Among the common steel corrosion control and protection measures, the most economical and effective is to use anti-corrosion paint (coating/plating), and in all paint (coating/plating) systems, zinc-containing paint (coating/plating) is indispensable. So far, its position in the field of heavy anti-corrosion is almost irreplaceable. Zinc is a light gray transition metal with active chemical properties. It can form a thin and dense film on the surface at room temperature to prevent further oxidation. It is precisely because of this film that zinc is widely used in steel, metallurgy, machinery, electrical, chemical and other fields, and it is one of the most important metals in modern industry. Compared with other metals, zinc is a relatively cheap and easily plated metal. It is a low-value anti-corrosion plating layer and is widely used to protect steel parts, especially to prevent atmospheric corrosion, and for decoration. The use of zinc in the industry is mainly hot-dip galvanizing, cold galvanizing, hot-spraying zinc, cold-spraying zinc and zinc-containing coatings (epoxy zinc-rich and inorganic zinc silicate).
Hot-dip galvanizing is to first pickle steel parts to remove iron oxide on the surface of the steel parts. After pickling, it is carried out in an ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride. It is cleaned, and then sent to a hot-dip plating tank. Through the reaction and diffusion between iron and zinc, a zinc alloy coating with good adhesion is plated on the surface of steel products. The outermost layer of the hot-dip galvanizing coating is a passivated zinc layer, and the zinc layer is a zinc-iron alloy and sherardized iron layer. The anti-corrosion period of hot-dip galvanizing is very long, which can reach more than 50 years. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. It is one of the most effective means to delay the environmental corrosion of steel materials. Compared with other metal protection methods, the protection characteristics of the physical barrier of the coating combined with the electrochemical protection, the bonding strength of the coating and the substrate, the compactness and durability of the coating, the maintenance-free and economical aspects, and In terms of its adaptability to the shape and size of the product, the hot-dip galvanizing process has unparalleled advantages.