Materials Selection for MgCl₂.6H₂O-based PCM Thermal Energy Storage System Available to Purchase

This paper presents the work carried out in ‘SEHRENE’ (Horizon Europe Project) to select suitable materials of construction for MgCl₂.6H₂O-based PCM (phase change material) thermal energy storage system. Commonly used construction materials, such as carbon steels, often have corrosion rates that limit their use in industrial PCMs. Metals that form passivating oxide films, such as Al, may give lower corrosion rates if fluxing of the oxide does not occur in the molten PCM. There have been suggestions to use Al alloy construction materials in PCM-based thermal energy storage (TES) systems where better heat transfer is essential, and carbon steel where structural integrity and cost-effective construction material is more suitable. This philosophy forms the core of the TES design in the above mentioned project. However, galvanic corrosion between the two dissimilar metals is a concern. To understand this further, carbon steel substrates were coated with Al, cut to expose Al-steel interface, and exposed to molten MgCl₂.6H₂O. The galvanic corrosion performance was determined by examining the cross-sections of specimens post-exposure. The cross-sectional metallographic analysis revealed that corrosion was detectable. However, no significant effect was discernable. The experimental work demonstrated that MgCl₂.6H₂O could be a potential PCM candidate for thermal energy storage system. The study also indicated coatings, such as thermally sprayed aluminum (TSA), could be considered for such applications to mitigate the corrosion issues based on the ease of application, availability, and cost.