As we all know, sintered NdFeB is easy to be oxidized and corroded. Over time, it will cause the attenuation and even loss of magnetic properties. Therefore, strict anti-corrosion treatment must be carried out before use. In addition to electroplating, NdFeB surface treatment can also be used chemical plating, electrophoretic coating, phosphating and other methods.
Purpose of Phosphating Treatment
There are two purposes for the phosphating surface treatment of sintered NdFeB permanent magnet, the first is to prevent corrosion as a process, and the second is to improve the surface epoxy infiltration.
1.Process Anticorrosion
Due to the low density and porous characteristics of the sintered NdFeB surface, the exposed magnet will be oxidized in the air, which is also called corrosion. Therefore, because the turnover and storage time of NdFeB magnets is too long, and the subsequent surface treatment method is not clear, the use of phosphating process to do simple anticorrosion treatment is very necessary and effective.
The phosphating process is simple and does not require equipment investment. The production process of phosphating consumes less, mainly consisting of acid, alkali and phosphating liquid. The production cost is low. After phosphating, the color of the product is uniform and the surface is clean. Vacuum packaging can be used to greatly prolong the storage time. The storage method is better than the previous storage method of oil immersion and oil coating. The complete phosphating film can resist the oxidation corrosion of normal atmospheric environment. Subsequent surface treatment of phosphating magnet products is very easy. The phosphating film can be completely removed by simple pickling, which will not have adverse effects on subsequent surface treatment (such as zinc plating, nickel plating, etc.), and the subsequent surface treatment process can be completed at any time.
2.Improve the Infiltration Performance
Some NdFeB magnets need epoxy adhesive bonding and painting. The bonding force of epoxy organic matter such as glue and paint needs the substrate to have good infiltration performance. The infiltration performance of phosphating film and epoxy organic matter is good, so it is necessary to use phosphating process to improve the infiltration performance of NdFeB magnet surface. Good wettability can ensure the bonding force of epoxy glue, epoxy paint and magnet.
