understanding cathodic protection and its applications · 2017-05-25 · stray dc current...

Jeff Schramuk NACE CP Specialist #7695

5/25/2017

www.cpsolutionsinc.net 1

1

UnderstandingCathodicProtectionand

ItsApplications

JeffSchramukNACECPSpecialist#7695

630‐235‐1559www.cpsolutionsinc.net

IEEE‐IAS/IESDinnerPresentation:5/24/2017

2

1. CorrosionProblemsFacingWaterUtilities

2. AssetManagement

3. CorrosionChemistrywithSpecificExamples

4. PipeMaterialsandCoatings

5. BasicCathodicProtection

6. CPforExistingWMsusinganAnodeRetrofitProgram

7. CathodicProtectionforNewWaterMains

8. CathodicProtectionPerformanceVerification

9. StrayDCCurrentInterference

TopicstobeCovered


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3

Section1

CorrosionProblemsFacingWaterUtilities

4

What’stheRestofthe(Unexcavated)PipeLookLike?


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5

StateoftheWaterIndustryReport– Year2016

TheTop3IssuesFacingtheWaterIndustrybyAllRespondents

1. Renewal & replacement ofaging water and wastewaterinfrastructure.

2. Financingforcapitalimprovements.3. Publicunderstandingofthevalueofwatersystemsand

services.

Source: “2016 State of the Water Industry: The Cornerstone Needs Support”, Journal AWWA, 108:7, Jul-2016, pp. 63-73.

6

Whatistheleadingcauseofmanywatermainbreaks?

Corrosion!


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WhatAre theConsequencesofPipelineFailures?

Water Main BreaksEnergy Pipeline “Incidents”

8

Section2

AssetManagement


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“Awaterutility’sassetmanagementplanisanoptimizationprocessthatattemptstomeetthecompeting

objectivesofcostminimizationandreliabilitymaximization.”

Source: Rubin, S.J., A Call for Reliability Standards, Journal AWWA, (Jan-2011)

AssetManagement:AReal‐WorldDefinition

10

Risk=(LikelihoodofFailure)x(ConsequenceofFailure)

EvaluatingFailureRisk:Probabilityvs.Consequences


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Section3

CorrosionChemistrywith

SpecificExamples

12

Practical

Definition

Scientific

Definition

TheTendencyofaMetaltoReverttoitsNativeState

ElectrochemicalDegradationofMetalasaResultofaReactionwithitsEnvironment

Corrosion:PracticalandScientificDefinitions


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Anode– Ametalelectrodeincontactwiththeelectrolytewhichcorrodes.Cathode ‐ Ametalelectrodeincontactwiththeelectrolytewhichisprotectedagainstcorrosion.Electrolyte – Asolutionorconductingmediumsuchassoil,waterorconcretewhichcontainsoxygenanddissolvedchemicals.MetalPath– Anexternalcircuitthatconnectstheanodeandthecathode.

FourComponentsofaBasicCorrosionCell

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Anodic Area(Metal Loss)

DC Current

Cathodic Area

(Protected)

Anodes&CathodesonaBuriedMetallicPipe


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ComponentsofaFamiliarCorrosionCell

CARBONROD(Cathode)

ZINCCASE(Anode)

NH4 andCl‐ Paste(Electrolyte)

WIRE(MetallicPath)

Whyistheopen‐circuitvoltageofacommon

flashlightbattery1.5volts?

