10 Cathodic Protection

Paint SchoolJPS-E/Cathodic/1

Organisation ChartOrganisation ChartJotun Cathodic ProtectionJotun Cathodic Protection

Jotun Cathodic

Protection

Jotun

Decorative

(Scandinavia)

Jotun

Protective

Coatings

Jotun

Decorative

Paints

Jotun

Marine

Coatings

Jotun

Paints

Jotun

Powder

Coatings

Jotun Group


Corrosion of a metal or alloyCorrosion of a metal or alloy

• Corrosion is a reaction between the metal and the surrounding environment

• The corrosion rate depends on the properties of the metal and the corrosivity of the environment.

• Corrosion is dissolution of the metal, among other things involving the release of electrons:

Fe Fe + 2e2+


What is cathodic protection ?What is cathodic protection ?

• Cathodic protection (CP) is a method for reducing the corrosion rate of a metal.

• The principle is based on “Supplying electrons to the base material”.

• This is done by either:– Connecting the structure to a more electro-

negative material (Sacrificial anode)

– Connecting the structure to an external electron source (Impressed current)


How to protect a structureHow to protect a structure

Corrosion Protection can be achieved by :

• Sacrificial Anode Cathodic Protection System

• Impressed Current Cathodic Protection System

Both systems supply electrons to the structure.

The structure will become more negative and metal dissolution will be prevented


Type of ProductsType of Products

• Sacrificial anodes

• Electrolytic descaling

• Impressed Current Cathodic Protection Systems (ICCP)

• Electrolytic Antifouling


• Zinc– Noranode

– Coral Z

• Aluminium– Coral A

– Coral A high grade

• Magnesium

Type ofType of Sacrificial AnodesSacrificial Anodes



• Cathodic protection engineering and design

• Sacrificial anodes

• Impressed current systems

• Electrolytic Antifouling Systems

• Magnesium strips (Electrolytic descaling)

• Grounding equipment


Type of ServicesType of Services

• Surveying, inspection and reporting


• Potential measurements

• Servicing and Log sheet evaluation

• Technical support and advice


Type of Products and ServicesType of Products and Services


• Servicing, inspection and reporting

• Sacrifical anodes

• Magnesium strips (Electrolytic descaling)

• Impressed Current Cathodic Protection Systems

• Electrolytic Antifouling System

• Log sheet evaluation

• Grounding equipment


Impressed Current Cathodic Protection Systems

• Transformer rectifiers

• Impressed current anodes

• Reference electrodes

• Monitoring equipment

• Shaft grounding equipment

• Rudder grounding



Type of productsType of products

Grounding equipment



• Earthing cables



Magnesium Strips for descaling

• Magnesium strips

• Clamps


For NorwayFor NorwayObjects to be Protected:Objects to be Protected:

• Ships

• Offshore platforms and rigs

• Subsea installations

• Subsea pipelines

• Harbour facilities

• Storage tanks

• Buried tanks and pipelines (onshore)


Objects to be Protected:Objects to be Protected:

• Ships

• Offshore platforms and rigs

• Subsea installations


• Harbour facilities (Sacrificial anodes)


Marine Marine Objects to be Protected:Objects to be Protected:

• Ships

• FPSO / FSU

• Mobile rigs

• Floating dry-docks

• Barges


Norwegian Sector. Offshore and IndustryNorwegian Sector. Offshore and Industry

Objects to be ProtectedObjects to be Protected::

• Offshore platforms– Fixed / floating

– Concrete / steel

• Subsea installations– (templates/

manifolds/ modules)


• Harbour facilities– Piles

– Sheet piles

• Buried tanks and pipelines (onshore)

• Storage tanks


Offshore and IndustryOffshore and Industry

Objects to be Protected:Objects to be Protected:

• Offshore platforms– Fixed / floating

– Concrete / steel

• Subsea installations– (templates/manifolds/ modules)


• Harbour facilities– Piles

– Sheet piles


• Iron (steel) in its natural state exist primarily as iron ore

• Energy added at melting and refining are released by the corrosion process

• Coatings reduce corrosion rate

• Cathodic protection supply energy to stop corrosion

Energy

Corrosion and corrosion protectionCorrosion and corrosion protection

Time

E 1

E 2

Iron ore

Refining

Rust = Iron ore

Corrosion

Pure metal or an Alloy Cathodic protection

Energy offered by Cathodic protectionCoating

reducescorrosion rate


Freely Corroding SteelFreely Corroding Steel

Cathode

2e-Anode

Cathode

Sea water (electrolyte)

Fe 2+

2e-

½ O2 + H2O + 2e 2OH --

2e- 2e-

Steel plate

½ O2 + H2O + 2e 2OH -- -- --


Potential, mV vs.

