Toward hydrophobicity without surface functionalization through organosilane sol gel coatings on nano-roughed aluminum substrate

Hydrophobic and superhydrophobic coatings can be fabricated through the traditional two-step method, including fabrication of hierarchical micro and nanoscale roughness along with surface modification using low energy materials like fatty acids and fluoropolymers. Using a low energy material is not suitable due to its weak chemical bonding to the surface, and also, some of the used materials are toxic. Herein, a novel method has been introduced to fabricate the hydrophobic coating using the Wenzel wetting model. The aluminum substrate was chemically etched to create the nano-roughed surface structure and subsequent silane-based coatings can lead to increase the water contact angle without using any surface functionalization with low energy materials. In addition to that, two type of silane-based sol-gel coatings (TEOS and TEOS/GPTMS) have been used to investigate the benefits of hybrid organosilane sol-gel coating. The results indicated that the increasing in the surface roughness of silane-based coatings using chemical etching of the substrate leads to increase the water contact angle to hydrophobic state, which is supported by the Wenzel wetting model. The corrosion mitigation behavior of silane-based coatings on different substrate (bare and etched aluminum) has been studied in details.