NdFeB Magnets: How to improve its corrosion resistance?

Improving the corrosion resistance of NdFeB magnets can be achieved mainly through the following two methods:
Enhance the corrosion resistance of the magnet itself:
Regulate the material composition and organization: By means of alloying, the material composition and organization of NdFeB magnets can be regulated to improve its corrosion resistance. For example, metal elements M1 (such as Cu, Al, Zn, Ga, Ge, Sn, etc.) can be added to the magnet to form Nd-M1 or Nd-Fe-M1 intermetallic compounds; or metal elements M2 (such as Co, Ti, Nb, Zr, V, Mo, W, etc.) can be added to form M2-B or Fe-M2-B intermetallic compounds. These newly formed intergranular phases have higher corrosion potentials than Nd-rich and B-rich phases, reducing the electrochemical difference with the main phase (Nd2Fe14B), thereby weakening the driving force of interphase corrosion.
Reduce the corrosion potential difference: Improve the composition, corrosion potential and conductivity of the intergranular phase to minimize the corrosion potential difference between different phases. This helps to avoid or reduce intergranular corrosion and reduce corrosion current density.
Adding specific elements: For example, adding Al elements. Studies have shown that the addition of Al can form a passivation film, inhibit the oxidation of magnets in the air, and thus improve the corrosion resistance of magnets.
Surface protection treatment of magnets:
Plating coating: Plating coating on the surface of magnets for protection. A protective layer can be formed on the surface of the material by chemical conversion, electroplating, chemical plating, electrophoresis, physical vapor deposition, coating organic coatings and other composite coatings. This protective layer can prevent corrosive media (such as O2, H2O or Cl-) from penetrating from the surface to the matrix, thereby protecting the matrix from corrosion.
In summary, improving the corrosion resistance of NdFeB magnets requires consideration of the material design and surface protection of the magnets themselves. Improving the internal structure of the magnet through alloying, reducing the corrosion potential difference, and forming an effective protective layer through surface protection treatment can significantly improve the corrosion resistance of NdFeB magnets, thereby extending their service life and broadening their application range.