As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE LT VERTICAL STABILIZER TORQUE BOX LOWER CHORD WAS FOUND CORRODED DURING VERTICAL STABILIZER TERMINAL FITTING REPLACEMENT. THE CAUSE IS PROBABLY DISSIMILAR METALS AND A LACK OF DRAINAGE. DUE TO A LACK OF ACCESSIBILITY, THE ONLY WAY TO FIND THIS DEFECT IS BY X-RAY INSPECTION.