11349 Chemical Induced Pitting Corrosion of Super Duplex Stainless Steel Umbilical Tubes

Monday, March 14, 2011: 9:50 AM
Room 351 C (George R. Brown Convention Center)
Heider A. Suarez*1, Robert J. Franco2, William E. Bond3, and Raju S. Pakalapati4
(1)ExxonMobil Production Company, Mobil Equatorial Guinea Inc.; (2)Exxon Mobil Production Co; (3)ExxonMobil Production Company, Production Projects; (4)ExxonMobil Production Company

Three new subsea umbilicals were installed in West Africa, after few months in service unexpected leaks occurred. A preliminary root cause analysis highlighted the possibility that a Low Density Hydrate Inhibitor (LDHI) continuously injected through the umbilical corroded the super duplex 2507 stainless steel tubes.

Umbilicals were taken out of service, dismantled and failure samples retrieved. A detailed failure analysis confirmed that super duplex tubes were properly manufactured and that the LDHI caused internal pitting of base metal and weld metal.

The paper describes the failure morphology and the factors that led to accelerated corrosion of super duplex stainless steel.