Graphite crucible is an advanced refractory material made of natural scaled graphite, silicon carbide, wax stone and other textures used for smelting and manufacturing copper, zinc, aluminum, lead, gold, silver and various rare metals. Although graphite crucibles are characterized by high bulk density, high temperature resistance, fast heat transfer, acid and alkali corrosion resistance, high temperature resistance and oxidation resistance, cleaning the crucible after use is very troublesome for the refining of individual raw materials.

The first task of cleaning the graphite crucible is to remove the chemicals from the crucible and then clean it. We need to decide what to clean depending on the substances left in the graphite crucible. In general, the binder on the graphite crucible is the residue of inorganic combustion. We can clean it with hydrochloric acid, most of which is soluble, and some residues containing carbon that cannot be dissolved with hydrochloric acid. Nitric acid is highly oxidizing and can be used for cleaning with proper heating.

For substances that are still difficult to remove, they can be boiled with dilute hydrochloric acid or dilute nitric acid. Please note that the hydrochloric acid used should not contain nitric acid, nitrates, halogens and other oxidizing agents. If dilute nitric acid does not clean, clean with molten potassium metabisulfate, sodium carbonate, or borax.

Graphite crucibles need to be kept clean and bright inside and out. After a long burn, the crucible may blur on the outside and penetrate deep inside, causing fragile rupture of the crucible, so unclean material must be removed. If the surface remains stained or darkened, use a fine sand without angles and wipe gently with water to restore the surface gloss.