1.What are the differences in the anti-corrosion mechanism comparison?
Basic anti-corrosion layer: zinc layer of ordinary galvanized corrugated sheet (sacrificial anode protection + physical barrier); zinc layer of galvanized color-coated corrugated sheet (same effect).
Additional protective layer: zinc layer of ordinary galvanized corrugated sheet has no additional protective layer; zinc layer of galvanized color-coated corrugated sheet has organic coating composite system (primer + topcoat + back paint)
Core protection mechanism: ordinary galvanized corrugated sheet is mainly protected by sacrificial anode of zinc; galvanized color-coated corrugated sheet is a triple mechanism of physical isolation + chemical passivation + sacrificial anode protection.
2.How is the improvement in anti-corrosion performance reflected?
Significantly extended atmospheric corrosion resistance life ◦ Ordinary galvanized sheet: In a typical industrial or marine atmospheric environment, the zinc layer will gradually consume, and "white rust" (zinc corrosion product) will appear. After 5-15 years, the substrate may rust (red rust).
Color-coated sheet: The life of color-coated sheet is 2 to 6 times that of ordinary galvanized sheet.
Enhanced scratch and cut corrosion resistance
Ordinary galvanized sheet cuts or scratches will quickly cause "cut corrosion", and the zinc layer consumption will accelerate.
Organic coating of color-coated sheet: Provides a flexible physical barrier to resist mechanical damage; The primer contains passivators such as chromate, which can delay the spread of corrosion at the cut; The self-healing properties of the topcoat (especially PVDF) slightly cover tiny scratches.
Significantly optimized chemical corrosion resistance
Ordinary galvanized sheet: Weak acid and alkali resistance, acid rain and industrial waste gas will accelerate the corrosion of the zinc layer.
Color-coated sheet: Topcoat (such as PVDF, epoxy primer) has excellent acid, alkali and solvent resistance; can resist industrial pollutants such as SO₂, NOx and acid rain erosion.
Anti-ultraviolet and wet heat aging ability
The zinc layer will powder and fail under long-term ultraviolet radiation. Color-coated topcoat (especially PVDF/SMP) contains ultraviolet absorbers and stabilizers, which can reflect or absorb ultraviolet rays and protect the zinc layer below.
3.What are the key improvement points that are more obvious?
From single protection to system protection:
The color coating makes up for the defects of pure zinc layer that is easy to be scratched, not resistant to acid and alkali, and quickly aged by ultraviolet rays, forming a composite protection system of "zinc layer + chemical passivation layer + dense polymer barrier".
The corrosion rate is greatly reduced:
In the laboratory salt spray test (ASTM B117): Ordinary galvanized sheet: white rust appears in 72 hours;
High-quality color-coated sheet (PVDF): no abnormality for more than 1000 hours.
Reduced life cycle cost:
Although the initial cost of color-coated sheet is 30%~100% higher, the long-term comprehensive cost is lower due to the extended maintenance-free period and reduced replacement frequency.
4.What are the precautions for using color-coated galvanized corrugated sheets?
Cut protection: The cut edge needs to be repainted with special paint, otherwise it will still be a weak point for corrosion;
Avoid contact with strong corrosive media: Direct immersion in concentrated acid or strong alkali will still damage the coating;
Selection and matching environment: PVDF or thick film SMP coating must be used in coastal or heavy industrial areas.
5.In what aspects does the anti-corrosion performance of galvanized color-coated corrugated sheet manifest itself?
Lifespan: Under the same environment, its service life is more than 2~6 times that of ordinary galvanized sheet; Protection strength: From relying on the "passive sacrifice" of the zinc layer, it has been upgraded to the triple protection of "active isolation + passivation + sacrifice";
Economical efficiency: The cost of the entire life cycle is reduced by about 30%~50% (reducing maintenance/replacement costs).