Biopolymers nanocomposite for material protection: Enhancement of corrosion protection using waterborne polyurethane nanocomposite coatings

Low volatile organic content based, cost effective and simple procedural nanocomposite coatings were prepared by solution blending technique. Waterborne polyurethane dispersion containing nanoparticles of ZnO, modified with biopolymers were successfully prepared and the resulting nanocomposites were coated on mild steel. The coatings with different loading levels of nano ZnO, which was modified with biopolymers of sodium alginate and lignosulfonate were prepared via ultrasonication method. Surface morphology of these nanomaterials were characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM); crystallinity by X-ray Diffraction (XRD) analysis. The effect of incorporating surface modified ZnO nanoparticles on the corrosion resistance of waterborne polyurethane coated steel was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. Also the surface wettability of the composite coating, studied through contact angle suggested that increase in dosages of nanomaterials does not affect the surface wettability of the coating. The results revealed that the increasing percentage of surface modified ZnO in waterborne polyurethane not only promotes the dispersion of the particles but also improves the corrosion performance of nanocomposite coatings. Corrosion results from Tafel plot and impedance analysis showed that the 0.3 wt% loading of ZnO surface modified with lignosulfonate gives better protection than sodium alginate. (C) 2016 Elsevier B.V. All rights reserved.