Facile formation of superhydrophobic silica-based surface on aluminum substrate with tetraethylorthosilicate and vinyltriethoxysilane as co-precursor and its corrosion resistant performance in corrosive NaCl aqueous solution

A facile sol-gel method has been developed to create a superhydrophobic surface on aluminum substrate with tetraethylorthosilicate (TEOS) and vinyltriethoxysilane (VTES) as co-precursor at room temperature. Firstly, nanometer sized silica particles were self assembled on the substrate through the hydrolysis of TEOS. Then, the silica particles were modified with vinylsiloxane through the hydrolysis and condensation polymerization of VTES. The emphasis was focused on investigating the influence of the molar ratio between NH3·H2O and ethanol on the surface morphology and wetting property. The surface morphology was observed by scanning electron microscopy (SEM), the chemical composition and bonding state of the surface were explored by energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS), and the wetting property of the surface was investigated by water contact angle measurement (WCA). The modified silica-based surface possessed the greatest static contact angle of 154.9°, exhibiting excellent superhydrophobic property. A hierarchical microstructure with spherical microparticles of around 2 μm decorated with nanoparticles of around 450 nm was observed on the film surface. The surface was covered by hydrophobic vinyl groups via the decoration of silica microparticles with vinyl-terminated siloxane nanoparticles as evidenced by EDS, FTIR and XPS. The corrosion resistant performance and durability of the superhydrophobic silica-based surface formed on aluminum substrate in corrosive NaCl solution were estimated by electrochemical impedance spectroscopy (EIS) measurements. The appropriate equivalent circuit model was put forward to fit and analyze the EIS data. The electrochemical result revealed that the corrosion resistant performance of aluminum was improved greatly by the superhydrophobic treatment.