BASIC MECHANISMS OF CORROSION AND CORROSION CONTROL FOR .

BASIC MECHANISMS OFCORROSION AND CORROSIONCONTROL FOR WATER ANDWASTEWATER SYSTEMSGraham E.C. Bell, Ph.D., P.E.Department Manager and Sr. VP

Walking Through the Minefield of CorrosionInternal Corrosion

Market Driver for Corrosion Control isEntropyOur “Business” is Guaranteed by aFundamental Law of Nature:DSuniverse 0

DEFINITION OF CORROSIONCorrosion is the deterioration of a substance orits properties as a result of an undesirablereaction with the environment.- NACE InternationalIt is irreversible and degenerative andrelated to the Second Law Thermodynamics“Energy spontaneously tends to flow only from being concentrated in one place to becomingdiffused or dispersed and spread out.”

Everything You Need to KnowAbout Corrosion4 Parts of a Corrosion Cell Anode (location where corrosion takes place)o Cathode (no corrosion)o Oxidation Half-ReactionReduction Half-ReactionElectrolyte (Soil, Water, Moisture, etc.)Electrical Connection between anode and cathode(wire, metal wall, etc.)Electrochemical corrosion can bestopped by eliminating any one ofthe 4 components

Electrochemical Corrosion CellMetallic Pathe- ionsA- ionsElectrolytic PathC

AnodeMetallic PathCathodeElectronFlowElectrolyte

Can you find the anode?

The Corrosion PuzzleAnodeCathodeCorrosionElectrolyteMetallic Path

Remove any piece of the puzzle and allic Path

U.S. Cost of Corrosion is about 3.1% of GDP(50% to 70% Related to Civil Engineering)2010 US GDP 14.72 TrillionU.S. Cost of Corrosion 460 Billion

Highway BridgesGas and Liquid Transm. PipelinesWaterways and PortsHazardous Materials StorageAirportsRailroadsGas DistributionDrinking Water and Sewer SystemsElectrical UtilitiesTelecommunicationMotor VehiclesShipsAircraft1.00Railroad CarsHazardous Materials TransportOil and Gas Expl.and ProductionMiningPetroleum RefiningChem., Petrochem., Pharm.Pulp and PaperAgriculturalFood ProcessingElectronicsHome AppliancesDefenseNuclear Waste Storage - 8.3 7.0 14B (2010) 0.3 7.0 5.0 63 B (2010) 36.0 (1998) 6.9 - 41B (2010) 23.4 2.7 2.2 0.5 0.9 1.4 0.1 3.7 1.7 6.0 1.1 2.1 1.5 20.0 35B (2010) 0.1 10 20 30 40Cost Of Corrosion Per Analyzed Economic Sector, ( x billion)Annual 1998

Objectives of the Most Infrastructure Projects Provide a 50 Year UsefulLife Useful life means:– Functionality Assured– Structural IntegrityMaintained– Operating Costs Controlled How do we do this?– Control the two timedependent degradationmechanisms Corrosion Fatigue Creep (Generally NotApplicable)

Two distinct and different types ofSituations:New Pipe (Lot of Options) Chance to Do it RightRight of Way Study through ConstructionExisting Pipe (Limited Options) “Sins of the father”Condition AssessmentFor both, Corrosion Control is a Process,not a Project.

Concepts of the Four Basic MethodsCorrosion ControlMaterial Selection/Design Details Choose materials compatible with environment. Do not create corrosion cell throughdesign/construction details.Corrosion Inhibitors Alter the environment adjacent to metal topassivate and protect metal. Concrete or mortar on steel are inhibitors

Concepts of the Four Basic MethodsCorrosion Control (continued)Cathodic Protection Electrochemically alter the surface condition ofthe metal to move the anodic reactionselsewhere.Coatings (exterior) and Linings (interior) Provide a barrier to the electrolyte and protectthe metal. Usually dielectric material thatprevents electron and ionic current flow.

Coatings and Cathodic ProtectionWork TogetherCathodic protection can be applied with outcoatings.Coatings should not be used with out cathodicprotection.Cathodic protection effectively protects defectsin the coating. In many environments actually repairs the coatinglocally by depositing minerals that plug the holes inthe coating

Effect of Cathodic ProtectionCurrentC.P. CURRENTANODE-0.65 voltIcorr 1 mACATHODE-0.50 voltBefore Cathodic ProtectionANODE-0.65 voltReductionincorrosioncurrentIcorr .3 mA CATHODE-0.60 voltAfter Cathodic Protection

Cathodic Protection Stops Leaks

are Directly Proportional toCurrent Capacity (Amps)Life Cycle Costs Construction OperatingCostsInitial/Construction costs AmpsOperating/Maintenance Costs AmpsAnything and everything you do to reducecurrent requirement saves .

CP Current Requirements forWater Industry PipingPipe MaterialCoating SystemCurrent Requirement(ma/sf)Steel/IronNone1 to 3SteelAWWA C2050.1 to 0.5Steel/IronDielectric CoatingAWWA C214, 217, 2220.0006 to 0.020Ductile Iron with PEAWWA C1050.020 to 0.040

Water vs. Wastewater: External CorrosionMechanisms are identicalCorrosion Control for Exterior is IdenticalMaterials, Design and Construction Practices Similar .But Wastewater construction does not typicallyaccount for the eventual need for cathodicprotectionooElectrical Continuity of Pipelines and StructuresElectrical Isolation for Appurtenances

Water vs. Wastewater:Internal CorrosionNot the Same At All.Corrosion Rates for wastewater can beextremely high.More often internal corrosion leads toproblemsThis is one reason why external corrosionis ignored.

