Robust superhydrophobic epoxy composite coating prepared by dual interfacial enhancement

Superhydrophobic surfaces with special wettability have a promising potential for self-cleaning, anti-fouling, and anti-corrosion applications. However, the practical applications of superhydrophobic coatings are currently limited by their poor mechanical strength and hydrophobic durability. Here, we report a superhydrophobic epoxy (EP) composite coating with improved durability, achieved by a dual interfacial enhancement. First, melt extrusion technology was used to enhance the bonding force between EP and polytetrafluorethylene (PTFE). Then, combining dopamine self-polymerization and sol-gel approaches, the interfacial strength between graphene-polydopamine (GP) and SiO2 was enhanced by in-situ growth of SiO2 on the GP surface. After modification with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS), the superhydrophobic EP-PTFE/GP-SiO2-POTS coating (WCA = 156.3 ± 1.5°, WSA = 3.5 ± 0.5°) was successfully prepared on a steel surface by electrostatic spraying. With the enhanced interfacial strength, the prepared composite coating demonstrated excellent mechanical performance, and could withstand 105 abrasion cycles with only 54.4 mg weight loss. Moreover, due to the induction effect of graphene, a special multilayered nano-micro-nano structure was formed by the evenly distributed nano-SiO2 particles on the coating surface, which is beneficial to extend its superhydrophobic duration. The prepared coating can maintain its superhydrophobicity even after being scratched or immersed in 3.5 wt% NaCl solution for 60 days. Therefore, the prepared superhydrophobic coating demonstrates great potential for application in anti-fouling, drag reduction, and other fields.