HYBRID NANOCOMPOSITES AS ANTICORROSIVE ADDITIVES IN WATERBORNE PAINTS

This PhD project is highly interdisciplinary and intersectoral since it is carried out in collaboration between the University of Padua (Industrial Engineering Department and Chemical Science Department) and the industrial partner Colorificio Zetagì. The focus of the project was to develop novel anticorrosive additives. The additives are intended to be used in standard two-component (2K) epoxy and acrylic primers instead of commercially available zinc phosphate (ZP) corrosion inhibitors. The aim of the research come from the limitations of conventional ZP corrosion inhibitors. These inhibitors are widely used, but still show poor performance in waterborne systems due to low solubility and weak dispersion within formulations. Limitations have a direct influence on corrosion performance, which manifests as insufficient long-term protection in artificial chambers (Salt Spray and Continuous Condensation tests) and inadequate barrier properties that can be evaluated by Electrochemical Impedance Spectroscopy (EIS). To overcome these challenges, an innovative strategy is proposed. This strategy included crosslinked polymeric nano-spheres that can act as nanocarriers for zinc-phosphate species. These nano-sized crosslinked particles have the characteristic to swell in good solvents but to remain insoluble. Once swollen, they can be loaded with phosphate and zinc species and incorporated into the primer formulations. The idea was that during the curing time of the coating, the polymer network of the primer would physically interpenetrate with the nano-spheres. This should create a denser and more compact structure of the final coating. That can provide both improved passive protection (better barrier properties) and active protection (through the controlled release of corrosion inhibitor). The research confirmed the hypothesis in 2K epoxy-based primers. Synthetised anticorrosive additives, based on the P4VP@ZP system, significantly enhanced corrosion resistance, both active and passive. On the other hand, in acrylic-based primers, there were pH-related compatibility issues. They influenced corrosion properties, so an additional optimization of the anticorrosive additive is required.