Corrosion Resistance of the Welded Joint of Submarine Pipeline Steel with Ferrite Plus Bainite Dual‐Phase Microstructure. Issue 11 (5th February 2015)

• Record Type: Journal Article
• Authors: Wang, YiPeng; Zuo, XiuRong; Li, JinLing
• Is Part Of: Steel research international. Volume 86:Issue 11(2015:Nov.)
• Page Start: 1260
• Page End: 1270
• Publication Date: 2015-02-05
• Subjects: acicular ferrite -- corrosion resistance -- ferrite plus bainite dual‐phase microstructure -- submarine pipeline steel -- the welded joint; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.201400309
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : In this work, the corrosion resistance of the welded joint and base metal of submarine X65 pipeline steel with ferrite plus bainite dual‐phase microstructure was investigated by electrochemical and immersion tests. The corrosion product films were characterized using X‐ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and optical microscopy. To research the development of pitting corrosion in each zone, pitting diameter statistics were finished under optical microscopy and the forming mechanism of pitting induced by inclusion was analyzed. The experimental results proved that the corrosion resistance of the welded joint was better than that of the base metal, both from the general corrosion and pitting corrosion standpoint. In the welded joint, the weld metal has the best corrosion resistance, and then was the heat affected zone (HAZ). However, there was little difference between parent metal (near HAZ) and base metal (far HAZ) on the corrosion resistance. XRD and EDS analysis showed that the composition of the outer rust layer was mainly composed of Fe2 O3, Fe3 O4, FeOOH, and Fe(OH)3, and the inner layer was consisted of Fe2 O3, Fe3 O4, and a little FeOOH. Combined with the microstructure of the each zones, it can be concluded that the best corrosion resistance of the weld metal attributes to the refined grain size. Due to a creation of a galvanic effect between the ferrite and bainite, the dual‐phase microstructure of the base metal and parent metal displayed weak corrosion resistance. Abstract : In this work, we have studied corrosion resistance of welded joint of X65 submarine pipeline steel with ferrite plus bainite dual‐phase microstructure. We have also finished the pitting diameter statistics and analyze the forming mechanism of pitting corrosion induced by inclusion. Finally, the reason of the difference in corrosion resistance are studied, from the view of microstructure.