Magnetic fluid based on mussel inspired chemistry as corrosion-resistant coating of NdFeB magnetic material

Finding durable coating onto NdFeB magnetic material is critical for its usage in harshly corrosive environment. In this report, to the best of our knowledge, magnetic fluid is proposed as the versatile coating to prohibit the corrosion of magnetic material for the first time. Mussel inspired chemistry for polydopamine coating and Michael reaction with addition of dodecanethiol lead to hydrophobic/superoleophilic nanostructured Fe3O4, which is utilized to prepare magnetic fluid. The spontaneous attraction force between NdFeB and magnetic fluid enables fluid as the coating to cover the magnet surface, showing exceptional inhibition effect to underneath metal. When immersed in 3.5 wt% NaCl solution for 30 days, corrosion current density of NdFeB covered with magnetic fluid is only 1.74 × 10−3 mA/cm2, which is approximately three orders of magnitude lower than that of bare NdFeB with corrosion current density 1.01 mA/cm2. Even after exposure for 8 days in more severe condition acidic, salt spray environment, magnetic fluid achieves the corrosion current density of 1.31 × 10−3 mA/cm2 without the occurrence of corrosion. In contrast, thick rust layer has formed on bare NdFeB during the same exposure period. Moreover, magnetic fluid covering on NdFeB behaves excellent self-healing property. Even being abraded and cut for multiple times, magnetic fluid still performs prominent corrosion inhibition to NdFeB, illustrating exceptional resistance to external mechanical damage.