testing of cp

8/12/2019 Testing of CP

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GUIDELINES FOR THE EVALUATION OF

UNDERGROUND STORAGE TANKCATHODIC PROTECTION SYSTEMS

MISSISSIPPI DEPARTMENT OF ENVIRONMENTAL QUALITY

OFFICE OF POLLUTION CONTROLUNDERGROUND STORAGE TANK BRANCH

P.O. BOX 10385JACKSON MS 3!"8!#0385

TELEPHONE$ %&01' !&1#51(1FACSIMILE$ %&01' !&1#50!3

))).*+,.-/+.-.-


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JULY 1 "00"


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TABLE OF CONTENTS

SECTION 1 2 GENERAL

1.1 Introduction .. 1

SECTION " 2 REGULATIONS

2.1 Rules . 2

SECTION 3 2 TYPES OF CATHODIC PROTECTION

3.1 General . 4

3.2 Galvanic Systems ... 4

3.3 Impressed Current Systems .. 4

SECTION 2 QUALIFICATIONS TO TEST CATHODIC PROTECTION SYSTEMS

4.1 Qualifications ... 5

SECTION 5 2 INSTALLATION4REPAIR OF CATHODIC PROTECTION SYSTEMS

5.1 Galvanic Systems ... 6

5.1.1 sti!"#

$an%s .... 6

5.1.2 &actory Coated 'etallic !ipin( . 6

5.1." )onfactory Coated 'etallic !ipin( . 65.1.4 'etallic !ipin( Installation*Repair .... 6

5.2 Impressed Current Systems .. +

5.2.1 Rectifier ,d-ustment

+

SECTION & 2 CATHODIC PROTECTION TESTING

6.1 /uipment

0

6.1.1 oltmeter*,mmeter . 0

6.1.2 Reference lectrode ... 1

6.1.3 3ead ires*$est !roes*'iscellaneous .. 11

6.2 $est Criteria . 12

6.3 olta(e IR7 8rops .. 1"

6.4 Stray Current ... 14

6.5 8issimilar 'etals*9imetallic Couples ... 15

6.6 :t;er $est Considerations . 16

6.7 Continuity $estin( ... 1+6.


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6.10.3 $an%s !rotected y Impressed Current .. 25

6.10.4 !ipin( !rotected y Impressed Current .. 26

6.1.5 =1 &oot Rule> for !ipin( . 2 approac; t;at ?ill ?or% at every site t;at ;as a cat;odic protectionsystem in operation. $;ereforeH t;e primary intent of t;is policy is to create a level playin( field in?;ic; everyone en(a(ed in t;e field of @S$ system cat;odic protection in t;e State of 'ississippiunderstands ?;at is eApected. $;e second focus of t;is policy is to provide t;at documentationsufficient to reproduce t;e results (enerated y a cat;odic protection tester must e estalis;ed inorder to conduct a valid cat;odic protection evaluation. $o t;is endH forms t;at must e utilied ?;enevaluatin( cat;odic protection are included in ,ppendiA E and 3 of t;is document.

It is furt;er necessary to understand t;at t;e creation of t;is policy ;as necessitated a compromiseto some de(ree. very effort ;as een made so as not to place an unduly ;ars; urden on t;e tan%o?ners and contractors ?;o operate in t;e State of 'ississippi. ,t t;e same timeH it is necessary toe protective of ;uman ;ealt; and t;e environment to t;e de(ree re/uired to ac;ieve t;e c;ar(e oft;e 'ississippi 8epartment of nvironmental Quality '8Q7. $;is document represents t;e est

efforts of t;e '8Q to assure t;at cat;odic protection systems operate as intended and effectivelymiti(ate corrosion ?;ile ein( mindful of t;e economic constraints t;at must e considered.

Some of t;e more important points estalis;ed ?it; t;is (uidance document areJ

1,ccess to t;e soil directly over t;e structure t;at is ein( tested must e provided.

2 9ot; =local> and =remote> structuretosoil potentials must e otained on (alvanic systems.3 =Instant off> potentials must e otained on all impressed current systems.4 Continuity*isolation must e estalis;ed ?;enever a cat;odic protection survey is conducted.5 @nder certain conditions a =corrosion eApert> must evaluate t;e cat;odic protection survey.6, person must meet certain minimum /ualifications in order to conduct an effective evaluation.

Simply conductin( a structuretosoil potential survey does not ade/uately evaluate a cat;odicprotection system. :t;er considerations t;at may need to e addressed are outlined in t;e teAt of

t;is document and includeJ continuity measurementsK evaluation of rectifier operationK currentdistriution amon( an impressed current anode (round edK consideration of volta(e dropsK

assurance of ?irin( inte(rityK continuity ondsK as uilt dra?in(s and ot;ers.

$;is policy is not intended to replace any statute or re(ulatory re/uirement concernin( t;e

installationH repairH operation or testin( of cat;odic protection systems. Rat;erH it is intended to state

t;e interpretation of t;e '8Q ?it; re(ard to t;e implementation of t;ose rules and re(ulations

applicale to @S$ cat;odic protection systems.

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SECTION " # REGULATIONS

2.1 R:+-

&ederal and state la?s re/uire t;at any component of a @S$ system t;at routinely contains product

and is in contact ?it; t;e soil must e protected from corrosion. If t;e @S$ component in /uestion isof metallic construction and it is in contact ?it; t;e soil and*or ?aterH it must e cat;odically

protected. If it is cat;odically protected it must also e coated ?it; a suitale dielectric material if t;e

metallic component in /uestion ?as installed after 8ecemer 22H 10++.

$;e rules also re/uire t;at all cat;odic protection systems must e evaluated ?it;in siA mont;s of

installation*repair and once every t;ree years t;ereafter. Consideration s;ould e (iven to evaluatin(

impressed current systems on an annual asis since t;ese types of systems are more susceptile tofailure or may e in need of ad-ustment on a more fre/uent asis in order to provide ade/uate

cat;odic protection.

$;e '8Q adopted veratim t;e federal @S$ rules found under Sutitle I of t;e Resource

Conservation and Recovery ,ct. $;e rules are pulis;ed in C;apter 4 !art 2+ of t;e Code of&ederal Re(ulation =$ec;nical Standards and Corrective ,ction Re/uirements for :?ners and:perators of @nder(round Stora(e $an% Systems>7. $;e re(ulations reference several industrycodes and practices and a listin( of t;ese may e found in ,ppendiA , of t;is document. &ollo?in(are t;e pertinent para(rap;s of 4 C&R 2+ t;at are related to cat;odic protectionJ

280.12 8efinitions

=Cat;odic !rotection> is a tec;ni/ue to prevent corrosion of a metal surface y

ma%in( t;at surface t;e cat;ode of an electroc;emical cell. &or eAampleH a tan%

system can e cat;odically protected t;rou(; t;e application of eit;er (alvanic

anodes or impressed current.

=Cat;odic protection tester> means a person ?;o can demonstrate an understandin(of t;e principles and measurements of all common types of cat;odic protectionsystems as applied to uried or sumer(ed metal pipin( and tan% systems. ,t aminimumH suc; persons must ;ave education and eAperience in soil resistivityH straycurrentH structuretosoil potentialH and component electrical isolation measurementsof uried metal pipin( and tan% systems.

=Corrosion eApert> means a person ?;oH y reason of t;orou(; %no?led(e of t;ep;ysical sciences and t;e principles of en(ineerin( and mat;ematics ac/uired y aprofessional education and related practical eAperienceH is /ualified to en(a(e in t;epractice of corrosion control on uried or sumer(ed metal pipin( systems and metaltan%s. Suc; a person must e accredited or certified as ein( /ualified y t;e)ational ,ssociation of Corrosion n(ineers ),C7 or e a re(istered professional

en(ineer ?;o ;as certification or licensin( t;at includes education and eAperience incorrosion control of uried or sumer(ed metal pipin( systems and metal tan%s.

280.20 !erformance Standards for )e? @S$ Systems

(1) 27 $;e tan% is constructed of steel and cat;odically protected in t;e follo?in(

mannerJ

(9) $;e tan% is coated ?it; a suitale dielectric materialK

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(2) &ieldinstalled cat;odic protection systems are desi(ned y a

corrosion eApertK

(3) Impressed current systems are desi(ned to allo? determination of

current operatin( status as re/uired in 2+."1 c7K and

(4) Cat;odic protection systems are operated and maintained inaccordance ?it; 2+."1 or accordin( to (uidelines estalis;ed y t;e

implementin( a(encyK or various industry codes and standards are

referenced ;ere L see ,ppendiA ,7.

2+."1 :peration and 'aintenance of Corrosion !rotection

(1) ,ll corrosion protection systems must e operated and maintained tocontinuously provide corrosion protection to t;e metal components of t;at

portion of t;e tan% and pipin( t;at routinely contain re(ulated sustances andare in contact ?it; t;e (round.

(2) ,ll @S$ systems e/uipped ?it; cat;odic protection systems must einspected for proper operation y a /ualified cat;odic protection tester in

accordance ?it; t;e follo?in( re/uirementsJ

(1) Frequency. ,ll cat;odic protection systems must e tested ?it;in 6

mont;s of installation and at least every " years t;ereafter.

(2) Inspection Criteria. $;e criteria t;at are used to determine t;atcat;odic protection is ade/uate as re/uired y t;is section must e in

accordance ?it; a code of practice developed y a nationallyreco(nied association.

(3) @S$ systems ?it; impressed current cat;odic protection systems must also

e inspected every 6 days to ensure t;e e/uipment is runnin( properly.

(4) &or @S$ systems usin( cat;odic protectionH records of t;e operation of t;ecat;odic protection must e maintained in accordance ?it; 2+.4"7 to

demonstrate compliance ?it; t;e performance standards in t;is section.

$;ese records must provide t;e follo?in(J

(1) $;e results of t;e last t;ree inspections re/uired in para(rap; c7 aoveK

(2) $;e results of testin( from t;e last t?o inspections re/uired in para(rap;7 aove.

2+."1 Repairs ,llo?ed

(5) it;in 6 mont;s follo?in( t;e repair of any cat;odically protected @S$systemH t;e cat;odic protection system must e tested in accordance ?it;

2+."1 7 and c7 to ensure t;at it is operatin( properly.

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SECTION 3 # TYPES OF CATHODIC PROTECTION

3.1 G++6/:

$;e t?o types of cat;odic protection t;at are typically installed on @S$ systems are (alvanicsacrificial anode7 and impressed current systems. ,n attempt to eAplain t;e principles involved int;e t;eory of cat;odic protection is eyond t;e scope of t;is document and it is assumed t;e reader;as a asic understandin( of t;e su-ect. Do?everH stated in t;e simplest termsH ot; of t;ese typesof cat;odic protection attempt to reverse t;e flo? of electric current a?ay from t;e metal t;at isintended to e protected from corrosion. 9ot; types of cat;odic protection prevent electric currentfrom leavin( t;e protected structure y supplyin( an electrical c;ar(e in t;e form of 8C po?ersufficient to overcome any current t;at ?ould ot;er?ise leave t;e structure. $;e ?ay in ?;ic; t;ere/uired electrical current is provided is ?;at distin(uis;es t;e t?o types of cat;odic protection.

