Robust superhydrophobic bilayer coating: Long-term anti-corrosion and anti-fouling resistance enabled by POSS star cross-linking and fluoride-modified SiO2 nanoparticles specific synergies

Durable superhydrophobic coating has become frequently investigated and reported, however, achieving concurrent mechanical robustness, long-term anti-corrosive and anti-fouling functionalities remains a formidable challenge. In this study, a polymer nanocomposite coating was created through the star crosslinking of polyhedral oligomeric silsesquioxane (POSS) and fluorinated polyimide (FPI) prepolymer. Subsequently, a superhydrophobic bilayer was created by using the aforementioned coating as base coating, hydrophobic polyolefin (POA) with high toughness and strong adhesive was selected to binder fluoride-modified SiO₂ nanoparticles (F-SiO₂) to construct robust superhydrophobic topcoat and simultaneously enhance the interfacial bonding between topcoat and base coating. Notably, the bilayer superhydrophobic coating exhibited robust mechanical durability, retaining its superhydrophobicity even after 100 cycles of sandpaper friction and 80 cycles of tape peeling. After a 50-day salt spray test, the superhydrophobic FPI/POSS@POA/F-SiO₂ bilayer coating demonstrated exemplary corrosion resistance, the low frequency impedance modulus (|Z|_0.01Hz) was still as high as 7.04 × 10¹⁰ Ω·cm², which is one order of magnitude higher than that of FPI/POSS-4 coating (3.17 × 10⁹ Ω·cm²) and three orders of magnitude higher than pure FPI coating (1.82 × 10⁷ Ω·cm²). In addition, the superhydrophobic coating also demonstrated self-cleaning and anti-fouling properties. The enhanced comprehensive performance for the superhydrophobic FPI/POSS@POA/F-SiO₂ bilayer coating can be ascribed to the improved compactness and physical barrier resulted from the POSS star crosslinking, as well as the strong inhibitory effect endowed by the robust superhydrophobic surface. This study offers a fresh perspective on the preparation of superhydrophobic bilayer coatings with outstanding long-term anti-corrosive and anti-fouling attributes, showcasing their potential and prospective practical applications.