Rustier front brakes

A while back our 2007 had a front wheel bearing failure. At the same time the mechanic did the front brakes and put on new rotors. The old ones would rust if it was wet out. Like actual rain. Otherwise they did not. The new ones build up surface rust if there is even a hint of moisture in the air. Misty overnight? In the morning they will make the crunchy brake sound, at least slightly. It goes away by putting it into neutral and stepping on the brakes, but it is annoying. Never had a set of rotors before that were this rust prone. Is this because they are new and it will be reduced as they age, or is the metal in these rotors just more rust prone than the originals? I have no idea what brand they used.