In various other uses, "junk alloy" means low strength, so my assumption is that this alloy is low cost, low quality, and suitable for use in less demanding applications.
All the websites I've found that compare the tensile strength of aluminum alloys use a different scheme to code the alloy, such as 6005 aluminum. If you know the 4 digit code of the ADC12 you can verify my hypothesis.
I suspect the ADC12 is used on beverage cans that end up in the trash. I find
Modern cans are typically produced through a mechanical cold forming process that first stamps a flat blank from a very hard material
Cold rolled sheet. The plate is usually alloy 3104-H19 or 3004-H19,
is aluminum containing approximately 1% manganese and 1% magnesium.
Aluminum beverage cans are made from two parts:
tank, usually made of EN AW-3104 sheet), and
Can lids are often made from EN AW-5182 due to its strength.
