Corrosion processes and their influence on the magnetic flux density of FeNbCuSiB alloys

This paper describes the effect of corrosion process in the magnetic flux density of FeNbCuSiB alloys and correlates with the Si content in the alloys and in the surface oxide layer after a corrosion process. The corrosion resistance of FeNbCuSiB alloys was studied by ordinary weight loss tests, the potentiodynamic polarization technique and spectroscopy impedance. The photoelectron spectroscopy was used in order to identify the compositional changes in the surface oxide layer. Two alloy compositions, Fe77.5Cu1Nb3Si2.5B16 and Fe73Cu1Nb3Si16.5B6.5, with different Si content were analyzed in two different conditions, amorphous and crystalline states, respectively. The Fe77.5Cu1Nb3Si2.5B16 alloy displayed lower corrosion resistance than the Fe73Cu1Nb3Si16.5B6.5 alloy. The increase of the Si amount in the alloy composition results in an improvement in the corrosion resistance. The enrichment of the Si content on the surface oxide layer was found to be responsible for the improved corrosion resistance. Losses in magnetic properties depend not only on the Si content but also on the structural state.