Cu/CuSO4 Zn-580 +500 Freely corroding steel

-700

-800

+250 Mixed potential ( Protection potential)

-900

-1000

-1080 0 Freely corroding Zinc

The Principle of Cathodic ProtectionThe Principle of Cathodic ProtectionPotentials vs. different Reference ElectrodesPotentials vs. different Reference Electrodes


Cathodic ProtectionCathodic Protection

Steel protected by a Sacrificial anodeSteel protected by a Sacrificial anode

A calcareous deposit is formed on the steel surface

2 e

Steel

ZincZn = Zn + 2 e

O2

2+ -

-

½ O2 + H2O + 2e 2OH -- --


Steel

Current Source

CurrentO2

2 e-

Permanent anode

Cathodic protectionCathodic protectionImpressed current systemImpressed current system

A calcareous deposit is formed on the steel surface

Reaction at the cathode

½ O2 + H2O + 2e 2OH -- --

Reaction at the anode

2 Cl ½ Cl2 + 2eH2O 2H + ½ O + 2e

-- ----+


Rapid corrosion

General corrosion

Some corrosion

100% Cathodic protection

Overprotection

Possible coating damage

Corrosion Potentials in SeawaterCorrosion Potentials in SeawaterZinc, Ag/Ag Cl and Cu/CuSOZinc, Ag/Ag Cl and Cu/CuSO4 R4 Reference Electrodeseference Electrodes

Increasing polarisation

Ag / Ag Cl Zinc

+ 0.50

- 0.25

+ 0.0

+ 0.25

- 0.55

- 1.30

-1.05

- 0.80

Potentials in volt

- 0.60

- 1.35

-1.10

- 0.85

Cu / CuSO4


Full cathodic protection

(Steel surface passivated)

Free corrosion of steelCorrosion reduction , %

vs Zn 450 400 350 300 250 mV

vs Ag/AgC1 -600 -650 -700 -750 -800 mV

Reduction of corrosion rate of steel by Reduction of corrosion rate of steel by cathodic protection. Moving seawatercathodic protection. Moving seawater

Negative polarisation, mV

0

50

87,5

0 50 100 150 200Actual potential of the steel


MarineMarineNecessary Information to do a CP DesignNecessary Information to do a CP Design

• Type of structure

• Design lifetime

• Coating system and condition

• Trade

• Surface area to be protected

– Drawings

– Tank capacity plan

• Ballasting period.

• Class / Safety restrictions


MarineMarineDesign Criteria Design Criteria

• Design lifetime


• Current density (Coating type and damages)

• Current distribution

• Electrolytic resistivity

• Environmental conditions / impacts

• Ballasting period.


ProtectiveProtectiveDesign criteriaDesign criteria

• Type of structure

• Surface area to be protected

• Design lifetime


• Protection potential

• Anode capacity

• Current distribution

• Electrolyte resistivity

• Environmental conditions / impacts

• Safety restrictions


Current Density Requirement Current Density Requirement Depends On:Depends On:

A. Environmental parameters

• Sea water composition and salinity

• Sea water temperature

• Specific resistivity of sea water

• Sea water velocity

• Other factors, marine growth

B. Steel surface

• Painted / not painted

• Steel temperature

• Coating system, if any

• Condition of coating system


Sacrificial Anode material selectionSacrificial Anode material selection

Main TypesMain Types

• Zinc

• Aluminium

• Magnesium

Anode material selectionAnode material selection

• Chemical composition

• Electrochemical performance

- Anode potential

- Stable current

- Consumption

• Anode corrosion pattern

• Price

• Class requirements


Initial/final design current densities in A/m2

Tropical

(> 20 oC)

Sub-Tropical

(12-20 oC)

Temperate

(7 - 12 oC)

Arctic

(< 7 oC)

0.150

0.090

0.170

0.110

0.200

0.130

0.250

0.170

0.130

0.080

0.150

0.090

0.180

0.110

0.220

0.130

Depth

(m)

0 - 30

> 30

Current density requirement Current density requirement acc. to DNV RP B401 (1993)acc. to DNV RP B401 (1993)


