Retina Macbook pro aluminum coating pitting/peeling off

I noticed 2 pits on the aluminum case where it started as a small dot. I thought it was a dust until I wiped it with a cloth and the hole got bigger; it was in fact peeling.

So, the retina macbook pros aluminum case is actually spray painted on, or what? Because I believe that one day the paint will peel off, unlike previous versions of macbooks where the case is carved out of a block of material; I'm not sure what material though but it seems more durable as my mums macbook pro which is older than mine doesn't have a single scratch nor peeling, dents yes, but not peeling.

Can someone please enlighten me on this issue.

Does warranty cover this?

Thank you