Fundamentals of hydrogen evolution reaction and its implications on near-neutral pH stress corrosion cracking of pipelines

2007 ◽  
Vol 52 (7) ◽  
pp. 2661-2667 ◽  
Author(s):  
Y.F. Cheng
Keyword(s):  
Stress Corrosion ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Neutral Ph ◽  
Ph Stress

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.

Statistical Predictive Modelling: A Methodology to Prioritize Site Selection for Near-Neutral pH Stress Corrosion Cracking

2010 ◽  
Author(s):  
Edgar I. Cote ◽  
James Ferguson ◽  
Nauman Tehsin
Keyword(s):  
Tensile Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Probability Of Detection ◽  
Predictor Variables ◽  
Neutral Ph ◽  
Proactive Management ◽  
Ph Stress ◽  
Axial Defects

Pipelines are subjected to both residual and applied tensile stresses, and can form near-neutral pH SCC (transgranular stress corrosion cracking) if the pipeline is exposed to a conducive environment and is made from a material that is susceptible to SCC. This transgranular SCC is an ongoing integrity concern for pipeline operators. As part of an SCC Integrity Management Program (IMP), it is necessary to perform integrity assessments and prioritize segments of the pipelines to manage the SCC threat. Ultrasonic crack detection in-line inspection tools have proven capable of locating SCC, but reliability of these tools is not absolute and the reduced probability of detection of subcritical flaws limits options for proactive management. Hydrostatic retesting is a very effective program for removing near-critical axial defects, such as SCC, but does not provide useful information as to the location of SCC along the pipeline. NACE Standard RP0204-2004 (SCC Direct Assessment Methodology or SCCDA) outlines factors to consider and methodologies to employ to predict where the SCC is likely to occur, but the standard acknowledges that there are no well-established methods for predicting the presence of SCC with a high degree of certainty. The trend in probabilistic modelling has been to focus on establishing deterministic relationships between environmental factors, tensile stress and SCC formation, and growth; these models have achieved varying degrees of success. The Statistical Predictive Model (SPM) was previously developed to predict the likelihood of occurrence of near-neutral pH Stress Corrosion Cracking (SCC) for the NPS 10 Alberta Products Pipeline (APPL). SPM Phase 5 uses selected predictor variables representing tensile stress, environmental, pipe-related, corrosion control and operational relevant factors to determine the Probability of Occurrence of SCC. Regression techniques were used to create multi-variable logistic regression models. The results for each model are checked at locations where SCC is known to be present or absent to assess predictive accuracy, then used to prioritize susceptible segments for field excavation. The relative strength of individual predictor variables provides insight into the mechanism of near-neutral pH SCC crack initiation.

APPLICATION OF INVERSE BROYDEN'S METHOD FOR COMPUTATIONAL ANALYSIS OF HYDROGEN CONTRIBUTION TO THE NEAR-NEUTRAL PH STRESS CORROSION CRACKING

2013 ◽  
Vol 10 (05) ◽  
pp. 1350033
Author(s):  
IGOR TELICHEV ◽  
OLEG VINOGRADOV
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Computationally Efficient ◽  
Material Degradation ◽  
Broyden’S Method ◽  
Neutral Ph ◽  
Ph Stress ◽  
Bcc Iron ◽  
Broyden's Method

An Inverse Broyden's Method was applied in the context of a molecular statics approach for the analysis of the contribution of hydrogen to the near-neutral pH stress corrosion cracking. A 3D crystal structure was tested numerically. It is shown that the Inverse Broyden's Method provides a computationally efficient technique to evaluate the effect of hydrogen on the material degradation. Simulation results demonstrated that atoms of hydrogen placed near the crack tip produced a strong effect on deformation and crack propagation in bcc iron leading to a 15–20% loss in a residual strength of numerically tested samples.

Mechanisms of High-pH and Near-Neutral-pH SCC of Underground Pipelines

2001 ◽  
Vol 123 (3) ◽  
pp. 147-151 ◽  
Author(s):  
John A. Beavers ◽  
Brent A. Harle
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Historical Information ◽  
High Ph ◽  
Neutral Ph ◽  
Underground Pipelines ◽  
Ph Stress

This paper provides an overview of mechanisms for high-pH and near-neutral pH stress corrosion cracking of underground pipelines. Characteristics and historical information on both forms of cracking are discussed. This information is then used to support proposed mechanisms for crack initiation and growth.

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