SIST EN 13509:2003
(Main)Cathodic protection measurement techniques
Cathodic protection measurement techniques
This European Standard deals with the cathodic protection against corrosion of buried or immersed metallic structures, detailing the measuring methods to be used for assessing the effectiveness of cathodic protection as well as the measurements and measures taken to monitor cathodic protection during operation.
Throughout the text, the measurement techniques are described primarily for pipelines.
However, they are sufficiently general to apply to other kinds of buried or immersed (except offshore) structures.
General principles with regard to cathodic protection are described in EN 12954. Other measurement methods specific to particular cases are described in other European Standards e.g. prEN 50162.
Messverfahren für den kathodischen Korrosionsschutz
Gegenstand dieser europäischen Norm ist der kathodische Korrosionsschutz von metallenen Anlagen in Böden oder Wässern. Sie beschreibt die Meßmethoden zum Nachweis der Wirksamkeit des kathodischen Korrosionsschutzes sowie Messungen und Maßnahmen für dessen Überwachung während des Betriebs. In dieser Norm werden die Meßmethoden weitgehend am Beispiel von Rohrleitungen vorgestellt. Sie lassen sich jedoch auf alle anderen metallenen Anlagen in Böden oder Wässern anwenden.
Techniques de mesures applicables en protection cathodique
La présente Norme européenne traite de la protection cathodique contre la corrosion de structures métalliques enterrées ou immergées. Elle présente en détail les méthodes de mesure a utiliser pour évaluer l'efficacité de la protection cathodique, ainsi que les mesures et les moyens nécessaires au contrôle de fonctionnement de la protection cathodique.
Dans le texte, les techniques de mesure décrites concernent principalement les canalisations.
Elles sont cependant suffisamment générales pour etre appliquées a d'autres types de structures enterrées ou immergées (sauf les structures offshore).
Les principes généraux concernant la protection cathodique sont présentés dans la norme EN 12954. D'autres méthodes de mesure spécifiques a des structures particulieres sont présentées dans d'autres Normes européennes comme par exemple le prEN 50162.
.
Merilne tehnike za katodno zaščito
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Messverfahren für den kathodischen KorrosionsschutzTechniques de mesures applicables en protection cathodiqueCathodic protection measurement techniques25.220.40Kovinske prevlekeMetallic coatingsICS:Ta slovenski standard je istoveten z:EN 13509:2003SIST EN 13509:2003en01-december-2003SIST EN 13509:2003SLOVENSKI
STANDARD
SIST EN 13509:2003
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13509May 2003ICS 25.220.40; 77.060English versionCathodic protection measurement techniquesTechniques de mesures applicables en protectioncathodiqueMessverfahren für den kathodischen KorrosionsschutzThis European Standard was approved by CEN on 27 December 2002.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and UnitedKingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2003 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13509:2003 ESIST EN 13509:2003
EN 13509:2003 (E)2ContentsPageForeword.3Introduction.41Scope.52Normative references.53Terms, definitions and symbols.53.1Terms and definitions.53.2Symbols.94Buried structure to electrolyte potential.104.1Electrical equipment.104.2Potential measurement.104.3Factors influencing the potential measurement.114.4Potential measurement techniques.134.4.1Measuring technique including IR drop (on potential measurement).134.4.2Measuring techniques to determine IR free potentials (Eir free).135Immersed structure to electrolyte potential.165.1Electrical equipment.165.2Potential measurements.165.2.1Direct potential measurement methods.165.2.2Indirect potential measurement method.176Other measurements.176.1Current measurements (d.c.).176.2Isolating joints.176.3Foreign structures.186.4Coating.18Annex A (informative)
Table A.1 - Electrodes for Potential Measurements in Soil and/orAqueous Media.19Annex B (informative)
Current reduction technique.20Annex C (informative)
Above ground surveys used to measure pipe to soil potential alonga buried pipeline.22Annex D (informative)
Above ground surveys used to assess the coating condition and tolocate coating defects.23Annex E (informative)
Special off potential measurements in stray currents areas.25Annex F (informative)
Explanatory note on the use of the intensive measurementtechnique and the calculation of the IR free potential (EIR free).26Annex G (informative)
Examples of typical coupons and external potential test probe forpipe.28Annex H (normative)
Accuracy of potential measuring equipment.29Annex I (informative)
Accuracy of current measurement.31Annex J (informative)
Evaluation of the resistance of isolating joints.33Annex K (informative)
Current injection test on isolating joints.35Bibliography.37SIST EN 13509:2003
