Galvanized coil is a thin steel sheet in which a thin steel sheet is immersed in a molten zinc bath so that a layer of zinc is adhered to the surface. At present, it is mainly produced by continuous galvanizing process, that is, galvanized steel sheet is made by continuously immersing rolled steel sheets in a plating tank with zinc melted; alloyed galvanized steel sheets. This kind of steel plate is also made by hot-dip method, but after it is out of the tank, it is heated to about 500 ℃ immediately to form an alloy film of zinc and iron. This galvanized coil has good paint adhesion and weldability. Galvanized coil is produced by continuous hot-dip galvanizing process with hot-rolled steel strip or cold-rolled steel strip as the substrate. The hot-dip galvanized sheet is sold as a rectangular flat plate after cross-cutting, and the hot-dip galvanized coil is sold as a coil after coiling.
Passivation: The zinc coating is passivated to reduce rust (white rust) under humid storage and transportation conditions. However, the corrosion resistance of this chemical treatment is limited and, moreover, hinders the adhesion of most coatings. This treatment is generally not used in zinc-iron alloy coatings. Except for the smooth surface, as a routine, other types of galvanized coatings are passivated by the manufacturer.
Oiling: Oiling can reduce the corrosion of steel plates under wet storage and transportation conditions, and re-coating the steel plates and steel strips after passivation treatment with oil will further reduce the corrosion under wet storage conditions. The oil layer should be able to be removed with a degreaser that does not damage the zinc layer.
Paint Sealing: Galvanized coils provide an additional anti-corrosion effect, especially fingerprint resistance, by applying a very thin film of a transparent organic coating. Improves lubricity during molding and acts as an adherent primer for subsequent coats.
Phosphating: The galvanized coil is treated by phosphating, so that the galvanized steel sheets of various coating types can be coated without further treatment except for normal cleaning. This treatment can improve the adhesion and corrosion resistance of the coating and reduce the risk of corrosion during storage and transportation. After phosphating, it can be used with a suitable lubricant to improve the molding properties.
Galvanized coil products are mainly used in construction, light industry, automobile, agriculture, animal husbandry, fishery and commercial industries. Among them, the construction industry is mainly used to manufacture anti-corrosion industrial and civil building roof panels, roof grilles, etc.; the light industry uses galvanized coils to manufacture household appliance shells, civil chimneys, kitchen utensils, etc. Corrosion parts, etc.; Agriculture, animal husbandry and fishery are mainly used for food storage and transportation, meat and aquatic products freezing processing tools, etc.;