Chemical durability of glazed surfaces

Chemical durability of glazes is previously mostly studied as corrosion of the glassy phase. In this work the focus is on corrosion tendency of the
typical crystalline phases in raw glazes. Fifteen experimental glazes were ball-milled of commercial raw materials. After fast-firing in industrial
kiln and traditional firing in laboratory furnace the glazes were immersed in aqueous solutions of different pH. Changes in the phase composition
of the surfaces were analysed with visual examination, XRD and SEM/EDX applying a procedure allowing to study the same crystal both before
and after immersion. The results indicate that wollastonite type crystals were attacked in all but the most alkaline solutions. Diopside, quartz and
corundum crystals did not show any marked attack. The interfacial layer around feldspar crystals as well as the glassy phase in the glazes corroded
in the most acidic and alkaline environments.