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Evaluation of Grooving Corrosion and Electrochemical Properties of H2S Containing Oil/Gas Transportation Pipes Manufactured by Electric Resistance Welding
Maksudur Rahman, Siva Prasad Murugan, Changwook Ji, Yong Jin Cho, Joo-Yong Cheon, Yeong-Do Park
Received: April 09, 2018; Revised: May 16, 2018; Accepted: June 15, 2018
Abstract: Electrical Resistance Welding (ERW) on a longitudinal seam-welded pipe has been extensively used in oil and gas pipelines. It is well known that the weld zone commonly suffers from grooving corrosion in ERW pipes. In this paper, the grooving corrosion performances of API X65 grade non-sour service (steel-A) and API X70 grade sour gas resistant (steel-B) steel electrical resistance welding pipelines were evaluated. The microstructure of the bondline is composed of coarse polygonal ferrite grains and several elongated pearlites. The elongated pattern is mainly concentrated in the center of the welded area. The grooving corrosion test and electrochemical polarization test were conducted to study the corrosion behavior of the given materials. A V-shaped corrosion groove was found at the center of the fusion zone in both the steel-A and steel-B ERW pipes, as the corrosion rate of the bondlines is higher than that of the base metal. Furthermore, the higher volume fraction of pearlite at the bondline was responsible for the higher corrosion rate at the bondline of both types of steel.