Questions about Aluminium Window Frames

Can anyone tell me:
a) Why aluminium has largely replaced steel as a material for metal window frames?
b) Aluminium windows can be installed directly onto the brickwork, or attached to a wooden sub frame which is then attached to the brickwork. What are the relative merits of each method?
c) Do Aluminium frames corrode?
Michael Chare
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On 07/01/2004 Michael Chare a wrote :

Aluminium doesn't corrode, steel does.

Installation into the wood sub frame would be a quicker job, but the wood frame will still need maintenance.

No. They might discolour a little due to the atmosphere, but they easily clean up.
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Harry (M1BYT) (Lap)
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Aluminium actually corrodes much more rapidly than steel. However, unlike steel, the corroded metal forms an excellent waterproof barrier that limits the depth of the corrosion to a microscopically thin layer.
Christian.
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Steel window frames are welded then galvanised. Definitely a process for big company mass production. Aluminium windows are made up from extruded sections and joining pieces so almost anyone could start making them with a relatively small outlay.
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