Transpassive corrosion mechanism of austenitic stainless steels in simulated bleaching solutions

Iva Betova, Martin Bojinov, Timo Laitinen, Kari Mäkelä, Pekka Pohjanne, Timo Saario

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    Abstract

    The transpassive corrosion of highly alloyed austenitic stainless steels - UNS NO8904, UNS S31254 and UNS S32654 - was investigated in simulated bleaching solutions containing 0.014 M SO42-, 0.017 M Cl-, up to 0.01 M oxalic acid and up to 0.0025 M diethylenetetraminepentaacetic acid (DTPA), pH 3.0 and 6.0, with conventional and rotating ring-disk electrode (RRDE) voltammetry, as well as electrochemical impedance spectroscopy (EIS). The transpassive oxidation rate of UNS S32654 was found to be much higher than that of the other two alloys. Oxalic acid addition resulted in a significant increase of the transpassive oxidation rate, whereas the addition of DTPA led to a decrease of that rate especially at a pH of 3. The general features of the impedance spectra demonstrate that transpassive dissolution is favoured for UNS S32654 and secondary passivation predominates for the two other steels. A kinetic model of the process is proposed, featuring a two-step transpassive dissolution of Cr via a Cr(VI) intermediate species and taking into account the dissolution of Fe(III) through the anodic film. The model has been found to be in quantitative agreement with steady state current vs. potential curves and impedance spectra. The kinetic parameters of transpassive dissolution have been determined and the relevance of their values is discussed.
    Original languageEnglish
    Title of host publication10th International Symposium on Corrosion in the Pulp and Paper Industry, ISCPPI. Vol. 1
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages323-336
    ISBN (Electronic)951-38-5724-7
    ISBN (Print)951-38-5720-4
    Publication statusPublished - 2001
    MoE publication typeA4 Article in a conference publication
    Event10th International Symposium On corrosion in the Pulp and Paper Industry, ISCPPI - Helsinki, Finland
    Duration: 21 Aug 200124 Aug 2001

    Publication series

    SeriesVTT Symposium
    Number214
    ISSN0357-9387

    Conference

    Conference10th International Symposium On corrosion in the Pulp and Paper Industry, ISCPPI
    Abbreviated title10th ISCPPI
    CountryFinland
    CityHelsinki
    Period21/08/0124/08/01

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  • Cite this

    Betova, I., Bojinov, M., Laitinen, T., Mäkelä, K., Pohjanne, P., & Saario, T. (2001). Transpassive corrosion mechanism of austenitic stainless steels in simulated bleaching solutions. In 10th International Symposium on Corrosion in the Pulp and Paper Industry, ISCPPI. Vol. 1 (pp. 323-336). VTT Technical Research Centre of Finland. VTT Symposium, No. 214