EN ISO 1461: The Hot Dip galvanizing Standard Explained
Technically reviewed by the Standards Committee, chaired by William Smith. EN ISO 1461:[2022].
The recognised standard for hot dip galvanized coatings on fabricated iron and steel articles, BS EN ISO 1461 sets out requirements for coating properties and the methods used to inspect and test them. It creates a consistent framework for the marketplace, helping purchasers specify with clarity, galvanizers work to defined requirements, and designers and end users have confidence in the corrosion protection being provided. In doing so, it supports informed decisions, clear communication and trust throughout the supply chain.
EN ISO 1461: Setting the standard for corrosion protection
EN ISO 1461 Coating Thickness for galvanizing
Hot dip galvanizing forms a protective zinc coating across the steel’s exposed surfaces. Coating thickness depends principally on steel thickness (see the table below), with surface condition and chemical composition also influencing the result.
The coating often exceeds the minimum thickness specified in EN ISO 1461. Where service-life estimates are based on these minimum values, a thicker coating can provide a longer period of protection under the same exposure conditions.
Further guidance on design and corrosion protection is provided in EN ISO 14713 Parts 1 and 2.
EN ISO 1461: coating minimum masses/ thickness on articles that are not centrifuged
| Articles & its thickness | Local coating (minimum) | Mean coating (minimum) | ||
|---|---|---|---|---|
| g/m² | µm | g/m² | µm | |
| steel > 6 mm | 505 | 70 | 610 | 85 |
| steel > 3 mm to ≤ 6 mm | 395 | 55 | 505 | 70 |
| steel ≥ 1,5 mm to ≤ 3 mm | 325 | 45 | 395 | 55 |
| steel < 1,5 mm | 250 | 35 | 325 | 45 |
| castings ≥ 6 mm | 505 | 70 | 575 | 80 |
| castings < 6 mm | 430 | 60 | 505 | 70 |
EN ISO 1461: coating minimum masses/ thickness on articles that are centrifuged
| Articles & its thickness | Local coating (minimum) | Mean coating (minimum) | ||
|---|---|---|---|---|
| Articles with threads: | g/m² | µm | g/m² | µm |
| > 6 mm (diameter) | 285 | 40 | 360 | 50 |
| ≤ 6 mm (diameter) | 145 | 20 | 180 | 25 |
| Other Articles: | ||||
| ≥ 3 mm | 250 | 45 | 325 | 55 |
| < 3 mm | 505 | 35 | 575 | 45 |
National Building Specification (NBS) for Galvanizing
Hot dip galvanizing can be specified using relevant clauses in the National Building Specification (NBS), including G10 – Structural steel framing. NBS also provides general guidance on corrosion protection.
For help identifying the appropriate clause for your application, contact Galvanizers Association.
National Structural Steelwork Specification (NSSS) and EN 1090-2
The galvanizer typically works as a specialist subcontractor to the steel fabricator, with whom they have a contractual relationship. The client’s galvanizing requirements should therefore be clearly included in the specification issued to the fabricator, who is responsible for communicating them to the galvanizer.
How can you achieve thicker Hot dip Galvanized coatings?
Thicker galvanized coatings can provide additional corrosion protection in particularly aggressive environments, although the minimum coating thicknesses specified in EN ISO 1461 are sufficient for most applications.
Where additional thickness is required, grit blasting before galvanizing can help achieve it. The steel’s section thickness and chemical composition also influence the result; in some cases, thicker coatings may be achievable without additional surface preparation.
Specifying reactive steel to increase coating thickness is appropriate only for certain applications. Any requirement for a thicker coating should be discussed and agreed with the galvanizer before specification, including its feasibility and the method used to achieve it.
EN ISO 1461 advantages
EN ISO 1461 - 8 reasons for Unrivaled corrosion Protection
A guaranteed minimum coating
EN ISO 1461 sets minimum local and mean coating thicknesses according to the thickness of the steel. These are produced by the galvanizing reaction itself, not by an applicator’s skill on the day, and gives specifiers a clear, measurable basis for quality assurance. However, in a small number of cases, unreactive, low-silicon steels can prevent the coating thicknesses required by EN ISO 1461 from being achieved.
Complete coverage, inside and out
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A coating that is part of the steel
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A coating that sacrifies itself
Zinc corrodes in preference to steel. If the coating is damaged, the surrounding zinc continues to protect the exposed steel and stops rust spreading beneath the coating.
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Thickness matched to the job
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Easy to inspect and verify
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Predictable, maintenance-free life
Because EN ISO 1461 guarantees a minimum coating thickness, coating life can be predicted. EN SO 14713-1 provides guidance on the expected corrosion rate in different environments. In most environments a maintenance free coating life 60 years may be achieved and in some cases a life of over 100 years might be achieved.
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