Corrosion Resistance

ZINCALUME® coated steel has superior long term corrosion resistance in most atmospheric conditions. This is achieved through the combination of the sacrificial protection of the zinc and the barrier protection of the aluminium. Test sites from around the world over a period of 25 years have provided a wealth of information about comparative performance of galvanised and ZINCALUME® coated steel products. Test sites are placed in many different environments, ranging from typical rural to severe marine. Corrosion rates are determined by exposing samples of ZINCALUME® coated steel and galvanised steel on standard test racks and regularly monitoring the coating performance over a number of years.

Though corrosion rates vary according to the severity of conditions, ZINCALUME® steel coatings out-perform galvanised coatings in almost all environments. This is particularly true in marine environments where ZINCALUME® coated steel will provide a significantly longer service life than galvanised steel. 


ZINCALUME® coated steel has a finely spangled silvery matt finish. After exposure the surface finish darkens over time as the resin coating weathers away. This change is a natural one and is visual only. The protective properties of the product are not affected.


ZINCALUME® coated steel is readily paintable using good quality primers and water-based acrylic topcoats. Paint manufacturers' instructions should be followed.

Dirt, grease and any loose materials must be cleaned off so the surface is clean and dry prior to the first coat being applied.

Unwashed Areas

Compared to galvanised steel, ZINCALUME® coated steel performs exceptionally well in areas not regularly washed by rainwater. However, as with any steel based product, regular washing of areas not naturally rain washed is essential to ensure that a satisfactory life is realised from the product.

Rainwater Systems

Rainwater collected from roofs clad with products made from ZINCALUME® coated steel and COLORSTEEL® prepainted steel, will comply with the provisions of NZBC G12.3.1, provided the water is not contaminated from other sources.

The first 25 mm of rainfall from a newly installed roof must be discarded before drinking water collection starts. Where a paint or paint system is applied to the roof, its suitability for the collection of drinking water must be established from the manufacturer.

Fire Testing

New Zealand Steel’s coated products have been tested in accordance with ISO 5660 Part 1 and Part 2 by CSIRO – Materials Science and Engineering, North Ryde, NSW, Australia.

The tests were performed in accordance with International Standard ISO 5660-1:2002 Reaction to fire tests – Heat Release, smoke production and mass loss rate – Part 1: Heat release rate (cone calorimeter method) and Part 2: Smoke production rate (dynamic measurement). All test specimens were exposed in the horizontal orientation with standard pilot operating.

The Group number was determined in accordance with Verification Method C/VM2 Appendix A Paragraph A1.2 and Paragraph A1.3 of the New Zealand Building Code. The Average specific extinction area was determined in accordance with Verification Method C/VM2 Appendix A Paragraph A1.2 of the New Zealand Building Code.


Group Number

Average specific extinction area


Group 1 - S



Group 1 - S



Group 1 - S



Group 1 - S