Bob speaketh:

As for 4616, well... despite all better judgment and prior warning,
I got a little crazy with a chemical blackener on the valve gear and
drivers. So the former is now staring to corrode, and the latter all
have bridged gaps.

Bob,
Bruce is right-Baking soda is the way to go to neutralise it. When I
use Blacken-it, after I'm satisfied with the blackening I place the
part into a cantainer of water with enough baking soda added as to leave
a small amount on the bottom. You probably can save your valve gear by
burnishing any corroded areas with a plastic wheel brush in the Dremel,
then soaking for a few minutes in baking soda solution, followed by a
distilled water rinse.

Hopefully you can scrape any bridging at the edges-this should take care
of the short if the insulating spacer is plastic. It may be more of a
challenge if the insulator is paper-we'll hope for the best. I recall
once reading somewhere on how to replace driver insulating spacers-it
might have been on the traintools Yahoo group.

When using Blacken-it, after everything is dry I also go over the wheel
treads, flanges, and any area where contact wipers touch with a plastic
wheel brush in the Dremel to remove any loose deposits.

Good Luck,
Rod Schaffter

--
"Science is wonderful at explaining what science is wonderful at
explaining, but beyond that it tends to look for its car keys where the
light is good."
Jonah Goldberg