As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CORROSION ON INTERCOSTAL ATTACHED TO STRINGER 20RH IN STA. FS= 310 TO FS= 319 AT MAIN AVIONICS COMPARTMENT. (E/E) (W1) TCI: 53-20-304
CORROSION LEVEL 2. INTERCOSTAL ATTACHED TO STRINGER 20RH IN STA. FS= 310 TO FS= 319 AT MAIN AVIONICS COMPARTMENT WAS REPLACED PER CRJ900 SRM 51-42-20-001-001-A01.