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Indexed by:Journal Papers

Date of Publication:2019-10-01

Journal:OCEAN ENGINEERING

Included Journals:SCIE

Volume:189

ISSN No.:0029-8018

Key Words:Subsea pipeline weldment; WMEA; Micro-cell corrosion; Macro-cell corrosion; FeCO3 film

Abstract:The localized corrosion behaviour of an X65 subsea pipeline weldment in CO2-saturated formation water was studied using weldment coupon and a novelly designed weldment multi-electrode array (WMEA). The dynamic progression of localized corrosion on different welding areas i.e. base metal (BM), heat affected zone (HAZ) and welding metal (WM) was probed by WMEA. The influences of the solution temperature and the steel microstructure on the localized corrosion of subsea pipeline weldment were analysed. The test results show that HAZ and WM would act as anodes registering a high corrosion rate which was controlled by both micro-cell corrosion and macro-cell corrosion below 50 degrees C. While, if the temperature increased higher than 50 degrees C, WM would transfer from major anode to significant cathode due to the preferential deposition of FeCO3 crystal on WM. Part areas of HAZ would act as the main anodic sites and maintain a high local anodic dissolution rate due to the macro-cell current which is induced by the inhomogeneous FeCO3 film covering.