A Study of the Effect of Different Iron Oxide Pigment Grades on Properties of an Industrial Latex Coating

By Chicago Society for Coatings Technology Technical Committee

Two red iron oxide pigments with similar properties but prepared by different chemical processes were obtained for evaluation. One process provided a pigment described as rhombohedral in shape; the other was described as spheroidal. The pigments were incorporated into an industrial latex coating formulation at the same pigment volume concentration.

Properties of the liquid formulations, wet applied films, dried films, and free films were measured. Representative tests run were viscosity, gloss, adhesion, and prohesion. Differences in the degree of coalescence, accelerated corrosion testing, surface appearance, and mechanical properties were observed.

Based on experimental data, conclusions were made attempting to correlate pigment morphology with coating properties. However, other inherent differences, such as particle size distribution, were found to obscure the singular effect of particle morphology.