3.2 G/:;/9 S


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SECTION 2 QUALIFICATIONS TO TEST CATHODIC PROTECTION SYSTEMS

4.1 Q/:9>9/97-

In order to test cat;odic protection systems in t;e State of 'ississippiH an individual must meet

certain minimum /ualifications. It is t;e intent of t;e '8Q t;at t;ose individuals ?;o meet t;eminimum /ualifications perform testin( in a manner t;at is consistent ?it; t;e policies of t;is(uidance document. S;ould an individual ?;o meets t;e minimum /ualifications as descried elo?not possess t;e %no?led(e and eApertise needed to properly evaluate a cat;odic protection systemHt;at individual s;ould not attempt to underta%e suc; an evaluation.

;ile it is not necessary to e an =eApert> to test cat;odic protection systems in most casesH its;ould e reco(nied t;at t;e proper evaluation of t;e t?o types of cat;odic protection systems mayre/uire differin( levels of eApertise. Impressed current systems are in;erently more involved andre/uire a ;i(;er level of understandin( t;an (alvanic systems. In additionH certain circumstances andconditions may eAist t;at ?ould preclude an individual from ma%in( an effective evaluation of acat;odic protection system ?it;out t;e assistance of someone ?;o is more /ualified.

9ecause t;e testin( of impressed current systems is in;erently more complicatedH someone ?;o isonly minimally /ualified as a =tester> s;ould reco(nie t;at ;e may or may not e ale to properlyevaluate all suc; systems. Galvanic cat;odic protection systems t;at are operatin( as desi(ned arenormally strai(;tfor?ard and a lesser de(ree of eApertise is needed to properly evaluate suc;systems. Do?everH troules;ootin( and*or repair of suc; systems may re/uire someone ?;o ;as a;i(;er level of eApertise t;an a person ?;o is only minimally /ualified as a tester.

Scenarios t;at re/uire an eApert to eit;er conduct or evaluate t;e cat;odic protection survey arelisted in Section or a

=cat;odic protection specialist>7 can e found at t;e ?e site of ),C International ???.nace.or(7.

3isted elo? are t;e minimum /ualifications necessary to test cat;odic protectionJ

1,nyone ?;o meets t;e definition of =cat;odic protection tester> as found in 4 C&R 2+.1 is

reco(nied as /ualified to test cat;odic protection.

2,nyone ?;o ;olds a certification from ),C International ?;ic; t;at or(aniation reco(nies at

a minimum as /ualifyin( t;at person as a cat;odic protection tester.

3,nyone ?;o is certified y t;e '8Q as a @S$ installer is reco(nied as ein( ale to testcat;odic protection systems provided t;ey are familiar ?it; t;e concepts involved and aide y

t;e re/uirements contained ?it;in t;is (uidance document. If a @S$ installer does notunderstand t;e asic concepts related to t;e testin(H maintenance and operation of cat;odic

protection systemsH t;at person s;ould not attempt to evaluate suc; systems.

S;ould it e determined t;at a '8Q certified @S$ installer is conductin( evaluations of @S$

cat;odic protection systems in a manner t;at is not consistent ?it; t;e intent of t;e '8Q policyH

t;ey may e su-ect to penalty and*or revocation of t;eir @S$ installer certification upon a

determination of (ood cause y t;e 'ississippi Commission on nvironmental Quality.

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SECTION 5 # INSTALLATION4REPAIR OF CATHODIC PROTECTION SYSTEMS

5.1 G/:;/9 S


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product>H it is not re/uired to meet t;e corrosion protection re/uirements and may e in contact ?it;

t;e soil or sumer(ed in ?ater ?it;out t;e need for cat;odic protection. Do?everH t;e pump ;ead

s;ould remain visile not uried7 so t;at any ovious corrosion prolems or lea%s t;at may e

present can e oserved and appropriate action ta%en to prevent or repair any lea%s.

R+=/96 # Some confusion eAists over ?;et;er or not metallic pipin( t;at ;as failed can e repaired ormust e replaced. =Repaired> as related to steel pipe involves t;e replacement of t;e section of pipet;at ;as failed. $;e entire run of steel pipin( does not ;ave to e replaced ut t;e repair mustconsist of replacement of t;e section of pipe t;at ;as failed. :nly steel pipe t;at is factory coated?it; a dielectric material fusion onded epoAy7 can e used to replace t;e failed section of pipere(ardless of ?;et;er t;e eAistin( pipe is (alvanied or coated steel. @nder no circumstances is itallo?ale to install (alvanied pipin( ?;en it is intended to serve as a product transfer line. 9ecauseof t;e compleAities t;at may e involved in t;e cat;odic protection of (alvanied steel pipin(H acorrosion eApert must evaluate and*or conduct t;e cat;odic protection survey after t;e repair.

E:+69/: C799< # 8ielectric unions are normally not installed if t;e pipin( is protected y an

impressed current system. It is essential t;at all metallic pipin( t;at is part of t;e @S$ system is

onded to t;e ne(ative circuit of t;e impressed current system if it is uried. It is normally desirale

to electrically isolate any metallic portion of t;e @S$ system t;at is not uried or sumer(ed in ?ater

from t;at portion t;at is uried*sumer(ed.

E:+69/: I-7:/97 # If metallic pipin( is (alvanically protectedH it is critical t;at effective electricalisolation is provided. &ailure to isolate t;e protected pipin( ?ill result in premature failure of t;esacrificial anodes. Isolation can e difficult to ac;ieve ?;ere cat;odically protected pipin( is presentunder dispensers t;at ;ave s;ear valves present. $;is is due to t;e re/uirement t;at t;e s;ear valvemust e properly anc;ored to t;e island form. !articular care s;ould e eAercised in t;ese instancesto assure proper isolation. If possileH t;e dielectric union s;ould e installed elo? t;e s;ear valveso t;at anc;orin( does not cause a continuity prolem.

S6+) J79- # !articular care s;ould e ta%en ?;en dealin( ?it; metallic pipin( t;at ismec;anically coupled ?it; t;readed scre? -oints. ,ny t;readed -oint in a metallic pipin( material canserve as a rea% in t;e electrical continuity of t;e pipin( system. It ;as een estalis;ed t;att;readed couple pipe -oints can develop enou(; electrical resistivity over time to effectively isolateeac; section of a pipin( system. &or ovious reasonsH t;is is ;i(;ly undesirale in a cat;odicprotection system and you s;ould ensure t;at electrical continuity is present et?een any sections ofpipin( t;at are intended to e protected. Mumper ?ires or ?eldin( may e necessary across eac;pipe couple in order to assure electrical continuity et?een eac; section of pipin(.

F:+ C7+76- # ,ny metallic fleAile connector includin( stainless steel7 t;at is utilied on a

pipin( system must e protected from corrosion. $;e fleA connector may e isolated from contact

?it; soil*?ater or cat;odically protected. If t;e fleA connector is cat;odically protectedH it must also

e coated*?rapped ?it; a dielectric material if it ?as installed after 8ecemer 22H 10++.

C7/9+ S=- # If metallic components of a pipin( system are installed in a containmentsumpH t;e sump must e maintained dry. If a sump contains ?ater and you are unale to %eep t;e?ater outH t;e metallic components must e protected from corrosion. $;e metallic components maye protected y installin( appropriate isolation oots in t;e case of fleA connectors7 or sacrificialanodes. If cat;odic protection is necessaryH t;e sump may or may not e filled ?it; clean sand to adept; ade/uate to ury t;e anode. 9urial of t;e anode may ;elp prevent an oAidation film fromformin( on t;e anode and causin( passivation7 in t;e event t;at standin( ?ater is not al?ayspresent in t;e sump. In eit;er caseH it is critical t;at t;e anode e installed ?it;in t;e containment

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sump. 8o not place t;e anode outside of t;e sump. )ote t;at any cat;odically protected component

installed after 8ecemer 22H 10++ must also e coated*?rapped ?it; a suitale dielectric material.

M9+* P9=9 # In t;ose instances ?;ere fier(lass reinforced plastic or fleAile pipin( is

connected to an eAistin( metallic pipe e.(. to eAtend a fuelin( island7H a cat;odic protection test

station or access to t;e soil ?;ere t;e t?o dissimilar materials are -oined must e provided. $;is isnecessary to effectively test t;e ade/uacy of cat;odic protection operatin( on t;e metallic pipin(.

5.2 I=6+--+* C66+ S


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SECTION & # CATHODIC PROTECTION TESTING

6.1 E,9=+

,lt;ou(; t;e e/uipment re/uired to test cat;odic protection systems is relatively simpleH it is

very important t;at t;e e/uipment e maintained in (ood ?or%in( order and is free of corrosion

and contamination. $;e asic e/uipment includes a voltmeter*ammeter multimeter7H referenceelectrodeH ?iresH clips and test proes.

It may also e necessary to ;ave a current interrupter for impressed current systems ?;en t;epo?er cannot e easily cut on and off at t;e rectifier. , clamp on type ammeter can e useful?;en troules;ootin( impressed current systems. ire locators can ;elp determine t;e locationof uried anode lead ?ires and ;eader cales. Dand tools to clean corrosion or dielectriccoatin(s from t;e surface of t;e structure you are testin( at t;e point of contact ?it; lead?ires*proes may also e necessary.

6.1.1 V7:++64A++6

, (ood /uality voltmeter*ammeter multimeter7 t;at ;as an ade/uate de(ree of accuracy is essential

for testin( cat;odic protection due to t;e lo? volta(e*current involved. 'ost =lo? end>

voltmeters*ammeters are not capale of ac;ievin( results accurate enou(; to ensure reliale results

and s;ould t;erefore not e used.

,ll testin( of cat;odic protection systems must e accomplis;ed ?it; a ;i(; internal resistanceimpedance of 1 me(o;ms or (reater7 voltmeter t;at is properly maintained and periodically

calirated in accordance ?it; t;e manufacturerBs recommendations. $;e voltmeter s;ould ecalirated at least on an annual asis. It is important t;at t;e voltmeter ;as a ;i(; internal resistance

in order to avoid introducin( a lar(e error ?;en measurin( structuretosoil potentials.

$;e voltmeter must ;ave a ;i(; de(ree of sensitivity and must e placed in as lo? a scale aspossile normally t;e 2 volt 8C scale ?or%s ?ell7 in order to accurately measure t;e small volta(es

associated ?it; cat;odic protection systems. ,ll volta(e measurements otained s;ould e recorded

as millivolts m7. &or eAampleH a readin( of 1.2" volts s;ould e recorded as 12" mK a readin(

of .+5 volts s;ould e recorded as +5 m.

oltmeters t;at ;ave a variale input resistance can e utilied to ensure t;at contact resistanceet?een t;e reference electrode and t;e electrolyte ;as een evaluated as a source of errorvolta(e drop7 in t;e oserved structuretosoil potential. $;is is accomplis;ed y c;an(in( t;e inputresistance and notin( ?;et;er or not t;e volta(e oserved c;an(es si(nificantly. If no volta(ec;an(e is oserved ?;en t;e input resistance is c;an(edH it can e assumed t;at contact resistanceis not causin( an error in t;e structuretosoil potential measurement.

