For those with 13" Cobra brakes, what's the solution to the rusty centers? I've had my new rotors on for only a week and the center (where the pad doesn't touch) is coated in rust. It looks terrible and can't be cleaned off.
Were they replacement brembo rotors or are they another brand? Perhaps if they are made in China, they might be more prone to oxidation (just speculating). I'm not a chemist, but I'm sure the oxidation rate of the actual rotor material depends on several factors...blah.
You could always try to prep that section of the rotor hat for paint, but sometimes a hasty paint job comes out looking a little "amateur-ish." If you do plan on painting it, do a good job with the prep work !