Fabrication of superhydrophobic bio-based polybenzoxazine/hexagonal boron nitride composite coating for corrosion protection

Abstract

Superhydrophobic coatings have attracted much attention in the field of anti-corrosion due to their excellent water repellency. In this work, a superhydrophobic bio-based polybenzoxazine/hexagonal boron nitride composite coating was fabricated for the corrosion resistance of mild steel (MS). Hexagonal boron nitride (h-BN) particles were introduced into cardanol/stearylamine-based benzoxazine (C-s) to construct a rough surface and enhance the stability of the coating. Gallic acid (GA), a natural polyphenol, was used as a curing agent to catalyze the ring-opening polymerization of benzoxazine. The differential scanning calorimetry results showed that GA could reduce the curing peak temperature of C-s from 260 °C to 173 °C. The as-prepared superhydrophobic coating (PC-s/GA/BN), of which the static water contact angle was 158.2 ± 2.4°, could withstand temperature treatments of −20 °C to 250 °C or acid/alkali immersion of pH values from 1 to 11 for 1 h. Furthermore, the PC-s/GA/BN coating could still maintain outstanding corrosion resistance after being immersed in 3.5 wt% NaCl aqueous solution for 30 days. This kind of stable superhydrophobic benzoxazine-based coating has great potential in the field of anti-corrosion.