Abstracts of papers to be presented hopefully during e-congress Madrid 2021
The 100 millivolt polarization criteria, when to use it and when not to use it
Jeffrey L. Didas – Abstract for CeoCor 2020 Madrid
The 100 millivolt polarization criterion is a very useful criterion. It is used all around the
world for pipelines and tanks and is quite successful in its application.
This paper will discuss the criterion, when to use it, when not to use it and have a few
examples of when this criterion is used incorrectly.
AC Corrosion at Other Frequencies
Dr. Andreas Junker Olesen Metricorr ApS. Copenhagen, Denmark email@example.com
AC corrosion on cathodically protected pipelines is commonly experienced due to
interference from high voltage transmission lines at a frequency of 50 or 60 Hz. In some cases, the source of interference may be low frequency AC transit systems (1/3 of the fundamental frequency) and in other cases higher harmonics of the fundamental frequency can be detected on pipelines. In this paper AC corrosion of cathodically protected steel is investigated using electrical resistance (ER) probes at various frequencies (16.6-360 Hz) and different CP levels in an artificial soil solution. The effect of frequency on basic aspects and understanding of AC corrosion, specifically in terms of alkalization mechanisms and
related time constants for involved processes, is discussed.
INTEGRATED SACP & ACIM
– a case study.
NEIL C WEBB* C.Eng. C.Sci. B.Sc.Eng. F.I.Corr F. & H.L.M.Corr.I.S.A. NACE Cathodic Protection & Corrosion Specialist Technical Director – Isinyithi Cathodic Protection (Pty) Ltd
DANIEL R HOVY** Pr. Eng. B.Eng (Hons) F.S.A.I.A.E. NACE Cathodic Protection Technologist
Technical Director – Isinyithi Electrical Protection (Pty) Ltd
Two new steel water pipelines (Majosi Pipe 23km long 800mm diameter and
Mogalakwena Pipe 3.6km long 800mm diameter) in rural remote areas in
South Africa were found to require both supplementary cathodic protection
due to corrosive soil conditions as well as AC mitigation due to the proximity
of high voltage AC powerlines. The areas were also known to be prone to
theft and vandalism.
The lack of medium voltage AC power in the area together with the risk of
vandalism favoured the use of sacrificial anode cathodic protection. The
pipeline coating was selected in order to minimise the current demand for the
cathodic protection system, but the high electrical resistance characteristic of
the coating had the consequence of increasing the level of AC mitigation
required to maintain safe touch potentials and minimise AC corrosion risk.
The pipeline coating integrity was analysed and ensured by means of close
An integrated cathodic protection and AC mitigation system utilising zinc
anodes without DC de-couplers was designed and installed. Pipe potential
and other key measurements were taken after a seasonal cycle which proves
the efficacy of the system.
This paper covers the CP design and ACM modelling process and presents
the successful commissioning data for the project.
* Neil Webb is an independent corrosion engineer with more than 40 years
experience in pipeline corrosion protection.
ESTIMATION OF THE CORROSION RATE OF BURIED METALLIC MATERIALS BY A NEURO-FUZZY EXPERT SYSTEM
M. Carboneras Chamorro1,*, A. Rodríguez Ortiz1, M.V. Biezma Moraleda2, J.C. Suárez Bermejo1
1 Grupo de Investigación en Materiales Híbridos, Escuela Técnica Superior de Ingenieros Navales, Universidad Politécnica de Madrid, Avda. Arco de la Victoria, s/n, 28040 Madrid
* Corresponding author: Mónica Carboneras Chamorro (email: firstname.lastname@example.org)
2 Departamento de Ciencia e Ingeniería del Terreno y de los Materiales, Escuela Técnica Superior de Náutica, Universidad de Cantabria, C/ Gamazo, 1, 39004 Santander
There is no doubt that determination of corrosion rate of metals in aggressive environments is critical to prevent future failures in service, thereby saving economic and social costs. However, it is well known that accurate estimation of corrosion rate is a difficult task because it needs to take into account the effect of many different and dynamic variables, which are involved in the electrochemical processes through relationships that are highly complex and difficult to quantify. This is the case of oil and gas buried pipelines, wherein corrosion is mainly linked with soil properties, leading to premature service failure. As attempt to address this issue, the present work proposes a neuro-fuzzy expert system for estimating the corrosion rate of buried pipes in terms of measurable environmental factors.
