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Article
Publication date: 17 December 2018

Ziqing Yang, Gan Cui, Zili Li and JianGuo Liu

In recent years, the demand for oil and gas pipelines has increased rapidly. Due to the restrictions of the pipeline routing, pipelines are generally laid in parallel or…

Abstract

Purpose

In recent years, the demand for oil and gas pipelines has increased rapidly. Due to the restrictions of the pipeline routing, pipelines are generally laid in parallel or in the same trench, which results in stray-current interference between the independent cathodic protection (CP) systems. The purpose of this paper is to study the interference between the long-distance parallel pipelines and to obtain the optimized operation for the CP systems.

Design/methodology/approach

In this study, first, the numerical model of parallel pipelines was established using the boundary element analysis software (BEASY). Second, the effects of horizontal distance between parallel pipelines, coating damage rate, soil conductivity and anode output current on the interference of parallel pipelines were studied. Finally, by varying the layout or the output currents of CP stations, an optimized operation scheme osf long-distance parallel pipelines was put forward.

Findings

Simulation results showed that with a decrease in soil conductivity or coating damage rate, the interference increased. Moreover, the interference decreased with an increase in horizontal distance between two parallel pipelines or a decrease in anode output current. It was found that there are three methods to reduce the interference between long-distance parallel pipelines: to reduce the output currents of CP stations, combined protection and to close part of the CP stations. Among them, to close part of CP stations was the optimized scheme because of the lowest operating and maintenance cost.

Originality/value

The optimized operation scheme proposed in this study can not only solve the interference between parallel pipelines but also provide guidance for the parallel pipelines to be built in the future. Reasonably arranging the cathodic protection stations using numerical simulation can avoid the interference in the cathodic protection systems, and reduce the construction cost.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 30 April 2020

Haijing Sun, Weihai Xue, Jiaxin Xu, Guoliang Chen and Jie Sun

The purpose of this work is to provide theoretical guidance and experimental analysis for optimized cathodic protection (CP) design of low alloy steel in deep water environments.

Abstract

Purpose

The purpose of this work is to provide theoretical guidance and experimental analysis for optimized cathodic protection (CP) design of low alloy steel in deep water environments.

Design/methodology/approach

In the present study, the CP criteria of 10Ni5CrMoV low alloy steel were investigated in a simulated deep water environment (350 m) regarding the theoretical protection potential and measured protection potential. The influences of hydrostatic pressure (HP) and temperature were also discussed in detail. The theoretical protection potential was analyzed with the Nernst equation, and the measured minimum protection potential was derived by extrapolating the Tafel portion of anodic polarization curves.

Findings

The results indicate that the minimum protection potential of low alloy steel shifts to a positive value in a deep-ocean environment. This can be attributed to the combined effects of HP and the temperature. Moreover, the temperature has a stronger influence compared with HP. The results suggest that the CP potential criteria used in shallow water are still applicable in the deep ocean, which is further confirmed through the SEM and x-ray diffraction analysis of the corrosion products resulted from the potentiostatic cathodic polarization experiments at −0.85 VCSE.

Originality/value

In recent decades, successful applications of CP for long-term corrosion protection of the steel components applied at a subsea level have enabled the offshore industry to develop reliable and optimized CP systems for shallow water. However, differences in the seawater environment at greater depths have raised concerns regarding the applicability of the existing CP design for deeper water environments. Hence, this research focuses on the CP criteria of low alloy steel in simulated deep water environment concerning the theoretical protection potential and measured protection potential. The influences of HP and temperature were also discussed.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 4
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 26 June 2009

I.A. Metwally and A. Al‐Badi

The purpose of this paper is to introduce a theoretical investigation of the pulse‐cathodic protection (PCP) systems to show how they behave under different operating…

Abstract

Purpose

The purpose of this paper is to introduce a theoretical investigation of the pulse‐cathodic protection (PCP) systems to show how they behave under different operating conditions. The effectiveness of the PCP system also is highlighted for a typical large‐scale configuration. The principal technical objectives of this paper are to answer three questions: Are the PCP systems effective in the desert fields? Although they have been approved, what is the reason for their lack of effectiveness in some coastal areas? What are the operation recommendations for the currently installed PCP systems and their future application?

Design/methodology/approach

The factors affecting the cathodic protection of well casings have been investigated theoretically by using a 3D field approach software package current distribution, electromagnetic fields, grounding and soil structure analysis. Cathodic interference with nearby well casings has been investigated thoroughly because corrosion of this kind is more serious than the anodic type. The performance of PCP systems has been analyzed with respect to obtaining better protection‐current distribution along the protected well casing at reduced anode current, together with reduced stray current (corrosion) at any nearby unprotected structure(s).

Findings

For uncoated well casings, protection current pulses are attenuated significantly and are smoothed out to be pure direct current after about 10 percent of the well‐casing buried length. High‐magnitude stray current can be found affecting any switched‐off well casings and hence they can be corroded faster from the top part than unprotected/remote wells, as are deeper well casings that may sustain considerable localized corrosion attack on the upper portions of the casing. Without the formation of a natural protective coating with high resistivity, the PCP system becomes malfunctioning, i.e. its performance becomes very similar to that of the conventional cathodic protection (CP) systems. This effect has been confirmed by field measurements in Oman, where magnesium hydroxide is minimally formed (in desert areas).

