Preparation and characterization of TiO2/acrylic resin composite coatings on sintered NdFeB permanent magnets by electrochemical deposition

The sintered Nd Fe B permanent magnets are widely used in various industries because of their excellent magnetic and comprehensive properties. However, they are seriously hindered to further developments and applications owing to its poor corrosion resistance. In this paper,TiO2/acrylic resin composite coatings were successfully prepared on the sintered Nd Fe B permanent magnets by electrochemical deposition for the first time, and the corrosion behaviors were investigated by using immersion testing and potentiodynamic polarization tests. It is found that the coating is a composite, being composed of polymerized acrylic resin as the matrix and nano-rutile TiO2particles（-200 nm） as the reinforcements. It is about25 lm in thickness and its surface and cross-section exhibit uniform and smooth with no pores, cracks, and other defects. Compared with those of the uncoated Nd Fe B magnets, the weight loss of the coated samples immersed in H2SO4 solution reduces by two orders of magnitude,corrosion current density decreases by four orders of magnitude, and the corrosion potential of the coated sample is shifted in the noble direction by 400 m V. The mechanisms of corrosive resistance enhancement were discussed.