what is this corrosion?

[Carol R. Beigel]

Hope some of you might know what is going on with this piano.  It is about a
14 yr old Kawai GS-30 and four years ago, the household sprinkler system
went off overhead while the owner was at work.  The piano was completely
closed (lid and fallboard down) and water was sprayed on the high polish
finish of this piano for an undetermined amount of time.  The immediate
observation was that water had not directly poured into the action or
pinblock area, but the action was damp and the keys were stuck.

The first piano tech on the scene pronounced it a write-off.  Actually, I
would too using my formula water + wood +  piano + plus insurance premiums =
insurance company replaces the piano.  However, for some reason, a second
technician was called out about a week or so later.  The piano had dried out
a bit by then, and he didn't feel that there was sufficient damage to the
instrument to rate an ethical pronouncement of piano replacement.  The piano
owner
had bought the instrument used.

Anyway, a decision was made to replace the strings and tuning pins that had
rusted from this accident - perhaps a dozen.  The insurance company settled
the claim  and covered all the repairs that Tech 2 thought necessary.
By the end of the repair work, several months later, no rust was apparent.

Now, four years later, corrosion is rampant, but in an odd way.  The new
strings and pins are fine. The speaking lengths of all the strings are fine.
Only on some sections where the strings cross  the understring felt is
there rust.  All the coils are rusted, but it almost looks to me like the
plating on the old tuning pins is rusting, not the coils themselves. There
is also rust on the INSIDE of the brass agraffe holes and at the bases of
the agraffes.

My guess is that the rust is appearing on the metal underneath the various
platings where the plating has worn off - like the edges of the tuning pins
that contact the tuning hammer tip; where string coils friction may have
scratched the plating on the tuning pins, and on the agraffes where the
strings passing thru the holes have worn the brass plating thin.  Perhaps
the rust appearing at the base of the agraffes is where the threads
underneath the agraffes are not solid brass, but plated steel.

Would a reasonable repair be to clean off the rust, and spray lacquer on the
tuning pins and coils and agraffes?  Would that hurt anything?

Could there have been something corrosive that eats plating sitting in the
sprinkler pipes?  I think residential fire sprinkler systems use PVC pipe,
not galvanized steel ones.

The insurance company says they settled the claim years ago and they are not
interested in funding anymore repairs.  I have been asked to give a second
opinion in this case, but I have never seen anything like it.  How about you
guys?

Carol Beigel