I am trying to get the estuechon(flared shell) off tub faucets to replace the washers on the valve stems. They are threaded on and have corroded so badly that I cannot turn them to remove so I can get to the valves. Does anyone have ideas on how I might get these off without tearing them to pieces? Thanks

A lot of the corrosion is probably actually soap scum -- Try pouring a pan of boiling water over the escutcheons to loosen up the tallow (real or synthetic).

Also, when things are really stuck, I try to tighten the offending piece just a bit to break the corrosion free before loosening.

Good luck.