Hydrochloric acid is an important inorganic chemical raw material, widely used in metallurgy, metal processing (steel pickling for rust removal and metal surface treatment), the petroleum industry (oil well acidizing), the chemical industry (production of chlorides, fuels, and synthetic catalysts), pharmaceuticals (drug synthesis and pH adjustment), the food industry (starch hydrolysis and amino acid production), water treatment (water purification), printing and dyeing, leather, etc.