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| Effects of Cathodic Polarization on Stress Corrosion Cracking and Hydrogen Embrittlement of X80 Steel in Seawater |
| Received:October 15, 2017 Revised:March 15, 2018 |
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| DOI：10.7643/ issn.1672-9242.2018.03.001 |
| KeyWord:stress corrosion cracking hydrogen embitterment cathodic polarization X80 steel slow strain rate test |
| Author | Institution |
| HU Ru-meng |
1.College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao , China;2.Key Laboratory of Marine Chemistry Theory and Technology, Ministry of China, Qingdao , China |
| DU Min |
1.College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao , China;2.Key Laboratory of Marine Chemistry Theory and Technology, Ministry of China, Qingdao , China |
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| Abstract: |
| Objective To study the inhibition effects of cathodic polarization of X80 pipeline steel to stress corrosion cracking and hydrogen embrittlement in seawater of different pH value. Methods The slow strain rate test, electrochemical test and SEM observation of fracture surfaces were applied. Results The hydrogen evolution potentials of X80 steel in seawater was about -940 mV (vs.SCE, similarly hereinafter). Shifting potential appeared in the positive direction when pH value of seawater was 3.5. The cathodic potential had strong influences on SCC susceptibility of the X80. It became more positive with the increase of cathodic potential. The susceptibility to hydrogen embitterment increased with shifting potential in the negative direction. When the polarization potentials were negative to -950 mV, the fracture surfaces exhibited quasi-cleavage fracture; at -1050mV, the steel reached into the dangerous zone of hydrogen embitterment, and the fracture was brittle. When the pH was 3.5, X80 steel was in danger of hydrogen embitterment. Conclusion Compared with natural seawater, X80 steel has a high sensitivity of stress corrosion cracking when the pH of seawater is 3.5. The sensitivity increases with the potential negative shift in both two kinds of seawater. |
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