As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PAX DOOR INTERCOSTAL 4TH FROM TOP ON AFT SIDE IS CORRODED, MARKED (NOTED AFTER INNER SKIN WAS LIFTED). C-CHECK RO 12/05/2020. PAX DOOR AFT DD4 INTERCOSTAL ORIGINAL MATERIAL THICKNESS IS 0.050", IAW CRJ 200 SRM. EXFOLIATED CORROSION AT MULTIPLE LOCATION AND MORE TWO ELEMENT AT GIVEN CROSS-SECTION OUT OF LIMITS, IAW CRJ 200 SRM. INSTALLED NEW AFT DD4 INTERCOSTAL, IAW CRJ 200 SRM AND BOMBARDIER DWG. LEAK CHECKS GOOD.