Hydrogen entry into pipeline steel under freely corroding conditions in two corroding media

Dey, Swapna; Mandhyan, A K; Sondhi, Sanjay; Chattoraj, I

doi:10.1016/j.corsci.2005.10.003

Cited by 40 publications

(15 citation statements)

References 9 publications

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“…Moreover, external environmental conditions cause free corroding processes, where hydrogen can appear on metal surface as result of cathodic counterpart of the anodic dissolution reaction. This fact has been proved by several studies [2][3][4]. Moreover, under service conditions when a cathodic protection system is in place, hydrogen charging of pipeline steels is possible too [4,5].…”

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confidence: 76%

“…This fact has been proved by several studies [2][3][4]. Moreover, under service conditions when a cathodic protection system is in place, hydrogen charging of pipeline steels is possible too [4,5]. As result, there is the problem of structural integrity of aging buried pipelines having cathodic protection [5].…”

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confidence: 82%

“…Such charging is not truly representative of the hydrogen entry conditions in real operating pipelines, where there is the situation of freely corroding system [15]. This fact was pointed out in work [4].…”

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confidence: 91%

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Hydrogen effect on local fracture emanating from notches in pipeline from steel API X52

2009

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The assessment of local strength at notches in pipeline steel API X52 has been done for conditions of cathodic hydrogen charging. The relationship between hydrogen concentration and critical (failure) loading has been found. The existence of some critical hydrogen concentration which causes the significant loss of local fracture resistance of material was also shown.Keywords: hydrogen charging of metal, hydrogen concentration, cathodic polarization, current density, acoustic emission, static load, critical stress, work of local fracture.Introduction. Nowadays, pipelines for gas and oil transportation are integral components of national and global economic infrastructures. There are huge plans for installation of new transcontinental pipelines that require increased attention to their reliable and safe operation. In this frame, the hydrogen degradation of pipeline steels is the important problem among other structural integrity problems.Specific long-term operation of pipelines promotes of steel hydrogenating process. First of all, pipeline steels encounter hydrogen during transport of sour crude oil and other petroleum products [1]. Moreover, external environmental conditions cause free corroding processes, where hydrogen can appear on metal surface as result of cathodic counterpart of the anodic dissolution reaction. This fact has been proved by several studies [2][3][4]. Moreover, under service conditions when a cathodic protection system is in place, hydrogen charging of pipeline steels is possible too [4,5]. As result, there is the problem of structural integrity of aging buried pipelines having cathodic protection [5].Second reason, which turns one's attention to the problem of hydrogen degradation of pipeline steels, is the fact that hydrogen is supposed to play a decisive role in a future energy system, when fossil fuels become scarce and thus expensive and/or unsuitable from ecological reasons. The number of aspects related to the technical feasibility and economics of developing a hydrogen energy infrastructure are presented and discussed in literature during last decades [6,7]. The possible use of existing pipeline networks for mixtures of natural gas and hydrogen offers a unique and cost-effective option to initiate the progressive introduction of hydrogen as part of the development of a full hydrogen energy system [6,8].In the present study, the assessment local strength at notches in pipeline steel API X52 has been done for conditions of cathodic hydrogen charging. The relationship between hydrogen concentration and critical (failure) loading has been found. The existence of some critical hydrogen concentration, which causes the significant loss of local fracture resistance of material, was also shown.Experimental Procedure. The objects of study were specimens from steel API X52 machined from real pipes of diameter D = 610 mm and wall thickness t =11 mm. The specimens were notched for modeling of the longitudinal external defects under operating internal pressure (Fig. 1). The chemical composition of...

