I have a Welte Licensee vacuum pump that I am rebuilding and
I like everything to look factory new when I finish it.  The cast
iron flywheel and other parts are all in excellent condition, with
no rust bleeding through the nickel-plated surface, but the surface
has tarnished and darkened with age and exposure to air pollutants
and I would like brighten it up if possible without resorting to
having the parts re-plated.

Are there any suggestions for doing this?  Is there any chemical
nickel cleaner that can be applied, or the parts dipped in, that will
make them look like new?

Thanks,
Dave Krall