Everyone wants to feel confident in their purchasing choices and what they specify to clients. Builders in particular need the assurance that building products will be robust and resilient for years to come, otherwise there is the risk of rectification issues and costs down the track – not to mention the possibility of a reputational hit as well.
When you think of building products such as steel, you would no doubt consider the material to be synonymous with strength and durability. After all, it commonly plays a role in various elements of a building, from your foundations and flooring systems to your framing, columns, roofing or beams. Therefore, given the essential part steel plays in building, you don’t want its strength or durability to be compromised by corrosion.
To protect steel from the effects of corrosion, steel manufacturers typically use galvanised coatings, which are known to be a tough, long-term solution. But there is more to galvanised steel than you may think.
In a nut shell, zinc is generally applied to steel during the galvanising process (with the zinc serving as a sacrificial coating since it will corrode before the steel). This may be accomplished in a number of different ways, for example, hot dip galvanising (HDG), zinc (thermal) spraying or electrogalvanising.
According to Arun Syam, Business Development Manager at Austube Mills (part of Infrabuild), these methods produce different thickness levels and therefore give your steel different life spans.
‘It is well known and scientifically established that for metallic coatings the zinc thickness is proportional to service life,’ he says. ‘Specifically, double the thickness and the service life is doubled in corrosive environments.’
This is noted in AS/NZS2312.2 ‘Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings, Part 2: Hot dip galvanising’ (see figure 1).
Arun says that there is a market misconception that all galvanised steel is the same, when in fact electrogalvanising – while providing some corrosion protection – has a thinner coating to HDG and is therefore not as rust resistant.
DuraGal®, a well-known and reputable light galvanised coating for steel pipe and tube products that uses the HDG process, has a minimum average galvanised coating of 100g/m2 both inside and out. This makes it not only strong but durable for Australian conditions in a number of corrosion applications as defined in Table 6.2 of AS/NZS2312.2 (except highly corrosive environments such as areas affected by breaking surf, immersed in corrosive soils, etc). The DuraGal tubular products you may see in a house, which are available nation-wide from Austube Mills through more than 200 distribution partners, include products used in flooring systems or house stumps, jambing studs, roof and verandah beams or verandah posts, patios, pergolas, sheds, garages, columns, trusses and fencing.
‘DuraGal has twice the protection and coating life of standard electrogalvanising,’ Arun says. ‘Some products offer less than half the zinc coating thickness of DuraGal, so builders and trades should be aware of the thickness levels of the galvanised products they purchase. Not all gal is DuraGal.’
Austube Mills has provided innovative steel solutions for Australian designs and conditions for more than 80 years, with all products third-party certified through ACRS to meet Australian Standards.
This article was compiled with contributions from DECO, Pryda, Global Scaffold and Austube Mills.