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confidence: 82%

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Hydrogen effect on local fracture emanating from notches in pipeline from steel API X52

2009

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“…It is often calculated from the steady hydrogen permeation flux through a steel membrane by assuming the hydrogen diffusion through the membrane is the rate‐determining step. In some environments, the steady hydrogen permeation is not observable in a short‐term experiment because of the topographic change or corrosion product deposit on the surface of charging side . The hydrogen permeation flux decreases with time after it reaches a peak value.…”

Section: Hydrogen Enrichment Around Crack Tipmentioning

confidence: 99%

Crack growth model for pipeline steels exposed to near‐neutral pH groundwater

2013

Fatigue Fract Eng Mat Struct

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A B S T R A C T This paper postulates a crack growth model for pipeline steels in near-neutral pH soil environments, on the basis of the experimental results reported in literature and the fundamental understanding of the corrosion fatigue crack growth dominated by hydrogen embrittlement mechanism. The comparison with the laboratory data indicates that this model can provide reasonable predictions for the dependence of the crack growth rates on the stress intensity factor, stress ratio, loading frequency, solution pH and electrochemical potential.Keywords corrosion fatigue; crack growth; steel.hydrogen adsorbed on the crack-tip surface or dissolved in bulk material, depending on the primary hydrogen source C B ¼ concentration of hydrogen dissolved in bulk material C 0 B ¼ the maximum hydrogen concentration being able to be achieved in steel exposed to groundwater with a specific pH Ccr ¼ the critical hydrogen concentration in the fracture process zone (FPZ) to cause the initiation of microcrack(s) C L cr ¼ the critical hydrogen concentration in the lattice of FPZ to cause the initiation of microcrack(s) CH ¼ local hydrogen concentration ahead of the crack tip C L H;max ¼ maximum hydrogen concentration in lattice ahead of the crack tip D H ¼ hydrogen diffusivity in steel d n ¼ coefficient to correlate the crack tip opening displacement to K/Es Y E ¼ Young's modulus f ¼ loading frequency H B ¼ binding energy of hydrogen trap J H ¼ hydrogen permeation flux k trap ¼ the ratio of hydrogen concentrations in trap to that in lattice L ¼ the phenomenological coefficient to characterise the effect of the tensile stress on the diffusivity m ¼ Paris' exponent n ¼ exponent for frequency dependent R ¼ the gas constant Rs ¼ stress ratio = smin/smax = Kmin/Kmax rFPZ ¼ the distance between the centre of FPZ and the crack tip T ¼ absolute temperature

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“…The effect of applied stress on pipeline SCC was investigated and found that stress would enhance local anodic dissolution of the steel at crack-tip, accelerating the crack propagation ( Ref 23). Moreover, a hydrogen-charging could increase the anodic dissolution rate of the steel, contributing to a high crack propagation rate (Ref [24][25][26][27]. There is thus a synergism of stress, hydrogen, and anodic dissolution at the crack tip of the steel.…”

Section: Introductionmentioning

confidence: 97%

Effect of Strain Rate on Cathodic Reaction During Stress Corrosion Cracking of X70 Pipeline Steel in a Near-Neutral pH Solution

Liu

Cheng

2010

J. of Materi Eng and Perform

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The effect of strain rate on cathodic reactions of X70 pipeline steel during stress corrosion cracking in a near-neutral pH solution was investigated by electrochemical impedance spectroscope and potentiodynamic polarization curve measurements as well as slow strain rate tests. A local additional potential model was used to understand mechanistically the role of strain rate in electrochemical cathodic reaction. It was found that an application of elastic stress would not affect the electrochemical stable state of the steel specimen at a macroscopic scale. Under a weak cathodic polarization, the interfacial charge-transfer process occurring on steel contains both cathodic and anodic reactions. Since the anodic reaction process is still significant, localized dissolution could occur even at such a cathodic potential, resulting in generation of corrosion pits. These pits could be the start sites to initiate stress corrosion cracks. Strain rate affects the corrosion reaction, which is associated with the generation of dislocation emergence points and slip steps on the specimen surface, resulting in a negative local additional potential to enhance the cathodic reaction locally.

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Hydrogen entry into pipeline steel under freely corroding conditions in two corroding media

Cited by 40 publications

References 9 publications

Hydrogen effect on local fracture emanating from notches in pipeline from steel API X52

Hydrogen effect on local fracture emanating from notches in pipeline from steel API X52

Crack growth model for pipeline steels exposed to near‐neutral pH groundwater

Effect of Strain Rate on Cathodic Reaction During Stress Corrosion Cracking of X70 Pipeline Steel in a Near-Neutral pH Solution

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