What was found
DURING C-CHECK, CORROSION AROUND NUTPLATE ON CENTER OMEGA BEAM, Y=0.0, GUSSET AT FRAME 20. MAINTENANCE BLENDED CORROSION AROUND NUTPLATE ON CENTER OMEGA BEAM GUSSET AT FRAME 20, MATERIAL LOSS IS WITHIN LIMITS IAW SRM 53-21-10. PREPPED, ALODINED, PRIMED AND TOPCOATED IAW CPM 51-21-04, 51-21-05, 51-21-06. THE ACFT WAS APPROVED FOR RETURN TO SERVICE.