[Philliphastings]

I haven't tried phosphoric acid yet for the simple reason that citric acid has shown no adverse aspects at all so far. The stuff is so harmless you could almost drink it and it certainly does no harm to plunge bare arms up to the elbows in when fishing out treated parts. It is apparently a by-product of the wine making industry...

Yes transmission oil works well where you need a lot of penetrating fluid. Very good for seized engines if poured into the cylinders and left to work it's magic and claggy gearboxes which have to be stripped down anyway.

Cheers

Phill