Localized corrosion properties of low interstitial ferritic, high purity austenitic and high chromium duplex stainless steels

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Abstract
Within the framework of a research aimed at characterizing the behaviour of new materials to pitting and crevice corrosion, an investigation has been made, using electrochemical techniques, of the following materials: ELI ferritic stainless steels (18 Cr‐2 Mo‐Ti; 21 Cr‐3 Mo‐Ti; 26 Cr‐1 Mo); high chromium duplex stainless steel (Z 5 CNDU 21‐08) and high chromium‐nickel austenitic stainless steel (Z 2 CNDU 25‐20); commercial austenitic stainless steels (AISI 304 L and 316 L) and laboratory heats of austenitic stainless steels with low contents of interstitials (LTM/18 Cr‐ 12 Ni, LTM/16 Cr‐ 14 Ni‐2 Mo).It was possible to graduate a scale of resistance to pitting and crevice corrosion in neutral chloride solutions at 40 C; in particular the two experimental austenitic stainless steels LTM/18 Cr‐ 12 Ni and LTM/16 Cr‐ 14 Ni‐2 Mo are at the same level as the AISI 316 L and 18 Cr‐2 Mo‐Ti, respectively.An occluded cell was developed and used for determining the critical potential for crevice corrosion (Elocalized corrosion). For the steels under investigation Elocalized corrosionis less noble than Epittingespecially for ELI ferritic 18 Cr‐2 Mo‐Ti and 21 Cr–3 Mo‐Ti.