Production process and key points of quality control of PPGI/PPGL coils

In the construction industry, PPGI (pre-coated galvanized steel coil) and PPGL (pre-coated galvanized steel coil) are highly favored for their unique performance and economy. However, their high quality is inseparable from advanced production processes and strict quality control.

Production process: analysis of the whole process from raw materials to finished products
The production of construction ppgi / ppgl coil is a complex and highly automated process involving multiple key steps. The following is a detailed analysis of the entire production process:
Substrate preparation: The substrate is the basis of PPGI/PPGL coils, and its quality directly affects the performance of the final product. The substrate is usually cold-rolled steel or hot-dip galvanized steel (PPGI) and galvanized steel (PPGL). Before entering the production line, the substrate needs to be pickled and degreased to remove surface oxides and oil stains to ensure the adhesion of subsequent coatings.

Chemical treatment: Before coating, the surface of the substrate needs to be chemically treated to form a uniform phosphate or chromate conversion film. This step not only enhances the adhesion of the coating, but also improves the corrosion resistance of the substrate.

Coating process:
Coating is the core link of PPGI/PPGL coil production, which is divided into three stages: primer coating, topcoat coating and backcoat coating:
Primer coating: The role of the primer is to enhance the adhesion between the coating and the substrate, while providing preliminary anti-corrosion protection.
Topcoat coating: The topcoat determines the appearance and weather resistance of the product. Commonly used coatings include polyester (PE), silicon-modified polyester (SMP) and fluorocarbon (PVDF).
Backcoat coating: The backcoat is mainly used to protect the back of the substrate to prevent scratches during transportation and installation.

Curing and cooling:
After coating, the coil will be cured in a high-temperature oven to fully harden the coating. Subsequently, the coil is cooled to room temperature by a cooling device to avoid deformation caused by thermal stress.

Cutting and packaging:
Finally, according to customer needs, the coil is cut into specified sizes and packaged in moisture-proof and scratch-proof packaging for transportation and storage.

Quality Control: A Key Factor in Determining Product Performance

Quality control of PPGI/PPGL coils is carried out throughout every step of production. Here are some key quality control points:

Substrate quality inspection :
The thickness, flatness and surface finish of the substrate must meet the standards. Any minor defects may result in reduced coating adhesion or poor appearance.

Coating thickness control :
The coating thickness directly affects the anti-corrosion performance and service life of the product. A coating that is too thin cannot provide adequate protection, while a coating that is too thick may affect flexibility and processing performance. Therefore, precise control of coating thickness is essential.

Curing temperature and time :
The temperature and time during the curing process need to be precisely controlled. Too high a temperature or too long a time will cause coating aging, while insufficient temperature may affect the hardness and adhesion of the coating.

Surface defect detection :
Surface defects such as bubbles, sagging, and scratches may occur during the production process. These problems can be discovered and corrected in a timely manner through a combination of online detection equipment and manual inspection.

Weathering test: The finished coils must undergo rigorous weathering tests, including UV aging tests, salt spray tests, and wet heat cycle tests, to ensure their reliability in actual use.