Composite coatings with polymeric modified ZnO nanoparticles and nanocontainers with inhibitor for corrosion protection of low carbon steel

Incorporation of zinc oxide (ZnO) nanoparticles and ZnO based nanocontainers with corrosion inhibitor Safranin into the matrix of standard zinc coatings is applied for preparation of coatings with improved corrosion protection for mild steel. A cationic polyelectrolyte polyethylenimine (PEI) is used to stabilize the ZnO suspension before electrodeposition of the ZnO nanoparticles on the steel surface. Encapsulation of Safranin is realized in polymer coatings on ZnO nanoparticles prepared using layer-by-layer assembly of polyacrylic acid (PAA) and PEI. The average size and surface charge of the PEI coated ZnO nanoparticles and ZnO based nanocontainers with inhibitor are identified using dynamic and electric light scattering methods and microelectrophoresis. The ZnO nanoparticles or ZnO nanocontainers are electrodeposited on steel (cathode) substrates at pH 7.5 to minimize the effect of ZnO dissolution. In a second step, ordinary zinc coatings are electrodeposited on the ZnO nanoparticles or ZnO nanocontainers covered steel samples from zinc sulfate electrolyte at pH 4.5-5.0. The surface morphology of the coatings and their corrosion behavior are studied by scanning electron microscopy and electrochemical methods potentiodynamic polarization and polarization resistance. The results show better corrosion protection of steel by composite coatings as compare to the bare zinc coating. The composite coating with inhibitor shows better protective characteristics in comparison with the other one. The two-step approach described herein can be used for preparation of composite coatings where preservation of particles functionality is required.