Aluminum-Zinc vs. Zinc-Aluminium vs. Galvanised

Aluminum-Zinc vs. Zinc-Aluminium vs. Galvanised

What is the secret sauce beyond our 50 year warranty?


GERARD’s research and development work combines laboratory work with real life exposure sites and more than 50 years of experience in the use of steel for roofs. GERARD Roofing Systems has experimental roofs that were installed almost 30 years ago and we continue to motor them.

In a severe coastal environment on the wild, rugged west coast of the North Island of New Zealand tiles made from three different substrates, galvanised steel (100% zinc), zinc-aluminum (95% zinc and 5% aluminium) and aluminum-zinc (43.5% zinc, 55% aluminium, 1.5% silicon) were installed side by side. The galvanized tiles had to be replaced after 14 years and the zinc-aluminum were replaced after 16 years.

The aluminum-zinc tiles remain in good condition after almost 30 years and will continue to be evaluated well into the future. The aluminum-zinc tiles show no signs of corrosion of the side laps or of the general surface area and certainly are proving superior to galvanised steel and zinc-aluminum tiles in other areas too, particularly in unwashed areas such as side laps or turn-ups under flashings.

In all of GERARD’s laboratory and real life testing, Aluminum-zinc steel continues to outperform the alternatives of galvanized and zinc-aluminum steels as the best roof tile material.


Even world’s largest steel manufacturer states that auminium-zinc outperforms galvanised and zinc-aluminum steel.

Hence GERARD Roofing System’s confidence that the aluminum-zinc substrate provides the longest life for its roofing tiles.

Your advantage

Aluminium-Zinc protection provides superior corrosion resistance making your GERARD roof lasting at least twice as long as a galfan steel roof.

That is why we can boldly give a 50-year warranty for your GERARD roof.