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Indexed by:Journal Papers

Date of Publication:2020-08-01

Journal:MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION

Included Journals:SCIE

Volume:71

Issue:8

Page Number:1386-1399

ISSN No.:0947-5117

Key Words:FeCO3 film; galvanic current; internal current; MERS; pipeline weldment

Abstract:A coupled multielement electrical resistance sensor (MERS) was designed to probe the nonuniform corrosion of an X65 pipeline weldment under a stepwise increasing solution temperature. In conjunction with electrochemical impedance spectroscopy (EIS) measurements, the initiation and propagation of the nonuniform corrosion on different welding areas, that is, base metal (BM), heat-affected zone (HAZ), and welding metal (WM) were well understood. The results show that the contributions of galvanic current (current flowing across the three different welding areas) and internal current (current flowing in a certain welding area) for the steel loss of BM, HAZ, and WM were significantly different under each solution temperature. The main contributor to the steel loss of HAZ gradually transformed from internal current to galvanic current with the solution temperature increasing. The WM would change from anodes to cathodes due to the preprecipitation of the FeCO3 crystals on WM when the solution temperature increased over 40 degrees C. The BM would transform from cathodes to anodes at 40 degrees C and the steel loss of BM was mainly induced by the internal current in BM over the whole test duration.