Improved active anticorrosion coatings using layer-by-layer assembled ZnO nanocontainers with benzotriazole

In the present work, a novel approach for the synthesis of nanocontainers by encapsulation has been presented, which are capable of responsive release of corrosion inhibitors (benzotriazole). Nanocontainers have been prepared using layer-by-layer (LbL) assembly of oppositely charged species of polyelectrolytes and inhibitor on the surface of ZnO. Synthesis of nanostructured zinc oxide was carried out initially using the sonochemical precipitation approach. The thickness of the layer, surface charge and functional groups present on each layer were identified using particle size distribution (PSD), zeta potential and FTIR analysis, respectively. The average initial size of the core ZnO was in nanosize range as observed in the TEM image. XRD analysis shows that ZnO contains wurtzite as a major phase. The release properties of polyelectrolyte modified ZnO nanocontainer have been investigated and the observed release rate characteristics show that these nanocontainers would be useful in the multifunctional coating formulations. Responsive release of inhibitor was quantitatively evaluated in water at different pH. Performance of nanocontainers was studied in corrosive environment by incorporating the nanocontainers in alkyd resin. Results of UV-spectroscopy at different pH, corrosion rate analysis and TAFEL plots of nanocontainers coatings on mild steel (MS) panel have been presented. It has been found that electrochemical current density decreased from 0.00355 to 0.0008 A/cm(2), when neat alkyd resin combined with 5% nanocontainers has been used in the coating. Corrosion results from Tafel plot and corrosion rate analysis shows that the 5 wt% loading of nanocontainers is useful and optimum for the sustained release of inhibitor for the applications in the marine coatings irrespective of the operating pH. (c) 2012 Elsevier B.V. All rights reserved.