Bio-inspired polybenzoxazine coating: Anti-corrosion and anti-abrasion performance enhancement through monomer design

Polybenzoxazine (PBZ) is a kind of high corrosion-resistant polymer, however, the brittleness and weak adhesion strength of PBZ have puzzled their applications. In this work, we introduced ether amine molecules into benzoxazine monomers via molecule design, and then copolymerized them with tannic acid (TA) to realize flexible PB-TA coating systems, aiming at achieving durable corrosion and abrasion protection for steel structures. It is found that the PB-TA copolymer gains favorable plasticity up to 39.44 % elongation. Meanwhile, TA provides more active sites and stronger hydrogen bond interaction, which increases the crosslinking density of PB-TA coating and achieves a high adhesion strength (13.57 MPa) to the mild steel substrate. Further experiments evidence that the PB-6TA coating (with 6 % mass of TA addition in the PBZ) presents high corrosion resistance (>10 9  Ω.cm 2 after 600 h salt spraying test), far beyond polyurethane and epoxy resin coatings. Also, the PB-6TA coating exhibits a higher anti-friction ability during cyclic wear corrosion test than the pristine PBZ coating. It is expected that this work may help boost the development of polybenzoxazine-based coatings with long-term corrosion resistance in harsh marine environments.