Having lived in the rust belt for many years, I learned early on how to remove rusted and stuck parts. Add some heat (not enough to melt lead) squirt on some penetrating oil and repeat 2 to 3 times. Usually the part will easily come apart after such treatment. It's worked on choke tubes, percussion nipples, and God only knows how many rusted on car parts.
Steve

Approach life like you do a yellow light - RUN IT! (Gail T.)