Influence of extender type of performance of modified lamellar zinc primers

Abstract

The objective of this work was to gain a deeper insight into the behavior of zinc primer, containing either lamellar zinc alone or lamellar zinc mixed with an extender by means of accelerated tests in salt spray (fog) chamber and a 100% relative humidity cabinet. Mica, kaolin, and synthetic calcium silicate were used as extenders. Several series of coatings were designed and manufactured employing the following binders: 20 cP chlorinated rubber, a vinyl copolymer, an unsaturated polymer, or an epoxy resin. A simultaneous analysis of the experimental data was performed taking into account that the best performance is attained at pigment volume concentration (PVC) values equal to or slightly lower than the critical one (CPVC). Results indicate that for every lamellar zinc primer, it is possible to select an extender of high oil absorption as the spacer of the zinc particles attaining both very good blistering resistance and anticorrosive performance.