Colour coated plate substrates usually use cold rolled steel strips, galvanized steel strips (galvanized and hot galvanized), aluminium steel strips, hot galvanized aluminium alloy steel strips, hot galvanized aluminium alloy steel strips, tin plated
steel strips, chromium plated steel strips, etc.
The cold-rolled steel strip can save the cost of intermediate coating. It has a smooth and beautiful appearance in the early stage, and has the processability of cold-rolled steel strip. However, any minor scratches in the surface coating will expose the cold-rolled steel strip to air, which will quickly produce red rust on the exposed iron. Therefore, these products can only be used for temporary isolation measures with low requirements and as indoor materials. Because of its poor corrosion resistance, it has been basically washed out.
Hot-dip galvanized steel strip is used on the base plate, and zinc layer and zinc-iron alloy coating are added in the middle, which greatly improves the corrosion resistance. It is the main product of domestic plating units at present. Hot-dip galvanizing is the formation of a compact zinc-iron alloy coating on the surface, which has better anti-corrosion effect. In addition to the protective effect of zinc, the organic coating on the surface of hot-dip galvanized color coated sheet also plays the role of isolation and protection against rust, and its service life is longer than that of hot-dip galvanized sheet. The zinc content of hot-dip galvanized substrates is generally 180 g/m2 (double sided). The highest zinc content of hot-dip galvanized substrates for external use is 275 g/m2. Hot-dip galvanized color coated sheets are the most widely used color coated products in China at present. It is a base plate with galvanized steel strip, which requires high cleanliness and thin coating. The product cured with organic paint is galvanized color coated sheet. Because the zinc layer of galvanized sheet is thin and usually contains 20/20g/m2 of zinc, the product is not suitable for outdoor wall and roof fabrication. But because of its beautiful appearance and excellent processing performance, it can be mainly used in household appliances, audio, steel furniture, interior decoration and so on.
Hot-dip galvanized aluminium alloy steel strip or hot-dip aluminium-zinc alloy steel strip is used on the substrate. Compared with pure galvanized steel strip, the chemical properties of the alloy coating are relatively stable, so the corrosion resistance is different. Tests under the same outdoor conditions show that the service life of aluminized galvanized sheet (strip) is more than four times that of galvanized sheet (strip). Hot-dipped aluminized galvanized sheet (strip) is used as color-coated substrate. The contents of gamble and aluminium are usually 55% Al-Zn and 5% Al-Zn.