Me4an (average) design current densities in A/m 2

Depth

(m)

0 - 30

> 30

0.070 0.080 0.100 0.1201)

0.060 0.070 0.080 0.100

1) Effect of any ice scouring are not included

Current density requirement Current density requirement acc. to DNV RP B401 (1993)acc. to DNV RP B401 (1993)

Tropical

(> 20 oC)

Sub-Tropical

(12-20 oC)

Temperate

(7 - 12 oC)

Arctic

(< 7 oC)


Coating CategoriesCoating CategoriesAcc. to DNV RP B401 (1993)Acc. to DNV RP B401 (1993)

Category I:Category I:

One layer of primer coat, about 50 microns nominal DFT (Dry Film Thickness)

Category II:Category II:

One layer of primer coat, plus minimum one layer of intermediate top coat, 150 to 250 microns nominal DFT.

Category III:Category III:

One layer of primer coat, plus minimum two layers of intermediate/top coats, minimum 300 microns nominal DFT

Category IV:Category IV:

One layer of primer coat, plus minimum three layers of intermediate top coats, minimum 450 microns nominal DFT.


Coating Category

Depth(m)

I II III IV

k1 = 0.10k2

0 - 30 0.10 0.03 0.015 0.012> 30 0.05 0.02 0.012 0.012

k1 = 0.05k2

k1 = 0.02k2

k1 = 0.02k2

where fc = coating break down factor

t = coating lifetime

k1 and k2 = constants dependent on coating properties

fc = k1 + k2 t

Coating Break Down FactorCoating Break Down FactorAcc. to DNV RP B401 (1993)Acc. to DNV RP B401 (1993)


ProtectiveProtectiveDesign Sacrificial Anode SystemDesign Sacrificial Anode System

A. Design criteria• Current density requirement

– initial

– mean

– final

• Design lifetime

• Anode material

B. Net anode weight requirementW= Exposed surface area (m²)

i = Mean current density (A/ m²)

C= Anode concumption rate (11.2 kg/year for Zn)

( 3.39 kg/year for Al)

L = Design lifetime

U = Utility factor (0.90, normally)

C. Initial and final current requirement

• I INITIAL = A * i init

• I FINAL = A * i final

D. Anode current system capacity

• Anode design (shape and size)

• Number of anodes


Jotun Anode AlloysJotun Anode Alloys

Coral A

• Al-Zn-In Alloy

• Increased consumption rate by increasing temperature

Coral Z

• Zn alloy according to U.S. Mil. Spec. A-18001

• Intergranular corrosion above approximately 45 ºC

Noranode

• Zn-Al-Mg Alloy

• Environmental friendly

• Mil. Spec properties below 25 ºC

• Cost effective at elevated

temperature.– Reduced intergranular corrosion

– Current capacity and consumption

rate relatively stable at increasing

temperatures

– Recommended above 50 ºC


Comparison of Cathodic Protection Systems Comparison of Cathodic Protection Systems General General AdvantagesAdvantages::

Sacrificial anode systems

• Simple, reliable and free from in-service operator surveillance

• System installation is simple

Impressed current systems

• Flexibility under widely varying operating conditions

• Weight advantage for large capacity, long life systems (reduced sea water drag)

• Low life cycle cost (LCC)• Low installation cost

for short term protection


Comparison of Cathodic Protection SystemsComparison of Cathodic Protection Systems

General General DisadvantagesDisadvantages::

Sacrificial anode systems

• Large weight for large capacity, long life systems.

• Response to varying operating conditions is limited.

• Hydrodynamic loadings can be high (Seawater drag)

Impressed current systems

• Relative complexity of system demands high level of design expertise.

• In-service operator surveillance required.

• Vulnerable to component failure or loss of power.


