Graphite crucibles have the characteristics of high volume density, high temperature resistance, fast heat transfer, acid and alkali corrosion resistance, high temperature strength, and high oxidation resistance. However, during the melting process, additives and impurities in the metal solution will form slag, which will adhere to the crucible wall. Due to the presence of additives in the slag, it will corrode the crucible wall. Therefore, it is recommended to remove the slag once a day. So, what are the cleaning methods?
Special tools should be used to remove the slag in a timely manner before it solidifies. The solidified slag will be difficult to remove, so be careful when cleaning to avoid scratching the crucible wall.
When multi-layer slag solidifies and remains on the crucible wall, it will corrode the crucible, affect its thermal conductivity, and cause cracking during heating expansion, thereby shortening the service life of the crucible.
We can use hydrochloric acid for cleaning, most of which are soluble. Some residues containing carbon components cannot be dissolved with hydrochloric acid. In this case, nitric acid can be used for cleaning because it has strong oxidizing properties and can also be heated appropriately during cleaning.
For substances that are still difficult to clean, they can be boiled in dilute hydrochloric acid or dilute nitric acid. Note that the hydrochloric acid used must not contain nitric acid, nitrates, halogens, or oxidants. If the dilute nitric acid cannot be cleaned yet, use potassium pyrosulfate, sodium carbonate, or borax to melt and clean.
Graphite crucibles need to be kept clean, both inside and outside should be bright. After long-term burning, the surface of the crucible may become dull and dull, and over time, it will penetrate into the interior, causing the crucible to become fragile and rupture. Therefore, it is necessary to remove any unclean substances. If there are still stains or black spots on the surface, use fine sand that has passed through the sieve without sharp edges, and gently rub with water to make the surface shiny.