1.What are the structural differences between the two?
Galvanized sheet:
Substrate: cold-rolled steel sheet (mild steel).
Coating: a layer of zinc (or zinc alloy) is hot-dip coated on the surface to form a "sacrificial anode" protection mechanism (zinc corrodes before iron).
Common types: GI (hot-dip pure zinc sheet): the zinc layer contains a small amount of aluminum, with a classic zinc flower appearance.
GL (zinc-aluminum-magnesium sheet): zinc + aluminum + magnesium, corrosion resistance increased by more than 30%.Color coated coil: Substrate: usually galvanized sheet (GI/GL) or aluminum zinc sheet (AZ) as the base layer (accounting for more than 90%).
Coating: Chemical conversion layer (such as chromium treatment): enhances the adhesion between the substrate and the coating.
Primer: Epoxy resin, rust-proof, sealed substrate.
Topcoat: Color coating (polyester/silicon modified polyester/fluorocarbon, etc.), providing decoration and weather resistance.
2.What is the difference in corrosion resistance?
Galvanized sheet: The zinc layer protects the steel base through sacrificial anodes, but the steel base will quickly rust after the zinc layer is consumed. The service life is significantly shortened in humid, acid rain, and salt spray environments.
Color-coated coils provide double protection:
Zinc layer sacrificial anti-corrosion (base layer)
Organic coating physically isolates corrosive media (surface layer).
PVDF topcoat can withstand salt spray for more than 1,000 hours, and its lifespan is 2-3 times longer than that of galvanized sheet.
3.What is the difference between the two in terms of decorative performance?
Galvanized sheet: only silver gray, with zinc flowers on the surface (the sheet without zinc flowers is smoother), no color selection, easy to leave fingerprints.
Color coated coil: Color: can be customized with any RAL/Pantone color number (such as white, blue, red, imitation wood grain, etc.). Surface: high gloss/matte/texture (suede, embossed), beautiful and hides scratches.
4.What is the difference in weather resistance between the two?
Galvanized sheet: The zinc layer turns gray and dark under ultraviolet light, and oxidizes faster under high temperature.
Color coated coil: The topcoat determines the performance.
PVDF: Extremely resistant to ultraviolet light, 20-year color retention rate > 90%, temperature resistance 120℃.
HDP: Good UV resistance, suitable for general outdoor use.
PE: Easy to powder and fade, suitable for indoor use.
5.What are the common misunderstandings about galvanized sheets and galvanized coils?
Color-coated coils do not need galvanized substrates? "
→ Wrong! Color-coated coils must rely on galvanized (or galvanized) substrates to provide bottom corrosion protection, otherwise the steel base will rust quickly after the coating is damaged.
"Can galvanized sheet replace color-coated coils for exterior walls?"
→ Not recommended! Galvanized sheet has no color, tends to be gray, and is prone to "white rust" (zinc corrosion product) without coating protection.
"Color-coated coils are easier to scratch than galvanized sheets?"
→ Partially correct. PE coating has a lower hardness, but PVDF/HDP coating can reach a hardness of 2H (pencil hardness), and its wear resistance is better than galvanized sheet.