While its true that the black coating will come off when you apply the brakes, it is untrue that ALL of it comes off.
You are left with the black zinc in the slits and dimples along with the inner and outer edges, this prevents rust on the entire piece because the pad prevents it on the contact points ant the zinc prevents it everywhere else... I love my slotted and dimpled for this reason, they always look great. (Performance is probably the same as stock, I did not notice a change...)
2011 Mustang GT, Black with Black stripe.
6 Speed Manual.
3.73 + Brembo Brake Package.
Charcoal Black Interior.
Appearance Package 4.(Hood Scoop and Rear Spoiler)