So, experiment results. I know the pictures are crappy but all I had available was my cell phone.
Lemon juice: safe for anodized aluminum, does take some of the oxidation off copper, but it doesn't shine it, just lightens it. Not impressed.
Vinegar + salt combination: didn't work that great for the copper (although I didn't boil it as the directions indicated), and it didn't strip the anodizing, but I think if I had rubbed the finish at all it would have damaged it. Thumbs down.
When Russ heard about this experiment he said it sounded like options for a fish & chips restaurant :)
I also tried a baking soda paste on a penny. My thought was that it wouldn't be a great option for chainmaille because of the links and nooks and crannies. It didn't work that great on a penny, either. Also not recommended for fish and chips.
I am still looking for a good option for cleaning copper without destroying the finish on anodized aluminum on the same piece. Know any?
9 hours ago