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Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

“Aldo Daccò” Corrosion and Metallurgy Study Centre, University of Ferrara, Via G. Saragat 4A, 44122 Ferrara, Italy
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Metals 2019, 9(5), 529; https://doi.org/10.3390/met9050529
Received: 31 March 2019 / Revised: 2 May 2019 / Accepted: 6 May 2019 / Published: 8 May 2019
(This article belongs to the Special Issue Corrosion Behaviour of Duplex Stainless Steels)
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Abstract

This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times. View Full-Text
Keywords: duplex stainless steel; pitting corrosion; intergranular corrosion; CPT; DL-EPR; FIB-SEM technique duplex stainless steel; pitting corrosion; intergranular corrosion; CPT; DL-EPR; FIB-SEM technique
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Zanotto, F.; Grassi, V.; Balbo, A.; Zucchi, F.; Monticelli, C. Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range. Metals 2019, 9, 529.

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