Study On Iron Electroplating Technics And Corrosion Resistance Of Sintered NdFeB

Sintered NdFeB permanent magnets possess outstanding magnetic properties such as high saturation, high coercive force and high energy products. It was used broadly as important functional materials in high technology sector. However, sintered NdFeB permanent magnets were corroded in humid environment easily because of the molding technology and its constitution and structure defects. To resolve the poor corrosion resistance and increase the service life of sintered NdFeB permanent magnets, electropating methods were used to provided an inoxidizing coating. Here, electropating Fe alloy were deposited on the surface and then do heat treatment to the pating to improve the anticorrosive of the NeFeB permanent magnets.It is necessary to do pretreatment before electropating on sintered NdFeB surface. These processes include plug process, oil removing process, pickling and activation process. The function of plug process was increasing the binding force of electropating coatings and substrate. However, the experiment result showed that the effect of plug process can’t be exhibited until a period of time. Saponification and emulsification in the oil removing process can bring a clean surface for subsequent processes without decompose the magnets after ultrasonic cleaning2to3minutes in the pH range of9to10and at a temperature of65℃. The picking and activation process of sintered NdFeB permanent magnets should not use the strong acid because it will corrode the magnets, so the weak acid was adopted.Current density and the temperature of plating solution affects electroplating most. It affect elec-troplating layer’s combination, hardness, porosity, surface topography, corrosion resistance and so on.In this work, we do lots of reaserch to study the influence of process parameters on electroplating, and we discover new heatretment to improve the corrosion resistance of NdFeB. The main results are as follows:1. With the increasing of the current density, the hardness and deposition rate increase, while corrosion rate and porosity descend, the surface of the plating surface becomes more and more detailed, the size of grain reduces. bonding strength reaches its maximum when current density is5A/dm2.2. With the increasing of temperature, the deposition rate porosity and grain size increase while micro hardness and corrosion rate reduce. bonding strength reaches its maximum when temperature is80℃.3. The corrosion resistance of the magnet improve greatly when we do suitable oxidation treatment.