As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSIDE DIAMETER WAS FOUND TO BE PITTED AFTER REMOVAL OF THE COATING CALLED URETHABOND 104. THIS COATING WAS APPLIED BY MFG. THE SURFACE APPEARED TO BE VERY ROUGH, ALMOST THREADED. THE CAUSE FOR THE CORROSION IS UNCERTAIN. A SUGGESTION FOR PREVENTION IS NOT POSSIBLE. MY SPECULATION WOULD BE THAT THE COATING IS NOT ADEQUATELY SEALING THE SURFACE FROM MOISTURE. (K)