Michael

My understanding of preservation of timber and metal taken from the sea floor is that the deterioration is probably so far advanced now that there will be very little that can be done to save the anchor.

Not because it had been on the sea floor for 150-200 years, but because it was taken out of its environment.  The problem is that the salt content of the timber and the metal is so high that this will just keep the corrosion going at a phenomenal rate.

I believe that the underwater archaeologists soak the timber in a weird concoction of organic solvents including glycol, for months or years.  The metal is soaked in special inorganic pickling solvents for months or years.  THe concentrations are gradually changed until conditions are back to neutral.

Consequently, saving the anchor as it currently exists is probably impossible.

Unless of course you can follow Deb's advice and build a big glass tank to hold cold seawater!!!  But y' gotta keep the oxygen out of the seawater, and keep the temperature down.

Sorry for the lack of helpful advice, but I reckon your friend is about to lose his anchor unless he replaces the timber, grinds all the corroded metal off (which will be all of it) and replaces them too.

Cheers

david