I

I

I

I

I

e-

Material Potential*PureMagnesium ‐1.75MagnesiumAlloy ‐1.60

Zinc ‐1.10AluminumAlloy ‐1.00MildSteel(New) ‐0.70MildSteel(Old) ‐0.50Cast/DuctileIron ‐0.50StainlessSteel ‐0.50to+0.10

Copper,Brass,Bronze ‐0.20Gold 0.20

Carbon,Graphite,Coke 0.40*MeasuredinVoltsversusaCu‐CuSO4ReferenceElectrode

16

Les

sA

ctiv

e M

ore

PracticalGalvanicSeries


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18

GalvanicCorrosionatBi‐MetallicPipeConnection

Photo Credit: Drinking Water Services, City of Ottawa, Canada


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New Pipe (anode) Old Pipe (cathode)

Old‐NewPipeConnectionCorrosionCell

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CorrosionCausedbyDissimilarSurfaceConditions

Scratches (anode) Threaded Coupling (anode)


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Concrete Encased Steel (less active cathode)

Steel in Soil (more active anode)

Similar Phenomenon: Guy Anchor Rod Corrosion for a Communications Tower

GalvanicCell– SameMetalsinaNon‐UniformElectrolyte

22

GalvanicCell– SameMetalsinaNon‐UniformElectrolyte


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Attheanode:2Fe 2Fe+2+4e‐

Atthecathode:O2+2H2O+4e‐ 4OH‐

Undisturbed Native Soil

O2

Trench Backfill

Undisturbed Native Soil

Trench Backfill

DC Current

Pipe bottom is usually most corrosive zone!

SpecificTypesofCorrosion– DifferentialOxygen

24

Cathodic Zone

Anodic Zone

DifferentialOxygenCorrosion:ASpecificExample

Photos courtesy of CP Solutions, Inc.


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SpecificTypesofCorrosion‐ Pitting

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PittingCorrosion:DuctileIron

Photo Credit: CP Solutions, Inc.


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PittingCorrosion:CarbonSteel


28

SelectiveMetalCorrosion‐ CastIronGraphitization



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29

Section4

PipeMaterialsandCoatings

30

Ifwaterandoxygencannotreachthemetalsurface,will

corrosionbestopped?

BasicElectrochemistry– CombinedReactions

Attheanode: 2Fe 2Fe+2+4e‐ (ironoxidation‐corrosion)

Atthecathode: O2+2H2O+4e‐ 4OH‐ (reductionofoxygen)

CombinedReaction(electrochemicaldissolutionofiron)

2Fe+O2+2H2O 2Fe+2+4OH‐

ConvertFerrousIrontoFerricIron(Rust istheResult)

2Fe+2+3OH‐ Fe2(OH)3

Note:Theelectronsjustfacilitatethereaction!


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31

EliminatingtheCorrosionCell

Ste

el

at -

600

mV

Cop

per

at -

200

mV

32

PrestressedConcreteCylinderPipe– CylinderForming

Photo Credits: Forterra, Inc.


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PrestressedConcreteCylinderPipe‐ WireWrapping


34

PrestressedConcreteCylinderPipe– ConcreteJacket



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MortarIntegrityonReinforcedConcretePipe

…but is there latent damage?

New installation looks good…

Photo Credits: CP Solutions, Inc.

36

PrestressedConcreteCylinderPipe– CorrosionFailures



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CoatedSteelPipe‐ Factory‐AppliedCoatingSystems

AWWA Standard C‐222 Polyurethane

Photo Credits: Northwest Pipe

AWWA C‐214 Standard Tape Wrap

38

LargeDiameterCoatedSteelPipe– InstallationPhotos



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CoatingIntegrityonCoatedSteelPipe

…but is there latent damage?New installation looks good…


40

Will my pipe coating resist damage from third‐party “hits” after burial?

ConsiderLongTermPipeCoatingDamage


Does it adequately resist soil stress?


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PipeCoating/TapeWrapping– Long‐TermEffectiveness


42

Pit‐CastIronWaterPipe(Circa1915)

Left Photo Credit: CP Solutions, Inc.

Right Photo Credit: Ductile Iron Pipe Research Association


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DuctileIronWaterPipe(Contemporary)

3/8” thick (Pressure Class 150)


Photo Credit: Ductile Iron Pipe Research Association

44

Poly‐WrapIntegrityonDuctileIronPipe

Photo courtesy of CP Solutions, Inc.…but is there latent damage?

