A rapid corrosion screening technique for grade 2707 hyper‐duplex stainless steel at ambient temperature

• Published in: Materials and corrosion 2024-02, Vol.75 (2), p.227-234
• Main Authors: Zhou, Yiqi, Cao, Xiaoying, Mahmood, Sultan, Engelberg, Dirk Lars
• Format: Article
• Language: English
• Subjects: Ambient temperature; bipolar electrochemistry; Duplex stainless steels; Electrochemistry; Ferrite; hyper‐duplex stainless steel; Kinetics; modified bipolar electrochemistry; Nucleation; pitting corrosion; Potential gradient; Test sets
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.202313943

The pitting corrosion behaviour of 27%Cr–7%Ni (2707) hyper‐duplex stainless steel (HDSS) at ambient temperature has been assessed using a novel bipolar electrochemistry test set‐up. Application of this technique generates a linear potential gradient at the surface of the HDSS 2707 test piece, which allows assessment of the pitting corrosion behaviour at ambient temperature. Pit nucleation and associated growth kinetics can be obtained and characterised. To assess pitting corrosion in high‐alloyed HDSS, the normal bipolar test method had to be modified by superimposing an auxiliary potential. This new test set‐up was demonstrated by characterising the nucleation of pits and associated pit growth kinetics. The latter occurred either at austenite/ferrite interphase or inside ferrite phase, with pit growth within the ferrite phase in the HCl environment. The method of modified bipolar electrochemistry, which involves the addition of an auxiliary potential, has been effectively employed for assessing the pitting corrosion of the hyper‐duplex stainless steel 2707 at ambient temperature. The pits are initiated at the junction of austenite and ferrite or inside of ferrite, then, propagate by consuming the ferrite.