Residues from leather nuts causing corrosion is an age-old problem,
and the only answer I have found is to substitute plastic nuts for the
leather ones.

In the organ world many an ancient tracker action has failed due to the
phosphor bronze tap wires breaking from corrosion, or adjustments
to the action have been thwarted by the wires snapping when trying 
to adjust the nuts.  The salts, as everyone should know, used in the
tanning process will attack brass, copper, bronze, and just about any
other type of metal they come into contact with.  There were brief
experiments with lacquering the threads, and even smearing them with
Vaseline, both of which were time consuming and did not solve the
problem in the long run.

Leather buttons (we call them buttons over here) are still available
from Kimber Allen, but the hide they are manufactured from is still
cured in the same old way.  I have to say that in this case the purists
will just have to bite the bullet and use modern plastic, which is what
they should have done 200 years ago, had plastic nuts been available.
Incidentally the plastic buttons sold by Kimber Allen are similar in
colour to the old leather ones, so they do look the part.

Cheers,
Paul Camps