As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A/C IS IN "C" CHECK, VISUAL INSPECTION POINTED TO POSSIBLE CORROSION IN RT INB MAIN FLAP. AFTER DISASSEMBLY OF FLAP THE AFT SPAR CHORD WAS FOUND TO HAVE CORROSION IN NUMEROUS PLACES. A REPLACEMENT MAIN FLAP HAS BEEN PURCHASED FOR INSTALLATION. DISCREPANCY ENTERED IN A/C LOG BOOK ON PAGE 0496, ITEM 1.