Thermal curing study of bisphenol A benzoxazine for barrier coating applications on 1050 aluminum alloy

Polybenzoxazine coatings were elaborated by dip coating of a solution, prepared from a commercial bisphenol A benzoxazine (BA-a), on a 1050 aluminum alloy. The monomer was dissolved in acetone and the influence of the different application parameters (withdrawal speed and viscosity of the solution) on the wet coating thickness was evaluated. A heat treatment was then performed on the coating to polymerize the benzoxazine monomer by a ring opening mechanism attested for by Fourier Transform Infrared spectroscopy (FT-IR) and followed by Differential Scanning Calorimetry (DSC). Dielectric Analysis (DEA) and Thermogravimetric Analysis (TGA) showed a particular behavior related to a partial decomposition taking place at 180 degrees C and associated with the creation of intermediary ionic and volatile species. Finally, the barrier protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) for 30 days in sodium chloride solution (0.1 M). The results showed an improvement of the impedance modulus from 10(4) Omega cm(2) for an uncoated aluminum to,a value as high as 10(9) Omega cm(2) with a 10-mu m thick polybenzoxazine coating. (C) 2014 Elsevier B.V. All rights reserved.