Phosphating is the process of forming phosphate chemical conversion film through chemical and electrochemical reactions, and the formed phosphate conversion film is called phosphating film. The main purpose of phosphating is to provide protection for the base metal and prevent the metal from being corroded to a certain extent; Used for priming before painting to improve the adhesion and corrosion resistance of paint film; Used for antifriction and lubrication in metal cold working. Phosphating technology has been applied in industry for more than 90 years, which can be roughly divided into three periods: the foundation period of phosphating technology, the rapid development period of phosphating technology and the wide application period.