As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - MAJOR REPAIR - DURING C-18 CHECK GALVANIC CORROSION WAS FOUND ON FLOOR SUPPORT STIFFENER AT LBL 11, BETWEEN BS 331 AND BS 341. MAINTENANCE REMOVED CORRODED FLOOR SUPPORT STIFFENER AT LBL 11, FROM BS 331 TO BS 341; FABRICATED A NEW REPLACEMENT STIFFENER PER DWG 65-45834; INSTALLED REPAIR PART IAW B737-300 SRM 51-40-02 FIG 12.