Eggshell skeleton reinforced, substrate-independent, mechanically robust, and corrosion-resistant superhydrophobic coating

Superhydrophobic materials with interfacial non-wetting and low surface energy properties hold great application potential. However, their practical use is restricted by limited mechanical robustness and the excessive reliance on fluorine-containing reagents. In this paper, we utilized discarded eggshells as a microscale skeleton to design a tri-layer superhydrophobic coating, achieving a synergistic enhancement in both mechanical robustness and anti-corrosive performance. The resulting surface exhibited a static water contact angle (WCA) and a sliding angle (SA) of 151.5 ± 1.3° and 5.0 ± 0.7° respectively. Tests involving 250 sandpaper abrasion cycles and 350 tape-peeling cycles showed that the prepared coating remained its superhydrophobicity, which attests to its outstanding mechanical robustness and effective interfacial adhesion. Additionally, the coating possessed superior self-cleaning and anti-fouling characteristics as well as outstanding anti-corrosion properties. Electrochemical impedance spectroscopy (EIS) further demonstrated a six-order-of-magnitude increase in both the surface charge transfer resistance and the low-frequency impedance modulus. The coating retained its superhydrophobicity without any signs of corrosion after 120 h of neutral salt spray testing and 120 days of outdoor atmospheric exposure, confirming its potential for long-term anti-corrosion applications. Additionally, the designed coating system can be conveniently fabricated on various substrate surfaces, greatly expanding its range of applications.