ISO 1461 – the British Standard for hot dip galvanized coatings on iron and steel articles – has recently been updated. The new 2022 version supersedes the 2009 version.
Several important changes have been made to the document. As the changes affect both us – as galvanizers – and you – our customers – we’ve listed them below:
The most significant changes to the document concern the galvanizing of ultra-low reactive steels, coating thickness measurements on ancillary elements, removal of flux residues and zinc ash, and the renovation of galvanized steelwork.
There has been no fundamental change to the method of assessment of coating thickness, but allowances for measurements on ancillary elements and ultra-low reactive steels have been introduced. The revised standard states that thickness measurements should not be taken on ancillary elements (e.g. brackets) unless specifically requested by the customer. Recognition that certain steel compositions can exhibit ultra-low reactivity during galvanizing (i.e., cannot satisfy the standard minimum coating thickness requirements) has been introduced. Articles produced from steel with a section thickness greater than 3mm which have a composition of ≤0.01 % silicon AND an aluminium content >0.035 %, that exhibit ultra-low reactivity during galvanizing, can now be subject to lower coating thickness requirements (see 6.5 below). The variation to the standard requirements must be included in the Declaration of Compliance if one is to be provided.
An important change has been made with regards to removal of flux residues. In the 2009 version, flux staining/residues were not permitted anywhere on the article, but the updated version now acknowledges that removal (including zinc ash) in some fabrications is practically impossible. Therefore, if ‘access is restricted, for example inside hollow sections’ flux residues and zinc ash are permissible.
The key changes to the content on renovation of galvanized steelwork are the requirement for the pigment in a zinc-rich paint to conform to ISO 3549 ‘Zinc dust pigments for paints — Specifications and test methods’ which has been removed but must still offer sacrificial protection to the steel; and also, more comprehensive information within Annex C – Renovation of uncoated or damaged areas.
1 Scope – No significant changes were made to the scope, however clarification to clearly state the standard specifies the general properties of, and test methods for, ‘hot dip galvanized’ coatings were incorporated.
2 Normative references – There has been slight changes to the standards contained within the normative references to reflect their status within the document. Notably, ISO 14713-2 ‘Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron and steel in structures — Part 2: Hot dip galvanizing’ has been included.
3 Terms and definitions – Five new terms, galvanizer (3.3), after-treatment (3.18), additional coating (3.19), wet storage stain (3.20), duplex system (3.21) have been introduced to allow for simplification of the main text.
4 General Requirements – No significant changes.
5 Acceptance inspection and sampling – No significant changes, except the minimum number of articles in a control sample can be subject to deviation following agreement within the supply chain. The new text now reads ‘Unless otherwise agreed, the minimum number of articles from each inspection lot that forms the control sample shall be in accordance with Table 1.’
6.1 Galvanized coating properties – Appearance – Clarification has been made that only the visible significant surfaces are subject to the appearance acceptance inspection. Flux residues and zinc ash shall be removed where they can affect the intended use of the HDG article, or its corrosion resistance requirement, unless access is restricted, for example inside hollow sections. Previously, flux residues were not permitted anywhere on the article.
The coating, when first examined by normal vision from a distance of not less than 1m shall be free from blisters (i.e. raised areas without solid metal beneath), roughness and sharp points (if either that roughness or sharp point can cause injury) and uncoated areas. The 2009 version also included ‘Nodules’, however this has now been omitted from the list of prohibited coating features.
6.2 Galvanized coating properties – Thickness – The greater relevance of ISO 2178 ‘Non-magnetic coatings on magnetic substrates — Measurement of coating thickness — Magnetic method’ amongst the other coating thickness measurement standards has now been acknowledged.
6.2.3 – Reference areas – now states that ‘Unless otherwise agreed, reference areas shall not be chosen from ancilliary elements, when they are significantly smaller than the main elements of a larger article’ due to being thinner or less reactive. Acceptance that flame-cutting, laser-cutting and plasma-cutting can lead to the steel being more unreactive during galvanizing and decreased cohesion of the coating has been made. The 2022 edition now reads ‘In order to obtain the required coating thicknesses more reliably and to ensure adequate cohesion or adhesion of the coating, flame-cut, laser-cut and plasma-cut surfaces should have been ground off and sharp edges should have been removed during fabrication and prior to delivery to the galvanizer.’
The minimum size of a reference area is now clearly defined as being 10cm2.
