Fluorine-free hydrophobic powder coatings: a sustainable approach using functionalized biogenic SiO2 for anticorrosion and antifouling applications

Superhydrophobic surfaces, known for their exceptional wettability characteristics, have recently attracted significant attention across various fields, including self-cleaning, anti-corrosion, antifouling, biomedical engineering, anti-icing, and oil-water separation. These surfaces, typically achieved through micro-nanostructured roughness and low-surface-energy modifications, offer practical applications in diverse environments. While hydrophobic polymers like Polytetrafluoroethylene (PTFE) and Polydimethylsiloxane (PDMS) have been widely explored, their adverse environmental and health impacts highlight the need for sustainable alternatives. In this study, we developed a solvent-free hydrophobic polyester/epoxy powder coating by incorporating different dosages of Hexadecyl Trimethoxy Silane (HTMS) and Vinyl Trimethoxy Silane (VTMS) functionalized biogenic SiO2 nanoparticles derived from rice husk. To benchmark our results, commercial PTFE was included in the formulation, allowing us to assess the hydrophobic efficacy of the bio-based modifications. The untreated coating initially exhibited hydrophilic properties with a contact angle (CA) of 86 degrees However, the incorporation of silanefunctionalized biogenic SiO2 nanoparticles produced hydrophobic surfaces, with the highest CA of 144 degrees achieved at a 20 wt. % HTMS-SiO2 loading. Further evaluations demonstrated enhanced practical properties, including anticorrosion, antifouling, and self-cleaning capabilities. Notably, while previous efforts in fluorine-free coatings have often relied on energy-intensive methods (e.g., plasma treatment, chemical etching) or non-scalable techniques (e.g., templating), few have combined bio-based additives with industry-relevant, scalable powder coating processes. This work fills that gap by introducing a waste-derived, scalable, and fluorine-free formulation that meets performance criteria for e.g., marine, architectural, and automotive applications. The results demonstrate a facile and sustainable strategy for designing multifunctional coatings, underscoring the real-world potential of biogenic nanomaterials in real-life superhydrophobic surface applications.