As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS IN BASE MAINTENANCE. FORWARD CARGO INTERCOSTAL CORRODED ON TOP FLANGE AROUND THE NUTPLATE AT FUSELAGE STATION 505 RBL11. REMOVED AND REPLACED INTERCOSTAL BETWEEN FUSELAGE STATIONS 505 AND 522 IAW AARD 51-00-05-1 AND DRAWINGS 143T5010 AND 451T2601.