New installation looks good…


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DIPAsphaltCoating– ATrueCorrosionBarrier?


Close‐up of abraded 1‐mil asphalt coating

Sticky label pulls off coating

Rip and tears in the poly wrapping leave the pipe exposed

Oxygen and water can travel

beneath the poly wrapping

Loose Polyethylene

Wrapping

Ductile Iron Pipe

Soil Contaminants

46

Haveyouevertriedtotrackdownajointleakwithinapoly‐wrappedwaterline?

LoosePolyWrapping– AnEffectiveCorrosionBarrier?


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Section5

BasicCathodicProtection

48

BasicCorrosion:CorrosionoccurswhereDCcurrent

discharges fromthemetaltotheelectrolyte.

CPObjective:Toallowyourstructuretoreceive DCcurrent

(becathodic)fromanexpendableanodeplacedinthesoil.

HowCathodicProtectionWorks


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Material Potential*PureMagnesium ‐1.75MagnesiumAlloy ‐1.60

Zinc ‐1.10AluminumAlloy ‐1.00MildSteel(New) ‐0.70MildSteel(Old) ‐0.50Cast/DuctileIron ‐0.50StainlessSteel ‐0.50to+0.10

Copper,Brass,Bronze ‐0.20Gold 0.20

Carbon,Graphite,Coke 0.40*MeasuredinVoltsversusaCu‐CuSO4ReferenceElectrode

49

Les

sA

ctiv

e M

ore

PracticalGalvanicSeries

50

Cop

per

-20

0mV

Ste

el

-600

mV

Mag

nesi

um

-1.7

V

1. Anode

2. Cathode

3. Electrolyte

4. MetalPath

GalvanicCorrosion– NoCathodicProtectionBenefit


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Cat

hode

Cat

hode

Ano

de

1. Anode

2. Cathode

3. Electrolyte

4. MetalPath

GalvanicCorrosionMitigatedw/CathodicProtection

52

TypicalHorizontalSacrificialAnodeInstallation

Sacrificial Anode

Coating Defect

Connection to Pipe

Grade


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RectifiedAnodeCathodicProtectionSchematic

54

DCcurrentisobtainedfrommorenoble(inert)metalanodespowered

byatransformer/rectifier

RectifiedAnodeCathodicProtectiononaPipeline



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15’SVAC– OpenFlightAugurInstallation

25’SVAC‐ HollowStemAugurInstallation


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100’DVAC‐ RotaryMudDrillInstallation

58

Section6

CathodicProtectionforExistingWaterMains

usinganAnodeRetrofitProgram


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AnodeRetrofitProgram(ARP)‐ Amethodtoinstallsacrificialanodestoburiedwatermains.

Since2003– Louisville(KY)WaterCompany

Since2004– DesMoines(IA)WaterWorks

Since1980’s– ManyOntario(Canada)WaterUtilities

MoreRecently– SeveralCaliforniaWaterUtilities

AnodeRetrofitPrograms– AnOverview

AnodeRetrofitProgram‐ Purpose

Reduce theNumberofBrokenWaterMains

ExtendServiceLifeofWaterMains

ReduceOperatingCostsofWaterMains



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DMWW’sLong‐TermMainBreakData(1992‐2015)

0

100

200

300

400

500

600

700

1992 1996 2000 2004 2008 2012 2016 2020 2024 2028

Num

ber

of A

nnua

l Mai

n B

reak

s

Data courtesy of Des Moines Water Works – Des Moines, IA

62

DMWW’sMainBreakRepairCosts(2001‐2015…)

$2,500

$3,500

$4,500

$5,500

$6,500

$7,500

$8,500

$9,500

$10,500

2000 2005 2010 2015 2020

Rep

air

Cos

t/M

ain

Bre

ak

Repair costs have increased >2.5 times since the year 2000



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TypicalAnodeRetrofitInstallationMethod

KeyholetoPipe&WireConnection

Exothermic Welding Tool Down the Hole

Testing the Wire Connection



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Alternative(Non‐Keyhole)InstallationMethods


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Howdoesoneverifythattheanodesareworkingandcanonemakeanestimateoftheanodes’effective

servicelife?

