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Determination of critical salinity of pitting and uniform corrosion of X60 under CO2-O2 coexistence environment

BaoJun Dong (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
Wei Liu (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
Fei Wu (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
JiaQi Zhu (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
Banthukul Wongpat (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
Yonggang Zhao (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
Yueming Fan (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)
TianYi Zhang (Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, China)

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 31 January 2020

Issue publication date: 11 March 2020

208

Abstract

Purpose

The salinity of the oilfield produced water has a significant effect on steel corrosion. The purpose of this paper is to study the influence of salinity on corrosion behavior of X60 steel and it also provides basic for material selection of gas wells with high salinity.

Design/methodology/approach

The weight loss experiment was carried out on steel with high temperature and high pressure autoclave. The surface morphology and composition of corrosion scales were studied by means of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry.

Findings

The results show that as salinity increases, the corrosion rate of X60 steel will gradually experience a rapid decline stage and then a slow decline stage. X60 steel is mainly exhibiting uniform corrosion in the first rapid decline stage and pitting corrosion in the second slow decline stage. The increase in salinity reduces gas solubility, which, in turn, changes the morphology and density of the corrosion scales of X60 steel. At low salinity, loose iron oxides generated on the surface of the steel, which poorly protects the substrate. At high salinity, surface of the steel gradually forms protective films. Chloride ions in the saline solution mainly affect the structure of the corrosion scales and initiate pitting corrosion. The increased chloride ions lead to more pitting pits on the surface of steel. The recrystallization of FeCO3 in pitting pits causes the corrosion scales to bulge.

Originality/value

The investigation determined the critical concentration of pitting corrosion and uniform corrosion of X60 steel, and the new corrosion mechanism model was presented.

Keywords

Acknowledgements

The authors acknowledge the support from National Natural Science Foundation of China (No. 51571027), National Key R&D Program of China (2016YFE0203600) and the National Environmental Corrosion Platform (NECP).

Citation

Dong, B., Liu, W., Wu, F., Zhu, J., Wongpat, B., Zhao, Y., Fan, Y. and Zhang, T. (2020), "Determination of critical salinity of pitting and uniform corrosion of X60 under CO2-O2 coexistence environment", Anti-Corrosion Methods and Materials, Vol. 67 No. 2, pp. 166-177. https://doi.org/10.1108/ACMM-06-2019-2147

Publisher

:

Emerald Publishing Limited

Copyright © 2020, Emerald Publishing Limited

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