Color-coated coils use hot-dip galvanized steel coils as the substrate, and the color-coated steel coils are first surface pretreated, then coated with one or more layers of liquid coatings by roller coating, and finally baked and cooled. Coatings used include polyester, silicon modified polyester, high durability, corrosion resistance and formability. PPGI is pre-painted galvanised iron, also known as pre-coated steel, coil coated steel, color coated steel etc., typically with a hot dip zinc coated steel substrate. Galvanized steel, PPGI, is coated completely with zinc. While Galvalume steel, PPGL is coated with aluminum, zinc, and a small amount of silicone.
The spray paint structure generally consists of five parts. 1) Topcoat: block the sun and prevent ultraviolet rays from damaging the coating; when the topcoat reaches the specified thickness, it can form a dense shielding film to reduce water permeability and oxygen permeability 2) Primer: It is conducive to strengthening the adhesion to the primer, making the paint film difficult to detach after water penetration, and improving corrosion resistance, because the primer contains corrosion-inhibiting pigments such as chromate, which can passivate the anode and improve corrosion resistance. 3) Coating: Generally, it is galvanized or galvalume, which has a great influence on the service life of the product. The thicker the coating, the better the corrosion resistance. 4) Substrate: Generally, it is a cold-rolled sheet, and different strengths determine the mechanical properties of the color-coated sheet. 5) Back paint: the function is to prevent the steel plate from corroding from the inside, generally a two-layer structure (2/1M or 2/2, primer + back paint). If bonding is required on the back side, a single layer construction is recommended.
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