If you look at Alcoa's specs, the difference in the alloys isn't just magnesium content. [1] See chromium, for example, which is in the alloy for the top but n

If you look at Alcoa's specs, the difference in the alloys isn't just magnesium content. [1] See chromium, for example, which is in the alloy for the top but not the body. Besides, even if you can make the body out of the resulting alloy, you can't make the top. [1] https://www.alcoa.com/mill_products/catalog/pdf/China_Specs/Can_Sheet_Specs.pdf https://www.alcoa.com/mill_products/catalog/pdf/China_Specs/...