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Article
Publication date: 29 March 2021

Ailing Wang, Yong Deng, Kaihong Li, Wenlei Li, Dongliang Yu, Gan Cui, JianGuo Liu and Zili Li

Alternating current (AC) corrosion is a type of corrosion that occurs in buried pipelines under AC stray current interference, which can increase the hydrogen…

Abstract

Purpose

Alternating current (AC) corrosion is a type of corrosion that occurs in buried pipelines under AC stray current interference, which can increase the hydrogen embrittlement sensitivity of pipelines. However, rare research works have been conducted on the hydrogen permeability characteristics of pipeline steel under AC stray current interference. The purpose of this paper is to study hydrogen permeation behavior of X80 steel under AC stray current interference.

Design/methodology/approach

In this paper, the hydrogen permeation behavior of X80 steel under AC interference is studied by AC hydrogen charging experiment in a dual electrolytic cell. The relationship between hydrogen evolution rate and hydrogen permeation flux is studied using the gas collection method. The difference between AC hydrogen permeability and direct current (DC) hydrogen permeability is also discussed.

Findings

The anodic dissolution caused by AC corrosion promotes the chemical desorption reaction of the adsorbed hydrogen atoms on the surface, reducing the hydrogen atom absorption ratio by 70%. When the AC is smaller than 150░ A/m2, the hydrogen permeation process is controlled by the hydrogen atom generation rate, and the hydrogen permeation flux increases with the increase in hydrogen atom generation rate. When the AC exceeds 400░ A/m2, the hydrogen permeation process is controlled by the absorption ratio. The hydrogen permeation flux decreases with the decrease in the absorption ratio. Under AC interference, there is a maximum hydrogen permeation flux that linearly correlates to the H+ concentration in the solutions.

Originality/value

The high-strength steel is very sensitive to hydrogen embrittlement, and X80 steel has been widely used in oil and gas pipelines. To date, no research has been conducted on the hydrogen permeation behavior of pipeline steel under AC interference, and the hydrogen permeability characteristics of pipeline steel under AC interference are not clear. The research results of this paper are of great significance for ensuring the intrinsic safety of high-strength pipelines under AC stray current interference.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 7 August 2021

Yanbao Guo, Zhenyuan Liu, Hui Huang, Deguo Wang and Renyang He

The corrosion of buried steel pipelines is becoming more serious because of stress corrosion, stray current corrosion and other reasons. This paper aims to study the…

Abstract

Purpose

The corrosion of buried steel pipelines is becoming more serious because of stress corrosion, stray current corrosion and other reasons. This paper aims to study the various alternating current (AC) interference densities on the stress corrosion cracking behaviors of X80 steel samples under cathodic protection (CP) in the simulated soil electrolyte environment by using an electrochemical method.

Design/methodology/approach

The change of corrosion rate and surface morphology of the X80 steel samples at various AC current densities from 0 to 150 A/m2 or CP potential between −750 and −1,200 mV in the soil-simulating environment was revealed by the electrochemical methods and slow strain rate testing methods.

Findings

The results revealed that with the increase of interference density, the corrosion potential of the X80 steel samples shifted to the negative side, and the corrosion pitting was observed on the surface of the sample, this may cause a danger of energy leak. Moreover, the corrosion rate was found to follow a corresponding change with the stress–strain curve. Besides, with the introduction of the CP system, the corrosion rate of the X80 steel working electrode decreased at a low cathodic potential, while showed an opposite behavior at high cathodic potential. In this study, the correlation between AC stray current, cathodic potential and stress was established, which is beneficial to the protection of oil and gas pipeline.

Originality/value

Investigation results are of benefit to provide a new CP strategy under the interference of AC stray current corrosion and stress corrosion to reduce the corrosion rate of buried pipelines and improve the safety of pipeline transportation.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 4
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 31 January 2020

JiaYu Zhou, Zili Li, JianGuo Liu, Xiao Xing, Gan Cui, ShouXin Zhang, Ran Cheng and YiShu Wang

The purpose of this paper is to quantify the influence of alternating current (AC) interference on hydrogen evolution reaction of X80 steel.

Abstract

Purpose

The purpose of this paper is to quantify the influence of alternating current (AC) interference on hydrogen evolution reaction of X80 steel.

Design/methodology/approach

The hydrogen evolution potential was obtained by cathodic potentiodynamic polarization curve. The instantaneous potential under AC interference was obtained by high-frequency acquisition with three-electrode system. Electrochemical impedance spectroscopy and Tafel polarization curves were used to study the influence mechanism of AC interference on instantaneous potential.

Findings

It was concluded that the hydrogen evolution reaction could occur on X80 steel under AC interference. There were critical AC current densities of about 100 to 200 A/m2, beyond which the cathode reaction of X80 steel changed from oxygen absorption to hydrogen evolution. Besides the pH value, the initial polarization potential EZ and impedance module of the steel/electrolyte interface under AC interference were also the factors that affected the critical AC densities in different solutions.

