As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ANNUAL INSPECTION, THE AFT WING SPAR STEEL ATTACHMENT FITTINGS INSIDE THE FUSELAGE WERE FOUND SEVERELY RUSTED, WAS ABLE TO BREAK OFF FLAKES OF RUST WITH A FINGERNAIL. THIS AREA SEEMS PRONE TO TRAP WATER. THE INSULATION HAD BEEN PREVIOUSLY REMOVED FROM THIS AREA. SUBMITTER RECOMMENDS A SMALL DRAIN HOLE TO REMOVE WATER.