Primastar power steering pump connector seized !! Help?

I have just removed the knackered power steering pump,but then pipe connector that screws into the pump union is seized to the pipe.I can't move it at all so once pipe and connector loosened i had to unwind the pump! How do i free off the pipe nut from the pipe.?
Tried soaking in wd for a day but still stuck and if i wind pump back on its 90degree out.
Any one had the same problem or got any advise.??