EN 13509:2003 (E)3ForewordThis document (EN 13509:2003) has been prepared by Technical Committee CEN/TC 219 "Cathodicprotection", the secretariat of which is held by BSI.This European Standard shall be given the status of a national standard, either by publication of anidentical text or by endorsement, at the latest by November 2003, and conflicting national standardsshall be withdrawn at the latest by November 2003.This European Standard should be considered as a basic document developing generalmeasurement techniques applicable for the protection of buried or immersed metallic structures.Annexes A, B, C, D, E, F, G, I, J and K are informative.Annex H is normative.This document includes a Bibliography.According to the CEN/CENELEC Internal Regulations, the national standards organizations of thefollowing countries are bound to implement this European Standard: Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg,Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the UnitedKingdom.SIST EN 13509:2003
EN 13509:2003 (E)4IntroductionThis European Standard describes the principles of the different methods of measurement used toassist in the design of the cathodic protection system of a buried or immersed metallic structure, forthe verification of its effectiveness and finally for its optimum operational conditions.It deals in particular with the measurement of the structure to electrolyte potential, which indicateswhether or not the cathodic protection criterion for the structure is met.Apart from specifying the factors, which may influence the measurement of the potential, thisEuropean Standard describes the different techniques possible and their suitability in varioussituations.Further, this European Standard provides parameters to be controlled and measurements to becarried out (potential, potential gradient, current and resistance measurements) to ensure the correctfunctioning of the cathodic protection system and its effectiveness for the entire structure.Several measurement methods described in general terms in the body of the standard are explainedin more detail in annexes. These methods differ from one another to account for differences in type orstate of the structure, the local environment and the degree of accuracy selected.Measurements on buried structures that are not easily accessible e.g. pipe networks in urban areasare difficult to implement and interpret. To take measurements without the full knowledge of theproblems associated with the measurement technique renders the interpretation of the measurementsdifficult and leads to incorrect decisions.One of the clauses of this European Standard therefore outlines the difficulties encountered whenmeasuring structure to electrolyte potentials, and suggests several methods of measurement that takeinto account, or avoid, these difficulties.Based on knowledge and experience, the most suitable measurement techniques can be selected asdescribed in this European Standard.In order to achieve effective and efficient cathodic protection, measurements should be performed bytrained, experienced and responsible personnel.Instrumentation used for measurement should be kept in good working order and should be subjectedto periodical calibration and safety checks.SIST EN 13509:2003
EN 13509:2003 (E)51 ScopeThis European Standard deals with the cathodic protection against corrosion of buried or immersedmetallic structures, detailing the measuring methods to be used for assessing the effectiveness ofcathodic protection as well as the measurements and measures taken to monitor cathodic protectionduring operation.Throughout the text, the measurement techniques are described primarily for pipelines.However, they are sufficiently general to apply to other kinds of buried or immersed (except offshore)structures.General principles with regard to cathodic protection are described in EN 12954. Other measurementmethods specific to particular cases are described in other European Standards e.g. prEN 50162.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from otherpublications. These normative references are cited at the appropriate places in the text, and thepublications are listed hereafter. For dated references, subsequent amendments to or revisions of anyof these publications apply to this European Standard only when incorporated in it by amendment orrevision. For undated references the latest edition of the publication referred to applies (includingamendments).EN 12954:2001, Cathodic protection of buried or immersed metallic structures — General principlesand application for pipelinesEN ISO 8044:1999, Corrosion of metals and alloys — Basic terms and definitions (ISO 8044:1999)3 Terms, definitions and symbols3.1 Terms and definitionsFor the purposes of this European Standard the following terms and definitions apply. For other termsand definitions related to corrosion refer to EN ISO 8044:1999 and to cathodic protection refer toEN 12954:2001.3.1.1anode backfillmaterial with a low resistivity, which may be moisture-retaining, immediately surrounding a buriedanode for the purpose of decreasing the effective resistance of the anode to the electrolyte3.1.2backfillsee anode backfill3.1.3bondmetal conductor, usually of copper, connecting two points on the same or on different structuresusually with the intention of making the points equipotentialSIST EN 13509:2003
