The acid pickling and phosphatizing process is a chemical and electrochemical reaction that forms a phosphate conversion film, which is called the phosphatizing film. The main purpose of phosphatizing is to: provide protection for the base metal, to some extent preventing corrosion of the metal; used as a primer before painting to enhance the adhesion and corrosion resistance of the paint film; and to act as a friction-reducing and lubricating agent in the cold working process of metals.