Abstract
Duplex stainless steels (DSSs) consist of ferrite and austenite phases with approximately equal volume fraction. They exhibit combined superior mechanical strength and corrosion resistance, therefore are increasingly used in various applications. However, under certain conditions, passivity breakdown may occur, leading to corrosion initiation, which is often related to weak points in the heterogeneous microstructure. To understand the influence of microstructure on the passivity and breakdown of DSSs requires local probing techniques that can be used in situ, so that corrosion initiation process can be correlated to the microstructure. Recent studies employing advanced scanning probe microscopy and synchrotron-based techniques, in combination with electrochemical measurements, have contributed to a deep understanding of the passive film, passivity breakdown, and corrosion initiation of DSSs, as well as the influence of microstructural and environmental factors. This mini review presents a short summary of recent literature focusing on the studies utilizing local probing techniques and synchrotron-based analyses.
Highlights
Duplex stainless steels (DSSs) contain ferrite and austenite phases with approximately equal volume fraction
Influence of Microstructure on Localized Corrosion Initiation Effect of nano-sized precipitate Cr nitrides in DSSs on their corrosion behavior was studied by electrochemical polarization and in-situ atomic force microscopy (AFM) measurements in 1M NaCl solution (Bettini et al, 2013, 2014). 2205 DSS exhibited a passive behavior despite of quenched-in Cr nitrides present in the ferrite, and preferential ferrite dissolution only occurred under transpassive conditions
The results show that finely dispersed quenched-in Cr nitrides in the ferrite do not cause localized corrosion, but elevated temperature can trigger localized corrosion initiation (Bettini et al, 2013). 2507 DSS at room temperature remained stable in a wide potential range of applied potential despite of presence of the Cr nitrides
Summary
Duplex stainless steels (DSSs) contain ferrite and austenite phases with approximately equal volume fraction. Influence of Microstructure on Localized Corrosion Initiation Effect of nano-sized precipitate Cr nitrides in DSSs on their corrosion behavior was studied by electrochemical polarization and in-situ AFM measurements in 1M NaCl solution (Bettini et al, 2013, 2014).
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