Electrodeposition of silane films on aluminum alloys for corrosion protection

In this paper, three types of protective silane films, methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and dodecyltrimethoxysilane (DTMS) were prepared on aluminum alloys AA 2024-T3 by electrodeposition technique. The Reflection-Absorption Fourier Transform IR (FTRA-IR) measurements showed that, the silane films were successfully deposited through chemical bonding between silane agents and Al alloys. Electrochemical impedance spectroscopy (EIS) tests indicated that in comparison with those by conventional “dip-coating” method, silane films electrochemically prepared at cathodic potentials exhibited obviously higher corrosion resistances. “Critical potential” was all observed for each silane system. Silane films prepared at this potential performed the highest corrosion resistance. The scanning electron microscopy (SEM) images indicated a potential dependence of surface morphology of silane films. The highest compactness was obtained at the “critical potential”. Due to the presence of long hydrophobic dodecyl chain in bone structure, DTMS films displayed the highest barrier properties.