Relationship between electrochemical characteristics and SCC of X70 pipeline steel in an acidic soil simulated solution
来源期刊：Acta Metallurgica Sinica2009年第1期
论文作者：Yingrui ZHANG Zhiyong LIU Guoli ZHAI Cuiwei DU Xiaogang LI
Key words：X70 steel; SCC; Electrochemical process; Acidic soil;
Abstract: Stress corrosion cracking (SCC) of X70 pipeline steel in simulated solution of the acidic soil in Yingtan in China was investigated using slow strain rate test (SSRT), SEM and potentiodynamic polarization technique. Experiment results indicate that X70 steel is highly susceptible to SCC as applied potential reduces, which is manifested in loss of toughness and brittle fracture. Constant polarization current can detect the occurrence of SCC. The lower the polarization current is the sooner stress corrosion cracking occurs. The SCC mechanisms are different at varying potentials. When potential is higher than open circuit potential, anodic process controls SCC, whereas when potential is far lower than open circuit potential, cathodic process controls SCC, and between these two potential regions, a combined electrochemical process controls the SCC. Stress or strain has a synergistic effect with electrochemical reactions to accelerate the cathodic hydrogen evolution process, which makes the X70 pipeline steel to be more susceptible to SCC.
Yingrui ZHANG1，Zhiyong LIU2，Guoli ZHAI2，Cuiwei DU2，Xiaogang LI2
(1.Mechanical Engineering Department,University of Rochester,NY,14627,USA;
2.Key Lab of Corrosion Erosion and Surface Technique Beijing,Corrosion and Protection Center,University of Science and Technology Beijing,Beijing 100083,China)
Abstract:Stress corrosion cracking (SCC) of X70 pipeline steel in simulated solution of the acidic soil in Yingtan in China was investigated using slow strain rate test (SSRT), SEM and potentiodynamic polarization technique. Experiment results indicate that X70 steel is highly susceptible to SCC as applied potential reduces, which is manifested in loss of toughness and brittle fracture. Constant polarization current can detect the occurrence of SCC. The lower the polarization current is the sooner stress corrosion cracking occurs. The SCC mechanisms are different at varying potentials. When potential is higher than open circuit potential, anodic process controls SCC, whereas when potential is far lower than open circuit potential, cathodic process controls SCC, and between these two potential regions, a combined electrochemical process controls the SCC. Stress or strain has a synergistic effect with electrochemical reactions to accelerate the cathodic hydrogen evolution process, which makes the X70 pipeline steel to be more susceptible to SCC.
Key words:X70 steel; SCC; Electrochemical process; Acidic soil;
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