Ndfeb Electroless Plating Process

NdFeB alloy, the third era permanent magnet, is widely used in electromotor industry and apparatus industry, etc. It has the advantage of distinguished magnetic properties, being machined easily and comparatively low price. But it is prone to be oxidized in common atmosphere, especially be heavily electrochemical eroded at humidity environment. Corrosion becomes the obstruction to broaden applications of NdFeB.In this thesis, anti-corrosion technology of NdFeB was investigated. Based on the thorough comprehension of the character of sintered NdFeB alloy, surface treatment technology was adopted to protect it against corrosion.As part of efforts to overcome this problem, Ni-P alloy was electrolessly plated on the surface of the NdFeB as the protective film. The effects of various pretreatment processes and electroless plating bath on coating properties have been investigated.Results have shown: (1) A better finish is generated by degreasing with alkaline cleaning agents and deoxidizing with 10% nitric acid and proper concentration of corrosion inhibitor and surfactant; (2) It is proved that NdFeB base can't be electrolessly plated directly with the acid plating bath, otherwise, the NdFeB will be badly deteriorated and the plating bath will be out of effect. The composite deposit was obtained from the acid plating bath based on electroless pre-deposite in the presence of alkaline plating bath. The results have shown that the composit coating is very effective for improving corrosion resistance; (3) The P% of the deposits surface is depended on the concentration of the reductant, operation pH and temperature. The corrosion resistance is enhanced by the increasement of the P% of the deposits surface. (4)The effect of heat treatment of non-crystal Ni-P coating was studied. Under the proper heat temperature, the hardness and the wear resistance enhanced with a steady corrosion resistance. (5) Soak tests show that the Ni-P deposits surface has better corrosion resistance to alkaline solution than saline and acid solution.