Organic-Inorganic Composite Passivation and Corrosion Resistance of Zinc Coated Ndfeb Magnets

Abstract

An organic-inorganic Composite passivation of Zn coated NdFeB magnets is carried out using Ce-containing compound and organosilane as source materials. Effects of silane content on the microstructure of Composite passivation layer are analyzed, and the corrosion resistance and corrosion mechanism of the passivated Zn/NdFeB specimens are deeply studied. Composition, elemental distribution, phase structure and morphology of the specimens are characterized by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. The corrosion resistance of the specimens was studied by polarization curve, electrochemical impedance spectroscopy, neutral salt spray text and mass gain test. Results show that adding an appropriate amount of silane during the passivating process can form a passivation layer combined with Ce, Si, and O. The optimized Zn(CS-1)/NdFeB achieves the highest NSS time of 840 h, which is twice that of single Ce salt passivated NdFeB specimens. Silane can build a framework for the passivation layer and make the passivation layer more compact. During the corrosion process, the corrosion medium invasion path is longer due to the support of the silane frame on the surface, so the corrosion resistance of Zn(CS)/NdFeB is greatly enhanced.

Keywords: NdFeB magnets, Organic-inorganic composite passivation, Zn coating, Corrosion resistance