Hydrogen Facilitated Anodic Dissolution Type Stress Corrosion Cracking of Pipeline Steels in Coating Disbondment Chemistry

1998 ◽  
Author(s):  
Scott X. Mao ◽  
J. L. Luo ◽  
B. Gu ◽  
W. Yu
Keyword(s):  
Stress Corrosion ◽  
Anodic Dissolution ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Strain Rates ◽  
Pipeline Steels ◽  
Dilute Aqueous Solution ◽  
Sims Analysis ◽  
Cracking Process ◽  
Secondary Ion

The stress corrosion cracking (SCC) of pipeline steels in coating disbondment chemistry (near neutral pH solution) was studied by using slow strain rate tests (SSRT), polarization techniques, SEM and SIMS (secondary ion mass spectroscope). It was found that SCC susceptibility increased as the applied electrochemical potential and strain rates decreased. Hydrogen (H) precharging or addition of CO2 facilitated the process of SCC, suggesting that dissolution and hydrogen ingress are involved in the cracking process. SIMS analysis showed that hydrogen could diffuse into steels around the crack tip during the SCC process, which would facilitate the dissolution rate of the steel and increase SCC susceptibility. A mechanism was proposed which shows that hydrogen enhances anodic dissolution type of SCC in dilute aqueous solution. A thermodynamic analysis of the SCC process was carried out, and was found to be consistent with the experimental results.

Modeling the Interactions of Hydrogen, Stress and Dissolution in Near-Neutral pH Stress Corrosion Cracking of Pipelines

2006 ◽  
Author(s):  
Frank Y. Cheng
Keyword(s):  
Stress Corrosion ◽  
Dissolution Rate ◽  
Crack Growth ◽  
Anodic Dissolution ◽  
Hydrogen Concentration ◽  
Stress Corrosion Cracking ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
Neutral Ph ◽  
Ph Stress

A thermodynamic model was developed to determine the interactions of hydrogen, stress and anodic dissolution at the crack-tip during near-neutral pH stress corrosion cracking in pipelines. By analyzing the free-energy of the steel in the presence and absence of hydrogen and stress, it is demonstrated that a synergism of hydrogen and stress promotes the cracking of the steel. The enhanced hydrogen concentration in the stressed steel significantly accelerates the crack growth. The quantitative prediction of the crack growth rate in near-neutral pH environment is based on the determination of the effect of hydrogen on the anodic dissolution rate in the absence of stress, the effect of stress on the anodic dissolution rate in the absence of hydrogen, the synergistic effect of hydrogen and stress on the anodic dissolution rate at the crack-tip and the effect of the variation of hydrogen concentration on the anodic dissolution rate.

Hydrogen in stress corrosion cracking of X-70 pipeline steels in near-neutral pH solutions

2006 ◽  
Vol 41 (6) ◽  
pp. 1797-1803 ◽  
Author(s):  
Bingyan Fang ◽  
En-Hou Han ◽  
Jianqiu Wang ◽  
Ziyong Zhu ◽  
We Ke
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Pipeline Steels ◽  
Neutral Ph

Stress Corrosion Cracking of Cold Worked Austenitic Stainless Steels in Laboratory Primary PWR Environment

2004 ◽  
Author(s):  
Francois Vaillant ◽  
Thierry Couvant ◽  
Jean-Marie Boursier ◽  
Claude Amzallag ◽  
Yves Rouillon ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Crack Depth ◽  
Austenitic Stainless Steels ◽  
Corrosion Cracking ◽  
Pressurized Water ◽  
Water Reactors ◽  
Cold Worked ◽  
Cracking Process

Austenitic Stainless Steels (ASS) are widespread in primary and auxiliary circuits of Pressurized Water Reactors (PWRs). Moreover, some components suffer stress corrosion cracking (SCC) under neutron irradiation. This degradation could be the result of the increase of hardness and / or the modification of chemical composition at the grain boundary by irradiation. In order to avoid complex and costly corrosion facilities, the effects of radiation hardening on the material are commonly simulated by applying a pre-strain on non-irradiated material prior to stress corrosion cracking tests. The typical features of the cracking process in primary environment at 360°C during CERTs included an initiation stage (composed of a true initiation time and a slow propagation regime leading to a crack depth lower than 50 μm), then a “rapid” propagation stage before mechanical failure. Pre-straining increased significantly CGRs and the mode of pre-straining could strongly modify the crack path. No significant cracking (< 50 μm) was obtained under a pure static loading. A dynamic loading (CERT or cyclic) was required and various thresholds (hardness, elongation, stress) for the occurrence of SCC were determined. An important R&D program is in progress to develop initiation and propagation models for SCC of austenitic SS in primary environment.

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