Bio-based superhydrophobic coatings from cashew nut for self-cleaning and long-term anticorrosion applications

Cardanol, a by-product from the cashew nut processing industry, has drawn extensive attention for constructing superhydrophobic coating. In this work, cardanol-based epoxy resin and cardanol-based benzoxazine were synthetized using cardanol as starting material. Bio-based superhydrophobic coating was prepared by a spraying method through the thermal curing of cardanol-based epoxy resin and cardanol-based benzoxazine in the presence of hydrophobic ZIF-8 (ZIF-8/PDTS) nanoparticles. The resulting coating exhibited excellent superhydrophobicity with a water contact angle (WCA) of 160.5 ± 1.3° and excellent self-cleaning property. The coating also demonstrated remarkable mechanical property without loss its superhydrophobicity even after experiencing abrasion (33 cycles), tape peeling (100 cycles), high temperature (up to 200 °C), and acidic and alkaline solutions treatment (pH = 1–13). More importantly, the coating on Q235 carbon steel surface had great anti-corrosion performance with the impedance modulus (|Z|0.01Hz) up to 1.4 × 1011 Ω·cm2 at low frequencies. The corrosion resistance of the coating could be repaired by respraying the coating solution. The work provides a valuable preparation strategy for sustainable superhydrophobic coatings from bio-mass cardanol that can be widely applied in the field of metal anticorrosion.