** Daniel Hovy is an independent consulting engineer with more than 30 years
experience in pipeline design and 7 years in electrical interference mitigation.
Casing measurements by coupons
CASTILLON François TEREGA
Coordination Technique/Expertise métiers
Terega, which operates a 5000 km long gas network in southwest of France, uses
permanents coupons on each test point (4000 TP) to asses the CP efficiency, by
disconnecting pipe/coupons measurements.
On the old Terega network, the preferred corrosion control method was isolating and
sealing the casing so there is no electrolyte in the space between the casing and the
carrier pipe. However, since 2005, Terega fills that area with an improved bentonite.
Casings are normally bare, while carrier pipelines are normally very well coated.
Normally, on each system pipe/casing, a test point must be installed to check the
insulation of the two structures This test station usually has wires, one or two to the
casing and one or two to the carrier pipeline.
To control the insulation system, you have to take a potential measurement of the
carrier pipeline and the casing by changing only the structure connection without
moving the copper/copper sulfate reference electrode.
If the two potential measurements are significantly different, the casing is not
shorted to the pipeline. Under normal conditions, the carrier pipeline should be
at a potential more negative than -0.85 volts DC, and the casing should be
between approximately -0.35 and -0.65 volts DC (a difference of between 200
to 500 mV).
If the two potential measurements are not significantly different (under 10 mV),
the casing may be shorted to the pipeline and additional testing is required
If the two potential measurements are different (under 100 mV), the casing
may be shorted to the pipeline at the other end of the casing and additional
testing is required
A very simple method can be applied with coupons to test the insulation system with
a very good accuracy, by coupons…
Assessing the effectiveness of cathodic protection in combined AC and DC interference conditions
M. Büchler and D. Joos
SGK Swiss Society for Corrosion Protection
Technoparkstr. 1, CH-8005 Zürich,
According to EN ISO 15589-1 the assessment of the effectiveness of cathodic protection
(CP) is based on IR-free potentials (EIR-free) measured on the protected structure.
EN 13509 describes the IR-free potential can be measured on coating defects
by means of the so-called Intensive Measurement. This extrapolation method allows
for calculating the IR-free potential based on the on- and off-potential in combination
with the concurrently assessed voltage gradients. Unfortunately, this method requires
DCVG indications of typically more than 30% or gradients larger than 150 mV, limiting
the application of the method to largest coating defects. In contrast, the oftenused
instant off potential (Eoff) may only be used in absence of any stray currents and
equalizing currents according to EN 13509. Equalizing currents can only be excluded
if all coating defects on the structure exhibit the same EIR-free. It is well known from
coupon measurements that this condition usually is not satisfied. Hence it must be
concluded that the same applies for coating defects on pipelines. As a consequence,
it is technically impossible to demonstrate effectiveness of CP in compliance with EN
ISO 15589-1 with modern pipelines, since the intensive measurement cannot be
used on the small DCVG indications and the instant off potential measurement may
not be used in presence of equalizing currents according to EN 13509. These aspects
are discussed and a new methodology for assessing the effectiveness of cathodically
protected structures is presented, which is also applicable in the case of
combined AC and DC interference conditions.
Managing AC corrosion risks – a case study
Christophe Baete – Elsyca
AC and DC interference threats are a large concern for many pipeline operators as coating performance and complexity of energy corridors increases. This results in considerable investm ent and survey or monitoring activities. Capital and operational costs ar under control when proper corrosion and safety risk assessment is performed, especially within colocations with third-party infrastructures that may change operational conditions of the power lines without any notice.
This paper discusses a pipeline integrity management approach for a buried pipeline subjected to AC corrosion. An existing mitigation system and monitoring program was reviewed through computational modeling predicting the AC corrosion likelihood of the entire parallelism according to ISO18086 and simulating real-time AC corrosion rates based on permanently monitoring of AC current loads of the powerlines.
pH variation under CP condition as a function of soil porosity.
Federico Martinelli-Orlando, Ueli Angst
ETH Zurich, Institute for Building Materials (IfB)
ETH Hönggerberg, CH-8093, Zürich, Switzerland email@example.com
pH variations were investigated in impressed current cathodic protection (CP) condition of steel samples in water saturated sandy soil. The aim of this work was to evaluate the pH variation under different protection current density and different soil porosity.
Carbon steel samples were buried in quartz sand saturated with a simulated soil solution. The pH variation was determined by means of planar optical sensors and iridium oxides (IrOx) sensors. Different soil porosities were obtained by dosing quartz sand with various granulometry.
The increase of pH at the sample surface occurred within the first 10 hours from CP application independently from the soil porosity. The alkalinity produced from CP is dependent on the cathodic current density. The pH gradient as a function of the distance from the steel surface is dependent on the soil porosity.
CP potential measurements on coupons: Enhanced assessment of stray current influences by fast data sampling
Cédric Dombard1, Kris Jans1
1 Fluxys Belgium S.A., Avenue des Arts 31, 1040 Brussels, Belgium
Deployment of remote-monitored OFF measurements on permanent coupons has been deployed on the Belgian high pressure natural gas network since 2015. A challenging measurement timing only 1ms after coupon disconnection was already used for many years for on-site measurements.
This timing was also used for the remote monitoring devices.
After several years of operations this document provides analysis of the data that is now available to assess the cathodic protection system, based on multiple field measurements.
Particular emphasis is set on the following aspects:
Monitoring and adjustement on CP levels to the appropriate level, adressing corrosion risks as well as possible overprotection issues
The consequence of the measurement timing on the retrieved data
The combination of AC and DC influences reflected on the probe measurement as a mixed potential
The approach in this paper aims to describe the strenghts and opportunities of the applied methodology, the possible application for the industry and could possibly be used in future CP criteria discussions.
Don’t just be in the industry, be a part of it
By Marguerite Forde
Young Pipeline Professionals Europe (YPPE) was inaugurated in 2018 with the primary aim of closing the generational skills gap within the pipeline industry. Targeted towards a membership base of young engineers entering the industry, YPPE serves to broaden knowledge and experience via live physical demonstrations, online content and creating an excellent networking platform. Steered by
well-respected veteran pipeliners looking to give something back, YPPE provides opportunities for young pipeliners to learn from experts and peers alike and encourages more active participation within the industry.
This presentation will focus on the benefits of establishing a young professionals network for pipeliners and industry across Europe and draw upon the successful models created by other YPP networks around the world.
Metallurgy and geometry: exploring two different solutions in order to minimize dezincification and stress corrosion cracking of brass.
S. FORTINa, A. PERROT b , E. FLEURYb, P. SOLEAUc, C. CARONd
a Engie, (firstname.lastname@example.org).
b GRTgaz, RICE (email@example.com, firstname.lastname@example.org).
c GrDF, (email@example.com).
d SAS CHUCHU DECAYEUX, (firstname.lastname@example.org).
Brass is widely used for manufacturing valves and connections in many applications the largest being potable water supply. In the case of α,β brass CuZn40Pb2 alloy (CW617N), two different field pathologies have been identified and studied by the Research & Innovation Center for Gas (RICE):
dezincification, which is characterised by the preferential dissolution of the zinc rich β phase.
stress corrosion cracking (SCC), a synergic effect of anodic dissolution, and mechanical
cracking resulting from residual (material processing), assembly (tightening torque,
misalignment) and operational (internal pressure) stresses.
In order to minimize cracking risk of the transfer valve and extend their lifespan, two different solutions were explored:
1. Metallurgical approach: transfer valves were processed using an alloy less sensible to dezincification: CuZn36Pb2As alloy (CW602N).
2. Geometrical approach: a new geometry was designed in order to minimize stress
concentration area along the transfer valve and avoid the contact between these areas and the environment, thus preventing both dezincification and cracking phenomena.
In each case (former and new alloy or design), laboratory tests were performed using an experimental protocol derived from the ISO standard 6957:1988 dealing with “Copper alloys —Ammonia test for stress corrosion resistance” to assess the sensitivity of the transfer valves to stress corrosion cracking. Those assessments were completed with dye penetrant analysis and microscopy observations in order to characterize the presence / absence or propagation of cracking and dezincification.
Keywords: Valves; corrosion; brass; dezincification; stress corrosion cracking.
Cathodic protection control of a buried and well
insulated pipe in presence of stray currents”
By Adrián Gomila GULDAGER ELECTRÓLISIS
The main factors to be considered to verify the effectiveness of the
cathodic protection of a buried pipe with a good coating, in presence
of stray currents will be reviewed.
• PC efficiency
• Cathodic protection criteria
• Potential measurement on the pipe
• Potential measurement on coupons
• Reliability of the reference electrodes
• Representativity of the coupons
• Complementary measurements
Stray current corrosion of steel in concrete: An assessment of the
influencing factors and their consequences on protection criteria
By David JOOS, SGK Zürich
The known model approach for AC corrosion is basically frequency independent in the range of 0.0 to 50 Hz and was investigated in detail at low frequencies. It was found at large amounts of anodic charge can be converted without corrosion by means of reand decharging the rust layer. This was already empirically proven by Bette in 2005 and has in the meanwhile been confirmed in further investigations.
These observations are of central importance in the assessment of the risk of facilities such as cathodically protected structures and structures embedded in concrete that are subject to stray current influence. For example, an 80-year-old railway infrastructure with average anodic influences of significantly more than 1 V has so far shown no damage, although according to the current standards there is an immediate need for action.
A further normative contradiction exists in the case of cathodically protected pipelines, which are subject to more stringent criteria regarding anodic influences than noncathodically protected pipelines. This problem has been solved pragmatically in the German DVGW GW 21 and is in good agreement with the present model approach.
However, it contradicts EN 50162.
As the revision of EN 50162 is currently under discussion, various tests have been
carried out to demonstrate the problem of corrosion of steel in concrete under the
influence of stray currents.
Streustromkorrosion von Stahl in Beton:
Eine Bewertung der Einflussfaktoren und deren Auswirkungen auf die Schutzkriterien
Der bekannte Modellansatz für Wechselstromkorrosion ist grundsätzlich im Bereich von 0.01 bis 50 Hz frequenzunabhängig und wurde bei tiefen Frequenzen im Detail
untersucht. Es wurde gefunden, dass grosse anodische Ladungsmengen ohne Korrosion über die Umladung in der Rostschicht umgesetzt werden können. Dies wurde bereits von Bette 2005 empirisch nachgewiesen und seither in weiteren Untersuchungen bestätigt.
Diese Beobachtungen sind von zentraler Bedeutung bei der Bewertung der Gefährdung von Anlagen, wie kathodisch geschützte und einbetonierte Strukturen, welche einer Streustrombeeinflussung unterliegen. So zeigt eine 80-jährigen Bahn Infrastruktur bei mittleren anodischen Beeinflussungen von deutlich mehr als 1 V bisher keine Schäden obwohl gemäss der aktuellen Normenvorgaben unmittelbarer Handlungsbedarf besteht.
Ein weiterer normativer Widerspruch besteht für den Fall von kathodisch geschützten Rohrleitungen, welche den strengeren Kriterien in Bezug auf anodische Beeinflussungen unterliegen als nicht kathodisch geschützte Rohrleitungen. Diese Problematik ist in der Deutschen DVGW GW 21 in pragmatischer Weise gelöst worden und ist in guter Übereinstimmung mit dem Modellansatz.