EN 13509:2003 (E)63.1.4buried structureany metal construction built or laid beneath ground level or built on ground level and then coveredwith earth3.1.5calomel reference electrodereference electrode consisting of mercury and mercurous chloride in a solution of potassium chloride3.1.6cathodic protection systementire installation, including active and passive elements, that provides cathodic protection3.1.7cell currentcurrent flowing in a corrosion cell3.1.8coating defectdeficiency in the protective coating (e.g. holidays, porosity)3.1.9coating resistance or structure to soil resistance (Rco)electrical resistance between a coated metal and the electrolyte expressed in ohms. It is determinedlargely by the size and number of coating defects, coating pores and the electrolyte resistivity3.1.10copper/saturated copper sulphate reference electrodereference electrode consisting of copper in a saturated solution of copper sulphate3.1.11couponrepresentative metal sample used to quantify the extent of corrosion or the effectiveness of appliedcathodic protection3.1.12d.c. traction systemelectrical traction system powered by direct currentNOTEIf these systems have the return circuit earthed at more than one point or are not completely isolatedthey can generate stray currents, which may cause corrosion damage.3.1.13d.c. industrial plantelectrical system, other than a traction system, powered by direct currentNOTEIf these systems use the earth as a part of the return circuit, they can generate stray currents, whichmay cause corrosion damage. Cathodic protection systems use the earth as a part of the circuit.3.1.14electrolyteliquid, or the liquid component in a medium such as soil, in which electric current flows by themovement of ions3.1.15electrolyte resistivity (r)the specific electric resistance of the electrolyte assuming that the electrolyte is homogeneousNOTEUsually expressed in Wm.SIST EN 13509:2003
EN 13509:2003 (E)73.1.16equalising currentscurrents that flow between areas of different polarisation after switching off the protection current.Equalising currents can be a source of error in measuring IR free potentials3.1.17external potential test probeinstallation comprising a coupon with an associated reference electrode to provide structure toelectrolyte potential measuring facilities devoid of IR drop errors3.1.18foreign anodesee Foreign Electrode3.1.19foreign cathodesee Foreign Electrode3.1.20foreign electrodeforeign electrode is either a foreign anode or a foreign cathode. A foreign anode is a metal or aconductive material in contact with the structure under consideration which has a more negativepotential than the structure and a foreign cathode is a metal or a conductive material in contact withthe structure under consideration, which has a more positive potential than the structure3.1.21foreign structuresany neighbouring structure other than the structure that is under consideration3.1.22galvanic anodeanode that provides cathodic protection current by means of galvanic action3.1.23holidaydefect in a protective coating at which metal is exposed to the environment3.1.24immersed structureany metal construction, or part of a construction laid in a liquid environment such as fresh water(rivers, lakes), brackish water (estuaries), or sea water3.1.25insulated flangeflanged joint between adjacent lengths of pipe in which the nuts and bolts are electrically insulatedfrom one or both of the flanges and the gasket is non-conducting, so that there is an electricaldiscontinuity in the pipeline at that point3.1.26interferenceany change of the structure to electrolyte potential, which is caused by foreign electrical sources3.1.27IR dropvoltage, due to any current, developed in an electrolyte such as the soil, between the referenceelectrode and the metal of the structure, in accordance with Ohm's Law (U = I .R)SIST EN 13509:2003
EN 13509:2003 (E)83.1.28IR free potential (EIR free)structure to electrolyte potential measured without the voltage error caused by the IR drop due to theprotection current or any other current3.1.29isolating jointelectrically discontinuous connection between two lengths of pipe, inserted in order to provideelectrical discontinuity between them, e.g. monobloc isolating joint, insulated flange3.1.30measuring electrodeelectrode with a stable potential in a given electrolyte used to determine the potentials of a structure inthat electrolyte. The potential of a measuring electrode in a given electrolyte has to be determinedwith respect to a reference electrode3.1.31measuring pointpoint at which the actual measurement takes place. In the case of structure to electrolyte potentialsthis refers to the location of the reference electrode3.1.32off potential (Eoff)structure to electrolyte potential measured immediately after synchronous interruption of all sources ofapplied cathodic protection current3.1.33on potential (Eon)structure to electrolyte potential measured with the cathodic protection current flowing3.1.34permanent reference electrodepermanently buried or immersed reference electrode designed for a long life and installed close to thestructure3.1.35polarisationchange in the potential of an electrode (e.g. structure) as the result of current flow to or from thatelectrode3.1.36potential gradientdifference in potential between two separate points in the same electric field3.1.37potential test probessee External Potential Test Probe3.1.38protected structurestructure to which cathodic protection is effectively applied3.1.39protection current (Ip)current made to flow into a metallic structure from its electrolytic environment in order to effectcathodic protection of the structureSIST EN 13509:2003