TechnicalEvaluationoftheDMMW’sARP


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EvaluatingtheEffectivenessoftheCPInstallation

Measuring CP Effectiveness at Buffalo Box Test StationTest Station between Sidewalk and Curb

68

DoesthedatashowthatretrofittingCPanodesonwatermainsactuallyreducesthemainbreakrates?

MainBreakReductionEvaluationoftheDMMW’sARP


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0

1

2

3

4

5

2000 2005 2010 2015

Ann

ual M

ain

Bre

aks

Example:MainBreakson2007AnodeRetrofitProject


70

EconomicEvaluationoftheDMMW’sARP

ButdoestheeconomicdatashowthatretrofittingCPanodesonwatermainsisactuallycost‐effective?


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DMWWAnodeRetrofitProgram:2004‐2011Summary

ARPinstalledon~82,000feetof6”‐ 16”castironmains

ARPcostsare$9to$15/ft.pipe

ARPcost~10‐15%ofbreakrepairs/pipereplacement

ARPresultedinaveragereductionof85%inmainbreaks

ARPaddsa~25‐yearservicelifeextensiontowatermains

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Section7

CathodicProtectionfor

NewLargeDiameter(>16”)WaterFeederMains


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CorrosionControlCriteria:NewWaterMains

A water utility must consider corrosion protection as part

of its design analysis for the following types of pipe

materials used for new water mains:

PrestressedConcreteCylinderPipe(AWWAC301)

DuctileIronPipe(AWWAC110)

WeldedSteelPipe(AWWAC200)

CathodicProtectionSystem– KeystoSuccess

1. Integrityofthepipe’scoating/wrappingsystem

2. Pipeiselectricallyisolatedfromforeignstructures

3. Pipemustbeanelectricallycontinuousstructure

4. Pipeconnectionsmustbeelectricallysecure

5. Installaccessibletestpointstoverifyeffectiveness

6. Installanodessimultaneouslywiththepipe

7474


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FlangeIsolationKitComponents

FIK components should always meet NSF‐61 requirements

Photos courtesy of Garlock Pipeline Technologies, Inc. –Wheat Ridge, CO

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IsolationCorporationStop

Photo courtesy of James Jones Company – Decatur, IL

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PipeSleeveIsolationSpacers

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Photo Credits: CP Solutions, Inc. (left) and Des Moines Water Works (right)

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CasingSleeve– TypicalPipeEndSeals

Link-Style End Seal Boot-Style End Seal

A suitable end seal prevents pipe-to-casing contact and also keeps soil/water

from entering into the casing annulus!



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WallPenetrationsonPipeWithCathodicProtection

GoodJob!

Pipeweldedtorebarof

concretewall!

Link-Style End Seal

Thru-Wall Pipe w/Anchor No isolation of pipe-rebar


ContinuityBondsatMechanicalPipeJoints

80

Ductile Iron Pipe w/Mechanical Joints Steel Pipe w/Rubber Gasketed Joints

80



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ExothermicWeldsandConnectionDevices

Proper surface preparation will

allow good weldsPhoto Credits: CP Solutions, Inc.

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ProperCoatingofExothermicWeldsConnections

Raw Connections before Coating

Finished Connections Ready to Backfill

Restorepolywrapoverteststationwires



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ASuitablePost‐TypeCPTestStationInstallation

Shown w/cap removed

Good Job!

84

Concrete pad is optional per owner

Terminal board is mounted to PE Pipe

Crushed gravel provides drainage

Good Job!

SuitableFlush‐TypeCPTestStationInstallation


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AnodesInstalledinanOpenPipeTrench

85Photo Credits: CP Solutions, Inc.

