You lose some it every time you recycle. Of course in theory you can treat all the aluminum waste and get every gram of metal back, but it's not viable in practice.
That doesn’t really do much to prevent recycling though. When the material is melted, anything like paint or plastic liners are burned off. The main issue that has to be handled are the vapors that are released. (They can be toxic and have to be handled.)
You can actually witness the formation of dross yourself if you make your own aluminum foundry (which is ridiculously easy if you have hair dryer, a coffee can, an empty propane canister, and some charcoal). My understanding is that aluminum oxidization contributes somewhat to this, but it's also caused by what's left over after the plastic and paint have burned.
Granted, I am in no way saying that recycling aluminum isn't 100% worth it. I was merely trying to address the issue before someone might have brought it up. (I've noticed some people despise the use of absolutes and always need to point out that nothing is absolute)
EDIT: For anyone interested in "recycling" their own aluminum, this is almost exactly what I did about 10 years ago, and it was a lot of fun. This guy's casting looks dreadful, though.
Yeah, the plastic liner and the paint add impurities that have to be removed, and of course those components are not recyclable, scant they may be. This isn't to say that the aluminum element itself isn't recyclable, but inevitably there's some loss because of impurities, so I added the disclaimer to save people time from replying with "Ackshually..."
> Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide).[134] An aluminium stack melter produces significantly less dross, with values reported below 1%.
That amount seems to fit with my amateur experience of melting aluminum cans. Dross pretty much floats up to the top of the molten aluminum, and you basically just scrape it off. Even bar stock aluminum from Home Depot would produce a small amount of it.
According to this page, aluminum is separated from dross in a separate process: