Underwater shear resistance and ventilation drag reduction performance of the fluorosilane-SiO₂ superhydrophobic coating

The air film captured by superhydrophobic coatings underwater can reduce the frictional drag of water flow on surfaces. However, the high shear forces of high-velocity water flow lead to the loss of the surface air film, reducing the drag reduction capability. In this study, a multi-stage structured fluorinated‑silicone resin/hydrophobic-silica composite superhydrophobic coating (FRFUNS) was prepared by cold spraying. The coating exhibited a high static water contact angle of 173.5° and a low sliding angle of 1.2°. The FRFUNS coating surface withstood the shear force of high-speed water flow at 8 m/s for 20 min and achieved a maximum drag reduction rate of 53.5% with 12.8 mL/s air flow rate under 1.0 m/s water flow velocity. Moreover, the coating displayed excellent mechanical performance. It demonstrated a minimum bending radius of 4.2 mm, impact resistance up to 25–50 cm, and adhesion meeting Grade 1 standards. This multi-stage structure and underwater ventilation system, constructed by a simple method, provides experimental evidence for application in fluid engineering fields.