Sie steht jedoch im Widerspruch zur EN 50162.
Da aktuell die Revision der EN 50162 diskutiert wird, wurden verschiedene Versuche durchgeführt, welche die Problematik der Korrosion von Stahl in Beton unter Streustrombeeinflussung zeigen sollten.
Advanced assessment of pipeline anomalies using an ANFIS model and 3D data processing
I. Montero a
a ENAGAS Transporte SAU; Pº de los Olmos, 19; 28005 Madrid, Spain.
A B S T R A C T
ENAGAS, in collaboration with the Technical University of Madrid (UPM) and the University of Cantabria (UC), has developed a powerful IT tool for assessment of gas pipeline’s anomalies (dents, dents+corrosion, dents affecting ductile girth welds or seam welds, dents associated to mechanical damage, injurious mechanical damage with concurrent visible indentation, ripples in pipe surface, metal loss due to corrosion, crack-like flaws, etc.) and for the analysis and assessment of pipeline life extension (metal loss due to corrosion, fatigue crack growth and crack growth due to SCC). It is based on main international recognized standards (ASME B31.8, ASME B31G, API 579-1/ASME FFS-1, BS 7910, NG-18,ISO 12747, etc.).
It includes a module for processing geometric data from any commercial 3D canningtools, by means of which Level 2 evaluations of multiple types of anomalies can performed. Furthermore,for the corrosion assessment has been developed an adaptive neuro-fuzzy model (ANFIS) with learning capacity from real data gathered in inspection campaigns.
THE CHALLENGES OF NEGLECT
M.Sc PrChemSA, F.Corr.I.S.A. M.S.A.C.I
Director – Isinyithi Cathodic Protection (Pty) Ltd
Reduction in the routine monitoring and maintenance of assets also affects
cathodic protection systems on buried infra-structure. A general lack of
monitoring and maintenance of pipeline cathodic protection systems can, and
does, result in reduced protection of the structure.
Obviously this has immediate consequences on the integrity of the infrastructure.
In addition, however, are the less quantifiable series of challenges associated
with a short-term “partial repair approach” when cathodic protection and AC
mitigation are a contractual requirement during the replacement of portions of a
pipeline. The challenges are increased when the pipeline in question forms part
of a broader pipeline reticulation network.
This paper will examine some of the challenges associated with temporary and
permanent cathodic protection systems for replacement portions of pipelines
within a reticulation network, particularly where stray current influences are
Pipeline Integrity Maintenance and Diagnosis,
with particular regard to Stress Corrosion Cracking
Lucio Di Biase, Scientific Consultant – Italy (Past President of CEOCOR 2009 – 2015)
Osvaldo Fumei,Direttore Technico Solaria Route d’Ajaccio 20260 Calvi France
Ranieri Cigna, University Rome La Sapienza – Italy
Stress Corrosion Cracking on steel gas or oil pipelines can generally be considered a
Nevertheless, in some cases, this phenomenon has been destructive on some specific
pipeline, while it is a potential risk for any pipeline, when the conditions its occurrence exist.
Apart from the Sulphide Stress Corrosion Cracking, another two main types of
Stress Corrosion Cracking are usually considered for steel pipelines:
– High pH Stress Corrosion Cracking ;
– Low pH (or near neutral) Stress Corrosion Cracking.
Stress Corrosion Cracking involves corrosive mechanisms and depends on the
steel susceptibility,the environment and the tensile stress. These conditions can be resumed as follows:
High pH Stress Corrosion Cracking:
High temperature (this usually happens downstream the Compressor Stations, especially for Oil Pipelines);
Mechanical Stress (usually variable mechanical stress, due to pressure working conditions);
Low level of Cathodic Protection (these are the conditions where the pH reaches values around 9,0).
Low (or near neutral) pH Stress Corrosion Cracking:
Coating Defect (CP current is usually shielded and cannot reach the metal,the relevant pH remains around 6,5 (the so-called Near neutral – Low pH).
