Insights into stress corrosion cracking mechanisms from high-resolution measurements of crack-tip structures and compositions

2008 ◽  
pp. 95-106 ◽  
Author(s):  
S.M. Bruemmer ◽  
L.E. Thomas
Keyword(s):  
High Resolution ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
Cracking Mechanisms

Validation of EMAT ILI for Management of Stress Corrosion Cracking in Natural Gas Pipelines

2014 ◽  
Author(s):  
Toby Fore ◽  
Stefan Klein ◽  
Chris Yoxall ◽  
Stan Cone
Keyword(s):  
High Resolution ◽  
Natural Gas ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Probability Of Detection ◽  
Gas Pipelines ◽  
Line Pipe ◽  
Natural Gas Pipelines ◽  
Electro Magnetic

Managing the threat of Stress Corrosion Cracking (SCC) in natural gas pipelines continues to be an area of focus for many operating companies with potentially susceptible pipelines. This paper describes the validation process of the high-resolution Electro-Magnetic Acoustical Transducer (EMAT) In-Line Inspection (ILI) technology for detection of SCC prior to scheduled pressure tests of inspected line pipe valve sections. The validation of the EMAT technology covered the application of high-resolution EMAT ILI and determining the Probability Of Detection (POD) and Identification (POI). The ILI verification process is in accordance to a API 1163 Level 3 validation. It is described in detail for 30″ and 36″ pipeline segments. Both segments are known to have an SCC history. Correlation of EMAT ILI calls to manual non-destructive measurements and destructively tested SCC samples lead to a comprehensive understanding of the capabilities of the EMAT technology and the associated process for managing the SCC threat. Based on the data gathered, the dimensional tool tolerances in terms of length and depth are derived.

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.

scholarly journals Effect of pH on Stress Corrosion Cracking of 6082 Al Alloy

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 578 ◽  
Author(s):  
C. Panagopoulos ◽  
Emmanuel Georgiou ◽  
K. Giannakopoulos ◽  
P. Orfanos
Keyword(s):  
Aluminum Alloy ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Al Alloy ◽  
Cracking Behavior ◽  
Effect Of Ph ◽  
Cracking Mechanisms ◽  
6082 Aluminum Alloy ◽  
6082 Al Alloy

In this work, the effect of pH (3, 7 and 10) on the stress corrosion cracking behavior of 6082 aluminum alloy, in a 0.3 M sodium chloride (NaCl) aqueous based solution was investigated. The stress corrosion cracking behavior was studied with slow strain rate testing, whereas failure analysis of the fractured surfaces was used to identify the dominant degradation mechanisms. The experimental results clearly indicated that stress corrosion cracking behavior of this aluminum alloy strongly depends on the pH of the solution. In particular, the highest drop in ultimate tensile strength and ductility was observed for the alkaline pH, followed by the acidic, whereas the lowest susceptibility was observed in the neutral pH environment. This observation is attributed to a change in the dominant stress corrosion cracking mechanisms.

High-resolution, in-situ, tomographic observations of stress corrosion cracking

2008 ◽  
pp. 439-447 ◽  
Author(s):  
T.J. Marrow ◽  
L. Babout ◽  
B.J. Connolly ◽  
D. Engelberg ◽  
G. Johnson ◽  
...  
Keyword(s):  
High Resolution ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking

Study on Transition of Stress Corrosion Cracking to Sharp Edge Corrosion for a Liquids Pipeline

2018 ◽  
Author(s):  
Jiajun (Jeff) Liang ◽  
Ziqiang (Alex) Dong ◽  
Mengshan Yu ◽  
Mariko Dela Rosa ◽  
Gurwinder Nagra
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Synergistic Effects ◽  
Management Strategies ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
Lessons Learned ◽  
Sharp Edge ◽  
Maximum Pressure ◽  
Arrest Growth