,n ammeter t;at ;as a very lo? internal resistance is necessary ?;en testin( impressed currentsystems in order to accurately determine t;e current output of t;e rectifier and*or individual circuits int;e system. GenerallyH ampera(e s;ould only e measured ?;ere calirated measurement s;unts

are present. ,lternativelyH a =clampon> type ammeter may e utilied in t;ose cases ?;ere s;unts

are not present.

$;e atteries in t;e portale multimeter must also e in (ood condition. 9atteries t;at are in poor

condition can cause unintended errors. If t;ere is any /uestion aout t;e condition of t;e atteries in

t;e multimeterH t;ey must e replaced.

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6.1.2 R+>+6++ E:+67*+

, standard copper*copper sulfate reference electrode also %no?n as a ;alf cell or reference cell7

must e utilied in order to otain structuretosoil potentials. $;e reference electrode must e

maintained in (ood ?or%in( condition and must e placed in t;e soil in a vertical position ?;en

conductin( a test.

:n t;ose sti!"#

tan%s t;at ;ave a !!4#

test stationH a reference electrode is permanently uried int;e tan% pit. Since it is (enerally not possile to determine ?;ere t;e permanent reference electrode?as installed on t;ese types of systemsH it is also necessary to conduct structuretosoil potentialmeasurements in t;e conventional manner i.e. ?it; a portale reference electrode in t;e soil directlyover t;e tan% and at a remote placement7. , tan% may not e passed on t;e asis of a structureto

soil potential otained ?it; a !!4#test station. 9ot; t;e local and t;e remote potential otained in

t;e conventional manner must indicate t;at ade/uate cat;odic protection ;as een provided

re(ardless of ?;at t;e !!4#

test station indicates.

'aintenance of t;e reference electrode is important for accurate results and includesJ

1. $;e coppersulfate solution inside t;e reference electrode s;ould e clear. If t;e solutionappears cloudyH t;is may indicate t;at t;e solution ;as ecome contaminated and t;ereference electrode s;ould e compared ?it; t;e %no?n standard as descried in para(rap;e elo?. S;ould it e necessary to replace t;e solutionH only distilled ?ater and ne? coppersulfate crystals s;ould e used. Acess coppersulfate crystals must e present in order toassure a saturated solution. @nder avera(e conditionsH it is usually a (ood idea to empty andreplace t;e solution every 2 or " mont;s.

2. $;e porous ceramic tip must e maintained moist at all times. If t;e tip is allo?ed to dry outHit may lose its porosity and a (ood lo? resistivity contact ?it; t;e soil ?ill not e possile.

!eriodic replacement of t;e tip may e necessary.

3. $;e copper rod inside t;e reference electrode s;ould periodically e cleaned ?it; nonmetallic sandpaper. 8o not use lac% metal oAide sandpaperH steel ?ool or any ot;er metallic

arasive as t;is can cause t;e copper rod to ecome contaminated. If t;e copper rod

ecomes contaminatedH it is est to replace t;e reference electrode.

4. $;e coppersulfate solution must e free of contamination or errors ?ill e introduced in t;ereadin(s you oserve. If t;e reference electrode is sumer(ed in ?ater or placed in moist

soils t;at are contaminatedH it is li%ely t;at t;e solution ?ill ecome contaminated.

5. $;e reference electrode t;at is used in t;e field must e periodically calirated. Do? oftent;e reference electrode needs to e calirated depends upon several different factors.

,mon( t;e more important factors t;at s;ould e considered are t;e fre/uency of use andt;e eAposure of t;e reference electrode to contaminants. ,s a (eneral ruleH calirations;ould e c;ec%ed once every ?ee% if t;e reference electrode is used daily. If t;e referenceelectrode is only periodically usedH caliration s;ould e c;ec%ed prior to eac; use.

Caliration of t;e reference electrode is accomplis;ed y comparin( it ?it; anot;er referenceelectrode t;at ;as never een used. $;e unused reference electrode t;at is to act as t;e calirationstandard s;ould e properly set up ready for use7 and must not ;ave ever een used in t;e field sot;at no c;ance of contamination eAists. Consideration s;ould e (iven to otainin( a referenceelectrode t;at is certified y t;e manufacturer to e properly calirated for periodic caliration of t;efield electrode.

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$o calirate t;e field electrodeJ

1. !lace t;e voltmeter on t;e 2 volt 8C scale or lo?er7 and connect t;e leads to t;e

reference electrodes as s;o?n in t;e illustration elo?.

2. !lace ot; t;e field electrode and t;e standard electrode in a s;allo? nonmetalliccontainer t;at ;as one to t?o inc;es of tap ?ater in t;e ottom of it. 8o not use

distilled ?ater. $;e reference electrodes must e placed vertically in t;e container

?it; t;e ceramic tip of eac; sumer(ed in t;e ?ater.

3. :serve t;e potential measurement displayed on t;e voltmeter. If more t;an 1 mpotential eAists et?een t;e t?o reference electrodesH t;e field reference electrodes;ould e properly cleaned and refilled ?it; ne? solution until t;e potential differenceis 1 m or less. If you are unale to ac;ieve a 1 m or less potential differenceafter cleanin(*reconditionin(H t;e field electrode must e discarded and a ne? oneotained.

4. In order to lessen t;e c;ance of cross contaminatin( t;e caliration electrodeH yous;ould leave t;e caliration electrode in t;e ?ater for t;e s;ortest time necessary to

complete t;e test.

FIGURE 1 # ILLUSTRATION OF REFERENCE ELECTRODE CALIBRATION

:3$'$R

$S$ 3,8S

0.00(2

8C

I) $DIS ,'!3 $D &I38 3C$R:8 IS ,CC!$,93F C,3I9R,$8SI)C $DR IS :)3F < m !:$)$I,3 8I&&R)C

CALIBRATIO

N

ELECTROD

E

12

I)CD

S

,$

R I)

!3,S$IC

C:)$,I)

R

6.1.3 L+/* 96+-4T+-P67+-4M9-+::/+7-

Fou s;ould ensure t;at t;e insulationmaterial of any lead ?ires is in (oodcondition. ,ny clips or proes used toma%e contact ?it; t;e structure to etested must e clean and free of

corrosion. ,spoolofsuitale ?ireofsufficientlen(t;

isnecessa

rytoconductcontinuityand*o

r =remote eart;> testin(. It is usuallynecessary to ;ave a proe t;at cane attac;ed to t;e end of a tan%(au(in( stic% in order to contact t;etan% ottom since it is not uncommon

for t;e test lead on sti!"# tan%s to

eit;er e missin( or discontinuous?it; t;e tan% s;ell. , pair of loc%in(pliers can sometimes e useful ?;enattemptin( to (et a solid connection.

11


18/71

6.2 T+- C69+69/

$;ere are t;ree test criteria t;at can e utilied to indicate if ade/uate cat;odic protection is ein(

provided to t;e structure ein( evaluatedJ

850 O # , structuretosoil potential of L+5 m or more ne(ative ?it; t;e protective currentapplied. $;is is commonly referred to as =+5 on> or t;e =on potential>. $;is criterion is normally t;e

only one availale for (alvanic systems since t;e protective current usually cannot e interrupted.

olta(e drops see Section 6."7 ot;er t;an t;ose across t;e structure to electrolyte oundary must

e ta%en into consideration ?;enever t;is criterion is applied. olta(e drops may ;ave a si(nificant

impact on t;e potentials oserved ?;en testin( impressed current systems ?it; t;e protective

current applied. $;ereforeH t;e +5 on criterion is not applicale to impressed current systems.

850 O>> # , structuretosoil potential of L+5 m or more ne(ative ?it; t;e protective currenttemporarily interrupted. $;is is referred to variously as =+5 off>H =polaried potential> or =instant offpotential>. $;is criterion is applicale to impressed current and (alvanic systems ?;ere t;e

protective current can e interrupted. Caution must e eAercised ?;en testin( impressed currentsystems to ensure t;at no active sacrificial anodes are also installed near t;e protected structure. Ift;ere are active anodes influencin( t;e oserved potentialH t;e +5 off criterion is not applicale.

$;e instant off potential is t;e 2nd

value t;at is oserved on a di(ital voltmeter t;e instant t;e po?eris interrupted. $;e first numer t;at appears immediately after po?er interruption must edisre(arded. ,fter t;e second numer appearsH a rapid decay depolariation7 of t;e structure ?ill

normally occur. In order to otain instant off potentialsH a current interrupter or a 2nd

person isnecessary. If a current interrupter is not availaleH ;ave t;e second person t;ro? t;e po?er s?itc; att;e rectifier off for " seconds and t;en ac% on for 15 seconds. Repeat t;is procedure until you aresure an accurate instant off readin( ;as een otained.

$;is criterion is considered y most to e t;e est indicator t;at ade/uate cat;odic protection ;as

een provided. $;ereforeH consideration s;ould e (iven to ad-ustin( t;e rectifier output up?ard until

t;e +5 off criterion ;as een met if t;is is feasile.

100 V P7:/69/97 #, polariation volta(e s;ift of at least 1 m. Commonly referred to as =1

m polariation> or =1 m s;ift>. $;is criterion is applicale to (alvanic and impressed current

systems ?;ere t;e protective current can e temporarily interrupted. it;er t;e formation or t;e

decay of at least 1 m polariation may e used to evaluate ade/uate cat;odic protection.

$;e =true> polaried potential may ta%e a considerale len(t; of time to effectively form on astructure t;at ;as ;ad cat;odic protection ne?ly applied. If t;e protective current is interrupted on ametallic structure t;at ;as een under cat;odic protectionH t;e polariation ?ill e(in to decay nearlyinstantaneously. &or t;is reasonH it is important t;at t;e protective current not e interrupted for anysi(nificant len(t; of time. GenerallyH not more t;an 24 ;ours s;ould e allo?ed for t;e 1 m

depolariation to occur. :n a ?ellcoated structure complete depolariation may ta%e as lon( as 60 days. Complete depolariation of uncoated structures ?ill usually occur ?it;in 4+ ;ours alt;ou(;it could ta%e as lon( as " days.

$;e ase readin( from ?;ic; to e(in t;e measurement of t;e volta(e s;ift is t;e instant off

potential. &or eAampleH a structure eA;iits an on volta(e of L+"5 m. $;e instant off volta(e is


19/71

$;e use of native potentials to demonstrate t;e formation of 1 m polariation is (enerally only

applicale ?;en a system is initially ener(ied or is reener(ied after a complete depolariation ;as

occurred. $;is is ecause it is necessary to leave t;e reference electrode undistured or returned to

t;e eAact position7 et?een t;e time t;e native and t;e final volta(e are otained.

