Influence of mill additives on vitreous enamel properties

Vitreous enamel coatings have been largely use industrially but few systematic studies have been carried out on the relationship between composition and final properties. The aim of this research was to study the influence of mill additives on the aesthetical, mechanical and chemical properties of black enamel applied by Electrostatic Dry Powder Application. Samples have been prepared maintaining the same base of the frits, color pigments and firing conditions, while different mill additives have been tested. The effect of the four different mill additives and their content on enamel properties was investigated and an additive free sample and a standard sample have been produced as references. Generally the addition of mill additives is essential in controlling the enamel porosity and therefore improving the enamel resistance. Not all the mill additives result to be soluble in the vitreous matrix in the defined firing condition and therefore microstructure of the samples results to differ. Enamel coatings properties were characterized and compared to reference samples by means of surface tests as gloss, color and roughness and their chemical and abrasion resistance was investigated.