Although stress corrosion cracking (SCC) growth is attributed to the synergistic effects of stress and corrosion, these two factors can just as easily become competing mechanisms, with stress cycles driving growth (hydrogen, the by-product of corrosion, may facilitate the growth), and corrosion working to blunt the crack tip and arrest growth. It follows that reducing the maximum pressure and cycling severity can slow down the crack growth or even stop it, and aggressive corrosion can further blunt the sharp crack tip. The Authors have observed, on a particular Polyethylene (PE) tape coated pipeline, instances where SCC has exhibited a propensity to corrode and convert into sharp edge corrosion. This is attributed to the combined effects of limited corrosion protection and low stresses. The focus of the paper is to assist operators in recognizing this phenomenon and integrate lessons learned into pipeline integrity management strategies.

Quantifying the Crack Tip Oxidation Kinetics Parameters and Their Contribution to Stress Corrosion Cracking in High Temperature Water

2010 ◽  
Author(s):  
Tetsuo Shoji ◽  
Zhanpeng Lu ◽  
He Xue ◽  
Yubing Qiu ◽  
Kazuhiko Sakaguchi
Keyword(s):  
High Temperature ◽  
Water Chemistry ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Oxidation Kinetics ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
High Temperature Water ◽  
Austenitic Alloys ◽  
Temperature Water

Stress corrosion cracking is the result of the interaction between crack tip oxidation kinetics and crack tip mechanics. Oxidation kinetic processes for austenitic alloys in high temperate water environments are analyzed, emphasizing the effects of alloy composition and microstructure, temperature, water chemistry, etc. The crack chemistry is investigated with introducing the effect of aging on reactivity of crack sides and the throwing power of bulk water chemistry. Oxidation rate constants under various conditions are calculated based on quasi-solid state oxidation mechanism, which are incorporated in the theoretical growth rate equation to quantify the effects of several key parameters on stress corrosion cracking growth rates of austenitic alloys in high temperature water environments, especially the effect of environmental parameters on stress corrosion cracking of Ni-base alloys in simulated PWR environments and stainless steels in simulated boiling water environments.

About the Role of Hydrogen in Stress Corrosion Cracking of a 7xxx Aluminium Alloy (Al-Zn-Mg)

2016 ◽  
Vol 877 ◽  
pp. 522-529 ◽  
Author(s):  
Loïc Oger ◽  
Eric Andrieu ◽  
Grégory Odemer ◽  
Lionel Peguet ◽  
Christine Blanc
Keyword(s):  
Mechanical Properties ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Local Stress ◽  
Corrosion Cracking ◽  
Hydrogen Trapping ◽  
Stress Tests ◽  
Fracture Modes ◽  
Cracking Mechanisms ◽  
Local Stress State

The effects of hydrogen during stress corrosion cracking mechanisms (SCC) have been highlighted for many years but hydrogen trapping mechanisms are not yet well understood for 7xxx aluminium alloys. The 7046-T4 Al-Zn-Mg alloy has been chosen for this study because its low corrosion susceptibility allows hydrogen embrittlement (HE) to be more easily distinguished during SCC tests. Tensile stress tests have been carried out at a strain rate of 10-3 s-1 on tensile samples after an exposure at their corrosion potential in a 0.6M chloride solution for 165 hours under an imposed loading of 80%Rp0.2. The results were compared to those obtained for samples pre-corroded without mechanical loading applied and healthy specimens. A loss of mechanical properties was observed for the pre-corroded samples and presumably attributed to the absorption, the diffusion and the trapping of hydrogen which affects a volume under the surface of the alloy and modifies its mechanical properties. Scanning electron microscope (SEM) observations highlighted a strong effect of hydrogen on fracture modes. The ductile-intergranular initial fracture mode observed on the healthy samples was partially replaced for the pre-corroded samples by a combination of two main fracture modes, i.e. brittle intergranular and cleavage, in relation with the nature of the hydrogen trapping sites and local stress state.

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