Pinturas pigmentadas con magnetita dopada: evaluación preliminar de propiedades anticorrosivas

Abstract

Pure magnetite and magnetite doped with three different concentrations of chromium and copper was lab synthesized. The relative performance of these products as anticorrosive pigments is compared with commercially available hematite (red iron oxide). Special mixtures of the pigments with a solventless epoxy binder were prepared maintaining the pigment volume contents near the practical critical value. The purpose was to distinguish the inhibitive action of pigments with the least possible influence from the barrier properties of the epoxy resin. The performance of mixtures applied on mild steel is characterized in accelerated outdoor exposure, in alternated immersion tests and in total immersion conditions. The latter test was monitored with open circuit potential and impedance measurements. Complementary tests with freestanding films were also performed. The results show that magnetite is not an inert pigment. Therefore presence of doping elements can improve the performance of anticorrosive magnetite paints. Based on this result, a complete formulation with pigment, solvent and additives is suggested and preliminarily tested in the lab aiming at producing an anticorrosive primer.