Transpassive Behavior of UNS N08367 Super Austenitic Stainless Steel in LiBr Solution

This study focuses on the transpassivity of super austenitic stainless steel (UNS N08367) in a LiBr solution using electrochemical techniques, i.e., cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy tests combined with the surface analysis technique, i.e., x-ray photoelectron spectroscopy (XPS). The transpassivity of UNS N08367 in 2.5 M LiBr solution corresponds to the dissolution of Cr, Mo, and Ni at high potentials. This study illustrates how the adsorption of intermediate Mo species is responsible for the appearance of an inductive loop in the Nyquist plot at low frequencies. The addition of alloying elements such as Cr and Mo successfully prevents localized corrosion; however, these alloying elements increase the susceptibility of this material to general corrosion by the formation of an anodic film. Nickel does not directly contribute to the formation of passive film in this alloy, as illustrated by the absence of passivation in the CPP curve and by the weak XPS signal on the passive film.