A Brief Review on the Chemical Stability and Corrosivity of Magnetocaloric Materials

Active magnetic regenerative refrigeration is an energy-efficient and environmentally friendly alternative to conventional vapor-compression refrigeration technology, which is associated with harmful chemical refrigerants and high carbon emissions having high ozone-depleting potential. The core component of AMR is a porous magnetocaloric material that undergoes millions of thermal and magnetic field cycles throughout the device's lifetime, while immersed in a heat transfer fluid. Despite significant research spanning almost four decades, the chemical stability of MCMs continues to pose a critical engineering challenge. In this mini-review, research on the corrosion of room-temperature MCMs is discussed. Particular attention is given to Gd, Gd5Si2Ge2, and La(Fe,Si)(13) and their compositional variants. Following a brief overview of the wide variety of corrosion monitoring methods used to evaluate magnetocaloric regenerator structures, corrosion inhibition mechanisms are discussed in the context of metallurgical, processing, and environmental factors. Finally, challenges associated with corrosion testing of magnetocaloric structures fabricated via additive manufacturing methods are presented.