The role of yttrium oxide on the corrosion resistance of BTSE silane films on AA6061

Abstract

Silane films have been successfully used as an alternative to toxic Chromate coatings for the corrosion protection of aluminum alloys. To further improve the performance of these silane films, rare earth elements are used. The present work aims at understanding the role of yttrium oxide for silane films applied on AA6061. The corrosion protection performance of silane film formed in bis-1,2-[triethoxysiyl]ethane silane (BTSE) solution doped with different contents of Y 2O 3 was investigated with potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS). The morphologies of silane film were observed using scanning electron microscopy (SEM). The results of potentiodynamic polarization curves, impedance spectroscopy (EIS) reveal that the presence of small amounts of Y 2O 3 in BTSE solutions can increase the corrosion resistance of the silane films in 3.5% NaCl solution. The formed film does not change the dynamic behaviors of the electrode reaction; it mainly inhibits the cathodic reduction reaction of electrochemical corrosion and acts as a physical barrier for the protection of aluminum alloy. The scanning electron microscopy (SEM) images indicated that the surface morphologies of silane films formed were flat and compact, with high cross-link density, when the contents of Y 2O 3 in BTSE solutions were 10mg/L and 20mg/L.