Impact of fluoroalkoxysilane incorporation on the mechanical properties of sol-gel coatings on stainless steel and glass surfaces

Organic–inorganic hybrid sol–gel coatings were prepared using 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-aminopropyltriethoxysilane (APTES) as precursors, with and without the incorporation of a fluoroalkoxysilane. The coatings were applied to stainless steel and glass substrates to evaluate the influence of the fluoroalkoxysilane on the physicochemical and protective properties of the resulting coatings. The GEAN coating, prepared without fluoroalkoxysilane using GPTMS (3-glycidoxypropyl-trimethoxysilane) and APTES (3-aminopropyl triethoxysilane) as precursors, exhibited hydrophilic characteristic with a water contact angle of 74°. In contrast, the incorporation of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) as a fluoroalkoxysilane in the coating composition (GEAND) significantly increased the hydrophobicity, achieving a water contact angle of 111°. In addition to modifying surface wettability, the incorporation of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) significantly enhanced the mechanical properties of the coating, including elasticity, impact resistance, and resistance to deformation. The physicochemical stability and adhesion performance of the coatings under humid and corrosive environments were evaluated through durability testing. The GEAND coating kept its adhesion and structural integrity for up to 720 h (30 days) under humid conditions, whereas the GEAN coating exhibited the loss of adhesion after 120 h (5 days). In salt spray testing, adhesion loss was observed in the GEAN-S and GEAND-S coatings after 24 and 48 h, respectively. These results demonstrate that the enhanced hydrophobicity imparted by the PFOTES-modified GEAND coating contributes to improve resistance to degradation under environmental conditions.