Fabrication of Epoxy Composite Coatings with Micro-Nano Structure for Corrosion Resistance of Sintered NdFeB

Abstract

A novel micro-/nano-structured coating for corrosion resistance of sintered NdFeB was constructed based on the synergetic effect between the “bridge” structure of nanoparticles and the “labyrinth effect” of micro-/nanoflakes. Iron-titanium nanopaste (ITNP) and micro-/nanoflake silver powder (MNFS) were added into epoxy resin to prepare an epoxy micro-/nano-composite coating material, and then the prepared composite coating material was coated on sintered NdFeB permanent magnets by air spraying, obtaining an epoxy composite coating with a micro-/nanostructure. The effect of the micro-/nanomaterials on the microstructure and corrosion resistance of the composite coatings was investigated, and the mechanisms of the enhancement in corrosion resistance were proposed. The results show that when immersed in 3.5 wt.% NaCl solution for 32 days, the ranking of the capacitive time constant radius and impedance modulus of the coatings at a lower frequency (Zf = 0.01 Hz) is pure EP < EP/ITNP < EP/MNFS < EP/ITNP/MNFS, respectively, and the salt spray test time of the EP/ITNP/MNFS coating is more than 720 h, which is more than twice that of the pure EP coating.