Hot Dip Galvanizing Standards

There are a number of Standards referenced in Australia dealing specifically with galvanizing including batch hot dip galvanizing.  The most important Standards are listed below.  There are many more local and international Standards that cover different aspects of hot dip galvanizing and zinc coatings.  If the one you are interested in is not listed below, the GAA can provide advice on the details of the Standard.

Australian Standards

The key galvanizing Standards in Australia are AS/NZS 4680 (batch galvanizing), AS/NZS 1214 (threaded fasteners) and AS/NZS 2312.2 (design and durability).

AS/NZS 4680: Hot-dip galvanized (zinc) coatings on fabricated ferrous articles

This Standard specifies requirements and tests for hot-dip zinc coatings on fabricated ferrous articles including structural steel, steel reinforcements, steel sheet fabrications, assembled steel products, tubular fabrications, fabricated wire work, steel forgings, steel stampings, ferrous castings, nails, and other small components.  AS/NZS 4680 applies to both centrifuged and non-centrifuged articles, but ‘stand-alone’ threaded articles are normally specified as AS/NZS 1214 (see below).

The key difference for this Standard from all the other galvanizing Standards is that the article to be hot dip galvanized is usually fabricated into a finished product prior to galvanizing, meaning the article will be ready to use once it leaves the galvanizing factory and all parts of the steel article are fully protected from corrosion.

The batch hot dip galvanized coating is described as the coating mass (g/m²) or thickness (µm or commonly stated as “microns”) on a single surface.  In most cases it is easier to measure the thickness of the coating, but the historical way of specifying the coating is by a mass designation.  For example, HDG600 means a fabricated article with a nominal coating mass of 600g/m² on a single measured area.

AS/NZS 1214: Hot-dip galvanized coatings on threaded fasteners (ISO metric coarse thread series)

This Standard specifies requirements for the mass, quality and testing of hot-dip galvanized coating on steel bolts, screws, nuts and other fasteners having ISO metric coarse threads, in the nominal size range M8 to M64 inclusive.  In 2016 this Standard was updated to be a direct text adoption of ISO 10684 except that ISO 1461 was replaced by AS/NZS 4680.  Major changes from the previous edition include the increase in size from M36 to M64 and the inclusion of property class 10.9 bolts, class 12 nuts and much more detail on thread tolerances for end users.

AS/NZS 1214 deals with the mass and adhesion of the coating and test methods.  It also defines the oversize tapped screw thread limits for internal threads, but does not deal with other dimensions which are as per the relevant fastener product Standards.

It is important to recognize HDG nuts are required to be hot dip galvanized as blanks and threaded only after hot dip galvanizing.  The relevant product Standards do not allow re-threading (that is, more than once after galvanizing).  In this case the uncoated nut thread is protected from corrosion by the galvanized bolt thread.

AS/NZS 2312.2: Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings – Part 2: Hot dip galvanizing

This Standard provides guidelines and recommendations regarding general principles of design and durability, appropriate for articles to be hot dip galvanized for corrosion protection.  It provides durability comparisons for structural articles coated to the various galvanizing standards listed above.

This Standard significantly builds on the advice contained in the 2002 edition of AS/NZS 2312 and provides much more information on good design practice.  The durability comparisons for the various coatings covered are particularly useful and will assist in the choice of appropriate product.

AS/NZS 2312.2 is based on parts 1 and 2 of the ISO 14713 series, but heavily modified and further developed for Australian use.

AS 1397: Continuous hot-dip metallic coated steel sheet and strip—Coatings of zinc and zinc alloyed with aluminium and magnesium

This Standard specifies requirements for continuously hot-dip metallic coated sheet steel and strip supplied in thicknesses up to and including 5.0 mm.

The coating on the strip is normally described by the coating mass (g/m²) as a total of the coating on both sides of the sheet/strip.  In general, the coating thickness on these products is considerably less than batch hot dip galvanized items of the same thickness.  For example, a coating designation of Z350 means the total mass on both sides is 350 g/m², or approximately 175 g/m² on a single area.  This means the thickness can be as low as 20µm and the durability will 2.5 to 4 times less than a batch galvanized item of the same steel thickness made to AS/NZS 4680.

AS/NZS 4792: Hot-dip galvanized (zinc) coatings on ferrous hollow sections, applied by a continuous or a specialized process

This Standard specifies requirements for the mass, quality & testing of hot-dip galvanized coatings applied to:

• Hollow sections galvanized on both surfaces in a specialized plant – e.g. signposts to HDG300;
• Hollow sections produced by welding pre-galvanized steel strip – e.g. DuraGal^PLUS Z135/135; and,
• Hollow sections galvanized on external surfaces only, using a continuous (in-line) process – e.g. DuraGal®.

The Standard does allow some items to be specified with different coating thickness (including no coating) on the inside of tubes, so the specifier should be clear as to the corrosion protection requirements of the project before specifying these products.  These products are not normally used in corrosive environments beyond C3 without a paint topcoat due to limited durability.

International Standards for hot dip galvanizing

The table below shows the common ISO and EN Standards and following this is the scope of the most important Standards.  These Standards can include the preface “EN ISO”, which means the Standard is a European normative that is otherwise identical to the ISO Standard.  ISO 1461 is the most commonly used International Standard.

North American Specifications for hot dip galvanizing

The table below shows the common used US and Canadian Standards.  ASTM A123 is the most common specified Standard.

SPECIFICATION

• • Hot Dip Galvanizing Standards
  • Standard Specification for Hot Dip Galvanizing
  • Warranties
  • Inspection of Hot Dip Galvanized Products
  • Hot Dip Galvanizing Inspector Program
  • Life Cycle Costing for Galvanizing
  • Life Cycle Cost Calculator