It is only necessary to conduct a 1 m polariation test on t;at component of t;e @S$ system?;ere t;e lo?est most positive7 instant off structuretosoil potential eAists in order to demonstrate

t;at t;e @S$ system meets t;is criterion. If t;e criterion is met at t;e test point ?;ere t;e potential is

most positiveH it can e assumed t;at it ?ill e met at all ot;er test locations.

6.3 V7:/+ %IR' D67=-

$;e effect volta(e drops ;ave must e considered ?;enever structuretosoil potentials are otained

durin( t;e survey of a cat;odic protection system. $;e concept of volta(e drops is a difficult and

controversial su-ect and a full discussion is eyond t;e scope of t;is document. Do?everH stated in

t;e simplest termsH a volta(e drop may e t;ou(;t of as any component of t;e total volta(emeasurement potential7 t;at causes an error.

$;e term IR drop is sometimes used and it is e/uivalent to volta(e drop. IR drop is derived from

:;mBs 3a? ?;ic; states t;at N I R. In t;is e/uationH stands for volta(eH I represents currentampera(e7 and R stands for resistance. 9ecause t;e oserved volta(e is e/ual to t;e ampera(e I7

multiplied y t;e resistance R7 a volta(e drop is commonly referred to as an IR drop. $;ere are

various sources of volta(e drops and t?o of t;e more common are discussed elo?.

C66+ F:7) # ;enever a current flo?s t;rou(; a resistanceH a volta(e drop is necessarily created

and ?ill e included ?;enever a measurement of t;e electrical circuit is conducted. In order to

effectively eliminate t;is volta(e drop ?;en testin( impressed current systemsH it is necessary to

interrupt t;e protective current. $;e ma(nitude of t;e volta(e drop otained on impressed current

systems is evaluated y conductin( ot; on and instant off potential measurements.

$o illustrate ;o? t;is type of volta(e drop contriutes to t;e potential oserved ?;en measurin(impressed current systems consider t;e follo?in( eAample. , potential of 05 m is oserved ?;ent;e rectifier is on. , potential of


20/71

R/9-+* E/6 # ,ll active anodes ?ill ;ave a volta(e (radient present in t;e soil around t;emproducin( a =raised eart; effect>. ,n anormally ;i(; more ne(ative7 potential ?ill e oserved if t;ereference electrode is ?it;in t;e volta(e (radient of an active anode. $;e ma(nitude or area ofinfluence of t;e volta(e (radient is dependent predominantly on t;e volta(e output of t;e anode andt;e resistance of t;e soil. @nfortunatelyH t;ere is no =rule of t;um> (uidance t;at can e (iven to

determine ;o? far a?ay you must e from an anode in order to e outside t;e volta(e (radient. Ifyou suspect t;e potential you otain may e affected y raised eart;H you s;ould ta%e a remotereadin( and compare t;e t?o.

9ecause of t;e raised eart; effectH it is necessary to place t;e reference electrode as far a?ay fromany active anode and still e directly over t;e structure7 ?;en otainin( local potentials on (alvanicsystems. Since t;e protective current can not typically e interrupted in (alvanic systemsH any effectt;is type of volta(e drop may ;ave is evaluated y placin( t;e reference electrode remote.!lacement of t;e reference electrode remote ensures t;at t;e reference electrode is not ?it;in t;evolta(e (radient of an active anode. Since it is desirale to eliminate any effect volta(e drops may;aveH it is necessary to otain ot; local and remote structuretosoil potentials on (alvanic systems.

,ny effect raised eart; may ;ave ?;en testin( impressed current systems is eliminated ytemporarily interruptin( t;e po?er.

6.4 S6/< C66+

,n unintended current t;at is affectin( t;e structure you are tryin( to protect is referred to as a straycurrent. Stray currents can cause rapid corrosion failure of a uried metallic structure and arecaused y an electric current flo?in( t;rou(; t;e eart; in an unintended pat;. If t;e metallic o-ectyou are tryin( to cat;odically protect is uried near t;e pat; of t;e stray currentH t;e current may=-umpon> t;e protected structure ecause it offers a lo?er resistance pat; for t;e current to flo?.$;e affected structure ?ill e cat;odic ?;ere t;e stray current enters ut ?ill e ;i(;ly anodic ?;eret;e stray current returns to t;e eart;. ,t t;e point ?;ere t;e current disc;ar(esH rapid corrosion oft;e structure intended to e protected ?ill occur.

,lt;ou(; stray currents are relatively rare on @S$ systemsH common sources includeJ a7 Railroadcrossin( si(nals po?ered y atteries7K 7 $raffic si(nals t;at ;ave induction type sensors uried in

t;e pavementK c7 !ortale or fiAed emer(ency po?er (eneratorsK d7 lectrical rail?ay systems suc;

as streetcars or su?ays in uran areasK e7 8C ?eldin( operations and ot;er types of industrialmac;inery or processes t;at utilie 8C po?er.

If unsteady readin(s are oserved on t;e protected structure and you ;ave determined t;at it is notecause of a ad electrical connectionH you s;ould suspect t;at stray current is affectin( t;eprotected structure. In some casesH a pattern can e seen in t;e potential ?;erey it alternateset?een t?o relatively stale readin(s. $;ese patterns can sometimes ;elp to identify t;e source oft;e stray current. If you suspect t;at stray current may e affectin( t;e @S$ systemH a t;orou(;investi(ation must e conducted as soon as possile y a /ualified corrosion eApert since straycurrent can cause a rapid failure of t;e affected structure.

C/7*9 I+6>+6++ # ;en t;e impressed current cat;odic protection system operatin( on t;estructure you are tryin( to protect causes an unintended current on some ot;er neary structureH t;istype of stray current is referred to as =cat;odic interference>. Cat;odic interference can cause a rapidfailure of t;e ?ater lines and ot;er uried metallic structures at t;e facility ?;ere t;e cat;odicprotection system is operatin(. If you oserve ?;at you elieve to e an anormally ;i(; morene(ative7 potential on a uried metallic structureH you s;ould suspect t;at t;e impressed currentsystem operatin( on t;e @S$ system is causin( cat;odic interference.

1

4


21/71

Instances ?;ere cat;odic interference may e present includeJ a7 copper ?ater lines t;at are not

onded to t;e impressed current system and ;ave a polaried potential of (reater t;an 2 mK 7

metallic fleA connectors associated ?it; fier(lass reinforced plastic pipin( t;at ;ave anormally;i(; more ne(ative7 potentials and are not onded to t;e impressed current systemK c7 sti!" tan%s

are uried at a facility ?;ere t;ere is an impressed current system operatin( and are not onded to

t;e ne(ative circuit. ;en t;e sti!" tan%s ;ave inc anodes and a potential more ne(ative t;an11 m more ne(ative t;an 16 m in t;e case of ma(nesium anodes7 is oservedH it is li%elyt;at cat;odic interference is occurrin(. 9ecause of t;e potential for stray current to impact sti!"

tan%sH it is normally necessary to ond t;em into t;e impressed current system.

, corrosion eApert must e consulted ?;enever cat;odic interference is suspected in order to

properly investi(ate and ma%e any repairs*modifications t;at may e necessary.

6.5 D9--99:/6 M+/:-4B9+/::9 C7=:+-

$;e effect imetallic couples may ;ave must also e considered ?;enever structuretosoilpotentials are otained durin( t;e survey of a cat;odic protection system. $;e concept of dissimilar

metals*imetallic couples and t;e impact t;ey can ;ave on t;e proper evaluation of cat;odicprotection systems is a difficult and controversial su-ect and a full discussion is eyond t;e scope oft;is document. Do?everH you s;ould e a?are t;at imetallic couples may sustantially influence t;estructuretosoil potentials of a tan% system to t;e eAtent t;at t;e 1 m polariation criterion is notapplicale. 9ecause t;e validity of t;e 1 m criterion may e suspectH consideration s;ould e(iven to only utiliin( t;e +5 m instant off criterion ?;en evaluatin( impressed current systems. ,rief discussion follo?s.

Caution must e eAercised ?;en evaluatin( steel @S$ systems t;at ;ave metals of lo?erelectroc;emical potential electrically connected to t;em. $ypicallyH imetallic couples are only ofconcern on impressed current systems since t;ose steel components protected y (alvanic systemsare electrically isolated from ot;er metallic structures. Copper is t;e metal of lo?er potential t;at iscommonly of concern. Sources of copper at @S$ facilities include t;e ?ater service lines and t;e

(roundin( system of t;e electrical po?er (rid. Since t;e ,C po?er supply to t;e sumersile turinepump s;ould e continuous ?it; t;e electrical service (roundin( systemH ?;ic; may in turn econtinuous ?it; t;e ?ater linesH a si(nificant amount of copper may e coupled to t;e steel @S$system.

$;e effect t;is type of imetallic couple ;as on t;e impressed current system can sometimes eclearly seen on t;ose @S$ systems t;at store fuel for emer(ency po?er (enerators. Commonlyt;ese (enerator tan% systems are installed ?it; copper supply and return lines. ;en t;ese tan%s?ere retrofitted ?it; an impressed current systemH t;e copper lines ?ere onded into t;e cat;odicprotection system. In t;ese instancesH it is not uncommon to oserve native structuretosoilpotentials on t;e @S$ system of 45 m or more positive.

If t;e native structuretosoil potential of t;e @S$ system is sustantially lo?er t;an ?;at you ?ould

normally eApectH it is li%ely t;at a si(nificant amount of copper is electrically onded to t;e @S$system. $ypicallyH t;e eApected native potential of a steel @S$ system s;ould not e more positive

t;an 5 m.

$o illustrate t;e effect of t;e coppersteel coupleH consider t;e follo?in( eAampleJ , steel @S$

system t;at is coupled to copper ;as a native structuretosoil potential of " m ?it; t;eimetallic couple intact. If t;e copper couple is ro%en t;e @S$ system native potential is 6 m.

it; t;e copper couple intactH t;e polaried off7 potential of t;e @S$ system 45 m. ,lt;ou(; t;e

volta(e s;ift satisfies t;e 1 m polariation criterion from " m to 45 m7H it is li%ely t;at t;e1

5


22/71

steel @S$ system is not ade/uately protected. $;is is ecause t;e @S$ system is not polaried at

least 1 m eyond t;e native potential of t;e steel. Since t;e true native potential of t;e steel @S$

system in t;is eAample is 6 mH you ?ould need to reac; a polaried instant off7 potential of


23/71


24/71

6.7 C799< T+-9

;en conductin( an evaluation of a cat;odic protection systemH it is normally necessary to estalis;t;at t;e cat;odically protected components of a @S$ system are eit;er electrically isolated orelectrically continuous dependin( on t;e type of cat;odic protection system. :;mmeters continuity

testers7 suc; as t;ose utilied to test automotive ?irin( circuits are not acceptale for use on uriedmetallic structures and s;ould never e used for testin( continuity of @S$ system components. $;e=fiAed cellmovin( (round> met;od and t;e =pointtopoint> met;od are t;e t?o commonly utilied?ays to test continuity and are discussed in more detail elo?.

