Active corrosion, should have been delt wiith many annuals ago.The Travelers and pre-76 airplanes are bad about their unprotected spars corroding. We have some various diameter spar hones that are used to remove fil-form corrosion from the far reaches inside the spar. then we paint them as best as we can. once the paint dries, Corrosion X can be applied.Need to click zoom original size to see it well