Effects of conductive polymers in coatings with zinc particles
The optimisation and Zn metal content reduction can be achieved using zinc with a lamellar particle shape and application of conductive polymers. Conductive polymers are expected to enhance the electrochemical effect of zinc metal in paints. Organic coatings with lamellar zinc particles also exhibit better mechanical properties. Optimisation of the amount of zinc lamellar particles could promote a wider use of this material in anticorrosion paints. The conductive polymers used in the work included polyaniline phosphate, polyaniline benzoate, and carbonised polyaniline. A solvent-based epoxy–ester resin served as the binder.
Preparation of model paints
Model paints consisting of this resin and containing different concentrations of polyaniline phosphate, polyaniline benzoate, and carbonised polyaniline were prepared. The paints were tested at the critical pigment volume concentration (CPVC) of Zn dust and at lower Zn dust concentrations, specifically 2% below the CPVC. The paints containing combinations of zinc and a conductive polymer contained the sum of the pigments just below the CPVC of the zinc dust species used. This implies a level of 39% of (PVCZn-lam) for the systems with lamellar zinc and a level of 61% of (PVCZn–sf) for the systems with spherical zinc.
Accelerated cyclic corrosion tests
The pigment volume concentration (PVC) of the conductive polymers in the zinc-containing paints was (based on results obtained previously) 1%, 5%, and 10% in the systems with lamellar zinc and 1%, 5%, 10%, and 15% in the systems with spherical zinc. The organic coatings were subjected to accelerated cyclic corrosion tests and electrochemical measurements. The sample containing polyaniline carbonate (PVC = 1%) and spherical zinc exhibited a significantly lower corrosion rate as compared to that of uncoated steel.
The study is published in: Journal of Coatings Technology and Research July 2019, Volume 16, Issue 4, pp 949–962.