Corrosion Mechanisms and Mitigation Strategies for Materials in Liquid Pb for Thermal Energy Storage at up to 700 °C

Liquid metals have significant potential as heat transfer media in low-carbon green energy technologies owing to their excellent thermal properties, stability at elevated temperatures and high heat transfer efficiency. Among these, liquid lead (Pb) is characterized by its low cost and low vapor pressure. However, the use of liquid Pb at high temperatures presents challenges, particularly with regard to corrosion, which can undermine the long-term performance and reliability of heat storage components. To date, only limited data is available on the corrosion mechanisms of structural materials in liquid Pb, especially at temperatures exceeding 600 °C. To address this, comprehensive corrosion tests have been conducted on a broad range of commercial materials, including austenitic steels, ferritic-martensitic (F/M) steels, non-ferrous alloys, and engineering ceramics. The corrosion tests were performed at an oxygen content of 2x10-7 wt.% at up to 700 °C, over a period of up to 5000 h. Further, corrosion mitigation strategies were studied, such as aluminizing through pack cementation and/or pre-oxidation. Austenitic steels, represented by 316Ti, undergo selective dissolution of austenitic stabilizing elements such as Ni and Mn, resulting in ferritization near the surface and, to a greater extent, liquid metal penetration. ... mehrAluminizing 316Ti has proven to be an effective protection against corrosion at lower temperatures. However, pre-oxidation is required for aluminized 316Ti at higher temperature due to the increased dissolution kinetics. P91, a commercial F/M steel, shows clear evidence of strong oxidation, but aluminizing can effectively mitigate this issue. Al-containing steels (>5 wt.% Al) form a protective alumina scale. Engineering ceramics demonstrate reasonable corrosion resistance. The presentation discusses the influence of chemical composition, microstructure, and pretreatments on the corrosion mechanism of the different types of materials.