Why Choose an ICCP System on HullWhy Choose an ICCP System on Hull

• Smooth hull, no drag

• Flexible dry-docking intervals

• Low cost for long term operation

• Long lifetime, minimum of maintenance

• No welding required at dry docking

• No risk of damaging internal Paint systems

• Fully automatic corrosion protection


Why Choose a SACP System on HullWhy Choose a SACP System on Hull

• Simple installation

• Maintenance free between dry docking

• Low cost for short term operation

• World-wide availability


Lifecycle Cost of CP SystemsLifecycle Cost of CP Systems

13000 DWT Car Carrier13000 DWT Car Carrier

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

US

D

ICCP

Al

Zn

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Years

Indicates Dry-docking Replacement of an ICCP component

Anodes and Reference electrodes can be replaced whilst in service.Normally, this is carried out at the dry-docking


Life Cycle Cost of CP SystemsLife Cycle Cost of CP Systems

Panamax BulkcarrierPanamax Bulkcarrier

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

US

D

ICCP

Al

Zn

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Years

Indicates Dry-docking Replacement of an ICCP component

Anodes and Reference electrodes can be replaced whilst in service.Normally, this is carried out at the dry-docking


Cathodic Protection of Cathodic Protection of Ballast Water TanksBallast Water Tanks

1. Impressed current systems are not practical, and in most Classification Societies not permitted.

2. Magnesium anodes are not permitted.

3. In cargo, or adjacent tanks where the flash point is below 60 deg. C, Aluminium anodes are only permitted where the kinetic energy can not exceed 27,5 kpm (275 J).

4. There are no restrictions on the positioning of Zinc anodes.


Tanks: Lloyd's register DNV

Segregated ballast 108 100 - 110

Dirty ballast 86 40 - 60

Washed cargo 108 80 - 90

Top wing 120 120

Coated (epoxy) 5 5 - 10

Soft Coats 20 - 40

Current density criteria mA/m 2

Current densityCurrent densityDesign CriteriaDesign Criteria


Example: Tanker vessel. Example: Tanker vessel. Clean ballast water. Upper wing Clean ballast water. Upper wing

tanktank

Anode information• Anode type : ZTL - 230• Gross weight : 23 kgs• Net weight : 21,2 kgs• Current output : 1,3 Amps

Input from customer• Area : 6400 m2 • Current density : 120 mA/m2

• Life time : 4 years• Ballast time : 50 %• Paint system : Unpainted


TanksTanksConversion Factors from Volume to AreaConversion Factors from Volume to Area

C.T :

W.T :

Forepeak :

D.B.T :

U.W.T :

Volume * 0.7 - 0.9

Volume * 1.5 - 2.5

Volume * 1,5 - 2.5

Volume * 0.5 - 0.6

Volume * 1.5 - 2.5

= Area m²

= Area m²

= Area m²

= Area m²

= Area m²

Examples:Examples:

Deck head is includedExact calculations must be based on drawings


Net weight:

6400 m2 x 120 mA/m2 x 4 yrs x 50% x 11,2 kg/A.yr ------------------------------------------------------ = 17203 kg 1000 100

17203 kg.No. of anodes: --------------- = 812 pcs : 812 pcs ZTL-230 21,2 kg/pc

Gross weight: 812 kg x 23kg/pcs = 18676 kg

Check of current requirement: 6400 m2 x 0,12 A/m2 = 768 Amp

Total current output : 1,3 Amp/pc x 812 pcs = 1055,6 Amp

Example: Tanker vessel. Example: Tanker vessel. Clean Ballast Water. Upper wing Clean Ballast Water. Upper wing

tanktank


Information required:

• Theoretical calculation of net weight of anodes

– From previous calculation

• Number of small compartments

Design of Sacrificial Anode System Design of Sacrificial Anode System

Double Bottom and Other Narrow TanksDouble Bottom and Other Narrow Tanks


Calculation:

Anode net weight:

Total net weight, kg = Net weight/pc

NOTE:NOTE: Usually, the number of compartments equal the number of pieces: Require one anode per compartment

Use nearest standard anode type

Design of Sacrificial Anode System Design of Sacrificial Anode System

Double Bottom and Other Narrow TanksDouble Bottom and Other Narrow Tanks

Number of compartments (pc)


Example: Tanker vessel. Example: Tanker vessel. Clean ballast water. Double Bottom Clean ballast water. Double Bottom

TankTank

Anode information• Anode type : ZTL - 230• Gross weight : 23 kgs• Net weight : 21,2 kgs• Current output : 1,3 Amps

Input from customer• Area : 6400 m2 • Current density : 120 mA/m2

• Life time : 4 years• Ballast time : 50 %• Paint system : Unpainted


Net weight:

6400 m2 x 120 mA/m2 x 4 yrs x 50% x 11,2 kg/A.yr ------------------------------------------------------ = 17203 kg 1000 100

