Regarding Charles Davis's query on plating [150928 MMD], in my
experience that is oxidation on the brass.  I would think that those
pipes might be solid brass.  It sounds like they weren't sprayed with
metal lacquer to seal them from the air.

There are several types of cleaners.  I have even used vinegar -- you
can try it.  If that doesn't work you could find Brasso or other brass
cleaners at a hardware store.  After cleaning them be sure to spray
metal lacquer on them or they will just tarnish again.  Good luck!

Dell Urry