Metroll Newcastle - Corrosion Protection

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Corrosion Protection

AS/NZS4600 requires that cold-formed sections must be adequately protected from corrosion attack. The protection options range from basic painting systems through to heavy galvanised coatings.

Before specifying the type of purlin, you need to consider the purlin manufacturing process, type of structure, climatic conditions, the proximity to salt sprays and maintenance provisions.

The zinc coating and quality-controlled galvanising process used in GALVASPAN® steel ensures a high standard of corrosion protection.

The two standards of corrosion protection used in GALVASPAN® steel are 350g/m² zinc coating weight and 450g/m² zinc coating weight. Both 300mm and 350mm purlin sizes are usually produced with 450g/m² zinc coating.

The zinc coating weight is the total weight of zinc on the base steel, and is usually referred to by the coating class, that is 350g/m² of zinc is class Z350. The respective coating classes represent approximate coating thickness of Z350 - 24µm and Z450 - 31µm of zinc on each side of the strip. Z450 purlins should be specified for environments requiring additional corrosion protection.

Base Metal Thickness	Coating Class	Total Coated Thickness (mm)
1.5	Z350	1.548
1.6	Z350	1.648
1.9	Z350	1.948
2.0	Z350	2.048
2.4	Z350	2.448
2.5	Z350	2.548
1.5	Z450	1.562
1.6	Z450	1.662
1.9	Z450	1.962
2.0	Z450	2.062
2.4	Z450	2.462
2.5	Z450	2.562
3.2	Z450	3.262


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