Z275 means a hot-dip galvanized coil whose zinc coating weighs 275 g/m² in total on both surfaces — the export standard for roofing, cladding and general construction GI. The base steel (usually DX51D+Z / SGCC / S350GD) is specified separately, and coating class runs from Z60 (indoor) to Z275+ (outdoor/corrosive). Nikasteel supplies Z275 GI coil 0.13–4.0 mm × 600–1500 mm with mill certificates — MOQ 5 t, FOB/CIF.
"GI coil" is the busiest product term in the coated-steel trade — and the marking on the coil decides both price and service life. This page unpacks the Z275 spec so you can order the right coating for your climate and code, not just the cheapest number on a quotation.
What Z275 Actually Means
- Z = zinc (pure zinc hot-dip coating, as opposed to GL/AZ aluminum-zinc or ZF zinc-iron alloy).
- 275 = minimum total coating mass, grams per square meter, both surfaces combined (ISO 1461 / EN 10346 basis).
- In practice: ≈ 19–20 µm of zinc per side. Coating is verified by weighing strips dissolved from the coil — ask for the coating test result on the mill certificate.
Choosing the Coating Class: Z60 to Z275 and Beyond
| Class | Zinc (g/m²) | Typical Duty | Typical Products |
|---|---|---|---|
| Z60–Z100 | 60–100 | Indoor, dry | Furniture tubes, interior panels, appliance back panels |
| Z120–Z180 | 120–180 | Light outdoor, sheltered | Ducting, profiles under soffit, agricultural interior |
| Z275 | 275 | Standard outdoor construction | Roofing sheets, cladding, purlins, fencing, greenhouse |
| Z350–Z450 | 350–450 | Marine / industrial | Coastal structures, heavy agricultural, silos |
| GL AZ150 | 150 (aluzinc) | High-heat + corrosion | Premium roofing, solar mounting, sandwich panel skins |
Rule of thumb: zinc life outdoors is roughly linear with coating weight — doubling zinc roughly doubles years to first rust. For coastal Southeast Asia and West Africa, Z275 is the working minimum; Z350+ or GL is worth the premium near the shoreline. GI vs GL aluzinc comparison →
Base Steel Grades (the Z Number Doesn't Tell You These)
| Base Grade | Standard | Character | Order For |
|---|---|---|---|
| DX51D+Z | EN 10346 | Bending/profiling grade, commercial quality | Roofing, general profiles (the default export grade) |
| SGCC | JIS G3302 | Japanese-system commercial grade | Buyers specifying JIS ecosystem |
| S350GD | EN 10346 | Structural, min yield 350 MPa | Purlins, structural decking, high-strength profiles |
| DX52D–DX54D | EN 10346 | Drawing qualities | Deep-drawn parts, appliance shells |
Standard Export Sizes for Z275 GI
- Thickness: 0.13–4.0 mm (roofing typically 0.16–0.5 mm; purlins 1.5–3.0 mm)
- Width: 600–1500 mm; most ordered: 914 / 1000 / 1219 / 1250 mm, or slit to your roll-former's width
- Coil ID: 508 or 610 mm · Coil weight: 3–10 t
- Spangle: regular / minimized / zero (zero for painting, regular for bare roofing look)
- Surface: oiled or passivated+oiled (anti-white-rust for sea transit)
Three Checks Before You Pay for a GI Order
- Coating proof: ask the mill certificate to list the actual zinc weight result (not just "Z275" as ordered). Reputable mills test every coil; traders sometimes skip it.
- Base grade on the MTC: Z275 on DX51D and Z275 on S350GD are different products at different prices — make the quotation name both.
- Anti-white-rust treatment: for sea transit to humid climates, insist on oiled or chromated+oiled surface, otherwise coils can arrive with white oxidation within weeks.
Estimate your tonnage before ordering with the GI coil weight calculator (coil kg, meters per ton, m² per ton), then see our GI/GL product page for the full supply range →
Need Z275 GI coil with real coating certificates?
Send thickness × width × tonnage to [email protected] or WhatsApp +86 191 5745 8011 — dated FOB/CIF quotation, MOQ 5 tons, mill certificates with actual coating results.
Request a GI Coil Quotation