Home

 

Standards

For hot-dip galvanizing specifications, quality requirements and test methods are given in the following international standard: EN ISO 1461 “Hot dip galvanized coatings on fabricated iron and steel articles – Specifications and test methods”.

General requirements

According to the standard the coating quality, thickness, structure and physical and chemical properties are influenced by steel composition, mass and the conditions during the hot-dip galvanizing process. Requirements for information between galvanizer and customer are specified in a series of appendices to the standard.

Normally the minimum quality requirement regarding coating thickness and surface appearance are in accordance with EN ISO 1461.

To make it possible to fulfill these above requirements, the customer should inform the galvanizer about steel composition and desired coating thickness according to standard.

Article and its thickness

Local coating thickness (min)

Ám

Mean coating thickness (min)

Ám

Steel > 6 mm
70
85
Steel > 3 - < 6 mm
55
70
Steel > 1,5 - < 3 mm
45
55
Steel < 1,5 mm
35
45
Castings > 6 mm
70
80
Castings < 6 mm
60
70

Fig. 1. Coating thicknesses required by EN ISO 1461: 2009.

Thicker coatings than required by ISO standards

In some cases, thicker coatings than those defined in EN ISO 1461 may be required. For example, in more aggressive environments or when extra durability is needed. In the Nordic countries thicker coatings may be ordered after agreement between customer and galvanizer. Information about how to achieve thicker coatings is given as a national appendix to EN ISO 1461.

In fig 2, the figures 115, 165 and 215 represent the coating thickness in micrometers at 6 mm steel thickness. In the two other columns, optimal and range values for silicon content which is required to achieve these thicker coatings are given.

 

Coating thickness group (Ám)

Optimal silicon level (%)
Silicon range (%)
Fe/Zn 115
0.18
0.15-0.21
Fe/Zn 165
0.25
0.22-0.28
Fe/Zn 215
0.32
0.29-0.35

Fig. 2. Optimal and range values for silicon when higher coating thicknesses are required.

Galvanizing of thin sheet steel

Thin sheet is hot-dip galvanized according to ASTM A525. The Swedish standard follows the zinc coating directives in the American standard, which is used internationally.

Symbol

Coating thickness (min)
in g/m2 *

Coating thickness (min)
in Ám**
350
350
300
(25)
275
275
235
(20)
225
225
195
(16)
200
200
170
(15)
140
140
120
(10)
100
100
85
(7)

Fig.3. Hot-dip galvanizing of thin sheet - coating thickness

* Coating on both side of a square meter.

** Coating in microns on one side of the sheet (only for information).

Branch standards

In Sweden, branch standards for the following aspects are given:


• Finishing and renovation

• Coating thickness control
• Coating adherence testing


For products with threads, special standards exist. In these standards, information about undercutting of outer threads (screw) or over cutting of inner threads are given.

 

Branch standard - Finishing and renovation

Branch standard - Coating thickness control

Branch standard - Adhesion test

 

 

 
Home