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The failure reason of epoxy-phenolic coating on the internal surface of BG90S steel tubing under sour gas environment

Guiyang Wu (Research Institute of Natural Gas Technology, PetroChina Southwest Oil and Gasfield Company, Chengdu, China)
Qiang Zhang (Research Institute of Natural Gas Technology, PetroChina Southwest Oil and Gasfield Company, Chengdu, China)
Nange Zhang (Research Institute of Natural Gas Technology, PetroChina Southwest Oil and Gasfield Company, Chengdu, China)

Pigment & Resin Technology

ISSN: 0369-9420

Article publication date: 24 January 2020

Issue publication date: 20 April 2020

93

Abstract

Purpose

Organic coatings are one of the most widely applied methods for corrosion protection of metallic materials such as the tubing used in sour gas field. However, such coatings usually encounter the risk of failure due to the harsh and complex environment. Therefore, the study of failure of the organic coating is highly significant.

Design/methodology/approach

In this paper, the effects of Cl-concentration, HCl content, hydrogen sulfide/carbon dioxide (H2S/CO2), temperature and flow rate on the failure of epoxy-phenolic coating on the internal surface of BG90S steel tubing were investigated using adhesion force measurement, metallographic microscope, electrochemistry impedance spectroscopy and Fourier transform infrared spectroscopy.

Findings

The results show that the Cl-concentration, HCl content and H2S/CO2 do not affect the failure process too much as the ion concentration increased. However, the flow rate at the high temperature is the most important factor affecting the corrosion resistance of the inner coating tubing. With the increase of the flow rate, the pore resistance of the coating shows a decreasing trend, and the rate of decrease in pore resistance is first rapid and then slow. It demonstrates that the penetration speed of the electrolyte solution into the coating varied from fast to slowly. A weakening influence of the flow rate on the penetration failure of the inner coating can be found as the increase of the flow rate. Once the HS-ions penetrate through the coating and reach at the coating/steel interface where H2 could be formed through the adsorption reaction, the coating failure occurs.

Originality/value

The failure of the coating depends on the penetration rate of water and ions, with the presence of exposed or punctured holes is accelerated and HS- was adsorpted by substrate Fe, and form H2 molecules between the coatings and substrate, that results failure of coatings.

Keywords

Acknowledgements

This research has been supported by the project 20150307-02 funded by Petrochina Southwest Oil&Gasfield Company. The authors would like to thank professor Xiankang Zhong who has tried his best to improve my paper.

Citation

Wu, G., Zhang, Q. and Zhang, N. (2020), "The failure reason of epoxy-phenolic coating on the internal surface of BG90S steel tubing under sour gas environment", Pigment & Resin Technology, Vol. 49 No. 3, pp. 181-187. https://doi.org/10.1108/PRT-08-2019-0069

Publisher

:

Emerald Publishing Limited

Copyright © 2020, Emerald Publishing Limited

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