On Sat, 18 Aug 2007 06:36:27 -0400, Michael Horowitz
wrote:

I can twist and turn various tubular parts on my restoration project
and hear rust rolling down the tube.

Assuming there is no serious corrosion, how is this treated? Does one
make any attempt to remove rust from these sealed tubes or simply
inject boiled linseed oil (etc.), slosh, drain? - Mike

what you need to get is an ultrasonic wall thickness tester.
I borrowed one used by a bulldozer company that was used to test
hydraulic ram wall thicknesses.
you need to know what the intended tube thickness was.
you calibrate the unit for steel sound propagation and just put the
probe to the tube. about 10 seconds later it gives a readout of wall
thickness.
I spent two nights going over my fuselage. thankfully there was no
wall thinning due corrosion and no internal corrosion.

as for killing rust I'd use linseed. I had an RLU Breezy project in
the hangar that was rusting all over. I mixed 50/50 linseed and
mineral turpentine and brushed it on over all the fuselage.
it killed the corrosion dead and two years later there still wasnt any
rust activity. that was on the outside of the fuselage.
inside the tubes the linseed will glue the rattles.

ac43-13 has some info as well.

Stealth Pilot