[AlwaysQuestioning]

Hi Guys. Why is it that aluminum has an oxide layer of aluminum oxide surrounding the metal, preventing it from reacting (somewhat) while more reactive metals like Ca and Mg don't? (Since they should in fact have a thicker layer?)

Is this a matter of the frequency of each metal's oxide being used as examples to explain this concept or is there another reason why (perhaps due to some special structure of the aluminum?)

Thanks.

[Archer]

I am no inorganic chemist so this is an educated guess at best but aluminium oxide is resistant to atmospheric gasses. Unlike MgO, which is hygroscopic (absorbs water from the atmosphere) and Calcium oxide which reacts with CO₂ forming carbonate.

Copper oxide, on the other hand, protects copper pipes used in plumbing  from further corrosion.

Again, I am no expert in the field but this would be my best guess, I invite a good inorganic chemist to correct my ignorance in the subject.