I don't have photos at the moment, because I left it at work, but I have a Kryptonite NY3000 U-lock that is suffering from rust. It will open, lock, and close, but it takes a great deal of force to open it once it's closed and locked. I have to bang the U part against whatever I lock my bike to in order to pry it open. It's nigh impossible to open with hands alone.
I don't know if it's rust, but I suspect it is. Is this common? Any ways to combat this preemptively or to restore a lock like this to normal functionality?