Forgive me I am a novice so I probably won't use the correct terms but here is my best. I am replacing my bathroom sink and upon removal I noticed the old galvanized drain pipe leading into the wall is severely corroted, rusted etc. The threading at the end which attaches to the remaining sink drain pipes is completely destroyed and I can not reattach. I have bought the new piece but can not get out the old. The piece is about 5 inches long, 2 inches wide and goes into a vertical pipe in the wall. I have tried pipe lubricant and purchased a super wrench. The thing has not budged. Any other suggestions?Please help.