Transpassive dissolution mechanism of Ni-based alloys in a simulated bleaching solution: Effect of alloying elements

Iva Betova, Martin Bojinov, Petri Kinnunen, Timo Laitinen, Pekka Pohjanne, Timo Saario, Martti Vilpas

    Research output: Contribution to journalArticleScientificpeer-review

    8 Citations (Scopus)

    Abstract

    The transpassive dissolution of several nickel-based alloys has been studied in a simulated bleaching solution (0.014 M SO2−4, 0.017 M Cl−, and 0.0025 M diethylenetriaminopentaacetic acid, DTPA, pH 2.8) by electrochemical techniques.
    The alloys have been prepared by welding superaustenitic stainless steels (UNS S31254 and S32654) with nickel-based filler metals (UNS N06625 and N06059). According to the rotating ring-disk voltammetric studies, the release of soluble high-valency products from the alloys plays a significant role in the transpassive potential region.
    Electrochemical impedance spectroscopic data point to a competition between transpassive dissolution and secondary passivation reactions. The experimental data have been compared to a previously proposed model for the transpassive dissolution of nickel-based alloys.
    The model treats the transpassive dissolution of Cr as a two-step reaction featuring a Cr(VI) intermediate. It assumes that the dissolution of Ni follows two parallel reaction paths, one of which involves a self-catalytic step.
    The kinetic parameters of the process for the studied alloys have been determined, and a discussion of the role of alloying elements such as Fe and Mo on the transpassive dissolution mechanism is given
    Original languageEnglish
    Pages (from-to)B499-B509
    JournalJournal of the Electrochemical Society
    Volume149
    Issue number11
    DOIs
    Publication statusPublished - 2002
    MoE publication typeA1 Journal article-refereed

    Keywords

    • alloy steel
    • dissolving
    • electrochemistry
    • austenitic stainless steel
    • electric impedance
    • passivation
    • catalysts
    • alloying additions
    • nickel alloys
    • nickel-based alloys

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