Corrosion resistance of the titania particles enhanced acrylic resin composite coatings on sintered NdFeB permanent magnets

In this paper, the nanometer titania particles enhanced acrylic resin composite coatings were prepared on sintered NdFeB permanent magnets by cathodic electrophoretic deposition. The microstructure, microhardness and wettability of the composite coatings were investigated. The corrosion resistance of the composite coatings was analyzed by H2SO4 solution immersion test, neutral salt spray test and electrochemical corrosion test, respectively. The results showed that the particles embedded in the acrylic resin matrix increased with increasing the concentration of the titania. At the same time, the microhardness of the composite coatings increased, while the contact angles decreased. Moreover, the particles presented uniformly dispersed distribution over the matrix as the concentration of the titania lower than 20 g/l. The weight loss of the composite coated NdFeB samples immersed in H2SO4 solution was much lower than that of the uncoated NdFeB, and the NSS time of the 20T-coated sample could reach 15 day. The corrosion current density of 20T-coated sample was nearly four orders of magnitude lower than that of the uncoated NdFeB as immersed in 3.5% NaCl for 8 h, and further increasing the immersion time from 24 h to 72 h, the corrosion current density increased, about two orders of magnitude lower than that of the uncoated NdFeB.