Sometimes one can find odd lots of Aluminum in a metal supply house.
I remembered an interesting article of how to test grade of Al that
one might want to keep the details in their notebook:
" ... Go find you some sodium hydroxide - I guess Red Devil drain cleaner is 100% sodium hydroxide.
7000 series Al should yield a dull black according to the last article.
7075: 1.2 - 2% copper, 5-6% Zinc
6061: 0.04 - 0.35% copper, 0.25% Zinc
The composition differences yield the different colors"
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