DX51D+Z275 is a continuous hot-dip galvanized steel with a low-carbon substrate and a zinc coating mass of 275 g/m2 on both surfaces. The Z275 designation is often written as Z275G in commercial listings, meaning the same thing: a total zinc coating of 275 g/m2, triple-spot minimum, per EN 10346. In practical terms the coating is about 19-20 micrometres of zinc per side, which places this grade in the medium-to-heavy range of galvanized products and explains its popularity for long-life building and structural applications.
What Z275 means for service life
Corrosion of the zinc layer follows the same rules everywhere, but the rate depends strongly on the atmosphere. In a clean rural environment with low sulphur dioxide and low chloride, a Z275 coating can protect the steel for more than 50 years before the first surface maintenance is needed. In urban and coastal atmospheres, where chlorides and pollutants accelerate zinc consumption, the same coating typically provides around 20 years of protection. These are practical planning figures, not guarantees; the actual life depends on orientation, shelter, drainage and the corrosivity category of the site, which can be assessed with reference to ISO 9223 and ISO 9224.
| Atmosphere | Typical service life of Z275 coating | Main corrosion driver |
|---|---|---|
| Rural, clean | More than 50 years | Rain and humidity |
| Urban | About 20 years | Sulphur dioxide and particulates |
| Coastal | About 20 years | Chloride from sea air |
Available dimensions and delivery forms
DX51D+Z275 coils are commonly stocked and produced in thicknesses from 0.4 to 2.0 mm, with the most frequently requested widths of 1250 mm and 1500 mm. Coils are supplied with an inner diameter of 508 or 610 mm, and coil weights are agreed per order. The product can also be delivered as cut-to-length sheets or slit strips, depending on the customer's downstream process. When ordering, specify thickness, width, coating mass, surface quality such as FB in EN 10346, and whether chromate passivation or oiling is required to protect the surface in transit.
Coating and grade alternatives
Z275 is a strong default, but not always the most economical choice. Where the application is deep drawing, DX52D+Z275 or DX53D+Z275 provide a softer substrate with the same coating. Where the part is load-bearing, for example a purlin or a structural profile, a structural GD grade such as S250GD+Z275 is specified, because GD grades guarantee higher yield strength. Where the atmosphere is coastal or the required life is longer, a zinc-aluminium coating such as DX51D+AZ150 offers a substantially longer corrosion life than a comparable pure zinc coating at similar coating mass. And where weight or cost matters, the zinc-magnesium coating DX51D+ZM310 delivers about 30% better corrosion resistance than Z275 at the same coating mass, which allows a lighter coating specification for the same service life.
Inspection before use
Before processing, check the mill certificate against the order: grade, coating mass, thickness and width tolerances, surface quality and the applicable standard. On the coil itself, inspect the outer laps for transit damage, edge damage and moisture stains. Cut-edge corrosion is normal where bare steel is exposed, and the edges should be protected if the parts will be exposed to a humid or coastal atmosphere. A simple bend test on a sample confirms that the coating adheres and does not spall at the bend radius used in production.
Frequently asked questions
1. Is Z275G the same as Z275?
Yes. Z275G is a commercial way of writing Z275. Both mean a total zinc coating mass of 275 g/m2 on both surfaces, triple-spot minimum, per EN 10346.
2. How long does DX51D+Z275 last outdoors?
In a clean rural atmosphere the coating can last more than 50 years; in urban or coastal atmospheres the planning figure is about 20 years. Actual life depends on corrosivity class, orientation and drainage.
3. What thicknesses and widths are available?
The commonly stocked range is 0.4-2.0 mm thickness with widths of 1250 mm and 1500 mm, supplied as coils, sheets or slit strips, with 508 mm or 610 mm inner diameters.
4. When should I choose ZM310 instead of Z275?
When the same service life is needed at a lower coating mass, or when the site is coastal and the corrosion load is high. ZM310 offers about 30% better corrosion resistance than Z275 at equal coating mass.
5. Is DX51D+Z275 suitable for structural use?
For non-load-bearing and lightly loaded parts, yes. For load-bearing profiles, use a structural GD grade such as S250GD+Z275, which guarantees higher yield strength.
6. Can Z275 coils be deep drawn?
Within the limits of the grade. For deep drawing specify DX52D+Z275 or DX53D+Z275, and verify the bend radius against the coating to avoid cracking at sharp corners.