Superhydrophobic Self-Cleaning Hierarchical Micro-/Nanocomposite Coating with High Corrosion Resistance and Durability

Due to their special wetting properties, bioinspired superhydrophobic coatings are used to protect various materials. However, contamination with corrosive liquids or mechanical damage causes the loss of water repellency of many superhydrophobic surfaces. Therefore, it is imperative to develop chemically stable and durable superhydrophobic coatings. In this work, we report a straightforward method to fabricate a metal–organic framework (ZIF-8)/SiO2 with hierarchical micro-/nanostructures, whose surface hydrophobicity is induced by polydimethylsiloxane (PDMS) modification. Notably, the surface of the resulting ZIF-8@SiO2/PDMS displays superhydrophobicity, together with a water contact angle (CA) of 157°. The superhydrophobic material is chemically stable, the water CA remaining above 150° even after exposure to a wide range of pH values (1–14) for 24 h. The electrochemical results showed that the coating exhibits a high corrosion potential (Ecorr = −0.321 V) and a very low corrosion current density (icorr = 1.442 × 10–11 A·cm–2) relative to an uncoated aluminum substrate (Ecorr = −0.711 V, icorr = 6.616 × 10–5 A·cm–2), indicating a high resistance to corrosion as a result of the coating. Also, electrochemical impedance spectroscopy showed that the charge transfer resistance is significantly increased by the coating. These results indicate that the ZIF-8@SiO2/PDMS coating with superhydrophobic properties has excellent corrosion resistance. In addition, the superhydrophobicity was proven for various droplets (i.e., water, tea, milk, coffee), an achievement related to the excellent self-cleaning performance: when the droplets roll off, surface contaminants are easily removed. The coating exhibited good mechanical properties, the CA being above 150° after 100 cycles of scrubbing with a pressure of 20 kPa. These excellent properties recommend the obtained superhydrophobic coating for various practical applications.