Also note: All rotors (whatever coating) will get rust on the part of the rotor the pad rubs on if the car sits for a while. The pads are constantly grinding down that portion of the rotor, so no coating will ever protect it. But after a couple miles of driving, any rust on that part will be removed by the pads.

But the zinc coating on my Gripforce rotors has held up great everywhere else, no rust on any other part of the rotor.