Failures by SCC in buried pipelines

Manfredi, C.; Otegui, J.L.

doi:10.1016/s1350-6307(01)00032-2

Cited by 106 publications

(45 citation statements)

References 2 publications

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“…Since the first case of stress corrosion cracking (SCC) was reported in 1965, the SCC behavior of pipeline steels has received much attention [1]. It is widely known that the SCC of pipeline steels can be categorized into two types, i.e., high-pH SCC and near-neutral-pH SCC [2,3].…”

Section: Introductionmentioning

confidence: 99%

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

Fan

Liu

Guo

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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Susceptibilities to stress corrosion cracking (SCC) of X80 pipeline steel in relatively concentrated carbonate/ bicarbonate solutions with different chloride ion concentrations or pH value at a passive potential of -200 mV vs SCE were investigated by slow strain rate tensile test. In order to explore the SCC mechanism and the evaluation criterion for the SCC susceptibility of the steel in passive state, electrochemical measurements were taken. Potentiodynamic polarization curves were obtained at different potential sweep rates, and electrochemical impedance spectroscopy measurements were taken after fast polarization to the passive potential. The effects of chloride ion and pH on SCC behaviors of X80 steel at the passive potential were also discussed. The results showed that the SCC mechanism of X80 pipeline steel was greatly influenced by the passive film formed in these solutions. The SCC behaviors followed the film suppressed anodic dissolution mechanism in these circumstances, because the filming process accounted for a considerable proportion of the overall electrode process. The criteria for evaluating the SCC susceptibility of the steel at passive potential were proposed and validated. Decreasing in the concentration of chloride ion or increasing in pH value resulted in the reduction in SCC susceptibility. The existence of chloride ion greatly lowered the passivation tendency and the film stability, while its concentration determined the dissolution rate of the steel matrix. Higher pH value was responsible for the stable and tenacious passive films and the high repassivation capability. It was also inclined to lower the anodic dissolution rate at crack tips by retarding the cathodic oxygen reduction.

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Section: Introductionmentioning

confidence: 99%

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

Fan

Liu

Guo

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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“…SCC has been recognized as a cause of failure since the 60's especially in gas pipelines that handle crude oil and natural gas at high pressures [6]. Buried pipelines usually show two types of SCC according to the pH: 1) SCC of high pH (9)(10)(11)(12), also known as classic SCC, and 2) SCC of low pH (6)(7)(8), also known as SCC of pH close to neutral. SCC in steels is related with two types of cracking: which are transgranular cracking (TGSCC) and intergranular cracking (IGSCC) and in some cases it occurs in mixed mode [7,8].…”

Section: Introductionmentioning

confidence: 99%

Stress corrosion cracking assessment of API X65 steel non‐conventionally heat treated

Natividad

Garcı́a

López

et al. 2015

Materials & Corrosion

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Stress corrosion cracking (SCC) susceptibility of API X65 steel nonconventionally heat-treated was evaluated through slow strain rate tests (SSRTs) using the synthetic soil solution NS4 at 20, 40 and 60 8C. Polarization curves (PCs) and corrosion potential (E corr ) measurements were also performed. The non-conventional heat treatment (HT) was made by heating plates at 1050 8C for 30 min followed by water quenching. The tensile strength of the heat-treated plates increased to values similar to API X80 steel. The SCC index obtained by ratios of mechanical properties indicated that X65 steel without HT is not susceptible to SCC whereas with HT is slightly susceptible to SCC. The SCC mechanism in the soil solution in the heat-treated plates was influenced by hydrogen diffusion as confirmed by the internal cracks and the brittle fracture observed in the specimens. The electrochemical study suggests that the corrosion process of X65 steel with and without HT occurs via a mix mechanism where the charge transfer resistance is influenced by a mass transfer process. Crevice corrosion features were found in the surface of the steel. It is likely that this type of corrosion could have sensitized the X65 steel and induced cracks when the steel was under tensile stress.

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“…Most of the defects begin on the exterior surface of pipe strings and grow as longitudinal cracks [3][4]. But in some key positions, such as girth weld, transverse cracks are the common defects on pipe strings [5][6].…”

Section: Introductionmentioning

confidence: 99%

Application of induced circumferential current for cracks inspection on pipe string

Yuan¹,

Li²,

Yin³

et al. 2016

AIP Conference Proceedings

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Abstract. Pipe strings (such as drill pipe, tube, pipeline, riser) are critical facilities in oil & gas industry, which are highly susceptible to cracks caused by stress corrosion and fatigue damage. The most common defects are longitudinal and transverse surface cracks on pipe strings in oil & gas industry. Conventional nondestructive testing (NDT) methods are inadequate for these surface cracks on pipe strings. In this paper, a full 360 circumferential current induced by a coaxial excitation coil is present for inspection of longitudinal and transverse surface cracks on pipe strings. The finite element method (FEM) is employed to obtain characteristics signals by analyzing the distorted electromagnetic field above the cracks. The induced circumferential current test system is set up and crack inspection experiments are carried out. The results show that both longitudinal and transverse surface cracks can be detected effectively at one pass scanning on pipe string using the induced circumferential current.

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Failures by SCC in buried pipelines

Cited by 106 publications

References 2 publications

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

Stress corrosion cracking assessment of API X65 steel non‐conventionally heat treated

Application of induced circumferential current for cracks inspection on pipe string

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