SteelWhat a coating class is
A zinc coating class fixes how much zinc a galvanized wire must carry, measured as mass per unit of wire surface in g/m². In both standards covered here, the required mass grows with the wire diameter, so a class is always read together with a diameter.
EN 10244-2
EN 10244-2 specifies the requirements for coating mass, other properties and testing of zinc and zinc alloy coatings on steel wire, including wire of round or other cross-section. The class letters have these general meanings:
- Class A relates to thick coatings, generally the final coating.
- Classes ending in B (for example B and AB) are usually, but not always, obtained by zinc coating followed by drawing.
- Classes C and D are the standard classes for low coating mass, usually made by hot dipping and then wiping.
The table shows the coating mass requirement for classes A, AB, B, C and D at four diameter bands, from the standard’s Table 1.
| Wire diameter d | Class A | Class AB | Class B | Class C | Class D |
|---|---|---|---|---|---|
| 1.40 ≤ d < 1.65 mm | 195 | 135 | 100 | 70 | 30 |
| 2.15 ≤ d < 2.50 mm | 230 | 170 | 125 | 85 | 45 |
| 2.80 ≤ d < 3.20 mm | 255 | 195 | 135 | 100 | 50 |
| 3.80 ≤ d < 4.40 mm | 275 | 220 | 135 | 110 | 60 |
Values are from the text of EN 10244-2:2023 and match the 2009 edition. The class and coating mass for an order are confirmed in the quotation.
ASTM A641
ASTM A641 covers soft, medium and hard temper zinc-coated (galvanized) carbon steel wire in coils for general use. Its zinc coating classes are Class 1, Class 3 (also designated A), Class 4, Class B, Class 5 and Class C. Class 2 has been removed from the general tables, and it is kept only in a supplementary requirement for nails and staples. Wire can also be ordered as “regular coating”, where the full surface is covered with zinc but no minimum mass is specified.
The table shows the minimum zinc mass in g/m² of uncoated wire surface for four diameters, in SI units. Class 4 and Class 5 are defined from 1.90 mm, so they exist for the 2.00, 3.00 and 4.50 mm rows. Only their columns are omitted. The standard gives inch-pound and SI values that are not exact equivalents, and each system is used independently.
| Wire diameter | Class 1 | Class 3 (also designated A) | Class B | Class C |
|---|---|---|---|---|
| 1.40 mm | 55 | 183 | 366 | 549 |
| 2.00 mm | 75 | 214 | 427 | 641 |
| 3.00 mm | 85 | 259 | 519 | 778 |
| 4.50 mm | 115 | 275 | 549 | 824 |
EN and ASTM classes are not interchangeable
The two standards define their coatings differently, and no table here converts one into the other. The letters show why. At a diameter of 3 mm, class B is 135 g/m² in EN 10244-2 and 519 g/m² in ASTM A641. The same letter means a different coating in each standard, and ASTM’s “A” is a designation of its Class 3, not EN class A.
When you request a quote, name the standard and the class, or give the coating mass you need in g/m². Our hot-dip galvanized wire page lists both standards. For how the coating is applied, see hot-dip vs electro-galvanized wire.
If you are buying for export, see how sourcing galvanized wire from Türkiye works, from the specification to shipping.
