Selective dissolution and stress corrosion cracking susceptibility of austenitic and duplex stainless steels in sodium sulfide containing alkaline solutions

Heikki Leinonen, Pekka Pohjanne, J. Romu, T. Saukkonen, T. Schildt, H. Hänninen

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

    2 Citations (Scopus)

    Abstract

    The role of de-alloying in stress corrosion cracking (SCC) of the austenitic EN1.4301 (UNS S30400) and duplex stainless steels EN 1.4362 (UNS S32304) and EN 1.4462 (UNS S32205) was evaluated in simulated hot liquor environments.
    The samples were tested at 190ºC using U-bend specimens in 100 g NaOH + 55 g Na2S and 15 g NaOH + 150 g Na2S caustic environments simulating hot white (HWL) and hot black (HBL) liquors, respectively. SCC and general corrosion was detected in the steel surface layers.
    In austenitic stainless steels, severe cracking was observed throughout the samples in both solutions. In duplex stainless steels, cracking was observed only in the affected surface layer in both solutions. In EN 1.4301 steel, selective dissolution of Fe and Cr and enrichment of Cr, Ni, S, O and Na was observed in the affected surface layer and on the wakes of the large SCC cracks depending on the solution. In HWL, Na was clearly enriched and Cr was both selectively dissolved and enriched at different parts of the affected surface layers.
    In HBL, Na enrichment was lower and Cr was selectively dissolved in the affected surface layers.
    In the duplex stainless steels EN 1.4362 and EN 1.4462, dissolution of Fe, Cr and Mo and/or enrichment of Ni, Cr, Mo, Na, S and O took place depending on the steel and test solution. Cr content of both steels remained unaffected in HBL.
    In HWL, Cr was enriched in the surface layer in the Mo-alloyed steel (EN1.4462) and remained unaffected in the non-Mo-alloyed steel (EN 1.4362).
    In HWL, Mo dissolved selectively from the affected surface layer, whereas in HBL Mo enriched in the surface layer in the Mo-alloyed steel.
    Na was enriched in the affected surface layer of both duplex stainless steels immersed in HWL.
    Original languageEnglish
    Title of host publicationCorrosion conference and expo 2012
    PublisherNational Association of Corrosion Engineers (NACE)
    Pages1364-1375
    Volume2
    ISBN (Print)978-1-6227-6078-7
    Publication statusPublished - 2012
    MoE publication typeA4 Article in a conference publication
    EventCorrosion conference and expo 2012: NACE International corrosion 2012 conference and expo - Salt Lake City, United States
    Duration: 11 Mar 201215 Mar 2012

    Publication series

    SeriesNACE - International Corrosion Conference Series
    ISSN0361-4409

    Conference

    ConferenceCorrosion conference and expo 2012
    Abbreviated titleCORROSION2012
    Country/TerritoryUnited States
    CitySalt Lake City
    Period11/03/1215/03/12

    Keywords

    • Alkaline solution
    • EDS analyses
    • selective dissolution
    • sodium sulfide
    • stainless steel
    • stress corrosion cracking

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