Abstract
Soft magnetic composites (SMC) have attracted a growing interest since they have the positive points in isotropic magnetic properties and high electric resistivity. They also have the advantage in fabricating complex shape products easily. In this experiment, water atomized iron powder with phosphate insulator coating around its surface was mixed with binder and three kinds of SMC specimens were prepared. The first one is prepared without binder (Sample A), the second one is prepared by using silicon resin as binder (Sample C), and the third one by using thermosetting polyimide (Sample D). In addition, the water atomized iron powder with MgO insulator coating (Sample B) was used, where the silicon resin and Bi-B system glass with low-temperature melting point were used as binder. Using these four kinds of samples, their corrosion behavior were investigated by electrochemical method. In the active zone, Sample D indicated the highest corrosion resistance due to the prevention of anodic reaction. It is because the added thermosetting polyimide prevents the penetration of corrosion solution into the sample. On the other hand, in the passive zone, Sample B showed the highest corrosion resistance due to the formation of uniform passive state film with good quality. It is because the added Bi-B system glass prevents both grain separation and exposure of newly-formed surface to corrosion solution.
