Transpassive dissolution of Ni-Cr alloys in sulphate solutions-comparison between a model alloy and two industrial alloys

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

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    The application of a general model for the transpassive dissolution mechanism of binary Ni-based alloys to industrial alloys, Alloy 600 and Alloy C276, containing Ni, Cr, Fe and Mo, in 1 M sulphate solutions at pH 0 and 5 is described. A comparison of the electrochemical behaviour of these two alloys to a binary Ni–15%Cr alloy is also included.
    The techniques used were ring-disc voltammetry, impedance spectroscopy and resistance measurements. Soluble high-valency products were found to be released in a considerable amount from all the materials. The presence of Mo in Alloy C276 was found to increase the transpassive oxidation rate in comparison to alloys 600 and Ni–15%Cr at pH 0, but the same effect of Mo is not so well pronounced at pH 5.
    The mechanism of transpassive dissolution was found to be similar on every material at pH 0. At pH 5 the mechanism of the transpassive dissolution on Alloy C276 at high overpotentials is different from that at low overpotentials or from that at pH 0.
    This change is concluded to be due to the increased effect of adsorbed intermediates at the film/solution interface. The model was found to reproduce the steady state current and the impedance spectra satisfactorily.
    Original languageEnglish
    Pages (from-to)1697-1712
    JournalElectrochimica Acta
    Issue number11
    Publication statusPublished - 2002
    MoE publication typeA1 Journal article-refereed



    • ni-based alloys
    • oxide film
    • transpassive dissolution
    • kinetic model
    • electrochemical impedance spectroscopy

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