TY - CONF A1 - Wetzel, Annica A1 - Morell, D. A1 - Ozcan, Ozlem A1 - Witt, Julia T1 - The Interplay of Anodic Passivation and Oxygen Evolution of Medium Entropy Alloys in Aqueous NaCl Electrolytes at Different pH N2 - Due to their favorable mechanical and anti-corrosion properties, medium entropy alloys (MEA) are of high academic and industrial interest as novel materials for engineering and catalytic applications. Previous studies on general corrosion behavior indicate high current densities at high anodic potentials for MEAs. Further investigations of the underlying transpassive dissolution and local corrosion behavior remain scarce. To understand the passivation behavior of MEAs CrCoNi and FeCrNi at high anodic potentials, the mechanisms of transpassive dissolution and the oxygen evolution reaction were investigated in this project. Scanning electrochemical microscopy (SECM) was applied in the interrogative mode for the detection of evolving metal species and oxygen. By means of ICP-MS analysis, dissolved metal species were quantified to provide a fundamental understanding on the transpassive dissolution. As the oxygen evolution reaction (OER) may contribute a large percentile to the observed current at high anodic potentials, SECM measurements were employed to analyze the onset of the OER. Potentiodynamic, potentiostatic and chronoamperometric techniques as well as different electrolytes were used to induce precisely controlled corrosion loads during the SECM experiments and for the ICP-MS analysis. Macroscopic corrosion properties of the alloys, electrical and chemical properties of the passive films were studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and X-Ray Photoelectron Spectroscopy (XPS), respectively. Finally, the analysis of the corrosion morphology and the potential of the surface before, during and after passivity breakdown was carried out by means of in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The presentation will summarize our results on the interplay of anodic passivation and oxygen evolution of MEAs in aqueous NaCl electrolytes. T2 - MRS Spring 2023 CY - San Francisco, California, USA DA - 10.04.2023 KW - Chemically Complex Materials KW - CCMat KW - Corrosion PY - 2023 AN - OPUS4-59405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -