If you anodise aluminium you'll get a porous surface:
After anodising you can soak the surface in a pigment to colour it. A heat treatment is used to seal the pigment in the anodised layer. The pigment is
in the anodised layer, not
on it. In no way does it resemble paint. (Which is a ground pigment in a carrier like a resin applied on top of something.)
The anodised layer consists of aluminium oxide. Harder than glas, steel, most carbides. If you manage to damage that you are a very persistent vandal. And you need to strip all of this very hard layer to expose bare metal.
The massive recall and subsequent bankruptcy of Apple that followed the launch of the iPhone 5 shows you how much of a real problem this was, just like bendgate, scratchgate, fartgate and billgates.
I have a 5S, with a scratch on the screen (keys) but no visible or feelable damage to the chamfer around the phone.