1. The base material of color steel coil can be cold-rolled coil or hot-dip galvanized steel. Although the organic coating part of color steel coil has a good anti-corrosion effect, there are still some small gaps in the organic coating. Air and water
may enter into the organic coating, which may cause rust of the base material. Therefore, the color steel coil made of uncoated base material has a short service life and is easy to spread after scratches, resulting in Coating flaking. The base material
of color steel coil is mainly galvanized steel plate or galvanized alloy steel plate.
2. The production process of color coating is divided into pretreatment of base material, chemical conversion film (non organic metal coating), organic non-metal coating. In addition, some production lines also have post coating process.
pretreatment: if the galvanized steel plate as the substrate does not directly enter a color coating process after production, it may appear rust (white rust), dust and other pollution during transportation. If these cannot be removed, the quality of
the color coating will be affected. The quality and all physical and chemical properties of the finished color coated roll are closely related to the pretreatment. In addition, after galvanizing production, oil is applied for rust prevention, and the
oil is removed before color coating production.
At present, most of the pretreatment methods are alkali solution degreasing.
4. Chemical conversion film: it has two functions: one is to further improve the anti rust ability; the other is to
improve the adhesion between the base material and the coating, and improve the coating performance of the substrate. Generally, there are three steps: first, phosphating, forming a large number of crystals on the metal surface, and then forming a phosphate
film on the metal surface with the phosphate solution; second, passivating and sealing, there are still some pores in the phosphate film, which react with the pores with chromate to form a protective film. The third is pure water washing, and the passivation
liquid is washed with desalted or deionized water
5. Organic coating: the organic coating is divided into primer and finish. The primer is not required to be high and can be painted in a smooth way. However, for the sake of production safety, the
primer and surface paint are generally painted in a reverse way. After coating process: after coating process includes printing, embossing, peelable protective film, lamination, etc., which increases the decorative and protective properties of color steel
plate. In addition, some foreign post coating processes are also used in cold rolling and galvanizing production lines, such as leveling and straightening.