As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING INSPECTION, LEVEL 3 CORROSION WAS FOUND ON 4 T-FITTINGS INSIDE THE LEFT WING AILERON. THE PROBABLE CAUSE IS DISSIMILAR MATERIALS (STEEL BOLTS IN ALUMINUM FITTINGS ATTACHED TO A COMPOSITE SPAR). THE FITTINGS WERE REPLACED AT RIBS 4, 11/12, AND 19. REFERENCE ATR SRM 57-61-10 PAGES 115 AND 116. THE TYPE OF CORROSION WAS EXFOLIATION. THE FITTING P/N ARE: S57610025200, S57610025204, AND S57610025202.