It depends on whether there is moisture on them when parked. A good hard drive to have the brakes warm when you part will evaporate any moisture.
I find that a few hard brake applications clean off the light surface rust. Do it like a brake pad bedding.
'95 Alpine M3 LTW
'00 Dakar M Roadster
'02 Topaz M3
Red/White SRF #4 (Chassis 561)