Corrosion Control/Cathodic Protection
for Aboveground Storage Tanks
Presented by:
James T. Lary
Corrpro Companies, inc.
1090 Enterprise Drive
Medina, Ohio 44256
jlary@corrpro.com
330-723-5082
Why is Corrosion Control
Important?
• Preserve Assets
• Reduce Maintenance Costs
• Reduce Inspection Cost
• Company/Government Requirement
• Preserve The Environment
IRON OXIDE REFINING MILLING
STEEL CORROSION IRON OXIDE
Corrosion of Metallic Structure
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
CP Installation on Double Bottom Tank
Galvanic Cathodic Protection
Structure
(Cathode)
Magnesium
Anode
CORRPRO
COMPANIES INC
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
MFL Floor
Inspection
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
REFERENCE CELL MONITORING TUBE
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
CP Applications for Re-bottomed or
New Tanks
New Floor Installation on Existing AST
CP Installation on Rebottomed Tank
Above Ground
Storage Tank Bottoms
with or without
Secondary Containment
Secondary Containment
4 Environmental Protection
4 Minimize Liability
4 State and Local Regulations
New Tank Construction with Liner
Anode & Reference Cell Placement
in High Resistance Sand
Ringwall Conduit for CP Wiring
Floor Plate Installation
Installation of CP System on
Lifted AST
System Energization
Impressed Current System
Rectifier
(-) (+)
Anode
Groundbed
Pipeline
(Structure)
Current
Flow
Inspection of CP System
Remote Monitoring of CP
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 jlary@corrpro.com
