For galvanized coils, the thin steel plate is immersed in the molten zinc tank, so that a thin steel plate with a layer of zinc is adhered to the surface. It is mainly produced by continuous galvanizing process, that is, the coiled steel sheet is continuously immersed in a galvanizing tank with molten zinc to make galvanized steel sheet; alloyed galvanized steel sheet. This kind of steel plate is also manufactured by hot dipping method, but immediately after leaving the tank, it is heated to about 500°C to form an alloy film of zinc and iron. This galvanized coil has good paint adhesion and weldability.

Surface treatment symbol

Passivation C

Oiled O

Lacquer seal L

Phosphating P

Do not process U

6.1 Passivation

Passivation treatment of the galvanized layer can reduce folding rust (white rust) under moisture storage and transportation conditions. However, the anti-corrosion performance of this chemical treatment is limited, and it hinders the adhesion of most coatings. This kind of treatment is generally not used on the zinc-iron alloy coating. In addition to the smooth surface, as a rule, the manufacturer will passivate other types of zinc coatings.

6.2 Oiling

Oiling can reduce the corrosion of steel plates under humid storage and transportation conditions. After passivation treatment of steel plates and steel strips, repainting oil will further reduce the corrosion under humid storage conditions. The oil layer should be able to be removed with a degreaser that does not damage the zinc layer.

6.3 Lacquer seal

By coating a very thin transparent organic coating film, it can provide an additional anti-corrosion effect, especially fingerprint resistance. It can improve lubricity during molding and serve as an adhesion base layer for subsequent coatings.

6.4 Phosphating

Through phosphating treatment, 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 performance.

6.5 No processing

Only when the buyer makes a request for non-treatment and is responsible for it, the steel plates and steel strips supplied according to this standard can be without passivation, oiling, paint sealing or phosphating and other surface treatments.