Effect of indole functionalized nano-alumina on the corrosion protection performance of epoxy coatings in marine environment

Abstract

The anticorrosive performance of epoxy-indole-modified alumina nanocomposite-coated mild steel was investigated by electrochemical impedance spectroscopy (EIS), scanning electrochemical microscopy (SECM) and pull-off adhesion method in natural seawater. The dispersibility of nano-alumina in the epoxy resin has been enhanced by the functionalization of nano-alumina by indole moiety. The resulting nanocomposite coating enhanced the anti-corrosion and adhesive properties of the coated mild steel. The corrosion protection performance of epoxy resin coating decreased significantly with increase in test time. However, the corrosion resistance and adhesion strength are not significantly decreased for the indole-modified alumina-epoxy coating. The N-O-Al bonds formed by the chemical interactions between -NH functional groups of indole and nano-alumina resulted in good resistance against corrosion. Moreover, the hydrophobic nature of modified nano-alumina prevented corrosive ions to enter into nanocomposite coatings. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) explained the improved protection against corrosion in the presence of the surface-modified nanoparticle. High protection properties and ionic resistances resulted due to the possible chemical interactions between polymeric matrix and surface-modified nanoparticles in nanocomposites. Field emission-scanning electron microscopy/energy-dispersive X-ray (FE-SEM/EDX) analysis was used to examine the surface characterization of the coated sample.