The use of an acid solution to remove scale and rust from steel surfaces is called pickling. It's a way to clean metal surfaces. Usually with pre-passivating treatment.
The parts are generally immersed in an aqueous solution of sulfuric acid or the like to remove thin films such as oxides on the surface of the metal. It is the pre-treatment or intermediate treatment of electroplating, enamel, and rolling processes.
Iron oxides (Fe3O4, Fe2O3, FeO, etc.), such as scales and rust, chemically react with the acid solution to form salts that are dissolved in the acid solution and removed.
Pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid, and mixed acids. The most commonly used are sulfuric acid and hydrochloric acid.
Pickling processes include impregnation pickling, jet pickling, and acid rust removal. In general, the impregnation pickling method is generally used, and the spray method can be used in mass production.