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Microenvironment evolution and SCC behavior of subsea pipeline within disbonded coating crevice in a seawater environment under cathodic protection

Wei Zhang (University of Science and Technology Beijing, Beijing, China and CNNC Nuclear Power Operations Management Co. Ltd. Haiyan, China)
Hongqun Liu (Suzhou Nuclear Power Research Institute, Suzhou, China)
Minglei Hu (CNNC Nuclear Power Operations Management Co. Ltd. Haiyan, China)
Wei Wu (University of Science and Technology Beijing, Beijing, China)

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 24 March 2021

Issue publication date: 25 May 2021

72

Abstract

Purpose

This paper aims to make clear the sensitive zone of subsea pipeline to stress corrosion cracking (SCC) under a disbonded coating.

Design/methodology/approach

The change of microenvironment under a disbonded coating in artificial seawater was analyzed by using a rectangular crevice cell. The SCC behavior of subsea pipeline was studied by slow strain rate tensile tests.

Findings

The microenvironment at the crevice bottom exhibits obvious acidification, Cl- aggregation and cathodic protection potential (CP) rise. Accordingly, the susceptibility of X70 steels to SCC is high due to the intensive anodic dissolution effect. At the opening, hydrogen atom can access into the steel and induce hydrogen embrittlement effect on account of the applied over-protected CP potential, resulting in a relatively high susceptibility to SCC. The corrosiveness of the microenvironment at crevice middle, however, is mild with proper CP potential; thus, the susceptibility of X70 steel to SCC here is lower than that obtained at the opening and the crevice bottom.

Originality/value

A rectangular crevice cell is built to survey the microenvironment evolution under a disbonded coating in situ. The sensitive zone of subsea pipeline to SCC under a disbonded coating is clarified.

Keywords

Acknowledgements

The authors acknowledge the financial support of the National Environmental Corrosion Platform of China (NECP).

Data availability statement: The raw/processed data required to reproduce these findings cannot be shared at this time as the data is related to an ongoing study.

Declaration of competing interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Citation

Zhang, W., Liu, H., Hu, M. and Wu, W. (2021), "Microenvironment evolution and SCC behavior of subsea pipeline within disbonded coating crevice in a seawater environment under cathodic protection", Anti-Corrosion Methods and Materials, Vol. 68 No. 2, pp. 77-84. https://doi.org/10.1108/ACMM-10-2020-2388

Publisher

:

Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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