Electrodeposited Metallic Coatings as a Manufacturing Route to Enhance the Durability of NdFeB Magnets

NdFeB rare earth magnets are widely used in high performance applications but suffer from poor corrosion resistance due to their multiphase microstructure and the preferential dissolution of rare earth rich intergranular phases. In this study, the corrosion behaviour of NdFeB magnets was investigated and the effectiveness of galvanic nickel coatings as a protective solution was evaluated. Microstructural and compositional analyses were combined with potentiodynamic polarisation tests, comparing bare and coated magnets with carbon steel. Coating adhesion was assessed by pull off testing according to ASTM D4541. The results show that NdFeB magnets are significantly more susceptible to corrosion than steel, while nickel exhibits a passive behaviour in the investigated environment. Galvanic nickel coatings provide effective protection and display adhesion comparable to that measured on steel substrates, demonstrating their suitability for corrosion protection of NdFeB magnets.