Niels Berkers asked: "Is there a way to clean the threaded rods without
damaging them?"

I have used Never-Dull to clean all sorts of metals with excellent
results.  It consists of cotton wadding saturated with mineral spirits
and petroleum chemicals.

I have not had to deal with this type of application, but would think
it would work well if the threaded rod can be chucked into a slow
drill.  Otherwise you can twirl the rod in your fingers while pinched in
the wadding as best you can.  It will be necessary to clean the rod to
remove the oily residue.  The stuff works relatively fast and has never
been destructive on the parts I have cleaned.

The product is available at many hardware stores.  A little goes a long
way.  http://www.nevrdull.com/index.htm

Don Shenbarger