86

AnodeTestStation– SectionView


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Section8

CathodicProtectionPerformanceVerification

88

.900 V

+

PRC in soil directly above pipe

-

Secure electrical contact to pipe

Area of Pipe “Measured”

Structure‐to‐SoilPotentialw/PortableReferenceCell

S/S potential measurement is the DC voltage difference between the PRC and the buried structure’s surface


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VM (‐) connected to second pipe test wire

VM (+) connected toPortable Reference Electrode

Voltmeter set on DC VoltsBlue = Pipe Wire (1 of 2)

Red = Anode Wire

CPPerformanceValidation– S/SPotentialData


Voltmeter set on DC millivolts

VM (+) & (‐) connected across

calibrated wire shunt

0.8 mV is equivalent to 80 milliamps

CPPerformanceValidation– AnodeCurrentOutputData



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91

Corrosionisthedegradationofamaterialduetoareactionwithitsenvironment

CPisachievedwhenthecathodicsitesarepolarizedintheelectronegativedirectiontothepotentialofthemostanodicsites.

Onlypracticalmethodtodeterminethisisbymeasuringstructure‐to‐soilpotentialdatausingastandardreferenceelectrode.

The“True”CathodicProtectionCriterion

92

-0.50 -0.60 -0.65 -0.60 -0.70 -0.58

-0.58 -0.60 -0.65 -0.60 -0.70 -0.58

-0.60 -0.60 -0.65 -0.60 -0.70 -0.60

-0.65 -0.65 -0.65 -0.65 -0.70 -0.65

-0.70 -0.70 -0.70 -0.70 -0.70 -0.70

1:StaticPotentials

5:Allsitespolarized

POLARIZATION

Polarizationreducesthe∆Valongthestructure

2:Mostpositivesitespolarizefirst

3:Nextmostpositivesitespolarize

4:Lastmostpositivesitespolarize


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Increasedwatermainservicelife

Increasedlevelofreliablewaterservicetocustomers

Increasedhealthandsecurityofthemunicipalwatersupply

Summary:TheRealBenefitsofCorrosionMitigation

Cathodicprotection saves$5 to$10forevery$1

spentresultingin…

Water Main Life Extension of least 25 years at acost that is much less than…

Directcostsofpiperepairsand/orwatermainreplacement.

Indirectcostsresultingfromwaterloss/servicedisruptions.

94

Section9

StrayDCCurrentInterference


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DCTransitSystemCausingElectrolyticCorrosion

96

EffectsofStrayDCCurrentfromDCTransitSystem

Unbonded Pipe Joints

Note Random Discharge

Anodic Areas


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StrayDCInterferencefromanRectified‐AnodeCPSystem

98

Corrosion Perforation

EffectsofForeignCPSystematPipeJoint

Note Bond Cable!


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ObservingandTestingforDCInterference

Observations:LookforchangesinS/Spotentialsalongthe

buriedstructureat

Discretetestpoints(discreteteststations)

Close‐intervalpotentialsurvey(CIPS)

Methodology

InterruptforeignallCPrectifiersandnoteS/Sduringboth

ONandOFFcycles

Recognition: AbnormalOperatingConditions

PositiveS/SshiftswiththeforeignrectifierONrequire

additionalinvestigation/mitigation99

100

JeffSchramukNACECPSpecialist#7695

630‐235‐1559www.cpsolutionsinc.net

DoYouHaveAnyQuestions?

All material in this presentation is, unless otherwise stated, the property of CP Solutions, Inc (CPSI). Copyright and other intellectual property laws protect these materials. Reproduction or retransmission of the materials, in whole or in part, in any manner, without the prior written consent of CPSI, is a violation of copyright law.

IEEE‐IAS/IESDinnerPresentation:5/24/2017

understanding cathodic protection and its applications · 2017-05-25 · stray dc current...

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