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Latest Standards for Hot Dip Galvanizing

The Australian steel business is booming as there are many government roads & rail projects currently in process. These growing works demand certain levels of national compliance, and one of the main areas of concern is galvanization.

Hot dip galvanization is a steel surface finish that can be essential to the durability of a finished structure. The galvanizing process produces a coating of a metallic zinc & zinc-iron alloy layer which bonds metallurgically to the steel base. This coating helps to prevent corrosion and ensure the longevity and strength of steel structures. Various coating thicknesses are necessary depending on the use of the steel product and the location of its installation.

In recent years, fresh standards have been released for hot dip galvanizing. These standards (AS/NZS 2312.2 and AS/NZS 4680) provide guidance for the minimum average coating thicknesses for various steel thicknesses as well as summarise the corrosion rate for galvanized steel in Australia’s climate. Hard Bakka follows these closely and uses the standards to guide our processes with hot dip galvanizing (HDG).

Meeting the Standards

Galvanizers must be able to comply to the specified standards to generate an acceptable product. Proper hot dip galvanizing (when completed to meet AS/NZS 4680 standards) should produce the maximum thickness coating possible relative to steel thickness. This results in consistently providing a longer life to first maintenance than any other galvanized coating.

Not all steels will produce coatings in accordance with the specified thicknesses, however. New research reveals that aluminium-killed steels are often produced with low levels of silicon, which has a negative impact on coating thickness. This composition can result in coating thicknesses as low as 10-20% below the recommended levels. The resulting thicknesses may be appropriate for areas of low corrosivity, but may not meet the specifications of regions with a higher climate impact. The outcome of the hot dip galvanizing process will be highly dependent on the existing steel composition.

There are options for increasing durability. In some cases, duplex coatings may be advisable, where hot dip galvanized products are top coated with a paint system. Products such as XLERPLATE® are subject to this steel composition issue, as they are composed of a small percentage of silicon. When using plate products such as these, abrasive blasting can help to obtain a HDG thickness which complies with AS/NZS 4680. In addition, a top coat of zinc-rich paint may be applied if the Al-killed steel is only a small part of a fabrication.

Hard Bakka’s Response to the Hot Dip Galvanizing Standards

As steel fabricators, Hard Bakka are committed to meeting existing steel standards in every project. When purchasing material to be hot dip galvanized for government works, or for products to be used in an environment of high corrosion, we inform our steel suppliers of the intended use. We communicate closely with our galvanizing service provider to ensure compliance on the finished steel products. We always advise on the best steel products and hot dip galvanizing processes to achieve the desired outcome. Hard Bakka also offer our clients a tested sample for approval before fabrication to ensure compliance with their project needs. By using only steel from the same batch, we can provide better consistency through the job roll-out. .

For the best in structural steel and metal work in NSW, call our team at Hard Bakka.