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Corrosion of stainless steel grades in molten NaOH/KOH eutectic at 250 °C: AISI304 austenitic and 2205 duplex
Author(s) -
Bozzini B.,
Barella S.,
Bogani F.,
Giovannelli G.,
Natali S.,
Scarselli G.,
Boniardi M.
Publication year - 2012
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201106386
Subject(s) - materials science , passivation , eutectic system , austenite , corrosion , metallurgy , electrochemistry , duplex (building) , linear sweep voltammetry , electrolyte , dielectric spectroscopy , cyclic voltammetry , alloy , electrode , composite material , microstructure , chemistry , dna , biochemistry , layer (electronics)
The present paper focuses on the corrosion of an austenitic (AISI304) and a duplex (2205) stainless steel grade in molten KOH/NaOH 50 w/o eutectic at 250 °C. Experimental activities have been performed consisting in electrochemical measurements (linear sweep voltammetry and electrochemical impedance spectrometry) complemented by metallographic (in‐plane and cross‐sectional SEM micrography), structural (X‐ray diffractometry) and compositional (EDX line‐profiles) characterisation of the materials attacked under electrochemically controlled conditions. Electrochemical measurements have shown that AISI304 exhibits a passivating behaviour, characterised by two passivation peaks and a transpassive threshold, while duplex, does not yield a clear indication of passivation. AISI304 was found to fail by intergranular corrosion and to be covered in both passive and transpassive conditions, by an incoherent scale, containing electrolyte species. Duplex samples, instead tends to fail by homogeneous attack and exhibit a range of scale structures, depending on the applied potential.