Study on Ni-Ni(S)-Ni(P) multilayer coating by friction-assisted jet electroplating on sintered NdFeB

In view of the corrosion failures of sintered NdFeB magnets in engineering, an Ni-Ni(S)-Ni(P) multilayer coating was prepared here via friction-assisted jet electroplating. As a comparison, Ni, Ni(S), Ni(P) single-layer, and Ni-Ni(S)-Ni(P) multilayer coatings were fabricated via jet electroplating without friction. The results revealed that the multilayer coating exhibited better physical and chemical properties compared to the single-layer coatings. After adding friction technology, the surface of the coating was smoother and the original cellular processes disappeared. In addition, the adhesion of the multilayer coating was up to 32.52 N, and the microhardness of the multilayer coatings increased from 557.43 HV to 626.5 HV, which was an increase of 12.39%. In terms of corrosion resistance, the self-corrosion potential of multilayers was up to -0.509 V, and the corrosion current density was as low as 3.564 x 10(-6) A/cm(2). Friction-assisted jet electroplating can effectively protect sintered NdFeB materials. (C) 2019 Elsevier B.V. All rights reserved.