17203 kg.No. of anodes: --------------- = 812 pcs : 812 pcs ZTL-230 21,2 kg/pc

Gross weight: 812 kg x 23kg/pcs = 18676 kg

Check of current requirement: 6400 m2 x 0,12 A/m2 = 768 Amp

Total current output : 1,3 Amp/pc x 812 pcs = 1055,6 Amp

Example: Tanker vessel. Example: Tanker vessel. Clean Ballast Water. Double Clean Ballast Water. Double

Bottom TankBottom Tank


ICCP - Log report ReadingsICCP - Log report ReadingsCurrent Output Development With Current Output Development With

TimeTime

100 -

80 -

60 -

40 -

20 -

| | | | | | 1 2 3 4 5 6

System capacityAmp.

Years

1. d

ock

ing

2..

doc

kin

g

3. d

ock

ing

Grounding (Loss of coating)

ExampleExample


Cathodic protection of tanksCathodic protection of tanksCurrent density at different coating breakdown ratioCurrent density at different coating breakdown ratio

Current density mA/m²

70

60

50

40

30

20

10

2

80

90

Tar Epoxy

Epoxy Mastic

Upper W

ing tank

0 5 10 20 30 40 50 60 70 80 90 100 110 120

100

Car

go/d

irty

bal

last

tank

s

Clean ball

ast t

anks f

ore-a

nd aft.

peak ta

nks

Cargo

/clea

n bal

last

tank

slower

win

g/dou

ble bot

tom

Soft coat / Flow coat

Coating breakdown


Ship hull: Current Density at Ship hull: Current Density at Different Paint DamageDifferent Paint Damage

Current density, mA/ m²

Paint damage, %

100

45

15

0 20 70

Not applicable: Repaint

ICCP is recommended,not sacrificial anodes

Sacrificial Anodes and ICCP can be used


*) Potential in seawater measured versus a copper/coppersulphate reference electrode

Galvanic Series in Sea WaterGalvanic Series in Sea WaterCorrosion Potentials vs. 3 Reference ElectrodesCorrosion Potentials vs. 3 Reference Electrodes

Graphite + 0.25 + 1.28 + 0.17Titanium 0 + 1.03 - 0.08Stainless steel (Passive) - 0.50 + 0.98 - 0.13Copper-Nickel (90/10) - 0.23 + 0.80 - 0.31Copper - 0.33 + 0.70 - 0.41Brass - 0.34 + 0.69 - 0.42Stainless steel (Corroding) - 0.35 + 0.68 - 0.43Mild steel - 0.66 + 0.37 - 0.69Aluminium - 0.80 + 0.23 - 0.88Zinc - 1.03 0 - 1.11Magnesium - 1.60 - 0.57 - 1.68

Metal / Alloy Ag / AgCl Zn Cu/Cu SO4


Corrosion Secondary structure

Pipeline

Anode+_

InterferenceInterference


2

TypeAnode current density

in seawater(A/m )

Consumption rate(kg/A year)

500 - 1000 < 1 x 10

500 - 1000 1000 - 5000

6 x 10 1 x 10

160 - 220 160 - 220

0,05 - 0,2 0,03 - 0,06

10 - 40 0,2 - 0,5

10 - 40 0,2 - 0,5

- 7 - 9

-6

-6

-5

2

MIXED METALOXYDE

PLATINIUM- Disc- Thread

LEAD-SILVERPb - 6% Sb - 1% AgPb - 6% Sb - 1% Ag

GRAPHITE

IRON-SILISIUMFe - 14,5% Si - 4,5% Cr

SCRAP IRON

Impressed current system anodesImpressed current system anodes


Anode performance dataAnode performance data

Anode Specific Closed circuit Driving Capacity Consumption types gravity potential vs. Zn voltage (Ah/Kg) rate (Kg/dm ) ( Volt) (Volt) ( Kg/ A*Year)3

Zinc

Aluminium

Magnesium

7.13 0 0.23 781 11.2

2.78 -0.02 0.25 2585 3.39

1.84 -0.47 0.7 1200 7.3


Aluminium AnodesAluminium AnodesSmall vesselsSmall vessels

This guide is based on a 3 year (36 month) replacement period (dry-docking interval).

Vessel Type Surface Anode Type Current Density - mA/m2 Number of Total Area (% coating breakdown) Anodes Weight

Kgs

Tug / Small Vessels 500 A - 50 25 (15 %) 32 160

Supply Vessel 2000 A - 80 20 (10 - 15 %) 60 480

Reefer / Container 4000 A -130 15 (5 - 10 %) 58 754

Tanker / Bulker 18000 A - 180 10 (2-5 %) 120 2160

This design is for the hull only and does not allow for the seachests, thruster tunnels etc..

