Cardanol‐based polybenzoxazine coatings: Crosslinking structures, hydrophobicity and corrosion protection properties

Abstract

Two bio‐based polybenzoxazine coatings, cardanol/3‐aminopropyltriethoxysilane‐based polybenzoxazine (PC‐aptes) and cardanol/stearylamine‐based polybenzoxazine (PC‐s), were prepared for corrosion protection on mild steel. The structures of polybenzoxazines were characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT‐IR). Due to the presence of long hydrocarbon chains and hydrogen bond networks, the PC‐aptes and PC‐s coatings showed high hydrophobicity, with static water contact angles of 106.0 ± 0.6° and 104.8 ± 1.6°, respectively. It was noted that the silane‐functionalized PC‐aptes coating had a dual‐crosslinked network of polybenzoxazine and polysiloxane, which could effectively inhibit the penetration of corrosive media. The results of electrochemical impedance spectroscopy (EIS) indicated that the PC‐aptes coating with higher crosslinking density exhibited superior corrosion resistance compared to the PC‐s coating.