1.Will sizing cause the color of the coated rolls to fade?
Fading is a chemical process, primarily caused by environmental factors such as ultraviolet radiation, chemical corrosion, high temperature, and humidity; it is an aging phenomenon of the coating polymer material.
Leveling is a physical process: it is the mechanical processing of unrolling and shearing rolled steel sheets into flat sheets. Proper, high-quality processing itself does not damage the chemical structure of the coating and therefore does not directly cause fading.
2.What are the risks of physical damage to the coating when the pre-coated coil is unrolled?
Scratches/Abrasions: Hard objects or accumulated impurities on the rollers of the leveling machine (especially tension rollers and straightening rollers), or an unclean production line, can leave fine or noticeable scratches on the steel plate surface. These scratches damage the integrity of the coating.
Consequences: The coating thins or peels off at the damaged areas, losing its protective ability. In the future, ultraviolet rays, moisture, and contaminants will directly penetrate through these areas, leading to "localized premature fading and corrosion," which looks like a problem that occurred after leveling.
3.What risks would arise from damage to the edge protective layer?
Shearing process: The initial cutting process exposes the raw metal edges of the steel plate.
Consequences: Without a protective coating, the cut edges are highly susceptible to rust. Once rust forms, it spreads beneath the coating or contaminates the surrounding surface, creating a "yellowish-brown stain and coating blistering starting from the edge," which appears as a color change from a distance.
4.What impact will the exposure of existing defects or color difference risks have?
Intra-roll color difference: During production, some color-coated coils may have slight color differences at the beginning, middle, and end of the roll. These differences are not easily noticeable when the coil is rolled up, but become more apparent when compared side-by-side after being unrolled into a large sheet, easily mistaken for "fading after processing."
Pre-existing damage: Pre-existing, minor coating defects within the coil become visible after unrolling.
5.How can I ensure that the color doesn't fade (too early) after the surface is opened?
Choosing color-coated coils with high weather resistance coatings (fundamental prerequisite):
PVDF coating: Excellent weather resistance and strong color and gloss retention (usually offers a 15-25 year quality guarantee), making it the first choice for outdoor and high-end applications. This is key to resisting UV fading.
HDP coating: High-performance polyester, with better weather resistance than ordinary polyester, offering high cost-effectiveness.
Ordinary polyester coating: Moderate weather resistance; fading and chalking are more noticeable with long-term outdoor use, suitable for indoor or short-term use.
Choose a reputable and professional leveling and sizing plant:
Clean production line: Ensure all conveyor rollers and straightening rollers are clean and free of impurities.
Equipment in good condition: Sharp blades, precise gap adjustment, and avoid tearing the coating.
Perfect edge treatment: After cutting, it is best to perform "edge coating" or "edge sealing," that is, apply a special protective paint to the cut metal edges. This is the most effective way to prevent edge corrosion.
Gentle lamination and packaging: Protect the board surface from scratches during transportation and storage.