Originality/value

This research quantified the hydrogen evolution capacity of X80 steel under AC interference, which could be applied to clear the effect of AC interference on hydrogen evolution reaction.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 31 January 2020

Hailing Li, Hongxia Wan, Shengrong Wang, Cuiwei Du and Dawei Zhang

This paper aims to investigate the effect of alternating current (AC) on corrosion, it is not yet clear about the exact mechanism of the corrosion induced by AC. Previous…

Abstract

Purpose

This paper aims to investigate the effect of alternating current (AC) on corrosion, it is not yet clear about the exact mechanism of the corrosion induced by AC. Previous reports indicated that AC corrosion was similar to the effect of continuous cathodic and anodic polarization on the corrosion process of the metals. Wan et al. studied the effect of negative half-wave AC on stress corrosion cracking behavior and mechanism of X80 pipeline steel in near-neutral solution.

Design/methodology/approach

This study attempted to understand the AC-induced corrosion by imposing the half-cycle AC on the X80 pipeline steel in an acid bicarbonate solution. The AC corrosion mechanism was determined by weight loss and potentiodynamic polarization curve measurements, as well as surface characterization.

Findings

The results show that the positive half-cycle AC accelerated the uniform corrosion in the NaHCO3 solution, the negative half-cycle AC would decrease the uniform corrosion and local corrosion was increased and some Ca and Mg deposited on the surface of X80 steel, so the corrosion rate decreased by negative half-cycle AC. The corrosion product was composed of α-FeOOH under the application of positive half-cycle AC. The oxygen reduction led to a local increase of pH near the electrode surface and led to the formation of α-FeOOH, which enhanced the protectability of corrosion products.

Originality/value

Researchers studied the effect of negative half-wave AC on stress corrosion cracking behavior and mechanism of X80 pipeline steel in near-neutral solution. However, the AC behavior and corrosion mechanism in acid solution are unknown. So to make clear about the corrosion behavior of metals in different polarization states and the mechanism involved, diode technology was used to research the AC corrosion, half-wave AC was applied on the metals after the full-wave rectified.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 2 March 2015

Jie Zhang, Jing Liu, Qian Hu, Feng Huang, ZhaoYang Cheng and JunTao Guo

The aim of this paper was to clarify the influence of tensile stress on the electrochemical behavior of X80 steel in a simulated acid soil solution and attempt to…

Abstract

Purpose

The aim of this paper was to clarify the influence of tensile stress on the electrochemical behavior of X80 steel in a simulated acid soil solution and attempt to understand mechanistic aspects of the corrosion behaviors of X80 under these conditions.

Design/methodology/approach

The electrochemical behavior of X80 steel at various tensile stresses was investigated in a simulated acid soil solution using electrochemical impedance spectroscopy, potentiodynamic scan measurements and surface analysis techniques.

Findings

The results show that as tensile stress was increased, the open-circuit potential decreased, the reaction activity increase, the reaction resistance (Rct)value became smaller by degrees, the corrosion product film resistance (Rf) first decreased and then increased and polarization current densities changed conversely. The corrosion product film was compact and continuous under the low stress, whereas it was relatively loose under high-stress conditions. Tensile stress promotes the movement of dislocations, which become active points when they move to the steel surface. The increase in the number of active points enhances the anodic dissolution rate and promotes the formation of corrosion product film whose blocking effect can decrease the dissolution rate. The corrosion rate of the specimen is determined by these two effects.

Originality/value

This research provides an essential insight into the mechanism of the electrochemical behavior of X80 steel in acid soil environments.

Details

Anti-Corrosion Methods and Materials, vol. 62 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 4 October 2019

Yu Fu, Jie Kou and Cuiwei Du

Pipelines are seriously corroded due to the close distance between pipelines and high voltage transmission lines. The purpose of this paper is to study the influence of…

Abstract

Purpose

Pipelines are seriously corroded due to the close distance between pipelines and high voltage transmission lines. The purpose of this paper is to study the influence of alternating current (AC) on corrosion behavior of X80 pipeline steel in coastal soil solution.

Design/methodology/approach

The corrosion behavior of X80 steel under different AC densities in coastal soil solution was investigated by electrochemical measurements and image processing technology. Furthermore, a quantitative description model of AC corrosion through fractal dimension of corrosion image was established.

Findings

The results show that under low AC density the X80 steel is mainly uniform corrosion, and once AC density reaches 150 A/m2, the corrosion morphology gradually turns to pitting corrosion with irregular circle. For another aspect, the fractal dimension of corrosion images shows that the two/three-dimensional fractal dimension increase with the increase of AC density, presenting a linear and an exponential relationship respectively. In addition, the variation of the three-dimensional fractal dimension is the same as that of average corrosion rate. The threshold of the increasing trend of fractal dimension as well as corrosion type is 150 A/m2.

Originality/value

The investigation provides a quantitative method to describe AC corrosion morphology through fractal dimension. Furthermore, the method is of benefit to process corrosion images automatically.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 6
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 30 August 2021

Haoping Peng, Zhaolin Luan, Jun Liu, Yun Lei, Junxiu Chen, Song Deng and Xuping Su

This paper aims to under the laboratory environment, the corrosion behavior of X80 pipeline steel in oilfield injection water in eastern China was studied by immersion test.

