Refractory paint

Abstract

Compositions of a refractory paint for marking refractory preforms based on corundum, mullite and their mixtures at the stages of molding, firing, and service within a temperature range of 1000–1600°C have been developed. Compositions of oxide mixtures Fe₂O₃-TiO₂-Cr₂O₃-CoAl₂O₄ are used to mark articles fired at a temperature up to 1550°C. Cobalt aluminate is synthesized previously. Articles fired at a temperature of 1550–1600°C are marked with a paint additionally containing at most 1% Fe₂O₃. Firing initiates the formation of solid solutions in the marking material. These solid solutions (frequently of spinel type) exhibit low evaporativity compared to pure oxides, which preserves color brightness and high legibility of the marking pattern. The consistency of the aqueous paint solution and the thickness of the applied marking layer depend on the state of the refractory surface to be marked (density of the surface layer, pore size, and surface roughness). The paint compositions allow marking of the article after molding, drying, preliminary or final firing. Refractory paints have found manufacturing application in casting of refractory alloys for marking melting crucibles, protective nozzles, cases, and other ceramic articles.