What was found
AFT CARGO BAY BS 1420 BETWEEN STRINGERS 27 R & 28 L, FRAME AFT FACE HAS CORROSION BELOW THE FAIL SAFE. REMOVED CORROSION FROM THE FRAME AFT FACE BELOW THE FAIL SAFE CHORD BETWEEN STRINGER 27R AND 28L IAW B757 SRM 51-10-02. PERFORMED UT THICKNESS INSPECTION WITH ASSET # 9710 PER B757 NDTM PT 4, 51-00-10, ORIGINAL THICKNESS .063, LOSS .012, REMAINING .051 AT LOWEST POINT IS OUT OF LIMITS IAW SRM 53-00-07 AND 53-60-07. REMOVED AND REPLACED BS 1420 FRAME SECTION FROM S27R TO S26L IAW SRM 51-40-02 AND DWG 146N1012 REV C , BB AND 146N1028 REV D, AK.