1.What are the core factors that determine durability?
Coating system: the foundation for long-term durability
Resin type (most critical): The chemical stability of different resins varies significantly, which directly corresponds to the life span range:
PVDF (polyvinylidene fluoride) coating: fluorine content ≥ 70%, strong UV resistance and chemical resistance, is currently the most durable system, with a life span of 15-25 years under normal environment, and can still reach 10-20 years under extreme environment.
FEVE (fluorocarbon resin) coating: moderate fluorine content, performance close to PVDF, life span of 12-20 years, more cost-effective.
SMP (silicon modified polyester) coating: weather resistance is better than ordinary polyester, anti-powdering and anti-discoloration ability is strong, life span is 8-15 years, suitable for medium corrosion environment.
PE (polyester) coating: conventional civilian grade, medium weather resistance, life span of 5-10 years, long-term exposure to strong ultraviolet rays or high humidity environment is prone to powdering and discoloration.
PVC (polyvinyl chloride) coating: general corrosion resistance, susceptible to high temperature aging, life span of 3-8 years, mostly used indoors or low-demand scenes.
2.How do environmental factors affect their lifespan?
High UV area: UV rays will accelerate the degradation of resin, causing the coating to lose gloss and powder, and the life span may be shortened by 20%-40%.
High humidity and high temperature area: The humid and hot environment accelerates the hydrolysis of the coating and the growth of mold, which may reduce the life span of the polyester coating from 8 years to 5 years, and it is necessary to rely on PVDF and other moisture and heat resistant systems.
Severe cold area: Freeze-thaw cycles may cause the coating to crack. If the coating is not flexible enough, the life span may be shortened by 50%.
3.How do substrates and pretreatments affect lifetime?
If the substrate is a hot-dip galvanized sheet (zinc layer thickness ≥ 60g/m²), even if the coating is partially damaged, the zinc layer can protect the steel plate through sacrificial anode action, delaying corrosion, and extending the life of the cold-rolled substrate by 5-10 years.
Surface pretreatment of the substrate can enhance the adhesion of the coating. If the pretreatment is poor, it may cause the coating to bubble and peel off early, making the estimated life invalid.
4.What impact does construction and maintenance have on lifespan?
Construction quality: If the coating is scratched or the joints are not well sealed during installation, local corrosion may spread, shortening the overall life by 20%-40%; if rivet-free connection is used, the life can be extended by 10%-15%.
Maintenance frequency: Regular cleaning can reduce coating degradation. The life of color-coated coils cleaned once a year is 10%-20% longer than that of those not cleaned for a long time; timely repainting after local damage can prevent the spread of rust and extend the remaining life by 50%.
5.What are the core estimation methods for durability?
Accelerated aging test method
The most commonly used quantitative method is to simulate extreme environments in the laboratory, accelerate coating aging, and then convert the actual life according to the "aging rate".
Test process:
Take the color coated coil sample and expose it in the aging box;
Regularly test the coating performance;
When the coating performance drops to the "failure threshold", record the aging time, and then convert the actual life according to the "acceleration factor".