Research limitations/implications

In reality, some of the PCP modules at the same station can have a slight deviation in the operating frequency and/or voltage. It is planned, therefore, that the investigation will be extended to simulate such cases and take into account the effect of multi‐layer soils.

Practical implications

Knowing the performance of PCP systems for protecting deep well casings is a critical issue for the oil industry.

Originality/value

The paper provides a sound basis on which oil producers can take decisions about the future application of the PCP systems, optimize their performance, and introduce application restrictions by studying all factors that affect PCP performance. The effectiveness of PCP in desert (sandy/rocky) soil, where calcium‐carbonate deposition predominates over magnesium‐hydroxide formation, has proven to be very similar to that of a conventional CP system. The reliability of artificial oil‐lifting systems will be increased by reducing oil production losses (“oil deferment”) and the rig mobilization, which has very high rent cost.

Details

Anti-Corrosion Methods and Materials, vol. 56 no. 4
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 17 May 2013

Mariela Rendón Belmonte, José Trinidad Pérez Quiroz, Benjamín Valdez Salas, Miguel Martínez Madrid, Andrés Torres Acosta, Jesús Porcayo Calderón and Miguel Schorr Wiener

The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the…

Abstract

Purpose

The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the operation of the protection system.

Design/methodology/approach

Steel rods were immersed in seawater and NaCl solution with applied cathodic protection. The experimental methodology included monitoring of corrosion potential (Ecorr), galvanic current (Igalv) protection potential (Eprotection) and the depolarization potential of steel during the time of exposure. In addition, the chemical composition of the steel surface was assessed using a Scanning Electron Microscope (SEM).

Findings

In this research it was determined that the effectiveness of the CP system was mainly attributable to the formation of an iron oxide film on the steel surface.

Research limitations/implications

It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X‐ray diffraction (XRD), to verify the presence of a protective oxide.

Practical implications

Deposits on the steel surface have the beneficial effect of reducing the current required for efficient protection. Deposit formation therefore is of economic interest, as it decreases the cost of protection.

Originality/value

A unique feature of cathodic protection in seawater is the formation of calcareous deposits on metal surfaces. Advantageous aspects of these deposits, such as decrease in cathodic current requirement, have been investigated by various authors from various viewpoints. However, very little attention has been paid to the impact of any iron corrosion product films; the present paper contributes useful understanding and explains the importance of the mechanism that controls the operation of the protection system.

Details

Anti-Corrosion Methods and Materials, vol. 60 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 13 September 2011

Shengnan Hu, Tao Zhang, Yawei Shao, Guozhe Meng and Fuhui Wanga

The purpose of this paper is to study the effect of cyclic hydrostatic pressure on the protective performance of cathodic protection (CP) system consisting of Zn‐Bi…

Abstract

Purpose

The purpose of this paper is to study the effect of cyclic hydrostatic pressure on the protective performance of cathodic protection (CP) system consisting of Zn‐Bi sacrificial anode and Ni‐Cr‐Mo‐V steel.

Design/methodology/approach

The anode and cathode polarization curves of the driving potential and current for CP were investigated in case of cyclic hydrostatic pressure (0‐3.5 MPa) and compared with that at atmospheric pressure. The morphologies of the anode material with and without corrosion products were observed by scanning electron microscopy.

Findings

The experimental results revealed that the cyclic hydrostatic pressure had significant influence on the CP system. The anode potential instantaneously responded to the cyclic hydrostatic pressure and the discharge performance decreased due to the deposition of corrosion product. Also, the CP system exhibited higher slope parameter under cyclic hydrostatic pressure, indicating that the CP system cannot provide adequate protection for Ni‐Cr‐Mo‐V steel.

Originality/value

The results presented in this paper clearly show the effect of cyclic hydrostatic pressure on the sacrificial anode CP system, and present a foundation for further research on the practical application of sacrificial anode under cyclic hydrostatic pressure environment.

Details

Anti-Corrosion Methods and Materials, vol. 58 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 2 March 2015

Mariela Rendón Belmonte, Miguel Martínez Madrid, José Trinidad Pérez-Quiroz, Benjamín Valdez Salas, Erick A. Juarez-Arellano and Miguel Schorr

The purpose of this paper was to characterize the surface of steel reinforcement of concrete under cathodic protection (CP), submerged in seawater, to understand the…

Abstract

Purpose

The purpose of this paper was to characterize the surface of steel reinforcement of concrete under cathodic protection (CP), submerged in seawater, to understand the surface changes due to the application of CP and their consequences on cathodic current requirements.

Design/methodology/approach

Reinforced concrete specimens with applied CP were immersed in natural seawater. The experimental methodology included monitoring of corrosion potential (Ecorr); measurement of galvanic current (Igalv), protection potential (Eprotection) and the depolarization potential of steel during the time of exposure; and electrochemical impedance spectroscopy (EIS). The chemical composition of the steel surface was assessed using X-ray diffraction (XRD).

