New Zealand Steel Limited introduced ZINCALUME®, zinc/aluminium alloy coated steel, to the New Zealand market in 1994. ZINCALUME® coated steel represents a significant improvement on the traditional zinc coated galvanised steel. Since its introduction, ZINCALUME® coated steel has been widely accepted and has the major share of the steel building products market.
The ZINCALUME® coated steel has been formulated to give a significantly longer service life than a galvanised coating. This is of particular value in New Zealand where the prevailing winds carry corrosive salt laden air many kilometres inland.
The ZINCALUME® steel coating combines the corrosion protection of aluminium with the sacrificial protection of zinc, giving the advantages of both metals. The resulting alloy coating enhances corrosion resistance, making it ideal for such applications as roofing and cladding.
ZINCALUME® coated steel is produced by a continuous hot dip process similar to that used to manufacture galvanised steel. While both ZINCALUME® steel and galvanised steel products have a steel base, galvanised steel has a coating of 100% zinc, whereas ZINCALUME® coated steel has an alloy coating of 43.5% zinc, 55% aluminium and 1.5% silicon.
In almost all applications, ZINCALUME® coated steel will out-perform galvanised steel. There are however, a small number of applications for which galvanised steel is more suitable.
Limitations Of Use
ZINCALUME® coated steel must not be used for:
- Formwork in contact with wet concrete
- Products to be embedded in concrete. However, where very small volumes of concrete are involved (e.g. splashes) which are able to cure quickly, there is little corrosive effect.
- Animal shelters where ammonia levels are constantly high.
- Fertilizer storage sheds and containers.
- Culverts, or where ZINCALUME® coated steel material is buried in the ground
- Water tanks.
- Highly alkaline environments (e.g. cement manufacture).
- Coolroom products.