Impressed Current Cathodic Protection for Parking Structures

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CONCRETE PRESERVATION ALLIANCE

The Concrete Preservation Alliance is a growing coalition of organizations committed to advancing best practices in the field of concrete preservation and infrastructure renewal.

Working together to promote education and awareness of concrete repair industry standards, new and innovative corrosion prevention technologies and sustainable construction practices.

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OUR MEMBERS

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WESAVESTRUCTURES.INFO

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Travis Marman, NACE CP2

Travis Marman, a NACE CP2, is a construction project developer with Vector Construction. Travis has over 10 years of experience with managing projects, operations, business development and estimating.

Travis received his Bachelor of Science in Concrete Industry Management from California State University-Chico.

Travis has worked extensively in areas related to cathodic protection installation, electrochemical chloride extraction, impressed current and post-tensioned structures.

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Topics

• What is Cathodic Protection

• Corrosion Basics

• Understand the differences between impressed current and galvanic cathodic protection systems

• Projects

• Slotted System • Mesh Overlay• Ebonex Anodes • Metalizing (Galvanic)

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Active Corrosion in Parking Structures

• Cast in Chlorides

• Marine Environments

• Deicing Salts

• Entrances / Exits • Drive Lanes

• Low Cover over Reinforcement

• Joints

• Ponding

• Coating

Corrosion Macro-Cell

Anode

Cathode

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Corrosion Cell in Concrete

Fe Fe2+ + 2e -

Fe2+ + 2Cl- FeCl2

2Fe(OH)2 + 1/2O2 Fe2O3 + 2H2O

1/2O2 + H2O + 2e - 2OH-

FeCl2 + 2OH- Fe(OH)2 + 2Cl-

2OH-

Fe3O4

γFe2O3

Fe3O4

γFe2O3

Anode

2e -

Cathode

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Widespread Corrosion

• Widespread Corrosion

• Determined by Evaluation

• Half-Cell Potential Testing • Corrosion that is active but hasn’t

started deteriorating

• Global Solutions - Impressed Current Cathodic Protection (ICCP)

• Longer life solution

• Requires maintenance

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Solution for Repairs

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Solution for Repairs / Localized Areas

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Corrosion Protection Systems

Galvanic Corrosion Protection Uses sacrificial metal anodes to provide galvanic current to the steel Minimal maintenance (low-voltage battery)

Impressed Current Cathodic Protection

Use an external power supply and inert anodes to distribute DC current to the steel Annual maintenance / monitoring required (adjustable power)

Electrochemical Treatments Change the chemistry of the concrete around the steel to facilitate passivationLong-term low-maintenance solution Protect against recontamination

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Corrosion Basics

A – anode

C – cathode

M – metallic path

E – electrolytic path

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Corrosion Circuit

Electrolyte: concrete, or water

V = IRDriving voltage is ~constant, so

Lower resistance, R, = Higher current, I

Anode (Corroding steel)-350 to -450 mV v CSE

Cathode (Passive steel)> -200 mV v CSE

Corrosion Current

(µA)Concrete

Resistance (ohm)+

0.2 to 0.4 V-

• Anode – Location where rust is formed

• Cathode – Location with no section loss

• Metallic path – steel

• Electrolyte – concrete• Requires Moisture

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What is Cathodic Protection?

• Cathodic protection (CP) • is corrosion control through the application of direct

current onto a metal, forcing it to become a cathode

• The anode delivers current into the electrolyte (metal loss, rust occurs at the anode)

• The cathode receives current from the electrolyte (The cathode is protected from section loss)

• Two main types of CP• Galvanic• Impressed current

Cathodic Protection • An anode system is

embedded or attached to the surface of the concrete.

• An external current source provides power required to overcome the oxidization (corrosion) reaction at the steel surface.

• Reference electrodes provide feedback and the ability to monitor operation.

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Cathodic Protection Circuit

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Cathodic Protection Circuit

+

- PermanentDC PowerSupply

Anode

Concrete

Reinforcing Steel

Electrical Connection to Reinforcing Steel

Anode

Cathode

RcRw

Steel

+-

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Parking Garage Downtown Minneapolis, MN

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MMO Ribbon Anode Slot System

MMO Ribbon Anode Slot System

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MMO Ribbon Anode Slot System

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MMO Ribbon Anode Slot System

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McCormack Building – Boston, MA

• Constructed 1972 -1975

• 22 Floors – Office Building in Beacon Hill area of Boston

• Had existing Titanium Mesh ICCP system

• ICCP system fell into disrepair

• Evaluate, remove damaged areas, and recommission system.

