Zincalume or Galvanised?

[ytbc]

Thanks for the advice on the Makita saw - the shack is now progressing - I am planning to clad it in corrugated iron - roof and walls - I have been told the galvanised iron is not as shiny as zincalume - or at least it isn't when gets older - any views on which is preferable? I would prefer something not to shiny as it is a bush block.

[echnidna]

dunno if you can still get galv. sheeting

[fordworkmate]

yuo can still get Gal corro. Any of the roofing suppliers will supply. It will fade but still takes a year or two to do so. Definitely a better look in the bush, We use it fairly often on heritage work.

[Harry72]

Galv is zinc isnt it?
Galv =electroplated in Zn?
Zincalume =hot dipped in Zn?
Anyone know?

[billrule]

I think you'll find that zincalume is a pretty hi-tech multi-layer process, probably involving electroplating steps, and a pretty good product for strength-for-lightness and durability (as long as all contacting metals are compatible). This compatability issue has been touched on elsewhere by those who know-(possibly on this forum-) but is important to get right.
Gal is (I think) on a heavier gauge sheet, and is a straight zinc coating- traditional and more "timeless"

[Bleedin Thumb]

Good question Harry.

I recently asked a similar question and I feel I may have gotten the wrong advise. My take on it is this -

The corrugated iron is now zincalum finished or colorbond finnished

I don't know what the old corrugated iron was ...if or not it was hot dipped zinc and I don't know if it is still available.

[Harry72]

I know at work when we dip metal into molten zinc it looks like zincalume after its cooled down.(it did have small amounts of lead in it as well tho bout .1%)

[echnidna]

Gal is plain zinc, I think the real old stuff mighta been hot dipped , dunno about the later stuff.

Zincalume is coated with an aluminium/zinc alloy, and is incompatible with gal sheet
(It doesn't even like galvanised roof screws)

[Barry_White]

Information from the horses mouth. Ex Lysaght Bluescope Rep/Manager.

Both Zincalume and Gal are hot dipped continuously on a machine that unrolls the flat steel coil on one end of the machine through a bath of molten zincalume or gal and the thickness of the coating is controlled by a blast of air across the surface of the steel and when it comes out of the machine it is rolled up again into a coil that can be up to 10 tonnes in weight.

This machine runs at high speed and and never stops through what is called an accelerator that allows them to join and cut the flat strip whilst the machine is continuously running.

The Colorbond is painted in a similar manner except it runs through a horizontal oven to dry the paint and the steel strip is supported on a cushion of air that runs for about 50 to 75 metres in length.

The gal coating is actually pure zinc and the zincalume is a mixture of zinc and aluminium.

Gal has a larger spangle than zincalume. As was said earlier gal will dull off to a dark grey and the zincalume will hold its shine for a very long time.

You can run water of gal onto zincalume but if you run water off zincalume onto gal the water will begin to remove the gal coating and expose the bare metal hence it will begin to corrode.

[BobL]

According to the bluescope steel site " ZnAl steel imparts corrosion resistance of up to four times the life of galvanised steel."

Zincalume has both the benefits of zinc and aluminium as an anti corrosion coverings. Aluminium forms a thin metal oxide coating over the steel reducing the amount of oxygen getting through to the steel underneath. The zinc acts as a sacrificial metal that grabs any oxygen preferential to the iron in the steel. Ideally one would cover the steel with Al but Al is more expensive than Zn and Al is not easy to bond to steel whereas an alloy of Zn/Al makes a good bond. Zn/Al is also more resistant to acidic rain than straight Zn.

[Different]

Information from the horses mouth. Ex Lysaght Bluescope Rep/Manager.

Both Zincalume and Gal are hot dipped continuously on a machine that unrolls the flat steel coil on one end of the machine through a bath of molten zincalume or gal and the thickness of the coating is controlled by a blast of air across the surface of the steel and when it comes out of the machine it is rolled up again into a coil that can be up to 10 tonnes in weight.

This machine runs at high speed and and never stops through what is called an accelerator that allows them to join and cut the flat strip whilst the machine is continuously running.

The Colorbond is painted in a similar manner except it runs through a horizontal oven to dry the paint and the steel strip is supported on a cushion of air that runs for about 50 to 75 metres in length.

The gal coating is actually pure zinc and the zincalume is a mixture of zinc and aluminium.

Gal has a larger spangle than zincalume. As was said earlier gal will dull off to a dark grey and the zincalume will hold its shine for a very long time.

You can run water of gal onto zincalume but if you run water off zincalume onto gal the water will begin to remove the gal coating and expose the bare metal hence it will begin to corrode.

Too true.
In my experience Gal last better lasting than Zincalume where Galvanic action is not a factor. Most notably in water tanks.

Ross

[ytbc]

Does spangle = shine? Ok here is an even harder question... I ordered gal from my supplier - lots of pre cut sheets - it has arrived and now my supplier has rung me to tell me that he made a mistake and ordered zincalume - should I put up with it and take it? I wanted gal but I am trying to work out whether zinc will be have much more shine. So we move onto ethics!

[silentC]

Spangle = the odd shaped patterns that form on the surface of the coating, a bit like flakes. Gives it that motley colour. The 'flakes ' on gal are much larger than zincalume.

I'd stick with the zincalume, it's a better, longer lasting product.

[echnidna]

gal will last longer if you are near the coast

[ytbc]

No I am not near the coast - rather in Central Victoria - does Zincalume dull off or does it always stay shiny?