The Interplay of Anodic Passivation and Oxygen Evolution of Medium Entropy Alloys in Artificial Seawater

Abstract

Medium entropy alloys (MEA) have gained increased interest in both academic and industrial sectors due to their favorable mechanical and anti-corrosion properties, rendering them ideal candidates for engineering and potentially catalytic applications. Although previous studies have shown high current densities at high anodic potentials for MEAs, a lack of understanding on the underlying transpassive dissolution and local corrosion behavior remains.This project aimed to investigate and compare the passivation behavior of MEAs CrCoNi and FeCrNi (equimolar) under high anodic potentials, focusing on the mechanisms of transpassive dissolution and the oxygen evolution reaction in artificial seawater. The study utilized various techniques such as scanning electrochemical microscopy (SECM) to instantaneously detect evolving metal species and oxygen, and inductively coupled plasma mass spectrocmetry (ICP-MS) to quantify the dissolved metal species. For these investigations, the alloys were subjected to precisely controlled corrosion loads employing potentiodynamic, potentiostatic, and chronoamperometric methods during the SECM experiments and subsequent ICP-MS analysis.Macroscopic corrosion and passive film properties were studied via potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and X-Ray Photoelectron Spectroscopy (XPS). Finally, in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to analyze the corrosion morphology and surface potentials before, during, and after passivity breakdown. Overall, this study aimed to provide a comprehensive understanding of the interplay between passivation, anodic dissolution and oxygen evolution of the MEAs in artificial seawater.