Mechanical Stress on a pipeline can normally be due to:
– Working conditions of the pipeline (e.g. the Pumping Stations);
– Stress due to soil conditions (subsidence, landslides etc.).
The paper resumes the results of a large research project developed in the laboratory and and various types of field measurements, with the characterization of the phenomenon and the localization of cracks in the real field before any failure could occur.
Determining the effectiveness of cathodic protection of buried pipelines 1 in casings
-An introduction to the German standard AfK 1/DVGW GW 20-
Dr. Ashokanand Vimalanandan
Open Grid Europe GmbH, Gladbecker Str. 404, 45326 Essen, Germany
The German standard AfK 1 (DVGW GW 20) regulates the engineering, installation and the condition assessment of buried pipelines in casings. In 2006 a pragmatic method for determining the cathodic protection was introduced by Schöneich. An electrical model builds the core of this method, which describes the condition of a pipeline within the casing. The remote on and off potential of the pipeline, on and off potential of the casing and the resistance between pipeline and casing are determined during inspection measurements. By using the electrical algorithm the electrical resistance in the spacing between pipeline and casing can be calculated (Ric). The calculated resistance is interpreted as a part of the spread resistance of all coating defects of a pipeline inside the casing. By conservative estimation of the minimal spread resistance of a circular coating defect (Rc, min) and comparing it to the actual calculated spread resistance Ric the effectiveness of cathodic protection can be interpreted.
Assessment of isolation between a metallic casing and a pipeline by means of remote monitoring and coupon
Automa S.r.l. – Via Casine di Paterno, 122/A – 60131 Ancona – Italia
Cathodic Protection Co Ltd – Venture Way – Grantham NG31 7XS – UK
Steel casings are installed to provide additional mechanical protection for pipelines crossing sites with possibility of significant mechanical stress (like roads, railways or watercourses) or areas with high population densities.
To guarantee that the CP applied to a pipeline in presence of a casing could work in an effective way, it is fundamental that no contact (electrical or electrolytic) would
exist between pipe and casing: the presence of a contact needs to be assessed and there are different techniques that can be used for this purpose.
In this paper, the technique proposed in Annex 2 from Cefracor Recommendation
PCRA n. 10 has been applied to check the presence and the type of contact between
a pipe and its casing in a real field experience by means of remote monitoring and coupon. Furthermore, the technique has been integrated with the ON/OFF cycling of the TR and different electrical resistive contacts have been simulated to check the conditions where the technique can give proper results.
Field experiences of LC Probes
RISE KIMAB, Box 7047, S-164 07 Kista
Nordion Energi AB, Box 362, S-201 23 Malmö
3CCC, Box 362, S-201 23 Landskrona
LC probes are perforation probes specially design for detecting local corrosion attacks. A number of probes were installed on the Swedish network for natural Gas in 2011. In order to evaluate the performance of the probes, two of them were drawn out of the soil in December 2019 and brought to laboratory for analysis.
The laboratory evaluation concluded that the corrosion pattern is local, independently of the corrosion cause. The aim of the probe is therefore fulfilled, namely to give an early warning in case of incomplete protection or stray current interference.
Role of bicarbonate ions and iron bacteria in forming tubercle relevant to graphitic corrosion of ductile iron (added 2021)
Fumio Kajiyama, Dr.
Tokyo Gas Pipeline Co., Ltd., 1-5-20, Kaigan, Minato-ku, Tokyo 105-8527, Japan
We experienced natural gas low pressure ductile iron pipe corrosion as high as 0,384 mm/y in aerobic soil with highly alkalinity that had been considered to be mildly corrosive as per AWWA C105-10. To elucidate this phenomenon, burial test of a ductile iron coupon was carried out in the same soil. Analyses of corrosion site of the coupon were made using electron probe micro analyzer and X-ray diffraction. Iron bacteria were identified. Other bacteria such as sulphate reducing bacteria were enumerated. Electrochemical techniques using corrosion potential, electrochemical impedance spectroscopy (EIS) and polarization curves were also applied to this study. In this paper, particular emphasis is placed on the role of bicarbonate ions and iron bacteria in forming tubercle relevant to graphitic corrosion of ductile iron.
