On the Depassivation Mechanism of Lean Duplex Stainless Steels and the Influence of the Partitioning of the Alloying Elements

International audienceThe depassivation of UNS S32304, S32202, and S32101 lean duplex stainless steels (DSS) in 26 wt% sodium chloride (NaCl) was investigated by potentiodynamic polarization to understand the selective dissolution processes in localized corrosion phenomena. Results showed that the depassivation of the three grades proceeds in two stages. First, the austenite is the only phase depassivated within the range of no more than 0.3 pH units, providing a single corrosion peak on the polarization curves of the DSS. Subsequently, the ferrite is also depassivated and provides a second corrosion peak at a more cathodic potential. Results are discussed in terms of the partitioning of alloying elements