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Types of galvanized steel sheet and their uses
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Short answer
Galvanized sheet is steel coated with zinc to protect it from rust. The main types are hot-dip galvanized with different coating masses (e.g. Z100, Z275), Galvalume (aluminium–zinc coated), pre-painted galvanized, and electro-galvanized with a thin coating. The heavier the zinc coating, the longer it resists rust outdoors.
Main types
| Type | Coating | Common uses |
|---|---|---|
| Hot-dip galvanized | Zinc (Z100 – Z275 and up) | HVAC ducts, roofing, cable trays, fabrication |
| Galvalume | Aluminium–zinc (e.g. AZ150) | Long-life roofing and cladding |
| Pre-painted galvanized | Zinc + factory paint | Coloured profiles, sandwich panels, doors |
| Electro-galvanized | Very thin zinc | Appliances and indoor parts painted later |
What does Z275 mean?
The number after Z is the zinc mass in grams per m² on both sides combined. Z275 means 275 g/m², about 20 microns per side. Z100 – Z140 usually suits indoor work, Z275 is preferred outdoors and for roofs, and coastal or harsh industrial sites need a heavier coating or Galvalume.
Spangle
Spangle is the visible zinc crystal pattern. Regular spangle suits unpainted work; zero (minimised) spangle gives a smoother surface and is preferred when the sheet will be painted.
What to put in your quotation request
- Thickness and size (sheets or coils, coil width)
- Required zinc class (e.g. Z275)
- Regular or zero spangle
- Quantity and delivery location
FAQ
Does galvanized sheet rust?
The zinc protects it for years, longer with a heavier coating. Cut edges and welds lose some protection and should be touched up with zinc-rich paint.
Galvanized vs Galvalume?
Galvanized is zinc-only; Galvalume uses an aluminium–zinc alloy that usually lasts longer against atmospheric corrosion on roofs.
General guidance — not an offer or commitment by BUILDORA.