Although it's been many years since I cracked a chemestry book, and
though I hate to disagree with George Imirie, based on conversations I've
had with Bob Stevens (owner of Betterbee, licensed distributor of gel-
formic) I doubt that linseed oil or petroleum jelly or stainless steel,
- not even snake oil(!) is going to help much with preventing corrision of
exposed metal in your hives.  If I recall correctly (and we all know how
well I recall), about the only thing formic acid doesn't eat through is
teflon!  The good news is that with PROPER USE, there won't be a lot of
formic acid in your hives if/when you use it and if/when you use it, it
won't be for prolonged periods.  YES, formic will hasten the depretiation
of your equipment.  NO, formic acid will not disolve your equipment
before your eyes.  And in the meantime, formic acid WILL kill both
mite species.

Aaron Morris - thinnking this is the real world, nothing's perfect :(