The base material of color steel plate can be cold-rolled coil or hot-dipped plated steel. Although the organic coating of color steel plate has good anticorrosive effect, there are still some small voids in the organic coating. Air and moisture may enter
into the coating and then rust the base material. Therefore, the color steel plate made of non-coated base material has a long service life. Short, and easy to spread after scratch, resulting in coating peeling. The base material of color steel plate
is mainly galvanized steel plate or galvanized alloy steel plate.
The production process of color coating is divided into pretreatment of substrate, chemical conversion film (non-organic metal coating), organic non-metallic coating, and some production lines also have post-coating process.
I. Pretreatment of Base
Galvanized steel sheets as substrates may be corroded (white rust), dust and other contamination during transportation if they do not enter a color coating process directly after production. If these can not be removed, it will affect
the quality of the paint. The quality and physical and chemical properties of finished color coatings are closely concerned with pretreatment. In addition, after galvanizing production, in order to prevent rust and paint, these oils should also be removed
before the production of color coating.
At present, alkali solution degreasing is the most commonly used pretreatment method.
II. Chemical conversion film
Generally, there are three steps: first, phosphating, first forming a large number
of crystals on the metal surface, then forming a layer of phosphate film on the metal surface with phosphate solution; second, passivation and sealing, the phosphate film still has some holes, using chromate to react with the holes to form a protective
3. Wash with pure water, wash with desalted or deionized water to remove passivating liquid.
III. Organic Coatings
Organic coatings are divided into primers and topcoats. The requirements of primers are not high and can be painted
smoothly. However, for the sake of production safety, primers and topcoats are generally painted in reverse mode.
Post-coating process: The post-coating process includes printing, embossing, peeling protective film, lamination and so on, which increases
the decorative and protective properties of color steel plate. In addition, some foreign post-coating processes also include leveling and straightening processes used in cold rolling and galvanizing production lines.