The adsorption and dissolution properties of iron surfaces in liquid lithium and lead under a fusion environment

Abstract

Liquid lithium (Li) and lead-lithium (Pb–Li) eutectic alloy in fusion devices could result in the degradation of iron (Fe)-based structural materials due to the dissolution corrosion. However, the properties and underlying mechanism of the dissolution corrosion are not well understood. By performing first-principles calculations, we investigate the dissolution corrosion of steels in liquid Li and Pb through energetics evaluation on the adsorption of Li and Pb atoms and the escape of Fe atoms on Fe surfaces (001), (110) and (111). Our energetics results indicate that both Li and Pb atoms energetically prefer to adsorb on the considered Fe surfaces, and further accelerate the escape of surface Fe atoms. The dissolution corrosion related to the adsorption and escape processes exhibits strong dependence on surface structures, the coverage of adsorbed Li or Pb atoms, and the temperature of working environment. In liquid Li, the intensity of the dissolution corrosion of the Fe surfaces can be ordered by (110) < (001) < (111) due to their surface structure properties, such as the coordination numbers. The increasing coverage of Li atoms increases the escape probability of Fe atoms from the surfaces, which could lead to severe dissolution corrosion. Moreover, increasing temperature aggravates the dissolution corrosion by promoting the adsorption of Li atoms from liquid phase on the surfaces. In liquid Pb, the dissolution corrosion of Fe surfaces is also surface structure, coverage and temperature dependent, however, is severer than that in liquid Li. Finally, the dissolution mechanism of Fe surfaces in Pb–Li alloys is proposed based on the dissolution properties in liquid Li and Pb.