1. At present, the commonly used method of cleaning corundum crucibles is the acid bubble method, because most of the sintered materials can basically react with acid. Acid bubbles are usually soaked in nitric acid. If the area to be removed is large, the soaking method can be appropriately increased. If the time still cannot be removed, it can be removed with ultrasonic assisted vibration. After cleaning, drying and cooling can be carried out.
2. The nitrate in the corundum crucible can be removed by thermal decomposition, but be careful not to speed it too fast when the temperature is raised to avoid cracking the crucible.
3. For some simple stains and residues, physical methods can be used to remove them. Those that can be easily and simply removed do not need to be too troublesome. For large areas of stains that cannot be removed using too many methods, consider replacing the crucible. After all, the meticulous sintering process will affect the result once some impurities are added.