Intumescent paint coating corrosivity ratings in the Australian atmosphere

Two key Australian Standards - AS 4312 and AS/NZS 2312.2 - provide information on the corrosion rate of steel under a range of atmospheric conditions around Australia.

These corrosive ratings form an integral part of specifying an intumescent paint coating system for a building project.

The other key criteria in creating a specification is, of course, the fire rating level (or FRL).

The CSIRO (as well as other organisations) have carried out extensive mapping to establish the corrosivity of the Australian climate. AS 4312 is the best source of Australian data for corrosivity of steel in the local environment.

The corrosion rate estimates for steel in the various standards are consistent and  interchangeable with the International Standards ISO 9223 and ISO 14713.1 for the purposes of service life estimates.

Generic examples
Specific examples
Dry indoors
Inside heated or air-conditioned buildings with clean atmospheres.
Commercial buildings
Arid/urban inland
Most areas of Australia at least 50 kilometres from the coast.
Canberra, Ballarat, Toowoomba and Alice Springs.
Inland 3-6 km for a less sheltered bay or gulf.
Adelaide and environs.
Can extend to within 1 km from quiet, sheltered seas.
Suburbs of Brisbane, Melbourne, and Hobart.
From 1 to 10 kilometres inland, along ocean front areas with breaking surf and significant salt spray.
May be extended inland up to 50 kilometeres by prevailing winds and local conditions.
Metro areas of Perth, Wollongong, Sydney, Brisbane, Newcastle and the Gold Coast
From 100 metres to 3-6 kilometres inland for a less-sheltered bay or gulf.
Adelaide and environs.
From 50 metres up to 1 kilometre inland, around sheltered bays.
Port Philip Bay and urban/industrial areas with low pollution levels.
Calm seashore
From 200 metres up to 1 kilometre inland in areas with rough seas and surf.
May be extended inland by prevailing winds and local conditions.
All coasts.
From the shoreline to 50 metres inland, around sheltered bays.
In the immediate vicinity of calm salt water such as harbour foreshores.
Surf seashore
Within 200 metres of rough seas and surf beaches.
May be extended inland by prevailing winds and local conditions.
More than 500 metres from the coast in some areas of Newcastle.
Severe surf shoreline
Surf beach shoreline regions with very high salt deposition.
Some Newcastle beaches.

AS 4312 includes maps showing estimates of corrosivity zones for several major cities of Australia.

In addition, detailed corrosivity maps for South Australia prepared by the South Australian government are available at SA Government Corrosion Environment Maps.

Other states may have similar resources.

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