As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WE REMOVED THE RH FUEL TANK TO REPLACE A FLEXIBLE FUEL LINE. UPON REMOVING THE FUEL TANK WE SAW EXTENSIVE EXFOLIATION CORROSION ON THE UPPER WING SPAR BEHIND THE FUEL TANK. THE AREA OF CORROSION EXTENDED 16 INCHES ALONG THE UPPER FORWARD SPAR I BEAM. AFTER REMOVING THE FLAKING MATERIAL, WE DETERMINED TO BE .060 INCH MATERIAL REMOVED. WE REMOVED THE WING FROM SERVICE.