Why can a porous refractory be unsuitable for contact with corrosive molten materials?

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traditional ceramics Stages in the slip casting of a thin-walled whiteware container. Clay powder is mixed in water together with a dispersing agent, which keeps the clay particles suspended evenly throughout the clay-water slurry, or slip. The slip is poured into a plaster mold, where water is drawn out by capillary action and a cast is formed by the deposition of clay particles on the inner surfaces of the mold. The remaining slip is drained, and the cast is allowed to dry partially before the drain hole is plugged and the mold separated. The unfinished ware is given a final drying in an oven before it is fired into a finished product.

A porous refractory is often unsuitable for contact with corrosive molten materials because its internal structure allows these substances to penetrate the material. While porosity is beneficial for blunting cracks and improving resistance to thermal shock, the presence of air spaces provides pathways for molten liquids to seep into the ceramic. This infiltration can accelerate degradation and compromise the integrity of the furnace lining. In applications such as glass-melting furnaces, where chemical resistance is critical, manufacturers instead produce denser ceramics with minimal porosity to prevent such corrosive damage.1