Passivation is a method to transform the metal surface into a state that is not easily oxidized, and to delay the corrosion rate of the metal. In addition, the phenomenon of an active metal or alloy in which the chemical activity is greatly reduced and becomes a noble metal state is also called passivation. If the corrosion product generated by the metal due to the action of the medium has a dense structure, forming a thin film (often invisible), which tightly covers the surface of the metal, it will change the surface state of the metal and become a corrosion-resistant passive state. Passivation treatment is the last process step in chemical cleaning, which is a key step, and its purpose is to prevent corrosion of materials. For example, after the boiler is pickled, washed with water, and rinsed, the metal surface is very clean, very activated, and easily corroded. Therefore, passivation treatment must be carried out immediately to form a protective film on the cleaned metal surface to slow down corrosion. Advantages of passivation 1) Compared with the traditional physical sealing method, after passivation treatment, it has the characteristics of absolutely not increasing the thickness of the workpiece and changing the color, improving the precision and added value of the product, and making the operation more convenient; 2) Due to the passivation The process is carried out in a non-reactive state, and the passivating agent can be added repeatedly, so the service life is longer and the cost is more economical. 3) Passivation promotes the formation of a passivation film with an oxygen molecular structure on the metal surface, which is compact and stable in performance, and has a self-repairing effect in the air at the same time. Therefore, compared with the traditional method of applying anti-rust oil, the passivation formed The passivation film is more stable and corrosion resistant.