Internal Corrosion of Wastewater Systems Dominated by Formation of Sulfuric AcidH2S 2O 2H2SO4Sulfur oxidizing bacteriaH 2SH 2SH 2SH 2SSO42- organic matterAnaerobicBacteriaS2- 2H S2- H2O CO 2H 2SSulfur Reducing BacteriaSludge and silt

“Indirect” Impact of Regulationson CorrosionH2S crown 30 ppmCleanH2S crown2-10 ppmpH 1-2WaterActof1980pH 3-4Reduced metal concentrations in sewageElevated levels of bacterial growth

Water Line ringInternal Corrosion

DIP for Force MainGas Pocket CorrosionInternal Corrosion

Corrosion Control for the Outside ofCMC or Concrete Water PipesAWWA C205, C300, C301, or C303Corrosivity of alignment must bedetermined Saturated ASTM G57 Soil Resistivity 1500 Ω-cmooo Chlorides 350 ppm in soilSulfates 2,000 ppm in soilNo fluctuating groundwater in pipe zone.pH 5.0

ReferencesAWWA Manual M27 – External CorrosionAWWA Manual M28 – Rehabilitation of WaterMainsAWWARF Report 90987 – External Corrosionand Corrosion Control of Buried Water MainsNACE International Standards SP0169;SP0207; Peabody Control of PipelineCorrosion

Things we try to avoid

Condition Assessment is Part of theAsset PreservationFinancial Motivation Shrinking BudgetsGASB 34Political Motivation Career Limiting EventsRegulatory Motivation Jail – Oil and Gas Model

Selection of Condition AssessmentTechnology Depends on Several FactorsBudgetAccessibility/Availability of AssetRisk ToleranceBest Practice is to use multiple methods

You can do something withoutTechnology! Design InformationLeak and Break RatesGeographical Information Where should I look?120Total Number of Blowouts During SummerHistorical Information10110080806957604740384849422002001 2002 2003 2004 2005 2006 2007 2008 2009Industry MetricsUse your brain .

Steel Reservoir Condition AssessmentsRaft Inspection Confined Space Limited ViewDry Inspections Unpopular to WD’s Limits Defectsand accessHatch Inspection Limited View Confined SpaceDive Inspections Hours of Boredom,Punctuated by Moments of Terror Clarity of View

Coating Replacement Recommended Based on CoatingCondition Above Waterline400292300258210Existing CP System may beDamaging Coating20010063316- Seminole #117- Seminole #218- Tw in Lakes #119- Tw in Lakes #2101- Jed Smith #12- Jed Smith #23- Kiimberly4- Mulw ood5- Upper Woolsey6 - Warner #17- Warner #28- Calabasas9- Dardenne10- Latigo11- McCoy13- Oak Ridge012- Morrison14- Saddle Peak15- Saddle Tree6831119111176214Extrapolated Current Requirement microamps/sq ft forProtection with Existing Coating ConditionSteel Reservoir Coating Condition AssessmentBased on Holistic Results 2001-2002

PCCP is a Complex Pipe Material.Composite pipe product Internal mortar or concreteliningSteel CylinderConcrete Core(s)High StrengthPrestressed WiresExterior Mortar Coating1942 “War Pipe” substitutehigh strength steel anndconcrete for steel18 to 250-inch diameterUp to 350 psi PressuresEarly EC-PCCP Section1.5 m to 6.5 m diameterEarly LC-PCCP Section0.5 to 1.3 m diameter

Due to its Materials of Construction,PCCP does not Leak Before it BreaksEach stick of PCCP contains stored energyequal to between 20 and 200 lbs ofdynamite.

The Integrity of PCCP is Directly Related to The Integrityof the WiresWires Break – Surge orTransientExterior Mortar DamagedCompression in Concrete CoreReducedSteel CylinderCorrodesConcrete Core in Tension CrackingPipe Leaks or Fails

For PCCP, Based on its Era of DesignInitial Estimate of Risk Can Be Made

Old SchoolCondition AssessmentInternal Inspections Pre-1992, the only way toinspect PCCP was to dewaterthe pipeline and perform internalinspections. Visual inspection identifiedunusual cracking or poorlydetailed joints. Sounding techniques locatedhollows or delaminationsresulting from a loss ofprestress. Human ear, 20 to 20k Hz After age 40, 20 to 16k Hz

Electromagnetic Inspection:“New” Assessment TechnologyIn 1999 & 2001, supplemented the internal“sounding” procedures with Remote Field EddyCurrent/Transformer Coupling measurements(RFEC/TC). “A simple analogy: think of RFEC/TC system as a radioreceiverThe prestressing wire behaves like the radio antennaWith no breaks in the continuity of the prestressingwire, the radio receives a clear signal from thetransmitting stationIf the continuity of the prestressing wire is broken, theclarity of the signal received is also reduced.”

Remote Field Eddy Current

Not all damage will be found bytechnology

False Positive and Negatives arePossible with All Techniques

Technology is only one club in theCondition Assessment Golf BagImagine trying to play an entire round ofgolf with a 7-iron. You can do it but you don’t score well.Generally, you need a driver and a putter atleast I do.Technology provides data, notinformation.

Closing Shots and ThoughtsThere are four ways to control corrosion Material Selection and DesignCorrosion Inhibitors and MonitoringCoatings and LiningsCathodic ProtectionTechnology is a powerful and expensivetool that needs to be used wiselyThere is no substitute for laying eyes andhands on the structure.

Choose materials compatible with environment. Do not create corrosion cell through design/construction details. Corrosion Inhibitors Alter the environment adjacent to metal to passivate and protect metal. Concrete or mortar on steel are inhibitors Concepts of the Four Basic Methods Corrosion Control