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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?

  • It would certainly discolor, but I'd think it would be fine for several years. Is the roof on the structure bad/missing and this is just a temp fix? – topshot Sep 18 '16 at 12:29
  • I plan to build something rather small but want to leave it outside and know someone who has aluminum sheets laying around for over 10 years now so I thought: "Why not ask them and slap an aluminum sheet on top to keep it relatively dry?" But before I do that, I'd like to know whether the sheet will corrode away. I have clear lacquer lying around, should I paint the sheet with that? Does it have any advantages / disadvantages? – UTF-8 Sep 18 '16 at 12:47
  • Aluminum will corrode when exposed to the elements especially water. ALUMINUM CORROSION - Common treatment for aluminum that will be exposed is to anodize it (which is a form of acid rusting of the metal). – spicetraders Sep 18 '16 at 15:07
  • It will turn into a nightmare of white powder. I would paint it at least. For serious protection, use the primers intended for aircraft. They're meant to spray, but that requires exceptional protective gear... So I brush/roller it. The amumin – Harper Sep 18 '16 at 23:24
  • Yes, it will easily corrode into a nightmare of white powder. Aluminum is a base metal like zinc or magnesium, not a noble metal like copper. Aluminum's desire to oxidize is what powers thermite and the Space Shuttle rocket boosters. I would paint it. If you are serious, I would use the primers intended for aircraft, typically have a notable green hue. You need serious protective gear to spray it, so I brush/roller it, and wear gloves. – Harper Sep 18 '16 at 23:27
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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.

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