Another vote for PB Blaster, great stuff. To demonstrate, I had a very stuck 9/16 shaft bolt on the leaf springs for the horse trailer, lots of Liquid Wrench used with no joy. Found some PB Blaster, and thourough drenching and 10 minutes wait, that bolt flew out of there with one hit of the 3 pound sledge. Examination of the rust to the shaft revealed PB blaster had worked its way along the entire length, breaking the rust seal.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.