Localized corrosion resistance of duplex stainless steels: methodology and properties; a review paper

Author: Peguet L.   Gaugain A.  

Publisher: Edp Sciences

E-ISSN: 1156-3141|108|4|231-243

ISSN: 0035-1563

Source: Revue de Métallurgie, Vol.108, Iss.4, 2011-12, pp. : 231-243

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Abstract

Increasing interest in duplex stainless steels is due to their ability to combine elevated mechanical properties (strength, fatigue...) and an optimal resistance to many types of corrosion like Stress Corrosion Cracking or Intergranular Sensitization. Given high chromium content of the standard and super-duplex steels along with molybdenum and nitrogen alloying additions, they also exhibit an excellent resistance to pitting and crevice corrosion in halide-containing media generally equivalent to austenitic and super-austenitic with similar Pitting Resistance Equivalent. Further aspects of the question are reviewed in introduction of the present paper including passive film and metallurgical features such as two-phase microstructure, presence of non metallic inclusions, precipitates or intermetallic phases. Then, this work addresses the problems of corrosion testing of duplex stainless steels. It is intended in particular to shed light on some points of practical importance regarding electrochemical characterization best practices. Thus, a reliable ranking of materials, including new lean grades, requires a relevant choice of corrosion criteria and polarization methods. The determination of both pitting potentials and critical pitting temperatures is achieved by using a combination of several electrochemical tests based on potentiodynamic, potentiostatic as well as galvanostatic experiments together with a statistical analysis when needed.