Effective incorporation of ZnO nanoparticles by miniemulsion polymerization in waterborne binders for steel corrosion protection

A nanohybrid waterborne binder was synthesized by miniemulsion polymerization with the incorporation of ZnO nanoparticles in order to increase the corrosion protection capability. This system was compared to a neat waterborne binder and to a physical blend of the binder with an aqueous ZnO nanoparticles dispersion. The hybrid dispersion was characterized by SEM and TEM, while the corrosion behavior of these latexes was investigated by electrochemical measurements (open circuit potential and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution), evaluating the effect of the incorporation of these nanoparticles into the polymeric matrix. The incorporation of ZnO nanoparticles by blending showed similar behavior to the neat coating despite flash rust reduction on the metal surface. In contrast, the hybrid binder prepared by miniemulsion polymerization has shown the best performance according to the values of pore resistance (R-i ) and coating capacitance (C-c). In general, this study shows how useful can be the miniemulsion polymerization methodology to design hybrid coating formulations, obtaining homogenous distribution of ZnO nanoparticles within the film. Indeed, a heterogeneous distribution can hinder the effectiveness and the corrosion protection capabilities of promising nanoparticles.