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Jorge Costa, P.E.

Corrosion Restoration Technologies

Division of Structural Group, Inc.

Jorge Costa, P.E.

Corrosion Restoration Technologies

Division of Structural Group, Inc.

Cathodic ProtectionUsing Thermal

Sprayed Zinc Anodes

Cathodic ProtectionUsing Thermal

Sprayed Zinc Anodes

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OutlineOutline

Corrosion of Steel in ConcreteCathodic Protection

Metalized Anode CP SystemsEquipment

Economic ConsiderationsCase Histories

Corrosion of Steel in ConcreteCathodic Protection

Metalized Anode CP SystemsEquipment

Economic ConsiderationsCase Histories

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Corrosion of Steel in ConcreteCorrosion of Steel in Concrete

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Corrosion Induced

Deterioration Sequence

1

2 3

oxygen,

chlorides,

moisture

cover

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Concrete as a Corrosion

Environment

Concrete as a Corrosion

Environment

High ResistivityLow Porosity

High Alkalinity (high pH)

High ResistivityLow Porosity

High Alkalinity (high pH)

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Corrosion in ConcreteCorrosion in Concrete

0.02

0.01

0.005

0.002

0.001

0.0005

CorrosionRate(inche

speryear)

pH

2 4 6 8 10 12 14

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Corrosion in Concrete

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Corrosion CellCorrosion Cell

AnodeCathode

Electrical path between anodeand cathode

Electrolyte (Ionic Path)

AnodeCathode

Electrical path between anodeand cathode

Electrolyte (Ionic Path)

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Corrosion CellCorrosion Cell

V

A C

Current flow

Ionic flow

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Corrosion Cells in Concrete

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Corrosion Induced CrackingCorrosion Induced Cracking

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Spalling and DelaminationsSpalling and Delaminations

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Corrosion ProductsCorrosion Products

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Structural Failures Caused by CorrosionStructural Failures Caused by Corrosion

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Time to failure

Time to cracking/spalling

Time to corrosion initiation

Period 1 Period 2

Period 3

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Corrosion Deterioration

Versus Time

Corrosion Deterioration

Versus Time

Lev

elofDete

rioration

CostofR

epair

Time

Exponential

Deterioration Curve

(1X)(10X)

(25X)

(100X)

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REBAR

Anode CathodeAnode

Patch

Patches and Ring Effect

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Concrete PilesConcrete Piles

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Corrosion in Concrete PilesCorrosion in Concrete Piles

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Corrosion in Concrete PilesCorrosion in Concrete Piles

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Cathodic ProtectionCathodic Protection

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Reduction or elimination of corrosion by

making the metal the cathode in a

corrosion cell. This is achieved by

means of an impressed direct current or

attachment to a sacrificial anode

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Delivers a small direct current through the

concrete to the steel.

Current is discharged into the concrete

from an anode.

Previously corroding anodic areas receive

current.

Anodic areas are converted to cathodicareas.

Corrosion is arrested.

Delivers a small direct current through the

concrete to the steel.

Current is discharged into the concrete

from an anode.

Previously corroding anodic areas receive

current.

Anodic areas are converted to cathodicareas.

Corrosion is arrested.

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CP System TypesCP System Types

Sacrificial or Galvanic Systems

Impressed Current Systems

Sacrificial or Galvanic Systems

Impressed Current Systems

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Sacrificial Cathodic ProtectionSacrificial Cathodic Protection

CCANew

Anode

Added

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Impressed Current Cathodic

Protection

Impressed Current Cathodic

Protection

CCA

Power

Supply

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Metalized Anodes for

Cathodic Protection

Metalized Anodes for

Cathodic Protection

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Sacrificial Cathodic Protection

SystemAnode (zinc) is coated on concrete surface

Anode is connected directly to steel

Voltage difference generates protective currentZinc corrodes and steel does not

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Impressed Current CPImpressed Current CP Small direct current is passed from a permanent

anode

External power supply connected between anodeand steel

Appropriate polarity and voltage to stop corrosionprocess

Current can be adjusted for zones according toexposure conditions and requirements

Small direct current is passed from a permanentanode

External power supply connected between anodeand steel

Appropriate polarity and voltage to stop corrosionprocess

Current can be adjusted for zones according toexposure conditions and requirements

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Thermal Sprayed CoatingsThermal Sprayed Coatings

Metallized Coatings

Process of spraying molten

metal on to a surface to form acoating

Feedstock material is brought to

molten or near-molten state by

a heat source.

Atomized particles are

propelled to a prepared surface

with a gas.

TS Coating is built up by proper

application technique.

Process is line-of-sight.

Resulting coating has unique

characteristics.

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Metalized CoatingMetalized Coating

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TS Coating Characteristics

Lamellar StructureLamellar Structure

HeterogeneousHeterogeneous

CompositionComposition

PlateletsPlatelets OxidesOxides

VoidsVoids

UnUn--melted particlesmelted particles

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Zn Metalized Coating

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Thermal Spray ProcessesThermal Spray Processes

Flame / Gas Guns

Wire Arc

High Velocity Oxy Fuel

Plasma

Other Systems

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Wire Arc Process

WIRE

GENERATOR

RECTIFIER

METALIZING UNITWIRE

GUN

COMPRESSOR

+

-

COATING

COMPRESSED AIR

CONTACT TIPS

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Metalizing EquipmentMetalizing Equipment

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Wire Arc Equipment

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Wire Arc Equipment

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Wire Arc Equipment

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Case HistoriesCase Histories

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Power Plant Cooling TowerPower Plant Cooling Tower

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Power Plant Intake StructuresPower Plant Intake Structures

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Parking Garage, PAParking Garage, PA

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C t l Hi h Ri B ildiCoastal High Rise Buildings

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Coastal High Rise BuildingsCoastal High Rise Buildings

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Port of Corpus ChristiPort of Corpus Christi

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Wiloughbee Spit Bridge VAWiloughbee Spit Bridge VA

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Wiloughbee Spit Bridge, VAWiloughbee Spit Bridge, VA

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Marine Laboratory, FLMarine Laboratory, FL

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Metalized Anode CharacteristicsMetalized Anode CharacteristicsThickness : 15 -20 mils

Porosity & Oxides < 6%

Life expectancy:

y 13-15 years in galvanic modey 20-25 years in impressed current mode

Special alloy composition (low Fe)

Bond strength 100 250 p.s.i.

Thickness : 15 -20 mils

Porosity & Oxides < 6%

Life expectancy:

y 13-15 years in galvanic modey 20-25 years in impressed current mode

Special alloy composition (low Fe)

Bond strength 100 250 p.s.i.

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Metalized Anode CharacteristicsMetalized Anode Characteristics Post application treatments

y Top coatingy Humectant

Quality Controly Thicknessy Bond strengthy General Condition

Prequalification of Applicatorsy Safetyy

Experiencey Training

Post application treatmentsy Top coating

y Humectant

Quality Controly Thicknessy Bond strengthy General Condition

Prequalification of Applicatorsy Safetyy Experiencey Training

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