increase of the transpassive dissolution rate of the alloys. The impedance spectroscopic results indicated that the addition of Mo increases the rate of the interfacial generation of positive defects and especially annihilation of negative defects. The present extension of the mixed-conduction model for anodic passive films was found to describe quantitatively the resistance and impedance spectroscopic data for Fe–25%Cr and Fe–25%Cr–10%Mo alloy, as well as earlier data on pure Cr. The same kinetic model can be used to describe the behaviour of the films on all these materials. It is thus most likely that a Cr-oxide-based film is formed which determines the behaviour of the Fe–25%Cr and Fe–25%Cr–10%Mo alloys as well.

    AB - This paper describes an extension of the mixed-conduction model to predict quantitatively the electrochemical behaviour and transport properties of anodic films on pure Cr, Fe–Cr alloys and Fe–Cr–Mo alloys in 1 M sulphuric acid solution. The anodic films on Fe–Cr–Mo alloys (12 and 25% Cr; 0, 5 and 10% Mo) were studied using rotating ring-disk voltammetry, impedance spectroscopy and resistance measurements. The addition of Mo to the Fe–Cr alloys was found to decrease the resistance of the film both in the passive and transpassive region. During the re-activation of the Fe–12%Cr–x%Mo alloys at negative potentials, soluble products were found to be released at a higher potential than during the re-activation of the Fe–12%Cr alloy. Re-activation proceeds to a lesser extent for the Fe–25%Cr alloy, and was not observed for the Fe–25%Cr–x%Mo alloys. The addition of Mo was also found to lead to a marked increase of the transpassive dissolution rate of the alloys. The impedance spectroscopic results indicated that the addition of Mo increases the rate of the interfacial generation of positive defects and especially annihilation of negative defects. The present extension of the mixed-conduction model for anodic passive films was found to describe quantitatively the resistance and impedance spectroscopic data for Fe–25%Cr and Fe–25%Cr–10%Mo alloy, as well as earlier data on pure Cr. The same kinetic model can be used to describe the behaviour of the films on all these materials. It is thus most likely that a Cr-oxide-based film is formed which determines the behaviour of the Fe–25%Cr and Fe–25%Cr–10%Mo alloys as well.

    U2 - 10.1016/S0013-4686(00)00713-1

    DO - 10.1016/S0013-4686(00)00713-1

    M3 - Article

    VL - 46

    SP - 1339

    EP - 1358

    JO - Electrochimica Acta

    JF - Electrochimica Acta

    SN - 0013-4686

    IS - 9

    ER -