F9+* C+:: # M7;9 G67* M+7* # $;e most commonly accepted met;od of conductin( acontinuity survey is referred to as fiAed cell L movin( (round. In t;is met;odH t;e reference electrodeis placed at a location remote from any of t;e cat;odically protected structures. !otentials of all t;emetallic structures present at t;e site are t;en measured ?it;out movin( t;e reference electroderefer to ,ppendiA for a more complete description7. 9ecause t;e conditions found at t;e referenceelectrode*electrolyte interface can c;an(e over a s;ort period of time causin( t;e oservedpotential to c;an(e7H it is important to conduct t;is type of testin( as /uic%ly as possile.

;en determinin( ?;et;er electrical continuity or isolation is providedH t;e follo?in( (uidelines are

(enerally accepted for fiAed cell L movin( (round surveysJ

1 If t?o or more structures eA;iit potentials t;at vary y 2 m or lessH t;e structures are

considered to e electrically continuous.

2 If t?o or more structures eA;iit potentials t;at vary y 1 m or (reaterH t;e structures

are considered to e electrically isolated.

3 If t?o or more structures eA;iit potentials t;at vary y more t;an 2 m ut less t;an 1

mH t;e result is inconclusive and furt;er testin( pointtopoint7 is necessary.

P79#7#P79 M+7* ,n easier and usually more accurate ?ay to test continuity is t;e =pointtopoint> met;od. it; t;is met;odH a reference electrode is not utilied. $;e t?o structures t;at are toe tested are simply touc;ed ?it; eac; lead of t;e voltmeter and t;e volta(e difference if any7 isoserved. &or eAampleH if you are tryin( to estalis; t;at electrical isolation eAists et?een a tan%and t;e fill riser associated ?it; t;at tan%H you ?ould simply touc; t;e fill riser ?it; one of t;evoltmeter leads and t;e tan% s;ell ?it; t;e ot;er voltmeter lead and oserve t;e volta(e difference.

;en conductin( pointtopoint testin(H any current t;at is flo?in( t;rou(; t;e @S$ components can

cause an inaccurate test result. Impressed current systems must e turned off.

;en determinin( ?;et;er electrical continuity or isolation is providedH t;e follo?in( (uidelines are

(enerally accepted for pointtopoint surveysJ

1 If t;e volta(e difference oserved et?een t;e t?o structures is 1 m or lessH t;e t?o

structures are considered to e electrically continuous ?it; eac; ot;er.

2 If t;e volta(e difference oserved et?een t;e t?o structures is 1 m or (reaterH t;e

t?o structures are considered to e electrically isolated from eac; ot;er.

3 If t;e volta(e difference oserved et?een t;e t?o structures is (reater t;an 1 m utless t;an 1 mH t;e result is inconclusive and furt;er testin( eyond t;e scope of t;is

document is necessary.1

8


25/71

6.7.1 C799< T+-9 7> G/:;/9 S t;e cat;odic protection current.1

9


26/71

IdeallyH t;e tip of t;e reference electrode s;ould e as close to t;e structuretosoil interface as is

practical in order to minimie t;e volta(e drop present in t;e soil due to resistivity. In practiceH aout

6 inc;es of soil et?een t;e tip of t;e reference electrode and t;e structure ein( tested ?or%s ?ell.

6.8.3 R+7+ P:/++

$;e remote potential represents t;e avera(e potential of t;e entire surface of t;e protected structure. $;e

purpose of remote placement is to eliminate any effect t;at raised eart; may e contriutin( to t;e

measurement of t;e structuretosoil potential and to overcome any effects s;ieldin( may ;ave.

!lacement of t;e reference electrode is considered remote ?;en it is placed in t;e soil a certain

distance a?ay from t;e structure t;at is ein( tested. $;ere are several different factors t;at

determine t;e distance necessary in order to reac; remote eart; and a full discussion is eyond t;e

scope of t;is document. Do?everH a remote condition can normally e ac;ieved ?;en t;e referenceelectrode is placed et?een 25 and 1 feet a?ay from any protected structure.

8ependin( on t;e conditions specific to t;e particular location ?;ere t;e cat;odically protectedstructure isH t;e minimum distance to remote eart; may e consideraly more t;an 25 feet.

$;ereforeH it is important t;at you estalis; t;at t;e reference electrode is truly remote ?;enotainin( a structuretosoil potential. In order to ensure t;at remote eart; ;as een ac;ievedH placet;e reference electrode at least 25 feet a?ay from t;e protected structure and oserve t;e potential.'ove t;e reference electrode out a?ay from t;e protected structure anot;er 1 feet or so andoserve t;e potential. If t;ere is no si(nificant difference in t;e t?o potentialsH it can e assumed t;atremote eart; ;as een ac;ieved. If t;ere is a si(nificant differenceH continue movin( t;e referenceelectrode out a?ay from t;e protected structure until no si(nificant difference is oserved.

;en selectin( a location to place t;e reference electrode to estalis; remote eart;H it is essentialt;at t;ere are no ot;er cat;odically protected structures e.(. natural (as lines7 in proAimity to t;ereference electrode. &orei(n cat;odically protected structures can cause an anormally ;i(; morene(ative7 potential t;at is not indicative of t;e remote potential of t;e structure you are measurin(. It

is also important t;at t;ere are no ot;er uried metallic structures in t;e vicinity of t;e referenceelectrode. ,ny metallic structure t;at is uried near t;e reference electrode could possile affect t;estructuretosoil potential t;at is oserved on t;e protected structure.

In addition to t;e aove considerationsH you s;ould attempt to select t;e remote placement suc; t;at

t;e reference electrode can =see> t;e structure you are testin(. $;is means t;at t;ere s;ould not eany uried metallic structure et?een t;e remote reference electrode placement and t;e protected

structure. If you suspect t;at s;ieldin( may e affectin( t;e oserved potentialH place t;e reference

electrode a?ay from t;e protected structure in a different direction.

6.8.4 G/:;/9 P:/++

,ll (alvanic cat;odic protection systems must e tested ?it; t;e reference electrode placed ot;

local and remote. In order to pass t;e structuretosoil surveyH ot; t;e local and t;e remotepotentials must indicate t;at ade/uate cat;odic protection ;as een provided. If neit;er t;e local ort;e remote potential satisfies one of t;e cat;odic protection criteriaH t;e structure fails t;e test. If oneof t;e potentials indicates ade/uate cat;odic protection ut t;e ot;er does notH t;e result of t;e testis inconclusive. If t;e test result is inconclusiveH repairs must e made or a corrosion eApert mustevaluate t;e data and*or conduct furt;er testin( to declare eit;er pass or fail.

2

0


27/71

6.8.5 I=6+--+* C66+ P:/++

Impressed current cat;odic protection systems are only re/uired to e tested ?it; t;e referenceelectrode placed locally. In order to pass t;e surveyH t;e potential otained ?it; t;e referenceelectrode placed locally must satisfy eit;er t;e +5 off or t;e 1 m polariation criteria. ;ile only

one test point is re/uiredH t;e tester s;ould otain structure to soil potentials from as many soilaccess points alon( t;e structure as is practical. If any of t;e potentials indicate t;at ade/uatecat;odic protection ;as not een providedH t;e structure s;ould e failed.

,lt;ou(; not re/uired y t;is (uidanceH it may e useful to place t;e reference electrode remotely

?;en testin( an impressed current system. $;e remote potential may provide additional information

y ?;ic; to evaluate t;e cat;odic protection system. Do?everH t;e structure may not e passedased on t;e remote potential itself. In all circumstancesH t;e potential otained ?it; t;e reference

electrode placed locally must indicate t;at ade/uate cat;odic protection ;as een provided.

,dditionallyH special circumstances may re/uire t;at a remote potential e otained ?;en testin(impressed current systems. &or instanceH if t;ere are active sacrificial anodes uried in closeproAimity to t;e structure ein( testedH t;e local potential may e influenced y raised eart;. $;evolta(e drop caused y t;e sacrificial anodes ?ould preclude t;e accurate measurement of t;e localstructuretosoil potential. If it is %no?n t;at sacrificial anodes are impactin( t;e potentials otainedlocallyH remote potentials must e otained.

$;e remote potential otained under t;ese special circumstances must meet eit;er t;e +5 off or t;e

1 m polariation criteria in order for t;e tested structure to pass t;e survey. ,n eAplanation must

e (iven in t;e =comments> of Section I of t;e '8Q impressed current cat;odic protection

evaluation form as to ?;y t;e remote potential must e considered. $;e remote potentials s;ould eindicated on t;e form y desi(natin( remote in t;e location code column of Section I.

&.! S79: A+--

,ll structuretosoil potentials t;at are intended to satisfy one of t;e t;ree acceptale criteria found inSection 6.2 must e otained ?it; t;e reference electrode placed in t;e soil. $;ereforeH t;e person

conductin( t;e evaluation must eit;er confirm t;at soil access is availale or ma%e prior

arran(ements ?it; t;e o?ner of t;e @S$ system to secure access.

@nder no circumstances is it allo?ale to place t;e reference electrode on concreteH asp;altH or any

ot;er pavin( material to ac;ieve satisfactory structuretosoil potentials. 3i%e?iseH t;e practice of

placin( t;e reference electrode on a crac% or eApansion -oint of a concrete or asp;alt pavin( is not

reco(nied as an acceptale met;od of otainin( satisfactory structuretosoil potentials.

!lacement of t;e reference electrode in an oservation monitorin(7 ?ell to otain a passin( readin(

is also not allo?ed. ;ile it may e useful to otain data y placin( t;e reference electrode on a

crac% in t;e pavement or in an oservation ?ellH t;e structuretosoil potentials otained y suc;

placement are not in t;emselves acceptale to demonstrate ade/uate cat;odic protection.

,ccess may e provided y drillin( ;oles t;rou(; t;e pavement or t;e installation of proper cat;odicprotection test stations. , practical ?ay to provide soil access is to drill a inc; diameter ;ole in t;epavement so t;at a =pencil> type reference electrode "*+ inc; diameter7 can e inserted t;rou(; t;epavement and into t;e soil. @pon completion of t;e surveyH t;e ;ole s;ould e filled ?it; a fuelresistant caul%in( material so t;at easy access can e provided at a later date. ,s an alternativeH at?o inc; ;ole could e drilled to allo? use of a standard reference electrode. , s;ort len(t; of !Cpipe could e epoAied in t;e ;ole and plu((ed ?it; a t;readed cap.

2

1


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Care must e ta%en t;at t;e remote location is not in proAimity to any ot;er cat;odically protected

structure e.(. natural (as lines7 or directly over any ot;er %ind of uried metallic structure. $;e

remote placement s;ould e suc; t;at t;e reference electrode is ali(ned ?it; t;e lon(itudinal aAis of

t;e tan%s and can =see> t;e anodes. $;is orientation is desirale in order to prevent s;ieldin(.

