Microstructural Analysis and Surface Modification of a Vitreous Enamel Modified with Corundum Particles

Enamel is a vitreous solidified compound with an inorganic composition, resulting from the melting or sintering of inorganic constituents and designed to form a protective surface layer. This coating develops excellent functional properties that justify its use in industrial applications where extreme environments require materials with good mechanical resistance and corrosion protection: storage silos, chemical reactors, heat exchangers, pipes, valves. In order to improve the coating mechanical resistance, hard particles can be introduced in the formulation of the enamel. Although the composition of these particles has been described in several papers, the influence of the additive size and concentration have not been studied in depth, in particular considering the actual trend in reducing the particles dimension. The aim of this work is the study of the properties modification produced in the vitreous enamel due to the addition of corundum particles (micro and macro) with different size and concentration. The microstructure has been evaluated by optical microscopy and scanning electron microscope. This study shows that the addition of Al2O3 particles modifies the typical enamelled microstructure, increasing the roughness, decreasing the adherence and reducing the closed porosity. These modifications depend strongly on the size and quantity of added particles.