Abstract

Purpose

This paper aims to under the laboratory environment, the corrosion behavior of X80 pipeline steel in oilfield injection water in eastern China was studied by immersion test.

Design/methodology/approach

First, the corrosion product film was immersed in oilfield injection water and the effect on the corrosion behavior and the corrosion reaction mechanism were constantly observed during this period. The effect was displayed by potentiodynamic polarization curve and electrochemical impedance spectrums (EIS) measurements. Second, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to observe and test the corrosion product film immersed in the oilfield water for 30 days.

Findings

The results indicate that the tendency of metal corrosion becomes weaker at an early stage, but strengthened later, which means the corrosion rate is accelerating. Besides, it is indicated by impedance spectroscopy that with the decreasing of the capacitance arc radius, the reaction resistance is reducing in this progress. Meanwhile, the character of Warburg impedance could be found in EIS, which means that the erosional components are more likely to penetrate the product film to reach the matrix. The corrosion product is mainly composed of the inner Fe3O4 layer and outer shell layer, which contains a large number of calcium carbonate granular deposits. It is this corrosion under fouling that produces severe localized corrosion, forming many etch pits on the metal substrate.

Originality/value

The experiment chose the X80 steel, the highest-grade pipeline steel used in China, to conduct the static immersion test in the injection water coming from an oilfield in eastern China. Accordingly, the corrosion mechanism and the effect of corrosion product film on the corrosion of pipeline steel were analyzed and discussed.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 7 June 2021

Shixiong Wu, Zhiming Gao, Da-Hai Xia, Meijun Wu, Yingjie Liu and Wenbin Hu

This paper aims to study the effect of temperature on the process and kinetic parameters of the hydrogen evolution reaction of X80 under cathodic protection (CP) in 3.5…

Abstract

Purpose

This paper aims to study the effect of temperature on the process and kinetic parameters of the hydrogen evolution reaction of X80 under cathodic protection (CP) in 3.5% NaCl solution.

Design/methodology/approach

Potentiodynamic polarization combined with the hydrogen permeation test is used to analyze the hydrogen evolution reaction (HER) process and the rate-determining step for which is diagnosed through the electrochemical impedance spectrum method. Then, the influence of temperature on kinetic parameters of HER can be known from the results obtained by using the Iver-Pickering-Zamenzadeh model for data analysis.

Findings

The results show that the HER proceeds through Volmer–Tafel route with the Volmer reaction acting as the rate-controlling step; Increasing temperature gives a higher activity of the HER on X80, it also accelerates the hydrogen desorption and diffusion of hydrogen into the metal.

Originality/value

There exist few studies on the topic of how temperature affects the HER process. It is imperative to conduct a relevant study to give some instruction in cathodic protection system design and this paper fulfills this need.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 8 November 2011

Shao Huai Qi, Zhang Qi Bin, Han Wen Li, Xie Bei Bei, Xu Zhong Ping and Huang Gui Bai

The purpose of this paper is to report the investigation of a low temperature application process for three‐layer polyethylene coating (3LPE) at 185‐195°C to meet the…

Abstract

Purpose

The purpose of this paper is to report the investigation of a low temperature application process for three‐layer polyethylene coating (3LPE) at 185‐195°C to meet the requirement of the coating temperature for X80 longitudinally welded pipe.

Design/methodology/approach

Plant coating and laboratory tests were performed to determine the properties of 3LPE coating coated at 185‐195°C.

Findings

The properties of the 3LPE coating, which was applied by using a suitable low temperature cured epoxy powder at temperature of 185‐195°C, were nearly the same as those of a 3LPE coating that had been applied at the normal coating temperature (200‐230°C).

Originality/value

Recommended acceptance criteria for 3LPE coatings applied at 185‐195°C are proposed. The research results met the requirements for external anti‐corrosion properties for X80 longitudinally welded pipe.

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Article
Publication date: 25 July 2019

Hongda Deng, Xianlong Cao, Yongbo Yan and Kuanya Xie

The purpose of this paper is to research whether microstructure varieties of zones at welded joints pose a tremendous effect on its corrosion in SC-CO2.

Abstract

Purpose

The purpose of this paper is to research whether microstructure varieties of zones at welded joints pose a tremendous effect on its corrosion in SC-CO2.

Design/methodology/approach

The interrelation between the corrosion and microstructure of base metal (BM), fine grain heat affected zone (FHAZ), coarse grain heat affected zone and weld metal (WM) in welded of X80 steel in water saturated supercritical CO2 was studied by using optical microscope, weight loss test, electrochemical measurements and surface analytical techniques.

Findings

The all subzones of X80 weld joints were attacked by SC-CO2 corrosion and showed flower-like corrosion scale spots consisted of granular FeCO3. The most severe corrosion appeared at WM due to lower proportion of ferrite to pearlite, but the slightest corrosion displayed at BM. GHAZ with larger grains and more polygonal ferrite exhibited more severe corrosion than that at BM. Due to its smaller grain, FHAZ displayed comparatively more severe corrosion to that at BM.

Originality/value

There exists close interrelation between the corrosion and microstructure of the welded carbon steel in water saturated supercritical CO2.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

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