Microstructural and diffusive properties of Cr solute in MgCl2–NaCl–KCl eutectic: A First-Principles molecular dynamics study

Abstract

The hot-corrosion-related mutual effect between the MgCl2–NaCl–KCl eutectic (MNK) and structural alloy materials is important for next-generation concentrated solar power (CSP) plants. However, little attention has been given to the feedback effect of in-situ corrosion impurities on eutectics, in which the Cr solute is among the most common corrosion products. In this work, first-principles molecular dynamics (FPMD) were introduced to investigate the interaction between the Cr solute and the MNK eutectic. The results showed inhibition of the native covalent Mg2+ bonding priority in the MNK eutectic after the introduction of the Cr solute. An oxidation-state-induced microstructural evolution from a metastable Cr cluster to a stable Cr coordination complex was revealed. The overall native ion diffusion was suppressed by Cr impurities, and the diffusion priority of specific ions was also affected. Furthermore, the valence-dependent intrinsic diffusion of Cr ions in the MNK showed a trade-off relationship with Cr concentration. This work elucidates the effect of the Cr solute on the microstructural and diffusive properties of the MNK eutectic and provides further guidance on experimental and simulation studies concerning Cr-related corrosion in MNK eutectics.