Study on the Critical Cl- Concentration for the Transition of Dominant Failure Mechanism of 304 Stainless Steel in OH- + Cl- Mixed Medium

HU Pan, YAN Wei - li, AI Zhi - bin, KONG Wei - hai, ZHANG Qiang, HU Jiu - shao

doi:10.16577/j.issn.1001-1560.2022.0218

2022 , Vol. 55 >Issue 8: 77 - 83

DOI: https://doi.org/10.16577/j.issn.1001-1560.2022.0218

Study on the Critical Cl^- Concentration for the Transition of Dominant Failure Mechanism of 304 Stainless Steel in OH^- + Cl^- Mixed Medium

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(1. National Safety Engineering Technology Research Center for Pressure Vessels and Pipelines, Hefei General Machinery Research Institute Co., Ltd., Hefei 230031, China; 2. Sinopec Zhenhai Refining & Chemical Company, Ningbo 315207, China)

Received date: 2020-09-08

Revised date: 2021-01-19

Accepted date: 2021-06-29

Online published: 2023-12-17

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Abstract

For studying the critical condition for the transition of the dominant failure mechanism of 304 austenitic stainless steel in OH-+ Cl- medium, the stress corrosion sensitivity of 304 austenitic stainless steel in the mediums of 10% NaOH and 15% NaOH solutions containing different Cl- content at 100 ℃ was investigated by slow strain rate test (SSRT). The surface morphology of the sample fracture and the composition of the corrosion product were characterized by scanning electron microscope (SEM) and energy dispersive analyzer (EDS). Result showed that Cl- could promote the occurrence of alkali stress corrosion of 304 austenitic stainless steel in 10% NaOH + nCl- (n = 100 ～1 000 mg/L) and 15% NaOH + nCl- (n =100～2 000 mg/L). With the increase of Cl- concentration, the interaction mechanism between Cl- and OH- changed from promotion into competition. When the Cl- concentration reached the critical value, the dominant failure mechanism of 304 austenitic stainless steel in OH-+Cl- mixed medium transformed to chloride stress corrosion (CSC). Besides, the critical concentration of Cl- within the scope of experiment for the transition of the dominant failure mechanism of 304 austenitic stainless steel in the mediums of 10% NaOH and 15% NaOH were 500 mg/L and 1 000 mg/L respectively.

Key words： 304 austenitic stainless steel; alkali stress corrosion cracking; chloride stress corrosion cracking; OH-+Cl- medium; failure mechanism

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HU Pan, YAN Wei - li, AI Zhi - bin, KONG Wei - hai, ZHANG Qiang, HU Jiu - shao . Study on the Critical Cl^- Concentration for the Transition of Dominant Failure Mechanism of 304 Stainless Steel in OH^- + Cl^- Mixed Medium[J]. Materials Protection, 2022 , 55(8) : 77 -83 . DOI: 10.16577/j.issn.1001-1560.2022.0218

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