Corrosion of Fe-based nanocrystalline alloys with soft magnetic properties

Iron-based nanocrystalline alloys have attracted increasing attention due to their good soft magnetic properties for industrial applications. These alloys combine low magnetic loss, high saturation magnetic flux density, low coercive force, and high permeability, which are important in soft magnetic materials applications. Corrosion not only decreases the service life of soft magnetic materials, creating the need for system replacement, but can also damage the soft magnetic properties of these alloys. This behavior can lead to serious consequences in several applications, e.g., when solenoid valves or magnetic sensors are used for controlling combustible fluids or pressure vessels. Therefore, in the past few years, considerable interest has focused on the effect of microstructure and composition on the corrosion of iron-based amorphous and nanocrystalline alloys and on the effect of corrosion on the magnetic properties of these materials. This paper describes the main families of nanocrystalline Fe-based alloys with soft magnetic properties and discusses their magnetic properties and applications. In addition, the effect of partial crystallization on corrosion resistance is examined, including a critical discussion about the mechanisms reported in the literature. Other points analyzed here are the relationship between nanocrystalline alloy corrosion and composition, the effect of main alloying elements such as Nb, Zr, and No, the effect of corrosion on the magnetic properties of nanocrystalline alloys, and trends for future investigations. The aim of this paper is to review the current body of knowledge about the corrosion of nanocrystalline Fe-based alloys with soft magnetic properties and to highlight the importance of corrosion on the behavior of nano crystalline soft magnetic materials. Copyright © 2010 by ASTM International.