Question 1: Will the pressing process of color-coated steel sheets always damage the paint?
The pressing process is a necessary step in the forming of color-coated steel sheets, and proper operation can minimize damage to the paint surface.
However, the risk of paint damage increases significantly in the following situations:
Process and design issues: The surface of the pressing rollers in the pressing equipment has hard scratches, the pressure is adjusted too high, or the designed bending radius is too small.
Insufficient material toughness: The color-coated steel sheet itself has poor flexibility, meaning the coating is not flexible enough, making it prone to cracking and peeling at bends.
Environmental influences: In low-temperature environments such as winter, the plasticity of the sheet decreases, making the paint film more prone to cracking during processing.
Substrate and coating adhesion problems: Poor adhesion of the passivation layer or primer on the substrate surface can cause the paint layer to peel off in regular, patchy pieces under forming stress.
Second question: Why is paint damage most common after molding?
This usually points to three main reasons:
Molding equipment problems: The equipment is the primary inspection point. Long-term lack of maintenance of the pressure rollers will cause them to become worn and no longer smooth; paint debris or shavings adhering to the equipment will scratch the subsequent sheet surface; improper equipment adjustment or incorrect selection leading to pressure or gap problems is also a major cause.
Material inherent problems: The color-coated coil itself may have quality defects. For example, improper handling during production (such as poor passivation) will result in poor adhesion between the coating and the steel plate, or moisture or dust during transportation and storage may cause paint peeling during molding.
Design and temperature issues: An excessively small bending radius will prevent the paint film from withstanding excessive tension and cause cracking. In addition, operating in low temperatures during winter increases the risk of damage; it is recommended to control the processing temperature above 5℃.
Three questions: What are the effects of the coating's quality and type?
The material's inherent properties are the primary determining factors.
Flexibility (T-bend performance): Coatings with poor flexibility will crack and peel off at the processed area when bent.
Coating adhesion: The bonding strength between the coating and the steel plate (including the galvanized layer and passivation layer) is crucial. Poor adhesion will directly lead to large-scale paint peeling off.
Coating type: Different coatings have different properties. For example, while fluorocarbon paint (PVDF) coatings have strong weather resistance, their flexibility is relatively poor, requiring more care during processing; the processing speed and pressure should also be adjusted according to the coating's inherent flexibility.
Four Questions: How to Prevent and Reduce Damage to the Paint Surface During Molding?
This can be addressed from four aspects: equipment, process, materials, and operation:
Inspect, maintain, and service equipment (most critical): Ensure the surface of the pressure rollers is smooth and undamaged, and precisely adjust the roller gap and pressure according to the sheet thickness.
Standardize cutting and operating procedures: Keep scissors sharp to reduce burrs, and place soft materials such as rubber mats on the worktable to prevent scratches.
Select superior materials: Choose high-quality color-coated sheets with good bending resistance according to molding requirements.
Utilize protective film effectively and standardize operations: Retain the original factory protective film on the sheet surface during key processing stages, and provide standardized operation training for operators.
Five Questions: What should be done and repaired if the paint surface is damaged?
In case of minor damage, remedial measures can be taken promptly:
Minor scratches without rust: If only the topcoat is slightly scratched and the primer is not exposed, a special repair paint can be sprayed or brushed on to cover it.
Deeper scratches but no corrosion on the substrate: If the primer has been damaged but not corroded, thoroughly clean the damaged area, sand the edges of the old paint to increase adhesion, and then apply the appropriate primer.
Severe damage or large-area peeling: If the damaged area is corroded, or if there is patchy, regular peeling, it usually indicates a quality defect in the original board. The supplier should be contacted immediately for handling.