I've run an endoscope inside quite a few of the chassis tubes on my chassis and the previous chassis too! The first thing I did after the first time was get some Dynax S50 in aerosol form and sprayed as much of the internals as I possibly could. There are lots of mouse-holes in the tubes that let the lance supplied with the aerosols inside the tubes. Give it another ten years and I'll be able to tell you if it was worth the effort or if the corrosion has found its way out through the tube walls, till then I am reasonably hopeful that it does quite a lot of good. One of the things I found inside the tubes was the number of holes that are drilled in the tubes but the insides are not de-burred leaving lots of thin sharp swarf attached to the tubes and lying inside them for the corrosion to get started on.
