To read the full version of this content please select one of the options below:

The corrosion behavior of X65 steel in CO2/oil/water environment of gathering pipeline

Yuanpeng Cheng (Department of Oil and Gas Storage and Transportation Engineering, Yangtze University, Wuhan, China andCollege of Pipeline and Civil Engineering, China University of Petroleum, Qingdao, China)
Yu Bai (College of Petroleum Engineering, Yangtze University, Wuhan, China)
Zili Li (College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao, China and Provincial Key Laboratory of Petroleum Storage and Transportation Security, Qingdao, China)
JianGuo Liu (College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao, China)

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 6 December 2018

Issue publication date: 22 February 2019

Abstract

Purpose

The purpose of this paper was to investigate the corrosion behavior of X65 steel in the CO2/oil/water environment using mass loss method, potentiodynamic polarization technique and characterization of the corroded surface techniques.

Design/methodology/approach

The weight loss analysis, electrochemical study and surface investigation were carried out on X65 steel that had been immersed in the CO2/oil/water corrosive medium to understand the corrosion behavior of gathering pipeline steel. The weight loss tests were carried out in a 3L autoclave, and effects of flow velocity, CO2 partial pressure and water cut on the CO2 corrosion rate of X65 steel were studied. Electrochemical studies were carried out in a three-electrode electrochemical cell with the test temperature of 60°C and CO2 partial pressure of 1 atm by recording open circuit potential/time and potentiodynamic polarization characteristics. The surface and cross-sectional morphologies of corrosion product scales were characterized using scanning electron microscopy. The phases of corrosion product scales were investigated using X-ray diffraction.

Findings

The results showed that corrosion rates of X65 steel both increased at first and then decreased with the increase of flow velocity and CO2 partial pressure, and there were critical velocity and critical pressure in the simulated corrosive environment, below the critical value, the corrosion products formed on the steel surface were loose, porous and unstable, higher than the critical value, the corrosion product ?lms were dense, strong adhesion, and had a certain protective effect. Meanwhile, when the flow velocity exceeded the critical value, oil film could be adsorbed on the steel surface more evenly, corrosion reaction active points were reduced and the steel matrix was protected from being corroded and crude oil played a role of inhibitor, thus it influenced the corrosion rate. Above the critical CO2 partial pressure, the solubility of CO2 in crude oil increased, the viscosity of crude oil decreased and its fluidity became better, so that the probability of oil film adsorption increased, these factors led to the corrosion inhibition of X65 steel reinforced. The corrosion characteristics of gathering pipeline steel in the corrosive environment containing CO2 would change due to the presence of crude oil.

Originality/value

The results can be helpful in selecting the suitable corrosion inhibitors and targeted anti-corrosion measures for CO2/oil/water corrosive environment.

Keywords

Acknowledgements

The work was supported by the National Natural Science Foundation of China (51301201). It was also supported by the National Science and Technology Major Project of China (2011ZX 05017-004).

Citation

Cheng, Y., Bai, Y., Li, Z. and Liu, J. (2019), "The corrosion behavior of X65 steel in CO2/oil/water environment of gathering pipeline", Anti-Corrosion Methods and Materials, Vol. 66 No. 2, pp. 174-187. https://doi.org/10.1108/ACMM-07-2018-1969

Publisher

:

Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited