Fabrication and characterization of alumina-silica/poly(o-toluidine) nanocomposites as novel anticorrosive epoxy coatings films on carbon steel

Alumina-silica/poly(o-toluidine) (POT) nanocomposites were designed from o-toluidine monomer by in-situ polymerization in the existence of nano-Al2O3-SiO2:SiO2 with a different ratio. The structure and the composition of the as-prepared nanocomposites were investigated in terms of Fourier-transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), zeta-potential and nonisothermal differential scanning calorimetry (DSC) methods. Epoxy resin (EP) was blended with the introduced-Al2O3:SiO2/POT composites using a solution combination technique. A qualitative evaluation provided using Cure Index (CI), Al2O3:SiO2/POT/EP nanocomposites can facilitate or hinder curing reaction depending on the different ratios of alumina to silica. The Al2O3:SiO2/POT/EP nanocomposites were painted onto the C-steel substrates, and its corrosion protection characteristics were examined by electrochemical (potential vs. time, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP)) measurements in 1.0 M HCl as corrosive medium and also compared with that of the composite POT/EP coating. The outcomes indicated that the coating systems containing Al2O3:SiO2/POT/EP nanocomposite has higher corrosion resistance than that of individual POT. The protection capacity values of coated systems POT/EP, Al: Si/POT/EP, 2Al:Si/POT/EP and Al:2Si/POT/EP were 75.2, 91.2, 86.7 and 97.5%, respectively. The existence of Al2O3-SiO2 nanocomposites improved the quality of the POT/EP coating by decreasing the porosity of the painting matrix. FESEM observations before and after the corrosion test confirmed that the occurrence of Al2O3-SiO2 nanocomposites improve the protection features of POT/EP coating.