As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - DURING C20 CHECK DISCOVERED CORROSION ON WEB AT BS 847 TO BS 896 AND BETWEEN BL 20R AND BL 25R. CORROSION WAS FOUND TO BE OUT OF LIMITS IAW BOEING 737-300 SRM 53-60-53-1A1 FIG 101. MAINTENANCE REMOVED WEB AND INSTALLED NEW WEB AT BS 847 TO BS 867 AND BETWEEN BL 20R AND BL 25R IAW BOEING 737-300 SRM 51-40-02-0G.