As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE RE-SKINNING THE LEFT UPPER INBOARD WING SKIN, WE FOUND CORROSION IMMEDIATELY OUT BOARD OF THE LEFT MAIN LANDING GEAR CASTING ON THE LOWER AFT SIDE OF THE MAIN SPAR INSIDE THE WING. THE CORROSION SEEING TO BE CENTRALIZED AROUND ONE RIVET AND RADIATING OUTWARD FROM THAT RIVET. THERE IS NO OTHER CORROSION IN THAT AREA OF THE WING.