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 degrees 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 degrees 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 x 10 11 Omega & sdot;cm 2 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.