EN 13509:2003 (E)93.1.40protection potentialstructure to electrolyte potential for which the metal corrosion rate is acceptable3.1.41silver/silver chloride electrodemeasuring electrode consisting of silver, coated with silver chloride, in an electrolyte containingchloride ions3.1.42silver/silver chloride reference electrodereference electrode consisting of silver, coated with silver chloride, in an electrolyte containing a fixedconcentration of chloride ions3.1.43standard hydrogen electrodereference electrode, used as a standard in laboratories, consisting of an inert metal, such as platinum,in an electrolyte containing hydrogen ions at unit activity and saturated with hydrogen gas at onestandard atmosphere3.1.44structuremetallic construction, whether coated or not, which is in contact with an electrolyte (e.g. soil, water)NOTEThe structure can represent a construction of great length, such as a pipeline, pipe networks, andunderground electric cables, or well casings as well as construction on a smaller scale such as piles, sheetpilings, tanks or other underground constructions.3.1.45structure to electrolyte potential (also called electrode potential)difference in potential between a structure and a specified reference electrode in contact with theelectrolyte at a point sufficiently close to, but without actually touching the structure3.1.46test probesee External Potential Test Probe3.1.47test stationinstallation that provides measuring and test facilities for the buried structure. Such installations willinclude cabling and structure connections3.1.48zinc electrodemeasuring electrode made from sufficiently pure zinc3.2 SymbolsICurrentEPotentialRResistanceJCurrent densityUVoltageaYeara.c.Alternating currentd.c.Direct currentSIST EN 13509:2003
EN 13509:2003 (E)10EAgMetal to electrolyte potential with respect to a silver/silver chlorideElectrodeECuMetal to electrolyte potential with respect to a copper/saturatedCopper sulphate reference electrodeEIR freeIR free potentialEKCIMetal to electrolyte potential with respect to a silver/silverChloride/saturated potassium chloride reference electrodeEnFree corrosion potentialEoffOff potentialEonOn potentialEpProtection potentialEHgMetal to electrolyte potential with respect to aMercury/calomel/saturated potassium chloride reference electrodeEHMetal to electrolyte potential with respect to a standard hydrogenreference electrodeEZnMetal to electrolyte potential with respect to a zinc electrodeIpProtection currentIsStray currentRcoCoating resistance (W)TTemperaturetTimerResistivity (W.m)4 Buried structure to electrolyte potentialCriteria for cathodic protection are generally based on the value of the structure to electrolytepotential. Measurement of the potential is therefore necessary in order to assess the effectiveness ofthe cathodic protection. This subclause describes different potential determination methods.4.1 Electrical equipmentThe type and use of the instrument for measurement should be suitable for the prevailing electricaland environmental conditions (see annex H).Instrumentation used for measurement shall be kept in good working order and shall be subjected toperiodical calibration and safety checks.4.2 Potential measurementSince only bare metal (e.g. at the coating holidays) is likely to suffer significant corrosion, themeasurement, indicating whether or not the protection potential Ep is fulfilled, would have to be maderight on the metal/electrolyte phase boundary, e.g. metal/soil boundary (see EN 12954).As this is not technically feasible, other techniques shall be applied to assess the effectiveness ofcathodic protection. The most suitable one has to be selected on the basis of the local conditions inthe field, e.g. coating type and quality, soil resistivity and presence of stray currents.Generally, structures to electrolyte potentials are measured using a reference electrode placed on thesoil surface (see Figure 1). Potential values of various normally used reference and measuringelectrodes with respect to the standard hydrogen electrode are listed in annex A.SIST EN 13509:2003
EN 13509:2003 (E)11Saturated calomel electrode shall not be used in soil or water because, among other things, the risk ofleakage of mercury from the electrodes.In case of disbonded coating, potential measurement may give incorrect indications 1.4.3 Factors influencing the potential measurementFigure 1 shows locations of reference electrodes for structure to electrolyte potential measurements.E(-)(+)1234Key1 and 2
Reference electrode locations3
Soil4
PipeFigure 1 — Possible locations of reference electrodes for measurement of structure toelectrolyte potentials
1 Where water flows between a loose coating and the structure surface, the potential measured is notrepresentative of the electrochemical phenomena that occur under the disbonded coating.SIST EN 13509:2003
EN 13509:2003 (E)12Disregarding minor errors, which are negligible in practice, the structure to electrolyte potentialcorresponds to the potential difference between the structure and the reference electrode at location(1), positioned in the immediate vicinity of the bare metal of the structure (e.g. at a coating defect of acoated structure). Since in practice, it is in most cases not possible to place the reference electrodeso close to the metal of the structure, the structure to electrolyte potential is therefore measured asthe potential difference between the structure and the reference electrode positioned at location (2).In the presence of currents in the soil between (1) and (2), however, placing the reference electrodeat location (2) will cause the measurement to be affected by errors. The value measured in this waydiffers from the value, which theoretically would be