Do you use anything for future corrosion prevention once they're cleaned up?
One product I use quite a bit for stuff like this is Dow Corning Molykote 3451. It is extremely resistant to water wash-out and harmless to most elastomers.The brake disc will come right off the next time they are due for replacement. I also use it between the wheel contact points and the disc itself.
Kind of like a poor man's Krytox but less expensive because it is a fluorosilicone. I find it useful for many automotive applications.