Evaluation of corrosion risk by DC stray currents : study of norme criteria (added 2021)
C.ROGIER;T.LUTZLERa, E. FLEURYa, A. LOPITAUXa, R. BOUAFFREa, F.CASTILLONb, S. FONTAINEc, L. HENRYd,
a) GRTgaz, Research & Innovation Center for Energy (RICE), Villeneuve-la-Garenne, France,
email@example.com,firstname.lastname@example.org, email@example.com and firstname.lastname@example.org
b) TEREGA, Technical Department, Pau, France, email@example.com
c) GRTgaz, Technical Department, Compiègne, France, firstname.lastname@example.org
d) GRDF, Technical Department, Paris, France, email@example.com
To assess and mitigate dynamic DC stray currents occurring on buried, coated and cathodically protected steel pipelines, different criteria can be used by the operators. Numerous works are conducted regarding the influence of DC stray currents involving lab experiments and data analyses from the field.
In Europe, the standard EN 50162 suggests a criterion based on a 24h current registration through a coupon connected to the pipeline. However, as the criterion has been considered to be subjective and restrictive, a new EN ISO standard with additional criteria is expected in 2021.
This study aims to present some results of laboratory tests conducted in the presence of cathodic protection and DC stray currents. The intensity, duration and frequency of DC influences as well as environment is considered in order to try to get a better understanding of the conditions intentionally leading to a loss of metal. Both aggressive and non-aggressive conditions lead to a proven loss of metal and the influence of the aggressiveness on this loss is studied. In addition, criteria from literature and/or field experience is tested to compare their relevance to the tested situations.
Cathodic protection and depolarisation phenomena in soils : remanence of protection after interruption of cathodic protection.
C. ROGIERa, T. LUTZLERa), A. FAKHRY a), E. FLEURY a), F. CASTILLON b), L. HENRY c), D. SELLAM d), Y. ZANNIER e)
a) GRTgaz, Research & Innovation Center for Energy (RICE), Villeneuve-la-Garenne, France, firstname.lastname@example.org,email@example.com, firstname.lastname@example.org and email@example.com
b) TEREGA, Technical Department, Pau, France, firstname.lastname@example.org
c) GRDF, Technical Department, Paris, France, email@example.com
d) GRTgaz, Technical Department, Compiègne, France, firstname.lastname@example.org
e) Storengy, Technical Department, Bois-Colombes,France,email@example.com
Cathodic protection is applied as an active protection on buried pipelines in addition to passive means of protection (i.e. coatings). The term « depolarisation » would indicate the pipes gradually going back to their free potential value after a cessation of the cathodic protection. From an operational point of view, interruptions of this cathodic protection may happen on the network, leaving pipes without active protection during a certain amount of time. It is of interest to gain information on the depolarisation phenomenon in order to study the residual protection on pipes, especially its duration. Three different parameters were studied in laboratory, using a three-electrodes cell, to analyse the influence of specific elements on the depolarisation phenomenon:
- Time duration of the applied cathodic protection ;
- Level (strength) of the applied cathodic protection ;
- Composition of the soil/ environment of the test.
After applying a cathodic protection on a coupon then stopping it, the passivation of the surface was assessed through potential and time evolution, as it is demonstrated that the coupon is still protected for a certain amount of time after the cathodic protection is discontinued. By using electrical resistance probe, the thickness loss is also studied to prove the presence of protection after the cathodic protection has been ended. The start of metal loss can be linked to a change of potential measured on the coupon after a certain amount of time, introducing the hypothesis of a pseudo-passive film or a deposit protecting the coupon. This study shows that the cathodic protection, even after being stopped, still has protective effects and that it would allow pipelines to be protected during works requiring the interruption of cathodic protection.
Keywords : cathodic protection, depolarisation, pipelines, corrosion