6.3 – Galvanized coating properties – Renovation – The circumstances where a lower (than 100μm) minimum repair coating thickness can be agreed, has been expanded to account for thinner galvanized coatings around the damaged area, for example, where aesthetics may be important.
6.4 – Galvanized coating properties – Adhesion – No significant changes, however a new ‘note’ has been added which recognises that cohesion of the galvanized coating can be affected by a steel being ultra-low reactive – as defined in ISO 14713-2 Table 1, Note 4. There is still not a suitable international standard for testing the adhesion of galvanized coatings.
6.5 – Galvanized coating properties – Acceptance Criteria – It is within this section where the adjustment for ultra-low reactive steels has been introduced. The new text reads:
‘For articles with steel section thicknesses greater than 3 mm, produced from steels with compositions ≤0,01% silicon that also have aluminium contents >0,035%, that exhibit ultra-low reactivity during galvanizing and therefore cannot satisfy the minimum galvanized coating thickness in Table 3, the next lowest category of steel article section thickness given in Column 1 of Table 3 shall be applied. In such cases, if a declaration of compliance must be provided then it shall state this variation including the adjusted minimum mean galvanized coating thickness requirement that has been applied to the inspection lot.
NOTE – Certain steels, including but not limited to, either steels suitable for laser cutting with chemical compositions as given in ISO 14713-2:2019, Table 1, Note 4 or steels with high surface smoothness, or both, can exhibit ultra-low reactivity during galvanizing (see ISO 14713-2) and the coating thickness achieved on such steel articles can possibly not be dependent on steel section thickness. These factors are beyond the control of the galvanizer and can also result in even lower coating thicknesses than given in the next lowest category of steel article section thickness given in Table 3.’
7 – Declaration of Compliance – The terminology has been modified, in ISO 1461:2009 this was referred to as a ‘Certificate of compliance’ whereas now it is called a ‘Declaration of compliance’. Clarification that this must meet the requirements of ISO 10474 ‘Steel and steel products — Inspection documents’ has been incorporated.
Annex A (normative) – Information to be supplied – An important sentence has been added to A.2– Additional information for provision by the purchaser, which states that ‘an indication of any ancillary elements within the article that must be considered as part of the significant surfaces from which reference areas might be taken (e.g. if the ancillary elements are safety critical).’ This is to account for the default procedure of not taking coating thickness measurements on ancillary components.
Annex B (normative) – Safety and process requirements – Venting and Drainage of Articles – Verification has been incorporated into this Annex that states the work presented for galvanizing should be in accordance with ‘either the guidance given in ISO 14713-2 or any further specific guidance for the articles to be processed that may arise from consultations with the galvanizer, or both.’
Annex C (informative) – Renovation of uncoated or damaged areas – Annex C contains considerably more guidance on the requirements for a zinc-containing paint used for repair than the previous version (Annex C.1 – Zinc-containing paints). See new guidance below.
‘A dry paint film that is capable of conducting electricity and which is in electrical contact with the basis metal will ensure that sacrificial protection is provided.
Other things being equal, sacrificial protection increases with increases in metallic zinc content in the dried film but does not increase further above approximately 94% by weight of zinc for paints containing zinc dust. However, other factors can be important.
A zinc-containing paint with a zinc dust content that is equal to or greater than 80% by mass in the dry film can be considered suitable for renovation of uncoated or damaged areas. Conformity of the zinc dust pigment, within a zinc-containing paint, with ISO 3549 is a further indication of suitability.
Zinc-containing paints based on lamellar shaped, rather than spherical, zinc particles may achieve adequate protection at lower contents of zinc in the dry film than for zinc dust paints with spherical particles.
Zinc-containing paints may also include an aluminium content for aesthetic purposes.’
Annex D (informative) – Determination of thickness – No significant changes.
Annex E (informative) – Corrosion resistance of galvanized coatings – Annex E has been updated to include supplementary information regarding the long-term, steady-state zinc corrosion rates given in ISO 9224 ‘Corrosion of metals and alloys — Corrosivity of atmospheres — Guiding values for the corrosivity categories.’ This is in appreciation that ISO 14713-1 ‘Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron and steel in structures — Part 1: General principles of design and corrosion resistance’ provides first year exposure corrosion rate data and is therefore conservative guidance.
If you have any queries regarding the updated standard, please contact the Premier Galvanizing Technical Team
You can also contact the Galvanizers Association Technical Department regarding the updated standard or its interpretation. Call their free Service Line on telephone: 0121 355 8838 or email Dr Desmond Makepeace at email@example.com.Next page