Corrosion Control/Cathodic Protection for Aboveground Storage Tanks
CorrosionCorrosion Control/CathodicControl/Cathodic ProtectionProtection forfor AbovegroundAboveground StorageStorage TanksTanks
Presented by: James T. Lary Corrpro Companies, inc. 1090 Enterprise Drive Medina, Ohio 44256 [email protected] 330-723-5082 WhyWhy isis CorrosionCorrosion ControlControl Important?Important?
•• PreservePreserve AssetsAssets •• ReduceReduce MaintenanceMaintenance CostsCosts •• ReduceReduce InspectionInspection CostCost •• Company/GovernmentCompany/Government RequirementRequirement •• PreservePreserve TheThe EnvironmentEnvironment IRON OXIDE REFINING MILLING
STEEL CORROSION IRON OXIDE CorrosionCorrosion ofof MetallicMetallic StructureStructure
CORRPRO COMPANIES INC
External Corrosion of Tank Bottom
Anodic Area Cathodic Area -600mV -550mV
SAND CURRENT FLOW
Corrosion Cell Caused by Foreign Material in Sand Cushion
Steel Tank Floor
CURRENT FLOW SAND CLAY Corrosion Caused by Poor Water Drainage
WATER
MOIST SAND DRY SAND New Steel Coupled to Old Steel
New Bottom (Anode)
CURRENT FLOW SAND
Old Bottom (Cathode)
SAND Floor
Conduit Anode Liner
CPCP InstallationInstallation onon DoubleDouble BottomBottom TankTank Galvanic Cathodic Protection
Structure (Cathode)
Magnesium Anode
CORRPRO C O M P A N I E S I N C
Recommended Practices API-651 - Cathodic Protection of Aboveground Petroleum Storage Tanks: “Galvanic anodes method is not practical for protection of large bare structures.”
NACE RP0193-2001 - External Cathodic Protection of On- Grade Carbon Steel Storage Tank Bottoms: “Galvanic protection systems can be applied to tank bottoms where the metallic surface area exposed to the electrolyte can be minimized through the application of a dielectric coating or the area is small due to the tank size or configuration.” Impressed Current Cathodic Protection
Return
Rectifier (-) (+)
Anode
CURRENT FLOW Rectifier Anode
(+) (-) Tank
Shallow Anodes Rectifier
(+) (-) Tank
Splice
Anode
Typical Depth 20’
Shallow Anodes Rectifier
Junction Box
+ -
Anodes Tank Tank Rectifier
(+)
(-) Tank Tank
Deep Anode MFLMFL FloorFloor InspectionInspection Cathodic Protection Monitoring (+)
-850mV
Tank Portable Reference Cell
Soil ?? ??
Rim Potential Measurements Directional Boring Under Existing AST Aboveground Test/Access Station Storage Tank
Grade
3’ Typical 2” ∅ PVC Monitoring Tube REFERENCEREFERENCE CELLCELL MONITORINGMONITORING TUBETUBE boveground torage Tank
Test / Access Station ade
3’ Typical Bullseye® Monitoring Reference Cell Tube Rim 25' Center 55' Rim On -1411 -698 -404 -601 -1455 Off -902 -664 -402 -578 -911 Potentials (mV) Aboveground Storage Tank
Test/Access Station
Grade
10’ ∅ 3” PVC 20% Typical Exposure
Anode Material Anode Tube ABOVEGROUND STORAGE TANK CATHODIC PROTECTION TYPICAL ANODE INSTALLATION
Tank Bottom
Slotted Pipe
Native Earth
Coke Breeze
Anode Material Centered in Coke Breeze Computer Guided Horizontally Bored Anode System Rectifier Anode Pipe
(+)
Monitoring (-) Pipe
Tank
Anode Splice Box Anode Pipe Leak Detection Monitoring Station CPCP ApplicationsApplications forfor ReRe--bottomedbottomed oror NewNew TanksTanks NewNew FloorFloor InstallationInstallation onon ExistingExisting ASTAST CPCP InstallationInstallation onon RebottomedRebottomed TankTank Above Ground
Storage Tank Bottoms
with or without
Secondary Containment Secondary Containment
4 Environmental Protection
4 Minimize Liability
4 State and Local Regulations NewNew TankTank ConstructionConstruction withwith LinerLiner AnodeAnode && ReferenceReference CellCell PlacementPlacement inin HighHigh ResistanceResistance SandSand RingwallRingwall ConduitConduit forfor CPCP WiringWiring FloorFloor PlatePlate InstallationInstallation InstallationInstallationInstallation ofofof CPCPCP SystemSystemSystem ononon LiftedLiftedLifted ASTASTAST System Energization Impressed Current System
Rectifier
( - ) ( + )
Anode Groundbed
Pipeline (Structure) Current Flow InspectionInspection ofof CPCP SystemSystem RemoteRemote MonitoringMonitoring ofof CPCP Internal Corrosion
Fuel Product
Water / Sediment
Anode Cathode Internal Corrosion
Anode Coating Bolt
Tank Bottom
Recommended Practices
API-651 - Cathodic Protection of Aboveground Petroleum Storage Tanks:
NACE RP0193-2001 - External Cathodic Protection of On- Grade Carbon Steel Tank Bottoms: Pipeline Inspection Tool
Presented by:
James T. Lary Corrpro Companies, Inc. World Headquarters 1090 Enterprise Drive Medina, Ohio 44256 Phone: 330-723-5082 Fax: 330-723-0694 Email [email protected]