In short
The number after the letter Z is the total zinc on both sides of the sheet in g/m². Z275 means roughly 20 µm of zinc per side and is recommended for outdoor use.
How to read the coating code
In EN 10346 the galvanized coating is designated by the letter "Z" and a number. The number is the minimum total on both sides of the sheet in g/m². For example, Z275 means at least 275 g of zinc per square metre across both sides.
Thickness equivalents
Since zinc has a density of 7.14 g/cm³, the coating thickness per side is approximately (coating ÷ 2) ÷ 7.14.
| Class | Total (g/m²) | Per side (approx.) | Recommended environment |
|---|---|---|---|
| Z100 | 100 | 7 µm | Dry indoor |
| Z140 | 140 | 10 µm | Indoor, HVAC |
| Z200 | 200 | 14 µm | Enclosed structures, general fabrication |
| Z225 | 225 | 16 µm | Semi-exposed areas |
| Z275 | 275 | 20 µm | Outdoor, roofing and cladding |
Which class should I choose?
- Indoor parts to be painted: Z100–Z140 is usually sufficient.
- HVAC ducting: Z140–Z200 is common.
- Outdoor, roofing, agricultural buildings: Z275 is recommended.
- Coastal and industrial atmospheres: consider a painted system over Z275.
Coating life depends on the corrosivity category of the environment (ISO 9223: C1–C5); state the application environment in your quote request for a precise assessment.
For a calculated table of life by environment, see: How long does galvanized steel last?
This article was prepared by the İpek Metal technical team. Contact us for values specific to your project.