Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Abstract

We investigate the transpassivity of superaustenitic stainless steel UNS N08367 in 2.5 M LiCl solution by using cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The CPP curve exhibits negative hysteresis, which indicates a transpassive dissolution process instead of pitting corrosion. The transition from the passive region to the transpassive region is characterized by EIS and equivalent circuit analysis. During the transpassive dissolution of the N08367 alloy, two reactions of adsorbed intermediates are dominant, as indicated by the two inductive loops at the transpassive region. The first inductive loop is associated with the faster reaction, i.e., the adsorption of Fe intermediates. This fast reaction is significantly influenced by the preferential dissolution of Fe during the transpassive dissolution. The second inductive loop is correlated with the adsorption of the Cr intermediate. In contrast to Fe, the Cr content on the surface increases in the transpassive region compared with the content in the passive region. The XPS spectra support the time and frequency domain approach for the preferential dissolution, and the dominant species resulted from the interfacial processes at the transpassive region.

Investigating the Influence of Cr and Mo Additions to Commercial Ni-Based Alloys Exposed to Neutral and Acidic Chloride Solutions

“…4, is similar to behaviour commonly found on active metal surfaces, generally attributed to coupled electrochemical reactions involving adsorbed intermediates. 1,39 Inductive responses have been reported during the dissolution of Fe-based alloys in acid media 11,[50][51][52][53] as well as for Ni, 54,55 Cr, 56,57 and Mo 58,59 systems. Since all of these elements are found in the studied alloys, inductive responses are to be expected.…”

Transpassive Metal Dissolution vs. Oxygen Evolution Reaction: Implication for Alloy Stability and Electrocatalysis

“…The obtained data are presented in Figures S15 to S20. Based on previous studies on stainless steels, [9a,29] the CrCoNi alloy seems to exhibit a high corrosion resistance without undergoing an apparent secondary passivation in the transpassive regime [30] . At polarizations below the transpassive region (−0.25 to 0.40 V), the EIS data in Figures S15, S16 and S17 indicate a perfectly passivated metal surface with a magnitude of the impedance | Z | = 0.25 MΩ cm 2 at 0.1 Hz.…”

“…Based on previous studies on stainless steels, [9a,29] the CrCoNi alloy seems to exhibit a high corrosion resistance without undergoing an apparent secondary passivation in the transpassive regime. [30] At polarizations below the transpassive region (À 0.25 to 0.40 V), the EIS data in Figures S15, S16 and S17 indicate a perfectly passivated metal surface with a magnitude of the impedance j Z j = 0.25 MΩ cm 2 at Hz. At transpassive polarizations (1.00 V and 1.15 V), Figures S18C and S19 C exhibit an inductive loop in the Nyquist plots, and the currents are mainly impeded by the solution resistance, suggesting increased ion conductivity of the oxide film.…”

Synchrotron XPS and Electrochemical Study of Aging Effect on Passive Film of Ni Alloys

“…The OCP vs time of exposure shows the variation of the potential of a sample as it is submerged in the electrolyte and begins to interact with it. 46 An increasing OCP with time is a typical indication for formation and growth of a protective oxide/hydroxide film on the metal surface. A metal with higher OCP, compared with another metal tested under same conditions, could be considered more noble.…”