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Titanium Mesh Overlay System

• Uses an expanded titanium mesh anode coated with a mixed-metal oxide (MMO)

• Current distribution provided by solid titanium ribbon that is welded to the mesh

• Pinned in place with plastic anchors

• Good option for areas that have low cover over steel reinforcement throughout the structure

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Titanium Mesh Overlay System

Cathode

Anode Ti Mesh Electrolyte

Metallic Path

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Titanium Mesh Overlay System

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Titanium Mesh Overlay System

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Brentwood Towers Parking Garage – Toronto, ON

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DAC-Anode® – Conductive Coating System• Successfully used for 30 years with 10-20

years of service life expected.

• DAC-Anode® WB o single component, electrically

conductive coating applied to the surface of the concrete

• DAC-Anode® Overcoat o Flexible acrylic, crack resistant and

weather resistant.

• Distribution wire - metallurgical clad tri-metal composite used for primary distribution of the protective current to the conductive coating

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DAC-Anode® – Conductive Coating System

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DAC-Anode® – Conductive Coating System

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DAC-Anode® – Conductive Coating System

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DAC-Anode® – Conductive Coating System

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DAC-Anode® – Conductive Coating System

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Heathrow Car Park – London UK

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Discrete Ceramic Anode System

• Drill and grout system for columns, beams and slabs.• Embedded anode distributes current evenly to all

reinforcement layers.• Titanium current distribution bars embedded in grout or

epoxy are very durable.• Elements can be coated afterward if required• Ceramic / titanium composite.• Different size anodes to accommodate different

geometries.

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Discrete Ceramic Anode System

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Discrete Ceramic Anode System

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Discrete Ceramic Anode System

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Three PNC Plaza – Pittsburgh, PA

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Arc-Sprayed Zinc (ASZ+ Metalizing)

• Process goes by many different names• Metalizing• Thermally Sprayed Coating / Zinc• Arc-Sprayed Anode

• System can either be used as galvanic protection or ICCP

• Involves installing a thin coating (12 to 18 mils) of metallic zinc to protect the reinforcement

• For ICCP, all near surface metals need to be removed• Like Dac-Anode, metalizing is installed on the soffit of

the concrete

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Arc-Sprayed Zinc (ASZ+ Metalizing)

To Rectifier

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Arc-Sprayed Zinc (ASZ+ Metalizing)

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Arc-Sprayed Zinc (ASZ+ Metalizing)

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Arc-Sprayed Zinc (ASZ+ Metalizing)

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Arc-Sprayed Zinc (ASZ+ Metalizing)

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ICCP System Wiring

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ICCP System Wiring

6. Battery Back-up

5. Rectifier Cards/(7 Zones)

4. Anode Wires (Red)

2. (Green) Wiring to Reference Cells3. Modem

7. AC Power input

Rectifier Cabinet

1. User interface

8. Data Collection

8. (Black) Wiring to Reinforcing Steel

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Remote Monitoring• Wireless technology advances allow

web-based CP system health monitoring

• Cellular & Satellite communication available

• System alerts sent in text message format

• Automated data collection

• Remote depolarization/ System interrogation

Remote Monitoring

11 Individually

Powered Zones

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ICCP Considerations

• Care must be used when designing and installing in locations with post tensioning

• Anchorages and couplers – galvanic protection

• Will require a long-term commitment to maintain and operated rectifier(s)

• Remote monitoring • Periodic maintenance

• Can be used in combination with galvanic systems

• Galvanic solutions for repairs / ICCP for locations with active corrosion

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System Selection and Project Development

• Non-destructive testing

• Concrete sampling and testing

• Chloride profile testing

• Corrosion potential surveys

• GPR mapping

• Corrosion rate testing

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System Selection and Project Development• Columns and Beams

• Joints

• Topside Deck

• Titanium Mesh Overlay• Titanium Ribbon• Discrete Ceramic Anode System

• Soffit

• Arc-Sprayed Zinc (Metalizing)• DAC-Anode

• Galvanic Solutions

• Traffic Coatings

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System Selection and Project Development

• Design

• Zones• Staging

• Generators, compressors, etc.• Power and Water

• Phasing

• By level, bay, etc.• Asset management - funding

• Dust and Noise

• Work Hours – Nights, Days, Weekends• Containment

• Cost

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Design

1. Size and location of ICCP zones and zone circuits,

2. Layout of anode and current distribution within each zone (overall plans, part plans, and typical sections),

3. Location, characteristics and enclosed electrical components of cabinets (power supply and main),

4. Location and characteristics of junction boxes and conduit,

5. Characteristics of wiring to be used,

6. Type and location of reference cells to be used,

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Design

7. Number, type and locations of negative connections to be used,

8. Special details around structural steel columns, shear heads, and for reinforcing steel passing through steel column flanges and webs,

9. Special details around existing concrete curbs and sidewalks,

10. Special details for handling reinforcing steel with low concrete cover,

11. Capacity and type of power supplies, and

12. Schematic diagram of ICCP system and reference cell circuits.

QUESTIONS?

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Contact Travis

Travis Marman

Construction Project Developer

Vector Construction

West Fargo, ND

Office: (701) 261-5579

TravisM@Vector-Construction.com

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