As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING ROUTINE HEAVY MAINTENANCE, EXCESSIVE PITTING AND EXFOLIATION CORROSION WERE FOUND ON THE LT WING UPPER SKIN, EXTERNAL SURFACE. THE CORROSION IS LOCATED ON THE WING SKIN JUST ABOVE BOTH THE FORWARD AND AFT SPARS. THE CORROSION APPEARS TO FOLLOW THE PATTERN OF THE BLACK "DO NOT WALK OUTSIDE" LINE PAINTED ON THE TOP OF THE WING. REPAIRED IAW RDAS FROM ACFT MFG.