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Correlation of high-hydrophobic sol-gel coatings with electrochemical and morphological measurements deposited on AA2024

Abstract:

The present paper is focused on studying the behavior of a modified silica sol-gel coating with a high contact angle deposited on AA2024-T3. The sol-gel coating was prepared by the copolymerization of 3-Glycydoxypropyltrimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (TPOZ). During the sol-gel synthetization procedure, commercial fluoro-emulsion solutions (CH and SA) were incorporated at different volume percentages. Prior to the sol-gel deposition by the spin-coating method, the aluminum substrate was ground with commercial sandpaper grit-220. Conventional measurements of the water-drop contact angle give values from 82.6° up to 118.9°. This indicates that the fluropolymer solutions modified the sol-gel's composition. This modification was evidenced by Fourier transform infrared analysis. The rugosity and morphology characteristics were measured by using atomic force microscopy and mechanical profilometry measurements. As the hydrophobic behavior increased, an increment of the rugosity profile was obtained. electrochemical impedance spectroscopy showed the highest protective properties of the sol-gel for the high hidrophobic coating. By means of electrochemical noise measurements, the rescaled range analysis was calculated for all modified sol-gel coatings. These results show that the higher the hydrophobic condition, the lower the fractal dimension. Thus, there is less corrosion activity. A hydrophobic surface modifies the macro-roughness, micro-roughness, and nano-roughness by smoothening the roughness profile. Copyright © 2016 John Wiley & Sons, Ltd.