The graphite crucible has the advantages of large bulk density, high temperature resistance, fast heat transfer,resistance to acid and alkali erosion ,high temperature strength and high oxidation resistance, so the graphite crucible is often used to prevent corrosion. Although the graphite crucible with acid alkali resistant ability, but for individual raw materials refining,the cleaning of the crucible after using is very troublesome.
The first cleaning work of the graphite crucible is cleaning the chemical substance out from the crucible and then we continue to clean, we decide which kind of material will be used to clean the graphite crucible according to the material what’s the residual material in the crucible, generally,the attachment on the graphite crucible is the residue after inorganic firing,most of them can be dissolved ,we can use hydrochloric acid to clean it up,some graphite crucibles contains carbon residue, it is not dissolved using hydrochloric acid , we can use nitric acid clean it because the nitrate has strong oxidation, we can heat the graphite crucibles properly when we clean it .
For those materials which need to be cleaned up in the graphite crucible , we can boil then in dilute hydrochloric acid or nitric acid, but we need pay attention to the hydrochloride , it may not contain nitrate, nitrate and halogen oxidant. We use potassium metabisulfite, sodium carbonate or borax molten cleaning If it still can’t be washed by the dilute nitric acid.
The graphite crucible need to keep clean, and it should be bright,the crucible may look dull after long after burning,it will goes into the inner of the graphite crucible result its rupture, and therefore we must clear the dirty materials. If there is still a stain or surface hair black, we soak the 100 mesh fine sand which has no sharp edges and corners by the water to rub the graphite crucible gently so that the surface to restore luster.