Findings

The application of CP leads to the formation of a deposit on the steel surface that according to XRD results, Pourbaix diagram and physical characteristics, is a protective oxide: magnetite (Fe3O4). This oxide causes a decrease in the corrosion rate and requires application of the protection current. It was found that the surface remained protected even after eight days when the CP system was interrupted.

Research limitations/implications

It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X-ray photoelectron spectroscopy, Mössbauer, to verify the presence of the magnetite.

Practical implications

Determination of the main cause of the decrease in current required for protection and deposit formation conditions will enable the design of a CP system to be optimized and economized. At present, the CP design considers only a constant current value for the duration of the protection time.

Originality/value

CP is a technique that has proven effective for the protection of metal structures. However, little attention has been devoted to the surface changes that occur under applied CP and their impact on the electrochemical behavior of the system. This paper describes the phenomena produced at the metal surface and determines kinetic parameters and their consequences on the CP behavior.

Details

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

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Article
Publication date: 27 March 2007

M. Sosa, R. Camacho, T. Pérez and J. González‐Sánchez

To evaluate the performance of two cathodic protection (CP) systems applied to steel reinforced concrete structures manufactured with calcareous aggregates and exposed to…

Abstract

Purpose

To evaluate the performance of two cathodic protection (CP) systems applied to steel reinforced concrete structures manufactured with calcareous aggregates and exposed to the tropical‐humid marine environment at the Yucatán peninsula in Mexico.

Design/methodology/approach

Rectangular concrete beams were manufactured using a water/cement ratio = 0.65, with and without the addition of NaCl in the mixing water. Specimens subjected to CP, eight to impressed current cathodic protection (ICCP) and eight to sacrificial anode cathodic protection (SACP) were partially immersed in natural seawater during 360 days. The half cell potential (HCP) and the current consumption were recorded during the total exposure time.

Findings

The measured HCP values of the steel rebar in the beams subjected to SACP did not attain protection potential levels. However, the galvanic couple Zn‐steel provided enough current for the protection of the steel. Visual inspection of concrete cores extracted from the beams indicated that corrosion products were not present at the steel‐concrete boundary. On the other hand, the ICCP applied to eight concrete beams provided excellent corrosion protection to the steel rebar.

Originality/value

This work revealed that the SACP system (thermally sprayed zinc) works well in high relative humidity environments and can be successfully used to protect steel reinforced concrete structures manufactured with calcareous aggregates which are endemic of the region and commonly used for infrastructure construction in the Yucatán peninsula.

Details

Anti-Corrosion Methods and Materials, vol. 54 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 3 January 2017

Ximing Li and Homero Castaneda

The purpose of this paper is to study the damage evolution (DE) of coated API5L-X52 steel pipe with cathodic protection (CP) in nature soil. Also, different coating…

Abstract

Purpose

The purpose of this paper is to study the damage evolution (DE) of coated API5L-X52 steel pipe with cathodic protection (CP) in nature soil. Also, different coating conditions, intact coating and coating with artificial holiday defect are considered to study the electrochemical behavior combined with soil properties and CP potential. An approach of electrochemical impedance spectroscopy (EIS) analysis is also developed.

Design/methodology/approach

This work developed a laboratory experimental set-up of coated pipeline under CP in nature soil. The electrochemical behavior has been investigated using EIS. The CP potential provided by a DC power supplier has been adjusted and recorded to maintain the protective potential of pipe at −850 mV vs Cu/CuSO4.

Findings

Various parameters were derived from the EIS fitting data by equivalent circuit models to illustrate the three DE stages of coated carbon steel in soil. Each stage changes faster for the artificial defect coating system compared to intact coating, especially at the initial water uptake and ion transport stage. The CP potential has been proved to be correlated to the soil properties, coating conditions and DE stages of pipeline samples.

Originality/value

This work is the first one to study DE of coated pipeline system under CP in soil. It introduces an electrochemical method to study coating defects which can promote to design the deterministic model to detect coating defects of buried pipe using AC impedance technique.

Details

Anti-Corrosion Methods and Materials, vol. 64 no. 1
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 February 1987

The cost of a vessel represents a substantial investment to the owner. During its working life it will be submersed in the sea — a corrosive environment from which it will…

Abstract

The cost of a vessel represents a substantial investment to the owner. During its working life it will be submersed in the sea — a corrosive environment from which it will need protection to avoid substantial additional costs for repair.

Details

Anti-Corrosion Methods and Materials, vol. 34 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 April 1995

C.O. Emenike

External corrosion prevention and control are addressed by coating/lining and cathodic protection (CP). Monitoring is usually by potential measurement using a standard…

Abstract

External corrosion prevention and control are addressed by coating/lining and cathodic protection (CP). Monitoring is usually by potential measurement using a standard half cell such as copper/copper sulphate or silver/silver chloride.

Details

Anti-Corrosion Methods and Materials, vol. 42 no. 4
Type: Research Article
ISSN: 0003-5599

1 – 10 of 154