The Role of Alloying Elements on Passive Film Evolution in Advanced Ni rich Alloys
Revealed by Synchrotron X-ray Measurements Combined with Chemical and Electrochemical Analyses
Time: Fri 2026-05-29 10.00
Location: F3, Lindstedtvägen 26
Video link: https://kth-se.zoom.us/j/64933209068?pwd=qaXW2YrW5BdkK3sbHyaKbsZ60oALdx.1
Language: English
Subject area: Chemistry
Doctoral student: MSc Josefin Eidhagen , Yt- och korrosionsvetenskap, Alleima AB, S-81181 Sandviken, Sweden
Opponent: Professor Kevin Ogle, Chimie-ParisTech, PSL Research University, CNRS, Institut de Recherche Chimie Paris, Paris 75005, France
Supervisor: Professor Jinshan Pan, Yt- och korrosionsvetenskap; Doktor Ulf Kivisakk, Alleima AB, S-81181 Sandviken, Sweden; Professor Edvin Lundgren, Lund Univ, Div Synchrotron Radiat Res, S-22100 Lund, Sweden
QC 20260429
Abstract
It is better for the planet to use material as long as possible. Corrosion-resistant Ni-rich alloys are used in demanding aqueous environments where long service life and reliable performance are critical. Their corrosion resistance depends on the formation of a thin protective oxide film on the surface, known as a passive film. Under more oxidizing conditions, however, this protective film can change in composition and structure, grow thicker, and eventually lose its protective character, leading to increased metal dissolution.
The aim of this thesis is to improve the understanding of passivation, oxide film evolution, and transpassive dissolution of Ni-rich alloys in aqueous environments, with particular focus on the role of alloying elements. To study these processes, electrochemical methods were combined with complementary techniques such as synchrotron X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GD-OES) to obtain information on oxide composition, oxidation states, and thickness. In parallel, dissolved species in the electrolyte were analyzed by ICP-OES and UV-Vis spectroscopy to provide information on metal release during anodic polarization.
The results suggest that molybdenum and niobium strongly influence how the oxide evolves at higher anodic potentials and confirms that chromium is essential for establishing and maintaining passivity. In Nb-containing alloys, chromium became depleted in the transpassive oxide, while molybdenum and niobium became the dominant oxide-forming species. In the absence of niobium, chromium together with molybdenum instead dominated the transpassive oxide. The results also indicate that molybdenum plays a dual role by contributing both to passive film stability and to dissolution-related processes in highly oxidizing environments. These findings provide new insight into the role of alloying elements, supporting material selection and alloy development for aggressive environments.
Overall, this work shows that passive film evolution on Ni-rich alloys is controlled by synergistic interactions between alloying elements, which influence selective oxidation, oxide growth, and metal dissolution. Transpassive behavior should therefore be understood not simply as a breakdown of the passive film, but as competition between continued oxide formation and dissolution. These findings provide new insight into the role of alloying elements, supporting material selection and alloy development for aggressive environments.