Magnetocaloric La(Fe,Mn,Si)13Hz Particles and Their Chemical Stability in Heat Transfer Fluids Employed in Magnetic Refrigeration

La(Fe,Mn,Si) 13 H z alloys are prominent solid-state refrigerants for magnetic refrigeration, given their outstanding magnetocaloric properties. However, their chemical stability is yet an issue to be further investigated, especially under the working conditions of magnetic refrigerators. These alloys should not corrode nor lose their magnetocaloric capabilities when in contact with the heat exchange fluids used in magnetic refrigeration. Such topics are addressed in this work by performing immersion tests with La(Fe,Mn,Si) 13 H z particles in two kinds of media: deionized water and deionized water containing a corrosion inhibitor (Entek), the latter medium being an usual heat exchange fluid for magnetic refrigeration. Corrosion products were detected at the surface of the particles after just 15 minutes of exposure in water in the absence of the inhibitor, and corrosion progressed over time, increasing the pH in the surroundings of the particles. After 10 weeks, there were clear signs of surface damage, and the thermomagnetic properties changed as well: the Curie temperature of the particles was shifted to higher values, and the magnetic transition was smeared out. In contrast, no changes were observed in the particles exposed to water containing the corrosion inhibitor for the same period: their microstructure remained stable, the pH of the exposure media did not vary significantly, and their thermomagnetic behaviour remained unchanged. Therefore, the presence of the inhibitor effectively avoided the occurrence of aqueous corrosion and preserved the microstructure and thermomagnetic properties of the La(Fe,Mn,Si) 13 H z particles.