J. Mater. Sci. Technol. ›› 2020, Vol. 49: 186-201.DOI: 10.1016/j.jmst.2019.10.023

• Research Article • Previous Articles     Next Articles

Development mechanism of internal local corrosion of X80 pipeline steel

Zhuowei Tana, Liuyang Yangb, Dalei Zhangb,*(), Zhenbo Wanga,*(), Frank Chengc, Mingyang Zhangd, Youhai Jina   

  1. a China University of Petroleum (East China), 266580, Shandong, China
    b School of Materials Science and Engineering, China University of Petroleum (East China), 266580, Shandong, China
    c University of Calgary, Calgary, AB CAN, T2N 1N4, Canada
    d School of Thermal Engineering, Shandong Jianzhu University, 250101, Shandong, China
  • Received:2019-05-14 Revised:2019-09-26 Accepted:2019-10-17 Published:2020-07-15 Online:2020-07-17
  • Contact: Dalei Zhang,Zhenbo Wang

Abstract:

The occurrence and development mechanism of internal local corrosion has always been a controversial topic, and especially under flow conditions. In this paper, an improved high shear force loop was experimentally used, and local flow field is induced by simulating corrosion defects on the surface of X80 pipeline steel specimens. The characteristics of corrosion products deposited on the surface of specimens in CO2-saturated NACE solution were investigated by means of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectrometry (EDS). The 3D micromorphology of the corrosion test surface after remove the corrosion scale used to measure the size of localized corrosion pit. Under the influence of local defects, the wall shear stress (WSS) and turbulent kinetic energy of local flow fields enhanced significantly, and pressure fluctuations in local flow field were induced. The results showed that the characteristics of surface corrosion products varied with flow velocity. The corrosion scales formed in various regions of specimens with defects exhibited different surface micro-morphologies and chemical compositions. Overall, these data offer new perspectives for better understanding the mechanisms behind local corrosion.

Key words: X80 pipeline steel, CO2corrosion, Flow conditions, Surface defects, Wall shear stress, Cavitation