FIGURE 2 REMOTE EARTH REFERENCE ELECTRODE PLACEMENT

DIGD,F 11

GR,SS

!,')$

25B L 1B EIE

',R$

R':$ ,R$DR&R)C C33

$,)ES!3,C')$

&.10." G/:;/9/::< P67++* M+/::9 P9=9

9ot; local and remote potentials are re/uired on all (alvanically protected metallic pipin(. ;enmetallic pipin( is protected y sacrificial anodesH several different possiilities eAist as to ?;ere?ould e t;e appropriate location to place t;e reference electrode to otain local potentials. Eno?in(

?;ere t;e anodes t;at are protectin( t;e pipin( are installed is of critical importance. ;en otainin(local potentialsH t;e reference electrode must e placed in t;e soil directly over t;e pipe to eevaluated at a point t;at is t;e most distant from any anode t;at may e alon( t;e pipe.

9ecause it is a common practice to ury pipin( anodes at t;e sumersile pump man?ay of a tan%H

t;e appropriate location to place t;e reference electrode to otain local potentials is at t;e

dispensers See &i(ure 57. Remote placement of t;e reference electrode is also necessary.

FIGURE 5 2 LOCAL REFERENCE ELECTRODE PLACEMENT FOR

GALVANICALLY PROTECTED PIPING HEN PIPING ANODES ARE

8IS!)SRS

!I!I)G

$,)ES

3:C,3 $S$ !:I)$S

R':$ ,3S: RQ@IR87

!I!I)G ,):8S


30/71

23


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;en t;e pipin( anodes are installed at t;e dispensersH t;e appropriate local reference electrode

placement ?ould e at t;e pipin( nearest t;e tan%s usually t;e sumersile turine pump man?ay7

as s;o?n in &i(ure 6. Remote placement of t;e reference electrode is also necessary.

FIGURE & 2 LOCAL REFERENCE ELECTRODE PLACEMENT FOR GALVANICALLYPROTECTED PIPING HEN PIPING ANODES ARE AT DISPENSERS

8IS!)SRS

!I!I)G

$,)ES!I!I)G ,):8S

3:C,3 $S$ !:I)$S R':$ ,3S: RQ@IR87

;en t;e pipin( anodes are located at ot; t;e tan%s and t;e dispensersH t;e reference electrode

must e placed at t;e approAimate center of t;e pipin( run to otain local potentials See &i(ure


32/71


33/71

25


34/71

,s ?it; t;e evaluation of any cat;odic protection systemH t;e location of t;e anodes in relation toreference electrode placement can e of critical importance. ;en selectin( t;e appropriate localplacementH it is necessary to place t;e reference electrode at t;e point over t;e structure t;at is t;emost distant from any active anode due to t;e effects of attenuation. ,ttenuation of t;e cat;odicprotection current may occur ?;erey effective protection is not ac;ieved at some point alon( a @S$

system. &or instanceH if all of t;e active anodes are alon( one side of a tan% edH current distriutionand attenuation may prevent sufficient protective current from reac;in( t;e side of t;e tan%s a?ayfrom t;e anodes. $;e preferred placement of t;e reference electrode ?ould e alon( t;e centerlineof t;e tan%s at t;e end opposite to t;at ?;ere t;e anodes are installed See &i(ure 17.

FIGURE 10 2 REFERENCE ELECTRODE PLACEMENT FOR TANKS PROTECTED BY IMPRESSEDCURRENT SYSTEM HEN ANODES ARE UNEVENLY DISTRIBUTED

RC$I&IR

,):8S

EIE ',R$

$S$ !:I)$S

If it is not %no?n ?;ere t;e anodes are installedH at least one measurement is re/uired alon( t;e

centerline of t;e tan%. $estin( s;ould e conducted at as many locations alon( t;e centerline of t;etan% as are availale. If soil access is availale at eac; end of t;e tan% and in t;e middleH all t;ree

structuretosoil potentials s;ould e recorded. If any one of t;e measured potentials does not meet

one of t;e acceptale criteriaH t;e structure s;ould e failed.

In additionH if it is possile to measure t;e individual circuits in an impressed current systemH adetermination can e made as to ?;ic; anodes are functional and ;o? t;e current is distriutedt;rou(;out t;e (rounded. Do? t;e current is distriuted s;ould e considered ?;en c;oosin(reference electrode placement ?;en conductin( a structuretosoil potential survey. If for instance itis %no?n t;at t;e ma-ority of t;e rectifier output current is directed to only t;ose anodes alon( oneend of a tan% edH t;e reference electrode s;ould e placed at t;e opposite end of t;e tan% ed.

&.10. P9=9 P67++* < I=6+--+* C66+

it; impressed current cat;odic protection systemsH pipe potentials are re/uired to e measured?it; t;e reference electrode placed locally. Must as ?it; any ot;er type of cat;odic protection systemH%no?in( ?;ere t;e anodes t;at are protectin( t;e pipin( are installed is of critical importance. 8ue tot;e ;i(; de(ree of variaility t;at eAists in anode placement and pipin( confi(urationsH structuretosoil potentials must e otained y placin( t;e reference electrode at ot; t;e tan% and dispenserend of any pipin( t;at is protected y impressed current See &i(ure 117.

2

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FIGURE 11 2 REFERENCE ELECTRODE PLACEMENT FOR METALLIC

PIPING PROTECTED BY IMPRESSED CURRENT SYSTEM

$S$ !:I)$

3:C,$I:)S

EIE ',R$

,):8S RC$I&IR

&.10.5 100 F77 R:+ >76 P9=9

&or ot; (alvanic and impressed current systemsH if more t;an 1 feet of pipin( eAists et?een anyt?o anodesH t;e reference electrode must also e placed at t;e midpoint et?een t;e t?o anodest;at are separated y more t;an 1 feet see &i(ure 127. In additionH if it is not %no?n ?;ere t;epipin( anodes are locatedH t;ere can e no more t;an 1 feet of pipin( et?een any t?o testpoints. $;is midpoint placement is in addition to any ot;er reference electrode placement t;at maye re/uired as noted aove in Sections 6.1.1 t;rou(; 6.1.4.

FIGURE 1" 2 100 FOOT RULE FOR METALLIC PIPING PROTECTED

BY GALVANIC OR IMPRESSED CURRENT SYSTEM

$S$ !:I)$ ='I8!:I)$> $S$ 3:C,$I:)

3:C,$I:)S

115 &$

EIE ',R$

RC$I&IR,):8S

2

7


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SECTION ( # DOCUMENTATION OF EVALUATION

7.1 D7+/97

,s ?it; any %ind of testin( or ?or% t;at is ein( performed at a @S$ facilityH it is critical t;at proper

documentation e made of all activities and test procedures. it;out proper documentationH t;eevaluation of a cat;odic protection system t;rou(; t;e application of a structuretosoil potential

survey is of little value.

,lt;ou(; it ;as een previously statedH t;e eAact location ?;ere t;e reference electrode ?as placedin order to otain a passin( structuretosoil potential is of critical importance and cannot e

overemp;asied. &or t;is reasonH an eAact description of ?;ere t;e reference electrode ?as placedfor eac; structuretosoil potential otained durin( t;e survey is an asolute necessity. &ailure to

properly document reference electrode placement ?ill result in t;e survey ein( deemed invalid.

,dditionallyH in order to effectively evaluate t;e survey of a cat;odic protection system it is essentialto e ale to clearly understand ;o? t;e survey ?as conducted. 3i%e?iseH ?;en a resurvey of aneAistin( system is ein( conducted it is important t;at t;e tester understands ;o? t;e previoussurvey ?as conducted. arious forms of documentation may e necessary in order to clearly conveyt;e procedures and survey results. In t;e sections t;at follo?H some of t;e more critical aspects ofdocumentation are discussed in more detail.

7.1.1 A- B9: D6/)9-

If any modification to t;e construction of t;e cat;odic protection system is made e.(. supplementalanodes7 it is necessary to s;o? t;e modification on t;e =as uilt> dra?in(s. If no as uilt dra?in( isavailaleH you must indicate t;e location of any anode addition on t;e site dra?in( t;at isconstructed as part of t;e evaluation. ,s uilt dra?in(s are re/uired ?;enever a cat;odic protectionsystem is installed or sustantially modified. $;e dra?in(s s;ould includeJ a7 ;o? many anodes?ere installedK 7 ?;at type of anodes ?ere installedK c7 ?;ere ?ere t;e anodes installedK d7 ;o?

deep ?ere t;e anodes installedK e7 ?;at type of ?ire ?as usedK f7 ;o? ?ere t;e ?ires ondedH etc.

7.1.2 S9+ D6/)9

;enever a cat;odic protection survey is conductedH a site dra?in( depictin( t;e @S$ systemH t;ecat;odic protection system and any related features of t;e facility must e constructed. In additionH

you must indicate on t;e dra?in( ?;ere t;e reference electrode ?as placed for eac; of t;estructuretosoil potentials utilied to otain a pass. &i(ure 1" is an eAample of a site dra?in( t;at

s;o?s t;e type of information t;at is necessary to properly complete t;e evaluation.

;ile it is understood t;at you ?ill not al?ays %no? ?;ere all of t;e pertinent components of t;e

cat;odic protection system may e uriedH all t;at is %no?n must e indicated. It is very important to

s;o? ?;ere t;e anodes are located on t;e site dra?in(. If you do not %no? ?;ere t;e anodes areuriedH volta(e (radients in t;e soil may ;elp you determine t;e approAimate location as descried

in t;e raised eart; discussion of Section 6.".

S;ould any modifications to t;e cat;odic protection system e madeH it is very important t;at suc;modifications e ot; visually indicated on t;e site dra?in( and a ?ritten narrative made t;atdescries t;e ?or% conducted. If as uilt dra?in(s are availaleH it is acceptale to utilie t;esedra?in(s for t;e purposes of meetin( t;e re/uirements of t;is section. ,ny modifications or c;an(esto t;e @S$ and*or cat;odic protection systems t;at ;ave een made since t;e construction of t;e asuilt dra?in(s must e included.

2

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FIGURE 13 2 EXAMPLE OF A SITE DRAING CONSTRUCTED AS PART OF

A UST SYSTEM CATHODIC PROTECTION SURVEY

I*9/+- 6+>+6++ +:: =:/++ %+- =79'T+ :7/97 7*+ %T#1 T#" +.' 766+-=7*-

NT#1 7 + 7*+ / 9- 9*9/+* 7 + MDEQ

>76 >76 +/ +- / /- ++ 7*+*.

I*9/+- /7*+ :7/97

D9-=+-+6-G/:;/9+* S++: P9=9

!" !4

STP /)/ as prescried in t;e '8Q cat;odic protectionevaluation form found in ,ppendiA E and 3 of t;is document. $;e terms =pass>H =fail> and

=inconclusive> are utilied for t;is purpose. $;ereforeH it is necessary to clarify ?;at t;ese termsmean and t;eir applicaility as related to t;e evaluation of cat;odic protection systems utiliin( t;e'8Q forms.

