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Cathodic ProtectionCathodic Protectionfor Onfor On--Grade Storage Tanks andGrade Storage Tanks and
Buried PipingBuried Piping
John FitzgeraldJohn Fitzgerald
CorrproCorrpro
Freshwater Spills SymposiumFreshwater Spills SymposiumApril 6April 6--8, 20048, 2004
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Preserve AssetsPreserve Assets
Reduce Maintenance CostsReduce Maintenance Costs Governmental ComplianceGovernmental Compliance
Preserve The EnvironmentPreserve The Environment
Why is Corrosion ControlWhy is Corrosion Control
Important?Important?
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What I Will Cover.What I Will Cover.
-- Causes of CorrosionCauses of Corrosion
-- SPCC/State/OPS RegulationsSPCC/State/OPS Regulations
-- Cathodic Protection ApplicationsCathodic Protection Applications-- Maintenance RequirementsMaintenance Requirements
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Spill Prevention Control andSpill Prevention Control and
Countermeasure (SPCC) RegulationCountermeasure (SPCC) Regulation
(Implementation Required by 2/18/05 )(Implementation Required by 2/18/05 )
-- Provide buried piping that is installed orProvide buried piping that is installed or
replaced after August 16th, 2002replaced after August 16th, 2002
protective coating andprotective coating and cathodiccathodic protection.protection.
-- Should a section of line be exposed for anyShould a section of line be exposed for any
reason it must be inspected for deterioration.reason it must be inspected for deterioration.If corrosion damage is found you must takeIf corrosion damage is found you must take
additional examination and corrective action.additional examination and corrective action.
with awith a
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Federal Level(Breakout Tanks)
a) Relieves surges in a hazardous
liquid pipeline system or b) receive
and store hazardous liquid transported
by a pipeline for reinjection andcontinued transportation by pipeline
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Breakout Tank Piping (DOT)
M
Main Line
Valve
OPS
Inspection
MeterM
ProductTank
(Breakout)
M
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-- Approximately 25% of States nowApproximately 25% of States now
requirerequire cathodiccathodic protection be installedprotection be installedand maintained on new, refurbished, orand maintained on new, refurbished, or
repaired tanks in contact with soil or sandrepaired tanks in contact with soil or sand
foundations.foundations.
-- A number of other states are in theA number of other states are in the
process of implementing regulationsprocess of implementing regulationsgoverning ASTs.governing ASTs.
State Level
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Terminal Tankage
Main Line
M
Valve
OPS
Inspection
MeterM
No OPSInspection
OPS Inspection Stops
(Enforcement Policy)
LoadingTerminalProduct
Tank
(Terminal)
Product
Tank
(Terminal)
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Corrosion Can be Defined as Either:
Practical
Tendency of a Metal to Revert
to its Native State
ScientificElectrochemical Degradation
of Metal as a Result of a Reaction
with its Environment
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IRON REFINING MILLING
IRON CORROSION IRON OXIDE
Corrosion - A Natural Process
OXIDE
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1) ANODE
2) CATHODE
3) ELECTROLYTE
4) ELECTRICAL
CONNECTION
Anode-600mV
Cathode
-550mV
-575mV
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CorrosionCorrosion ofof MetallicMetallic StructureStructure
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Anodic Area
( - )
Current Flow
Cathodic Area
( + )
Structure
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SANDCURRENT FLOW
Corrosion Cell on TankBottom
CLAY
Steel Tank Floor
ANODEANODECATHODECATHODE CATHODECATHODE
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DRYSAND
MOIST SAND
WATER
Corrosion Caused byPoor Water Drainage
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New Bottom (Anode)
CURRENT FLOW
SAND
SAND
New Steel Coupled to Old Steel
Old Bottom (Cathode)
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Galvanic AnodeCathodic Protection
Current is obtained
from a metal of a higherenergy level
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PRACTICAL GALVANIC SERIES
Material Potential*
Pure Magnesium -1.75
Magnesium Alloy -1.60
Zinc -1.10Aluminum Alloy -1.00
Cadmium -0.80
Mild Steel (New) -0.70
Mild Steel (Old) -0.50
Cast Iron -0.50
Stainless Steel -0.50 to + 0.10
Copper, Brass, Bronze -0.20
Titanium -0.20
Gold +0.20
Carbon, Graphite, Coke +0.30
* Potentials With Respect to Saturated Cu-CuSO4 Electrode
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Structure
Magnesium
Anode
Current Flow
Galvanic Cathodic Protection on
Coated Pipeline
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Cathodic Protection Test Station
Test
Station
Magnesium
Anode
Coated Pipe
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FLANGE INSULATION KIT
INSULATING UNIONS
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Typically limited to new piping, that has agood quality coating and electrical isolation.
