Achieving Strong Corrosion Protection for Magnetic Refrigeration Materials via Electroplated Nickel Coatings

Abstract Magnetic refrigeration based on magnetocaloric effect (MCE) is considered to be a new generation of green refrigeration technology. However, the corrosion of MCE materials caused by water‐based heat transfer fluids hinders its long‐term service application. Traditional compositional regulation method is difficult to ensure a balance between large MCE and high corrosion resistance. Herein, a Ni‐electroplating method is proposed to significantly improve the corrosion resistance while remain the high MCE in typical La(Fe, Si) 13 ‐based (LFS) materials. The self‐corrosion current density of LFS decreases by an order of magnitude from 2.64 × 10 −6 A cm −2 to 5.12 × 10 −7 A cm −2 after nickel coating. Besides the protection of nickel coating, a nanoscale oxide passivation film is formed on the nickel coating surface after immersion in deionized water, which further protects the sample from corrosion. The LFS/Ni shows a very low corrosion rate of 0.0347 g m −2 h −1 after immersion for 60 days, ≈80% lower than that of pure LFS. Moreover, the high thermal conductivity ( λ ) of Ni also improves the λ of LFS/Ni 3 times higher than the one before coating. Compared with benchmark Gd and other LFS materials with corrosion modification, LFS/Ni exhibits excellent comprehensive performance in all aspects of MCE, suggesting nickel‐electroplating as an efficient method to promote the long‐term application of magnetic refrigeration.