One of the guys on here told me about the automatic transmission fluid mixed with acetone to create a great penetrating oil. It's supposed to beat PB and Liquid Wrench by a whole lot so I'd give that a try. I had a corroded stem. It was aluminum stem and steel fork. I ended up using a hacksaw and cut the aluminum stem and then pulling out the fork and replacing it completely. It didn't really bother me since the fork was chipped itself.