If the particular location is lacking any of the
above, an impresses current system may bewarranted.
Galvanic Anodes
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Anode Cathode
Water / Sediment
Fuel Product
Internal Corrosion
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Internal Corrosion
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CoatingAnode
Bolt
Tank Bottom
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Conventional CP Systems forConventional CP Systems for
ASTsASTs
-- Shallow (Distributed) AnodesShallow (Distributed) Anodes
-- Deep AnodeDeep Anode GroundbedGroundbed
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Impressed Current Transformer Rectifier UnitImpressed Current Transformer Rectifier Unit
I d C t S t
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Rectifier
Anode
Groundbed
( - ) ( + )
Pipeline(Structure)
Current
Flow
Impressed Current System
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TankTank
Anode
Splice
Typical Depth 20
Shallow Anodes
Rectifier
(-)(+)
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Shallow Anodes
Tank
Rectifier
(-)(+)
Anode
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Anodes
Junction
Box
Rectifier
-+
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Directional Boring Under
Existing AST
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ABOVEGROUND STORAGE TANK
CATHODIC PROTECTION
3
PVC 20%
Exposure
Anode Material
Anode Tube
10
Typical
Test/Access
Station
Grade
Aboveground
Storage Tank
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New/Refurbished ASTBottoms with or without
Secondary Containment
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Secondary Containment
Environmental Protection
Minimize Liability
State and Local Regulations
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New Tank Construction with LinerNew Tank Construction with Liner
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Anode & Reference Cell PlacementAnode & Reference Cell Placement
in High Resistance Sandin High Resistance Sand
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Liner
Floor
AnodeConduit
CP Installation on Double Bottom TankCP Installation on Double Bottom Tank
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CP Installation onCP Installation on RebottomedRebottomed TankTank
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Installation of CP System onLifted AST
Installation of CP System onInstallation of CP System onLifted ASTLifted AST
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Maintenance of CathodicMaintenance of Cathodic
Protection SystemsProtection Systems
-- Conduct Annual TestingConduct Annual Testing
-- Meet NACE Criteria/StandardsMeet NACE Criteria/Standards
-- Conduct BiConduct Bi--Monthly RectifierMonthly RectifierChecksChecks
-- NACE Qualified TechniciansNACE Qualified Technicians
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NACE Cathodic Protection Criteria
-850mV or more negative with currentapplied
-850mV Instant off
-100mV shift between Instant off and
Native
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Annual Cathodic Protection Survey
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Tank
Rim Potential Measurements
Portable Reference Cell
Soil
(+)
????
--850mV850mV
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Rim 25' Center 55' Rim
On -1411 -698 -404 -601 -1455
Off -902 -664 -402 -578 -911
Reference Cell
Bullseye
MonitoringTube
Test / Access
Station
boveground
torage Tank
de
3
Typical
Potentials (mV)
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Test
Station
Structure
Stray Current Monitoring Test StationStray Current Monitoring Test Station
Computerized Potential Logging Survey
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p gg g y
Reference Cells
Pipeline
TestStation
Backpack ComputerUnit
Chainer/Wire
Dispenser & Counter
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Monitoring
Record volts and amps s
Compare values to target setting
Conduct annual cp survey by NACE engineer
Maintain cp records
every 30-60 day
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BiBi--Monthly Rectifier CheckMonthly Rectifier Check
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Visual Check of Volts/AmpsVisual Check of Volts/Amps
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Record KeepingRecord Keeping
-- Provides HistoryProvides History
-- Computer Records/Data CollectionComputer Records/Data Collection
Remote MonitoringRemote Monitoring
Hand Held ComputersHand Held Computers
Close Interval SurveysClose Interval SurveysData PrintoutsData Printouts
Flagging of Problem AreasFlagging of Problem Areas
Priorit ize Action ItemsPrioritize Action Items--As Built DrawingsAs Built Drawings
-- Store Data & Records for LifeStore Data & Records for Life
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Recommended Practices
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Recommended Practices
API-651 - Cathodic Protection of Aboveground Petroleum
Storage Tanks:
Galvanic anodes method is not practical for
protection of large bare structures.
NACE RP0193-01 - External Cathodic Protection of On-Grade
Metallic Storage Tanks:
Galvanic protection systems can be applied to tank
bottoms where the metallic surface area exposed to
the electrolyte can be minimized through theapplication of a dielectric coating or the area is small
due to the tank size or configuration.
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QuestionsQuestions