The calculation is the same, but with specific current densities.


This guide is based on a 3 year (36 month) replacement period (dry-docking interval).

Vessel Type Surface Area

Anode Type Current Density Number of pieces

Total- mA/m2 Gross

(% coating breakdown) Weight - Kgs

Tug / Small Vessels 500 Z-85 25 (15 %) 54 459

Supply Vessel 2000 Z-160 20 (10 - 15 %) 92 1472

Reefer / Container 4000 Z-270 15 (5 - 10 %) 80 2160

Tanker / Bulker 18000 Z-200 10 (2-5 %) 316 6320

This design is for the hull only and does not allow for the seachests, thruster tunnels etc.. The calculation is the same, but with specific current Densities

Zinc AnodesZinc Anodes


Principle : Effect of using CP Principle : Effect of using CP

Corrosion Curves depend on - Coating condition - CP-design

Coating breakdown

CP installed

CP and coating at newbuilding

Time

Corrosion


Steel passivation by sacrificial anodesSteel passivation by sacrificial anodes

Paint

Steel

Rust

Without Cathodic Protection

Paint

Steel

With Cathodic ProtectionAnodeAnode current

Seawater

Seawater

Calcareous layer


Ships hull: Current density as Ships hull: Current density as function of coating breakdownfunction of coating breakdown

Coating breakdown Current density

2 - 5 % 10 mA/m2

5-10 % 15 mA/m2

10-15 % 20 mA/m2

15-20 % 30 mA/m2

20-25 % 40 mA/m2

25-30 % 50 mA/m2


Location Current density

SeachestsThruster tunnelPropeller nozzleRudderRudder flapsAnti-suction tunnelsPropeller (Uncoated) Azimuth propeller

40 mA/m2

150 mA/m2

150 mA/m2

100 mA/m2

150 mA/m2

100 mA/m2

500 mA/m2

150 mA/m2

CP of ships:CP of ships:Additional Areas Requiring Protection.Additional Areas Requiring Protection.


Sacrificial Anode SystemSacrificial Anode System

Aluminium alloy anodes Zinc alloy anodes (technically equal)

Aluminium is recommended prior Aluminium is recommended prior to zinc because:to zinc because:

Aluminium anode weight is approx. 1/3 of zinc Total price for equal protection: Al. anodes

approx 1/2 of Zinc anodes Lower installation costs due to weight difference


Cathodic ProtectionCathodic Protection

ICCP - Impressed Current SACP - Sacrificial Anodes EAF - Electrolytic Antifouling System for

seawater systems (CUPROBAN) Slip ring arrangement for propeller shaft

Coatings and Cathodic ProtectionCoatings and Cathodic Protection

The Single Source SolutionThe Single Source Solution


Sacrificial Anode System Sacrificial Anode System DisadvantagesDisadvantages

Increases the frictional resistanceAdds weight to the vesselThe shipyard often supply the anodes at a

very low price (charge more for installation)


Cathodic protectionCathodic protection

Sacrificial Anodes or Impressed CurrentSacrificial Anodes or Impressed Current

Anodes increase the frictional resistance compared with impressed current systems

Adds weight to the vessel Aluminium anode weight is approx. 1/3 of zinc Total price for equal protection:

Al. anodes approximately half the price of Zinc anodes


Location of Pitguard AnodesLocation of Pitguard Anodes

Web Frame

Web Frame


Type of products Type of products Grounding EquipmentGrounding Equipment



• Earthing cables


Slipring ArrangementSlipring Arrangement

Shaft

Silver Graphite Brush

Steel Slipring

Earth to Hull

mV meter

Silver Inlay


Slip Ring ArrangementSlip Ring Arrangement

• Protects against spark corrosion in the engine bearings– Very high cost to replace bearing

– The vessel cannot operate with damaged bearings

• Reduces corrosion on propeller– Extends propeller life

– Reduces polishing needs on the propeller


Slip Ring ArrangementSlip Ring Arrangement

Grounding of the propeller and shaftFixed to intermediate shaft in engine roomBeneficial if SACP or ICCP systems are

used


• Thank You !

Documents

10 Cathodic Protection