Compared to galvanized or galvalume coils, pre-painted steel coil involves the longest production chain. Starting from hot-rolled steel as raw material, then cold-rolled to precise thickness, width, and flatness. Subsequent steps include annealing, metallic coating (galvanizing or galvalume), and finally the color coating process, resulting in the vibrant, finished corrosion-resistant prepainted galvalume steel coil.
Complete Production Workflow:
The core manufacturing stages for pre-painted coil are pre-treatment, coating application, and curing.
A standard double-Coat double-Bake process is as follows:
Uncoiling → Stitching → Degreasing → Chemical Pre-treatment → Primer Coating → Primer Curing → Cooling → Finish Coating → Finish Curing → Cooling → Inspection → Trimming/Slitting → Recoiling.
Pre-treatment Process: This phase cleans the substrate to remove oils and contaminants, followed by a conversion coating and passivation treatment. The resulting chemical film is essential for promoting strong adhesion between the metal and the paint layers.
Coating Process: The roll coating method is predominantly used. In this technique, a pick-up roll transfers paint from a pan to an applicator roll, which forms a controlled wet film. This film is then precisely applied to the steel strip surface.
Key advantages of this method include:
High-Speed Production
Exceptional Transfer Efficiency (nearly 100%), minimizing waste
Adjustable Coating Thickness via roll gap, pressure, and speed settings
Versatility in coating one or both sides simultaneously.
