What Is Hot Plating

There are two kinds of thin plate zinc plating: hot plating and electroplating. The thickness of hot galvanized zinc layer is generally 60~300g/m2 (single side), which is used for parts requiring strong corrosion resistance. The galvanized zinc layer is 10~50g/m2 (single side), which is mainly used for painted parts or unpainted parts with low corrosion resistance requirements.

The hot plating method is divided into flux method and shielding gas reduction method according to the pretreatment method. The flux method is to pickle the annealed steel plate, remove the oxides on the surface, pass through the flux tank containing ZnCl2 and NH4Cl, and then enter the molten zinc tank for galvanizing. The protective gas reduction method is widely used for continuous hot galvanizing of strip steel.

The strip steel is first heated by flame in the preheating furnace to burn off the residual oil on the surface, and at the same time, an iron oxide film is formed on the surface; Then it is heated to 710~920 ℃ in the reducing annealing furnace containing H2 and N2 mixed gas to reduce the iron oxide film into sponge iron. After the surface cleaned and activated strip steel is cooled to a temperature slightly higher than that of molten zinc, it enters a zinc pot at 450~460 ℃, and the zinc layer thickness is controlled by using an air knife. Finally, it is passivated by chromate solution to improve white rust resistance.