What is the purpose of pickling white corundum powder?
Removing metal impurities
During the pulverization process (e.g., roller grinding), metal impurities such as iron, nickel, and chromium may be introduced due to equipment wear, or small amounts of metal oxides (such as Fe₂O₃) may remain in the raw material. Pickling typically uses acidic solutions such as hydrochloric acid (HCl) and sulfuric acid (H₂SO₄) to dissolve the metal or metal oxide into soluble salts through a chemical reaction. For example:
Iron impurities react with hydrochloric acid: Fe + 2HCl = FeCl₂ + H₂↑
Iron oxide reacts with hydrochloric acid: Fe₂O₃ + 6HCl = 2FeCl₃ + 3H₂O
Dissolves some non-metallic impurities
Acidic solutions can dissolve small amounts of impurities，further improving the purity of the micropowder.