As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AIRCRAFT WAS IN FOR HEAVY CHECK, MAINTENANCE REPORTED LEVEL 2 CORROSION ON THE RT FLOOR SILL AT FR12. MAINTENANCE REMOVED AND REPLACED THE RT FLOOR SILL AT FR12 IAW SRM 51-43-02, 51-41-02 & 51-40-02. AIRCRAFT IS CURRENTLY STILL OUT OF SERVICE FOR HEAVY CHECK COMPLETION.