Enhanced corrosion resistance of polybenzoxazine coatings by epoxy incorporation

Polybenzoxazine/epoxy composite coating has been developed on mild steel (MS) substrates by a thermal curing method. The reaction between two components was characterized by Fourier transform infrared spectroscopy (FTIR). The effects of incorporating epoxy on the corrosion resistance of coated steel were investigated by open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy, respectively. The resulted composite coated samples exhibit significant enhancement on the corrosion resistance of MS with the corrosion current reduced by more than one order of magnitude, and the enhancement is improved with an increase in the epoxy content, which benefits from the dual crosslinking network of the composite coating through the incorporation of epoxy. In addition to enhancing the coating barrier performance, all coated samples are substantially hydrophobic with a contact angle of above 100 degrees before and even after the polarization measurements.