OP rod?
I believe that there are two types of piston rod, mine is a one piece deal with the rings machined onto the rod no seams and I have not yet had a rust problem. You might try removing it from the operating slide, it's pinned in place and unscrews, soak or spray with Kroil, (the rod is hollow) and air dry or use a hair drier. Don't forget to remove the operating spring and guide before trying to unscrew the piston rod!
Remember that when reassembling you screw the rod in all the way and back out two complete turns before replacing pin.
I assume we are talking about the piston rod, and below is away from the muzzle?
I believe that there are two types of piston rod, mine is a one piece deal with the rings machined onto the rod no seams and I have not yet had a rust problem. You might try removing it from the operating slide, it's pinned in place and unscrews, soak or spray with Kroil, (the rod is hollow) and air dry or use a hair drier. Don't forget to remove the operating spring and guide before trying to unscrew the piston rod!
Remember that when reassembling you screw the rod in all the way and back out two complete turns before replacing pin.