High Entropy Alloys Passivation, Dissolution and Corrosion – Tapas2020

High-entropy alloys (HEA) represent an emerging class of materials showing an exceptional combination of physical properties but their development is hindered by their multi-element complexity of their composition. The goal of this project is to identify the role of the individual alloy elements in determining passive film stability and formation kinetics for a family of high entropy alloys. These results should open a path towards the identification of the optimum composition / microstructure for corrosion resistance.

We will use novel state of the art methods such as elementally resolved electrochemical techniques to directly measure in real time the formation of the passive film and its elemental composition. These measurements will be complemented by in situ electrochemical impedance spectroscopy to monitor the electrical properties of the film. Additional studies will be used to monitor the “self healing” or repassivation following a mechanical scratch or electrochemical activation. The role of microstructure on pitting sensitivity will be investigated locally by single capillary electrochemical techniques to inject chemical reagents such as chloride ion into a specific spot.

These experiments will be conducted on a matrix of alloys elaborated in house with variable composition and microstructure. Model passive films will be synthesized on inert substrates (magnetron sputtering) will also be prepared so as to investigate the electrochemical stability and electronic properties of the oxide film independently of the alloy matrix.

This information may be used for an intelligent, mechanism driven navigation through the compositional space of high entropy alloys with the ultimate goal of developing a new high entropy alloy of enhanced corrosion resistance.