S350GD+Z275 hot-dip galvanized structural steel to EN 10346. Minimum yield 350 MPa with 275 g/m² zinc coating both sides, built for load-bearing outdoor structures where corrosion failure is not an option. Available in coils, slit strip, and cut-to-length sheets from 0.15 mm to 6.0 mm. Mill-direct from BOMIS Steel with EN 10204 3.1 test certificates.
S350GD+Z275 is a hot-dip galvanized structural steel covered by EN 10346. The grade breaks down as: S for structural, 350 for minimum yield strength of 350 MPa, GD for hot-dip galvanized, and Z275 for the zinc coating weight. That means 275 grams per square meter on each side of the sheet. Among the standard galvanized coating weights, Z275 is the heaviest commonly stocked for structural grades, which makes it a practical choice for outdoor load-bearing work where maintenance access is limited and replacement costs are high.
| Specification | Details |
| Steel Grade | S350GD+Z275 (EN 10346) |
| Thickness Range | 0.15 mm – 6.0 mm |
| Width Range | 600 mm – 1500 mm (custom slitting available) |
| Zinc Coating | Z275, 275 g/m² double-sided |
| Surface Finish | Zero spangle / Small spangle / Regular spangle / Large spangle |
| Surface Treatment | Chromated, chrome-free passivation, anti-fingerprint (AFP), oiled, dry |
| Base Substrate | Cold rolled or hot rolled coil |
| Coil Weight | 8 – 10 metric tons (custom weight available) |
| Order & Logistics | Details |
| MOQ | 10 metric tons |
| Lead Time | 10 – 20 working days after deposit |
| Loading Ports | Tianjin, Qingdao, Shanghai, or client-nominated |
| Packing | Seaworthy export: waterproof paper, steel strapping, wooden pallet |
| Property | Value | Standard |
| Yield Strength (Rp0.2) | ≥ 350 MPa | ISO 6892-1 |
| Tensile Strength (Rm) | 420 – 550 MPa | ISO 6892-1 |
| Elongation (A80) | ≥ 14% (≤ 3 mm thickness) | ISO 6892-1 |
| Hardness | 130 – 210 HV | ISO 6507 |
| Cold Bend | 180° bend, no cracking | ISO 7438 |
Z275 applies 275 g/m² of zinc per side. That is nearly double the zinc in a Z140 coating and a meaningful step up from Z200. In salt spray testing per ISO 9227, Z275 panels pass 1,000 hours before red rust shows up. Z140 panels under the same conditions start showing rust around 400 to 500 hours. For structures that sit outdoors for decades (transmission towers, industrial frames, grain silos), the heavier coating buys extra years of service life before any maintenance needs to happen.
The zinc layer is metallurgically bonded during hot-dip processing. It will not flake, peel, or delaminate during bending, roll-forming, or stamping, provided your tooling is rated for 350 MPa material.
Both carry the same Z275 zinc coating. The difference is in the steel underneath.
| Property | S350GD+Z275 | DX51D+Z275 |
| Grade Type | Structural (microalloyed high-strength) | Cold-forming (low-carbon mild steel) |
| Yield Strength | ≥ 350 MPa | ≥ 140 MPa |
| Tensile Strength | 420 – 550 MPa | 270 – 350 MPa |
| Elongation | ≥ 14% | ≥ 22% |
| Formability | Needs pre-drilling for deep draws | Direct press and bend with no pre-treatment |
| Best Fit | Structural framing, chassis, towers | Ductwork, enclosures, appliance panels |
Choose S350GD when load-bearing matters. Choose DX51D when you need to form complex shapes without cracking. The zinc protection is the same either way. It is the mechanical demand that decides which grade fits.
We run two continuous hot-dip galvanizing lines with air-knife coating control, inline annealing, and post-treatment passivation: chromated or chrome-free, whichever your market requires. Monthly output across all grades averages over 10,000 metric tons, so volume orders ship on schedule without bottlenecking.
Every coil ships with a mill test certificate to EN 10204 3.1. Our in-house lab runs zinc weight checks (gravimetric and XRF), tensile and bend testing, and salt spray exposure per ISO 9227. Third-party inspection through SGS, Intertek, or Bureau Veritas is available on request.
Custom processing is standard for us: cut-to-length sheets, precision slit coils, specific coil weights as low as 3 tons for trial orders. Mixed container loads with multiple gauges or widths are routine for our export accounts.
How much longer does Z275 last compared to Z140?
In neutral salt spray testing per ISO 9227, Z275 goes past 1,000 hours before the first red rust appears. Z140 typically reaches 400 to 500 hours under the same conditions. Real-world life depends on the exposure. Coastal zones, industrial areas, and high-humidity environments eat zinc faster than dry inland sites. As a rough rule of thumb, Z275 gives you roughly double the outdoor service life of Z140 before the base steel needs any attention.
Can you supply S350GD+Z275 as slit coils instead of full-width?
Yes. We slit from mill-width master coils down to your specified width. The minimum slit width depends on the thickness you order. Send us your target dimensions and we can confirm feasibility the same day.
Does roll-forming or bending crack the zinc coating?
No. The zinc is metallurgically bonded to the steel during the hot-dip process, not applied as a surface paint or film. It handles 180° cold bends without flaking or peeling. But at 350 MPa yield, your forming equipment needs more force than it would for a mild grade like DX51D. Make sure your roll-forming tooling and die clearances are spec’d for structural-grade steel.
What sheet sizes do you stock off the shelf?
Common cut-to-length sizes are 2000 mm, 2440 mm, and 3000 mm. Custom lengths are available. We can also ship full coils if you prefer to shear and blank locally.
What paperwork comes with each order?
Mill test certificate to EN 10204 3.1 as standard, covering chemical composition, mechanical properties, zinc coating weight, and surface quality. Third-party inspection through SGS, Intertek, or Bureau Veritas can be arranged for an additional fee.
