Research On NdFeB Electroless Plating Ni-P-Al₂O₃ Alloy

NdFeB alloy as the third-era permanent magnetic material is widely used in many industries because of its outstanding properties, such as excellent magnetic properties and machinability, and comparatively in damp heat atmosphere, which leads to a severe electrochemical corrosion. Poor corrosion resistance is the obstruction to broaden applications of NdFeB alloy. In this thesis, reports on corrosion mechanism and anticorrosion treatment of NdFeB are reviewed. On this basis, electroless plating of Ni-based alloy is employed to NdFeB Magnet to enhance its corrosion resistance.In this paper, samples with electroless plating coating are made after fore treatment, alkali plating, acidic plating and passivating treatment. The orthogonal design is used in the alkali plating and acidic plating experiments. And the corrosion resistances of Ni-P-Al2O3 composite coatings are examined and evalued by polarization curve measured. And its components are analysed by XRD and SEM. At last, its micro-hardness, wear reisitance, binding force, porosity and deposition rate are studied in this paper.Results show that the Ni-P-Al2O3 composite coatings made by the optimizing technology during 20 min for alkaline plating,30 min for acid plating and 10 min for passivation, has higher micro-hardness and wear resistance than Ni-P coatings and it porosity is close to 0. When the Ni-P-Al2O3 composite coating is immersed in the 3.5 wt% NaCl solution it doesn't rust. So the coating layer has fine corrosion resistances.