As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YYC - LEFTHAND WING, LEFTHAND WING FUEL TANK PANEL 522BT, PANEL REBATE WS 79.700 TO WS 117-500, FRETTING CORROSION ON TOP SURFACE OF REBATE AROUND PANEL ANCHOR NUT ATTACH HOLES. REPAIRED IAW Q400 SRM 57-10-30-320-002, RD 8/4-57-424, ISSUE 1 AND HORIZON AIR EA 6-57-298.