The mechanism of the transpassive dissolution of chromium in acidic sulfate solutions

Martin Bojinov, Gunilla Fabricius, Timo Laitinen, Timo Saario

    Research output: Contribution to journalArticleScientificpeer-review

    34 Citations (Scopus)

    Abstract

    The transpassivity of chromium in 1 M sulfate solutions (pH 0 and 5) was studied by steady‐state polarization, rotating ring‐disk electrode voltammetry, and impedance spectroscopy in combination with the contact electric resistance technique.
    Ring‐disk electrode measurements in the transpassive region indicated the dissolution of Cr mainly as Cr(VI) and partly as Cr(III). The conductivity of the anodic film strongly increased in the transpassive potential range, probably due to the formation of Cr(VI) species.
    A kinetic model for the transpassive process was advanced to explain the observed experimental features. It comprises two dissolution paths of Cr as Cr(VI) and one as Cr(III). The formation of a Cr(IV) intermediate and a continuous change in the valence state of Cr at the film/solution interface are considered. Kinetic equations for both steady state and impedance response were derived and compared to experimental results to determine the reaction rate constants.
    Original languageEnglish
    Pages (from-to)2043-2050
    JournalJournal of the Electrochemical Society
    Volume145
    Issue number6
    DOIs
    Publication statusPublished - 1998
    MoE publication typeA1 Journal article-refereed

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