Can I use a sheet of aluminum as a roof above some small structure and just leave it there for years without painting it? I heard it will corrode on the surface and lose its sheen but will there be substantial damage to the sheet like when you leave a sheet of steel outdoors and after a few years, the sheet is gone?
Aluminum Corrosion
aluminummaterials
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Soundproofing as it relates to windows is all about mass -- the denser the materials, the more sound reduction you'll get. PVC is, indeed, typically more dense than the far more lightweight aluminium and so will will resist noise transfer more. However, the amount of surface area made up by the frame is absolutely dwarfed by the glass itself. Any differences in the frame will be massively overshadowed by the properties of the glass, make it a moot point.
PVC/Vinyl windows do a far better job of restricting conductive heat as they are a much better insulator than aluminium. Aluminium is really one of the worst materials to use from an insulation standpoint.
However, PVC/Vinyl will eventually "melt" in a hot environment. Recycled PVC will do so far faster than virgin PVC, but even the latter will eventually sag enough that opening and closing the window will be tricky. Assume maybe 15-20 years.
Aluminium will last indefinitely. That and the price are typically the two big selling points of that material.
In short, neither has a true advantage from a soundproofing perspective (the glass does quite a bit, though) but PVC is a better choice from an insulation standpoint if you are willing to replace the window every 15 years or so. If you don't care about the insulation value and don't want to replace the window, then aluminium is the way to go.
Typically you would need to drill a pilot hole and then thread with a thread cutting tool such as this:
however, since you are only using 2mm aluminium it should be soft enough for you to cut your own thread. Note: this will never be as clean as using the proper threading tool:
your problem is that you used a self tapping screw, I would recommend that you drill a pilot hole slightly smaller than your intended hole, then use a machine screw to create the thread (basically by tightening the screw into the pilot hole)
A bonus, is that you can also look out for Thread cutting machine screws. In this case your pilot hole must be just big enough to fit the tip of the point (as you can see it tapers at the end)
Best Answer
Aluminum will not corrode in normal outdoor conditions unless there is galvanic activity (electricity). This is why aluminum roofs should be held down using aluminum nails; steel nails will cause the aluminum to corrode.