What was found
MCN - MAJOR REPAIR - DURING C-04 CHECK GALVANIC CORROSION WAS FOUND ON UPPER SURFACE OF FLOORBEAM Y189, AFT SIDE OF FR 20. MAINTENANCE REMOVED CORROSION AND FOUND MATERIAL LOSS TO BE OUT OF LIMITS; REMOVED FLOORBEAM TRACK Y189, FR 20; FABRICATED A NEW REPLACEMENT FLOORBEAM TRACK; INSTALLED REPAIR PART IAW A320 SRM 51-42-11, FIG 18, PG 39-42.