measured against the reference electrodepositioned at location (1). The difference between the two potential measurements is equal to thealgebraic sum of all the ohmic voltage drops (IR drops) in the soil between locations (1) and (2) due tocurrents flowing in the environment.E(2) -E(1) = åIR dropsTable 1 lists the different currents, which may cause IR drops.In the case of cathodic protection currents from the structure's own protective systems, the potentialsmeasured at location (2) are generally more negative than the potential at location (1). In lowresistivity soils the IR drop caused by these currents may reach several tens of millivolts, while in highresistivity soils it may reach a few volts.In the case of equalising currents, cell currents and stray currents, the potentials measured at location(2) may either be more negative or more positive than the potential at the location (1), according tothe sense of currents. In soil, equalising currents and cell currents may cause IR drops of up to a fewtens of millivolts and stray currents from d.c. traction systems may cause IR drops of up to a few tensof volts.For all currents from foreign sources a distinction should be made, as to whether the potentialgradient caused by these currents is nearly constant with distance in the vicinity of the structure to beprotected (case of remote source) or not (case of nearby source). In addition, currents from foreignsources, which fluctuate rapidly with time, should be differentiated from those, which are constant withtime. The burial depth of the structure also influences the IR drop.SIST EN 13509:2003
EN 13509:2003 (E)13Table 1 — Currents causing IR drops between the structure being protected and the referenceelectrode at location (2) in Figure 1 and examples of possible measuring techniques fordetermining the IR free potential for each type of currentItem No.Type of currentPossible measuring techniques,e.g.Subclause1.Currents specific to the system1.1Protective currentOff potential measurementExternal potential test probe4.4.2.14.4.2.41.2Equalising currentIntensive measurement techniqueExternal potential test probe4.4.2.34.4.2.41.3Cell current (remote foreign electrodes)Intensive measurement techniqueExternal potential test probes4.4.2.34.4.2.42.Currents from remote foreign sources2.1Not fluctuating with time, e.g. protectivecurrents, equalising or cell currentsIntensive measurement techniqueExternal potential test probes4.4.2.34.4.2.42.2Fluctuating with time, e.g. from d.c.traction systems, d.c. industrial plants,telluric currentSpecial off potential measurementIntensive measurement techniqueExternal potential test probes4.4.2.24.4.2.34.4.2.43.Currents from nearby foreign sources3.1Not fluctuating with time, e.g. protectivecurrents, equalising or cell currentsExternal potential test probes4.4.2.43.2Fluctuating with time, e.g. from d.c.traction systems or d.c. industrial plantsSpecial off potential measurementsExternal potential test probes4.4.2.24.4.2.44.4 Potential measurement techniques4.4.1 Measuring technique including IR drop (on potential measurement)Potential measurements conducted while the protective current is on are referred to as "on potentialmeasurements". The values obtained (on potentials Eon) contain various unknown IR drops (see 4.2),which can change with time and position of the reference electrode. The readings do not reflect thepotential at the metallic electrolytic phase boundary.On potential measurements are mostly used for monitoring cathodic protection, particularly wherestray currents from d.c. traction systems occur. In this case, in order to obtain meaningful values, onpotentials should be recorded over a period of time consistent with the interference level and variationover time (see prEN 50162).4.4.2 Measuring techniques to determine IR free potentials (Eir free)The following subclauses describe techniques, which may be applied to evaluate the IR free potential.They are differentiated by the type of current causing the IR drop (Table 1).SIST EN 13509:2003
EN 13509:2003 (E)144.4.2.1 Off potential measurements (instantaneous off potential technique)The instantaneous off potential technique may be used to eliminate IR drops caused by protectivecurrent (Table 1, item 1.1) where equalising currents, cells currents due to foreign anodes or foreigncathodes and stray currents are not present. The values obtained are referred to as off potentials, Eoff.For the steel/soil system, the potential measured against the reference electrode at location (2) inFigure 1 within one second after the protective current is switched off is usually sufficiently accurate.Depolarisation may occur relatively quickly for some metal/electrolyte systems, e.g. lead/soil, and forsome steel structure where cathodic protection has been newly applied or the structure is bare. Thecurrent reduction technique described in annex B may be used in such cases.The ratio between the "on" and "off" switching periods shall be chosen to avoid significantdepolarisation. In this way, the longer the measurement campaign duration is (e.g. 24 h), the higherthe ratio between the "on" and "off" periods shall be.Close Interval Potential Survey (CIPS) described in annex C takes on/off pipe to soil potentialmeasurements at regular intervals (about 1 to 2 m) along the pipe.4.4.2.2 Special off potential measurementsIn areas with stray currents fr
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.