Every one I have seen has had corrosion of varying degrees in this area, and this includes several aeroplanes that spent most of their life in "dry" conditions. In several cases, complete leaves were just dust, once the spar was opened up. It was not visible with the fuel tanks removed, and "tap" tests didn't reveal the extent of the damage.
Thanks for your input Leadie, I have no doubt you have found this problem, however one must then ask why Cessna then hasn't put out an AD on this specific problem rather than saying we want you to pull your entire aircraft apart because we found a problem with corrosion within the wing spar?
This also does not address the other issue that bought me into this debate in the first place, ie the U bolts on spring undercarriage having a mandatory time life of three years, that my old mate is 1st class B/S and only does Cessna a disservice in the ongoing sale of their product. Thanks for allowing me my 2c worth and I shall refrain from further comment.
Cheers
A172