,n evaluation conducted y an individual ?;o is only /ualified as a cat;odic protection tester must

result in one of t;ree conclusionsH passH fail or inconclusive. If t;e person conductin( t;e evaluation

is /ualified as a corrosion eApertH t;e evaluation must result in eit;er pass or fail.

P/-- # $;e term =pass> as related to Section I and II testerBs*corrosion eApertBs evaluation7 of t;e

'8Q (alvanic*impressed current cat;odic protection system evaluation forms is ta%en to mean t;at

t;e structuretosoil potential survey indicates all of t;e protected structures at a facility meet at least

one of t;e t;ree accepted criteria.

!ass as related to Section I and I potential survey7 of t;e respective '8Q

(alvanic*impressed current cat;odic protection system evaluation forms means t;at t;e individual

structure t;at is ein( tested meets at least one of t;e accepted criteria.

F/9: # $;e term =fail> as related to Section I and II testerBs*corrosion eApertBs evaluation7 of t;e

'8Q (alvanic*impressed current cat;odic protection system evaluation forms means t;at t;e

structuretosoil potential survey indicates t;at t;ere are one or more protected structures at a facility

t;at do not meet any of t;e accepted criteria.

&ail as related to Section I and I potential survey7 of t;e respective '8Q (alvanic*impressed

current cat;odic protection system evaluation forms means t;at t;e individual structure t;at is ein(

tested does not meet any of t;e accepted criteria.

I7:-9;+ # $;e term =inconclusive> as related to Section I testerBs evaluation7 of t;e '8Q

(alvanic*impressed current cat;odic protection system evaluation forms means t;at a person

/ualified only as a tester is unale to conclusively evaluate t;e cat;odic protection system and a

corrosion eApert must =ma%e t;e call>. , cat;odic protection tester must indicate inconclusive

?;enever one or more of t;e conditions listed in Section


39/71

t;ere ?ill e instances ?;ere t;e eApertise of someone ?;o is more /ualified and etter

understands t;e principles involved ?ill e necessary.

Some of t;e more ovious scenarios ?;ere a person ?it; a level of eApertise e/uivalent to a=corrosion eApert> Tas defined in Section 2.1 2+.127 of t;is documentU are necessary are (iven

elo?. If any of t;e conditions (iven elo? are metH a corrosion eApert must evaluate t;e surveyresults otained y a tester and*or conduct furt;er testin( and complete Section II of t;e'8Q cat;odic protection system evaluation forms7. If t;e structuretosoil potential survey isconducted y a person ?;o is /ualified as a corrosion eApertH completion of Section II of t;e'8Q forms7 is all t;at is necessary.

, corrosion eApert is re/uired to evaluate and*or conduct t;e survey ?;enJ

1. Supplemental anodes are added to a (alvanic cat;odic protection system and an

accepted industry standard is not follo?ed and*or properly documented.

2. Supplemental anodes or ot;er c;an(es in t;e construction of an impressed current

system are made.

3. It is %no?n or suspected t;at stray current may e affectin( t;e protected structure.

4. $;e repair and*or addition of supplemental anodes to are steel*(alvanied pipin( t;at is

(alvanically protected see Section 5.1."7.

5. ,n inconclusive ?as declared ?;en testin( a (alvanically protected structure ecauseot; t;e local and t;e remote potentials did not indicate t;e same result one indicated

pass ut t;e ot;er indicated fail7.

,lt;ou(; not specifically listed aoveH it s;ould e reco(nied t;at t;ere mi(;t e additional

circumstances t;at may arise t;at ?ill re/uire evaluationH and*or desi(n y a corrosion eApert.

7.3 / 9> + E;/:/97 R+-: 9- F/9:

It is important to properly notify t;e tan% o?ner if an evaluation of t;e cat;odic protection system

fails. )ecessary repairs s;ould e accomplis;ed ?it;in 0 days of receipt of t;e =failed>

evaluation. $;e tan% o?ner is responsile for ensurin( t;at t;e cat;odic protection system is

maintained in a manner t;at ?ill provide ade/uate corrosion protection to t;e @S$ system.

,s it is reco(nied t;at many factors may cause

a lo?er t;an desired durin( a structureto soil

surveyH t;ere may e several different courses

resolve t;e =fail>. &or instanceH it is not

uncommon to simply retest a sti! cat;odic

protection survey at a later date and ac;ieve a

passin( result. volta(e to

e otained

of action

appropriateto "

# tan%

t;at ;as

failed a

$;ereforeH a 0day retestin(period is allo?ed ?;enever afail is otained durin( ?;ic; noaction is necessary to repair ormodify t;e cat;odic protectionsystem. $;is applies only tot;ose (alvanic and impressed

current systems t;atappear to e in (ood?or%in( condition. Ift;ere are oviousprolems ?it; a systemor you are unale toac;ieve a pass ?it;int;e 0day ?indo?H t;e

tan%o?nermustma%eanyrepairsand*ormodific

ations t;at are necessary toac;ieve a pass. Repairs and*ormodifications must ecompleted as soon as practicalut no more t;an 0 dayss;ould e allo?ed aftereApiration of t;e =0 day?indo?>.


40/71

31


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APPENDIX B 2 GLOSSARY

100 V POLARIATION 2 :ne of t;e t;ree criteria t;at are commonly accepted as indicatin( ade/uate cat;odic protection ;as eenac;ieved. It is typically measured y interruptin( t;e protective current on an impressed current system. ;en t;e current is interruptedH an

=instant off> potential is recorded and t;e structure under cat;odic protection is t;en allo?ed to depolarie until a c;an(e of at least 1 m in

potential is oserved. )ot more t;an 24 ;ours s;ould e allo?ed for t;e depolariation to occur ?;en conductin( t;is test.

850 ON 2 :ne of t;e t;ree criteria t;at are commonly accepted as indicatin( ade/uate cat;odic protection ;as een ac;ieved. It ismeasured ?it; t;e protective current applied and is typically t;e only measurement possile ?it; (alvanic systems since t;e anodes cannot

e disconnected. $;is criterion is not applicale to impressed current systems since a lar(e portion of t;e =on> measurement can e

comprised of a volta(e drop ?;en t;e protective current is applied.

850 OFF :ne of t;e t;ree criteria t;at are commonly accepted as indicatin( ade/uate cat;odic protection ;as een ac;ieved. It ismeasured ?it; t;e protective current interrupted eit;er t;e po?er is cut off to t;e rectifier or t;e sacrificial anodes are disconnected7. $;is

criterion is considered y most to e t;e est indicator t;at ade/uate cat;odic protection ;as een provided.

ANODE 2 $;e electrode of an electroc;emical cell ?;ere oAidation corrosion7 occurs. it; respect to cat;odic protectionH it can e

t;ou(;t of as t;e place ?;ere electrons leave t;e surface of a metal. Common (alvanic anodes are inc and ma(nesium.

AMPERE %AMP' 2 $;e asic unit of current flo? in an electric circuit. ,mpera(e can e t;ou(;t of as =(allons per minute> in a ?ater

system.

AS BUILT DRAINGS 2 8ra?in(s t;at s;o? ;o? a system ?as actually installed in t;e field. SometimesH unforeseen factors preventt;e installation of a system as it ?as intended in t;e desi(n dra?in(s and t;is is ?;y it is important to ;ave detailed and accurate =as uilt>

dra?in(s.

ATTENUATION # $;e protective effects of cat;odic protection current diminis; as you move a?ay from t;e source of t;e protectivecurrent. $o illustrate t;isH on an impressed current system ?;ere t;e (round ed is installed only on one side of t;e tan% edH t;e end of t;e

tan%s a?ay from t;e (round ed ?ill receive less protective current t;an t;e side of t;e tan%s closest to t;e anodes. ,ttenuation of protective

current applies to (alvanic systems as ?ell.

CATHODE 2 $;e electrode of an electroc;emical cell ?;ere reduction and no corrosion7 occurs. it; respect to cat;odic protectionH it

can e t;ou(;t of as t;e place ?;ere current enters t;e surface of a metal.

CATHODIC PROTECTION 2 $;e tec;ni/ue of causin( t;e entire surface of a metallic structure to ecome a cat;ode ?it; respect toits eAternal environment soil7. $;is is accomplis;ed y supplyin( an electric current sufficient to overcome t;e tendency of naturally

occurrin( electrical currents to leave t;e metallic structure.

CATHODIC PROTECTION EVALUATION 2 $;e interpretation of ?;et;er or not a cat;odic protection system is providin( sufficientcorrosion protection. ,n evaluation incorporates all cat;odic protection testin(H surveysH rectifier operation*output measurementsH

consideration of volta(e dropsH condition of dielectric coatin(sH continuityH ond inte(rityH circuit inte(rity and any ot;er factors or site specific

conditions t;at may ;ave an influence on t;e operation and effectiveness of a cat;odic protection system.

CATHODIC PROTECTION SURVEY 2 Refers to t;e process ?;erey all of t;e structuretosoil measurements necessary tocontriute to t;e final evaluation of a system are otained.

CATHODIC PROTECTION TEST 2 Refers to t;e process ?;erey only a sin(le structuretosoil measurement is otained.

CONTINUITY 2 ,s related to cat;odic protectionH continuity means t;at t?o metallic structures are electrically continuous. it;impressed current systems all protected structures must e continuous and t;is is normally accomplis;ed t;rou(; t;e use of ?ires referred to

as continuity onds.

CORROSION 2 $;e deterioration of a material usually a metal7 caused y an electroc;emical reaction ?it; its environment. Corrosion

of metals involves t;e flo? of electrons current7 et?een an anode and a cat;ode. Corrosion ?ill occur ?;ere t;e electrons leave t;esurface of a metal.

CURRENT TEST 2 , met;od of temporarily creatin( an impressed current cat;odic protection system on a (alvanically protectedstructure so t;at it can e determined ;o? muc; protective current is necessary in order to ac;ieve ade/uate cat;odic protection. $;is is

normally done y connectin( a 12volt attery to t;e structure to e tested and to a temporary anode.

DIELECTRIC MATERIAL 2 , coatin( t;at does not conduct electricity. arious coatin(s are utilied and some eAamples are t;e

=fusiononded epoAy> found on factory coated steel pipin( and coal tar epoAies commonly found on sti!"#

tan%s.


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DISTRIBUTED GROUND BED 2 @sed to descrie an anode confi(uration in ?;ic; t;e anodes are more or less e/ually distriuted

around t;e metallic structure t;at is intended to e protected.

ELECTROLYTE 2,s related to @S$ cat;odic protection systemsH electrolyte refers to t;e soil and*or ?ater surroundin( t;e metallic

structure t;at is under cat;odic protection.

ELECTROMAGNETIC INTERFERENCE 2 ,s related to corrosion protectionH it is an eAternal electrical current t;at causes an errorin a voltmeter measurement. Sources are commonly associated ?it; ;i(; volta(e ,C po?er linesH radio fre/uency transmitters and airport

radar systems.

FAIL 2 See Section


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PASS 2 See Section t;e metallic structure t;at you tryin( to measure.

