Corrosion-resistant coatings in molten salts suggested by computational phase-stability diagrams

Abstract

Molten salts enable numerous industrial applications, yet trace impurities such as moisture accelerate corrosion despite the salts’ chemical stability. Existing phase stability diagrams, often useful for corrosion analyses, disregard such impurities, underscoring the need for an impurity-aware, holistic framework. Here, we present a computational framework for impurity-inclusive phase stability diagrams in molten salts. Using chloride melts as model systems, we demonstrate three-dimensional stability maps with pO2- and pH as the coordinate plane, revealing how moisture and oxygenated species influence the phase stability of structural materials. Applied to 56 Fe-, Cr- or Ni-containing binary systems, these diagrams quantitatively predict that boriding or siliconizing markedly improves the corrosion resistance of Fe and Cr, and provide explicit purification targets for molten chlorides. The predictions are verified with electrochemical characterizations and static corrosion tests. Our results provide a practical guide to designing molten salt-stable materials or synthesis protocols in molten salts.