As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SURFACE CORROSION ON LOWER SURFACE OF MIDDLE INTERCOSTAL INSIDE STRUCTURAL BOX AT AFT OTBD CORNER OF LT MLW WW. GAINED ACCESS, FOUND 4 EA INTERCOSTALS CORRODED. REMOVED CORROSION & BLEND IS OUT OF LIMITS. FABRICATED REPLACEMENT INTERCOSTALS & INSTALLED IAW SRM.