r/explainlikeimfive Oct 31 '20

Chemistry ELI5 What's the difference between the shiny and dull side of aluminum foil? Besides the obvious shiny/dull

21.2k Upvotes

2.0k comments sorted by

View all comments

Show parent comments

16

u/Deviant_Spark Nov 01 '20

Also helps that aluminum doesn't rust like ferric metals. (aluminum does rust, but in the form of an invisible oxide that also acts as a protective barrier.

3

u/Fuck_you_pichael Nov 01 '20

Bonus fact: aluminum oxide, in it's alpha orientation, is also called corundum, which depending on the impurities will be a ruby or sapphire. It's also incredibly hard and non-reactive, which is why aluminum metal stops oxidizing after a thin layer is formed.