Any ideas on how to free a rusted ball on B&W hitch?

Heat is my first thought. That always seems to work well to free a metal to metal sticking problem. I would heat the socket area while trying to keep the heat away from the ball. Hopefully the socket will expand enough that tapping on the ball will free it. Just make sure there's nothing flammable under the pickup bed near to the hitch plate.

Or take a large pipe wrench with a piece of pipe on the end for leverage and try to wiggle the steel block back and forth to loosen whatever is holding it in place.

Or if you have access to a gooseneck trailer I would connect it to the ball, drive around on a (not too) bumpy surface to help loosen and then use the trailer landing gear to raise up on the ball

Hook it to a trailer and lift

This can be very difficult. Keep spraying PB blast and tap on it everyday this seems to work most time. U may have go to a wrecker shop put cable around and give a tug

agesilaus wrote:
I assume this ball does not have a nut on it that's stuck. Take it by a welding shop and have them put the torch on it and then whack it when it's really hot. Other solution is a big pipe wrench with a cheater bar

No, this is a square steel block with chamfered edges that gets flipped over and fills the hole in the bed for a gooseneck hitch. No threads no wrenchable surfaces. OP, you may be able to have someone weld a bar to the top of the hitch to give you leverage to wiggle it loose. You could also call B&W. They have always been helpful to me. Mine started to get corroded after a year in this New York Salt so I never put it back in. I just leave the hole open.

I assume this ball does not have a nut on it that's stuck. Take it by a welding shop and have them put the torch on it and then whack it when it's really hot. Other solution is a big pipe wrench with a cheater bar