Production process and material selection requirements of color coated steel coil

The base material of the color coated coil can be cold rolled coil or hot-dip galvanized steel. Although the organic coating part of the color coated coil has a good anti-corrosion effect, there are still some small gaps in the organic coating. Air and water may enter the organic coating, which may rust the base material. Therefore, the color coated coil made of uncoated base material has a short service life, and it is easy to diffuse after scratching, causing the coating to peel off.

The base material of color coated coil is mainly galvanized steel sheet or galvanized alloy steel sheet. The production process of color coating is divided into pretreatment of substrate, chemical conversion film (non organic metal coating), organic non-metallic coating, and post coating process in some production lines.

1、 Substrate pretreatment If the galvanized steel plate used as the base material does not directly enter a color coating process after production, rust (white rust), dust and other pollution may occur during transportation. If these cannot be removed, the quality of color coating will be affected. The quality and all physical and chemical properties of the finished color coated coil are closely related to the pretreatment. In addition, after galvanizing production, oil is applied for rust prevention, and these oils should also be removed before color coating production. At present, the most commonly used pretreatment method is alkaline solution degreasing method.

2、 The chemical conversion film has two functions, one is to further improve the antirust ability, the other is to improve the adhesion between the substrate and the coating, and improve the coating performance of the substrate. Generally, there are three steps: first, phosphating. First, a large number of crystals are formed on the metal surface, and then a phosphate film is formed on the metal surface with a phosphate solution; The second is passivation and sealing. There are still some holes in the phosphate film, and chromate is used to react with the holes to form a protective film. The third is pure water washing, which uses desalted or deionized water to wash the passivation liquid. 3、 Organic coating Organic coating can be divided into primer and finish. The requirements for primer are not high, and it can be painted in color. However, in order to ensure production safety, the primer and finish are generally painted in reverse.

Post coating process: post coating process includes printing, embossing, strippable protective film, lamination, etc., which increases the decorative and protective properties of color coated boards. In addition, some foreign post coating processes include leveling and straightening processes used in cold rolling and galvanizing production lines.