-9#P3TANK 2, steel tan% manufactured to t;e standard created y t;e Steel $an% Institute t;at comes from t;e factory ?it; a =preen(ineered> cat;odic protection system. $;e =!"> means t;at t;e steel tan% is protected in t;ree ?aysJ 17 , protective dielectric coatin( is

factory appliedK 27 Sacrificial anodes normally inc7 are factory installed on t;e tan%s and "7 dielectric us;in(s are installed to facilitate

electrical isolation of t;e tan%.

STRAY CURRENT 2 ,n electrical current t;at travels alon( an unintended pat;. )ormally t;ou(;t of as a current from some eAternalsource t;at enters a protected metallic structure at one point t;at t;en eAits at anot;er point. $;e point ?;ere t;e stray current eAits t;e

protected structure can e su-ect to intense corrosion and failure may rapidly occur.

STRUCTURE#TO#SOIL POTENTIAL 2,lso %no? as =pipeto soil potentialB or =structuretoelectrolyte potential> L $;e

difference in

t;e potential of t;e surface of a uried metallic structure and t;e electrolyte soil7 t;at surrounds it ?it; respect to a reference electrode in

contact ?it; t;e electrolyte soil7. Can e t;ou(;t of as t;e volta(e difference et?een a uried metallic structure and t;e soil t;at it is uried

in.

VOLTAGE 2 $;e asic unit of force in an electric circuit. olta(e is e/uivalent to pounds per s/uare inc; in a ?ater system.

VOLTAGE %IR' DROP 2 it; respect to @S$ cat;odic protection systemsH volta(e drops may e t;ou(;t of as any volta(e t;at causesan error in t;e oserved structuretosoil potential. ;enever a current is flo?in( t;rou(; a resistanceH a volta(e drop is present and is part

of t;e volta(e measurement otained.


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APPENDIX C

GENERALIED INTERPRETATION OF STRUCTURE#TO#SOIL POTENTIAL MEASUREMENTS

%VOLTAGES' OBTAINED ON GALVANIC CATHODIC PROTECTION SYSTEMS

3isted in t;is tale are some (eneralied oservations t;at can e applied to t;e interpretation of structuretosoil

potentials. 8ependin( on t;e specific site conditions and ot;er factorsH differin( interpretations are possile.

VOLTAGE %V' ON GENERALIED INTERPRETATION

POSITIVE$est leads are reversed ne(ative s;ould e connected to t;e reference electrode and t;epositive s;ould contact t;e structure you are testin( in order to oserve ne(ative volta(es7.

Could indicate t;at stray current is affectin( t;e structure consult ?it; a corrosion eApert7.

@sually occurs ?;en you are attemptin( to measure a structure t;at ;as a test lead t;at is not

0 7 #100 continuous ?it; t;e tan%. 9ecause you are measurin( t;e potential of a copper ?ire ?it;reference to t;e coppercopper sulfate ;alfcellH t;e potential is ero or very near it. 8isre(ard

test lead and ma%e direct contact ?it; t;e protected structure.

#101 7 #3!!$ry a(ain L , readin( in t;is ran(e is not normally seen on an under(round steel structure.Could indicate t;at steel structure is electrically connected to a si(nificant amount of a more

nole metal e.(. copper7. ery corroded lo? caron steel may also e indicated.

#00 7 #5!!Steel structure does not meet re(ulatory re/uirements. @sually means t;at t;e steel structure;as no cat;odic protection. Aistin( sacrificial anodes could e completely =urnedout> or ?ere

never t;ere to e(in ?it;.

Steel structure does not meet re(ulatory re/uirements. @sually means t;at t;e steel structure;as anodes ut for ?;atever reasonH somet;in( is causin( a lo? readin( t;at may indicate

#&00 7 #8!ade/uate cat;odic protection ;as not een provided. $;e anodes may e tryin( to protect astructure t;at re/uires more current t;an t;ey can produce. $;e protected steel structure maynot e electrically isolated from all ot;er metallic structures conduct continuity testin(7. $;eenvironmental conditions may not e favorale at t;e time you are attemptin( to otain t;e

readin(. Retest durin( t;e neAt 0 days to see if an acceptale readin( can e otained.

Steel structure protected y inc anodes meets re(ulatory re/uirements and cat;odic

#850 7 #1100protection is -ud(ed to e ade/uate. Readin(s in t;is ran(e are ?;at you ?ould eApect on most

sti!"#

tan%s t;at ;ave not een modified and are readin( =(ood> since nearly all come from t;e

manufacturer ?it; inc anodes.

Steel structure protected y ma(nesium anodes meets re(ulatory re/uirements and cat;odic

#850 7 #1&00protection is -ud(ed to e ade/uate. Readin(s in t;is ran(e are ?;at you ?ould typically eApecton steel pipin( t;at is readin( =(ood> since ma(nesium anodes are (enerally installed on

pipin(. Fou may also find readin(s up to 16 m on a sti!"#

tan% t;at ;as een retrofitted or?as supplied at t;e factory ?it; ma(nesium anodes.

MORE olta(es more ne(ative t;an 11 m are t;eoretically not possile if t;ere are only incNEGATIVE THAN anodes installed. If you ;ave a readin( more ne(ative t;an 11 m and you are sure

#1100 ITH INCma(nesium anodes are not presentH you s;ould suspect t;at stray current may e affectin( t;ecat;odically protected structure. , corrosion eApert s;ould e contacted immediately since

ANODES ONLY stray current can cause a corrosion failure in a relatively s;ort period of time.

MOREolta(es more ne(ative t;an 16 m are t;eoretically not possile ?it; any sacrificial anodecat;odic protection system. If you ;ave a readin( more ne(ative t;an 16 m on any

NEGATIVE THAN (alvanic cat;odic protection systemH you s;ould suspect t;at stray current may e affectin( t;e#1&00 cat;odically protected structure. , corrosion eApert s;ould e contacted immediately since

stray current can cause a corrosion failure in a relatively s;ort period of time.

If t;e voltmeter readin(s vary you s;ould suspect t;at stray current may e affectin( t;e

VARIABLEcat;odically protected structure. SometimesH t;e stray current can cause a pattern to developt;at is reco(niale. ,n eAample ?ould e t;e on*off pattern of a neary 8C po?ered ?eldin(

operation. , corrosion eApert s;ould e contacted immediately since stray current can cause acorrosion failure in a relatively s;ort period of time.

If t;e voltmeter ?ill not stailieH it usually means t;at t;ere is a ;i(; electrical resistance

RAPIDLYsome?;ere. C;ec% all lead ?ires and connections and ma%e sure t;at you are ma%in( a solidand clean metal to metal connection. Soil ?;ere t;e reference electrode is placed could e too

FLUCTUATING dry. ,dd ?ater to t;e soil or ?ait until a ;eavy rain occurs and try a(ain. !etroleumcontaminated soils may cause a ;i(; contact resistance. $;e tip of t;e reference electrode may

need to e cleaned or replaced.


46/71

APPENDIX D

GENERALIED INTERPRETATION OF STRUCTURE#TO#SOIL POTENTIAL MEASUREMENTS

%VOLTAGES' OBTAINED ON IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS

3isted in t;is tale are some (eneralied oservations t;at can e applied to t;e interpretation of structuretosoil

potentials. 8ependin( on t;e specific site conditions and ot;er factorsH differin( interpretations are possile.

VOLTAGE %V' GENERALIED INTERPRETATION

ANY POSITIVECan indicate t;at t;e structure you are attemptin( to measure is not onded to t;e impressedcurrent system conduct continuity testin(7. Stray current could e affectin( t;e protected structure

VOLTAGE OR consult a corrosion eApert7. !ositive and ne(ative ?ires could e reversed ne(ative must e to0 TO #100 protected structure and positive to anode7. $est leads are reversed positive lead s;ould contact

ON 76 OFF structure and ne(ative lead s;ould e connected to reference electrode7. Could indicate t;at youare measurin( t;e potential of a copper ?ire.

#101 7 #3!! $ry a(ain L , readin( in t;is ran(e is not normally seen on an under(round steel structure. Couldindicate t;at steel structure is electrically connected to a si(nificant amount of a more nole metal

ON 76 OFF e.(. copper7. ery corroded lo? caron steel may also e indicated.

#00 7 #5!! @sually means t;at t;e steel structure ;as no cat;odic protection. Aistin( impressed currentanodes could e completely =urnedout>. Continuity of anode lead ?ires positive circuit7 could e

ON 76 OFF ro%en. )e(ative onds on t;e protected structures may e ro%en or noneAistent.

@sually means t;at t;e steel structure ;as some protection ut for ?;atever reasonH somet;in( iscausin( a lo? readin( t;at may indicate ade/uate cat;odic protection ;as not een provided. $;e

impressed current system may e tryin( to protect a structure t;at re/uires more current t;an it#&00 7 #8! can produce rectifier output too small7. $;e impressed current system may not e capale of

ON 76 OFF effectively distriutin( t;e re/uired current to all parts of t;e structure you are tryin( to protect notenou(; anodesH anodes improperly installedH soil resistivity too ;i(;7. $;e steel structure t;at isintended to e protected may not e electrically continuous ?it; t;e ot;er metallic structures underprotection conduct continuity testin(7. $;e environmental conditions may not e favorale at t;e

time you are attemptin( to otain t;e readin(. Retest durin( t;e neAt 0 days.

#850 76 MORESteel structure may or may not e ade/uately protected. @sually indicates t;at t;e impressedcurrent system is providin( current to t;e structure alt;ou(; t;e readin( normally includes a lar(e

NEGATIVE volta(e IR7 drop. 9ecause t;e flo? of current t;rou(; t;e soil causes a volta(e dropH t;e on

ONpotential cannot e used to indicate t;at ade/uate cat;odic protection ;as een provided. Instant

off potentials must e utilied to demonstrate cat;odic protection.

#850 76 MORE Steel structure protected y impressed current system meets re(ulatory re/uirements andcat;odic protection is -ud(ed to e ade/uate. , potential measurement of +5 m or more

NEGATIVE ne(ative ?it; t;e protective current temporarily interrupted +5 off7 is considered to e t;e est

OFF indicator t;at ade/uate cat;odic protection ;as een provided.MORE Instant off potentials more ne(ative t;an 122 m are t;eoretically not possile. If you oserve an

NEGATIVE THAN instant off potential more ne(ative t;an 122 mH you s;ould suspect stray current is affectin( t;e#1""0 V OFF protected structure. Consult a corrosion eApert immediately since stray current can cause a rapid

corrosion failure of t;e protected structure.

MORE@sually means t;at a ;i(; resistance eAists in t;e (round ed t;at is causin( a lar(e volta(e drop.$;is condition is normally evident y c;ec%in( t;e rectifier output since t;e volta(e is very ;i(; ut

NEGATIVE t;e ampera(e is relatively lo?. Do?everH you s;ould e cautious ?;en anormally ;i(; volta(esTHAN #"000 are oserved since t;is can ;ave a detrimental effect on cat;odically protected structures or t;e

ONanodes may e rapidly depleted. Stray current

testing of cp

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