corrosion and cathodic protection phenomena · 2018-03-14 · cathodic protection systems are most...

Corrosion and Cathodic Protection Phenomena

Karpira Kavir Company

www.k a p ik a c o .c om

KAR PIRA KAVIR COMPANY

Corrosion and Cathodic Protection Phenomena

Corrosion is the gradual destruction of materials (usually metals) by chemical reaction with its

environment.

In the most common use of the word, this means electrochemical oxidation of metals in reaction

with an oxidant such as oxygen. Rusting, the formation of iron oxides is a well-known example

of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the

original metal. Corrosion can also occur in materials other than metals, such as ceramics or

polymers, although in this context,

the term degradation is more common.

Corrosion degrades

the useful properties of materials and

s t ruc tu res inc lud ing s t reng th ,

appearance and permeability

to liquids and gases.

Sacrificial anode protection

For effective CP, the potential of the steel surface is polarized (pushed) more negative

until the metal surface has a uniform potential. With a uniform potential, the driving force

for the corrosion reaction is halted.

For galvanic CP systems, the anode

material corrodes under the influence

of the steel, and eventually it must be

replaced. The polarization is caused

by the current flow from the anode to

the cathode, driven by the difference

in electrochemical potential between

the anode and the cathode.

Corrosion 1.1.

1.2.1.

Cathodic protection 1.2.

32

Many structural alloys corrode merely from exposure to moisture in air, but the process can be

strongly affected by exposure to certain substances. Corrosion can be concentrated locally to

form a pit or crack, or it can extend across a wide area more or less uniformly corroding the

surface. Because corrosion is a diffusion-controlled process, it occurs on exposed surfaces.

As a result, methods to reduce the activity of the exposed surface, such as passivation and

chromate conversion, can increase a material's corrosion resistance. However, some

corrosion mechanisms are less visible and less predictable

Cathodic protection (CP) is a technique to control the corrosion of a metal surface by

making that surface the cathode of an electrochemical cell. Cathodic protection systems

are most commonly used to protect steel, water, and fuel pipelines and tanks; steel pier

piles, ships, and offshore oil platforms.

Impressed Current Cathodic Protection



For larger structures, galvanic anodes cannot economically deliver enough current to provide

complete protection. Impressed current cathodic protection (ICCP) systems use anodes

connected to a DC power source (such as a cathodic protection rectifier). Anodes for ICCP

systems are tubular and solid rod shapes of various specialized materials. These include high

silicon cast iron, graphite, mixed metal oxide or platinum coated titanium or niobium coated

rod and wires.

Impressed current cathodic protection 1.2.2.

4



2.1.Transformer Rectifier

Specification:

The transformer-rectifier will be composed of:

An input unit.

A regulating unit of the output voltage.

Intelligent adjustment with reference electrode.

Output option in constant Voltage, constant current and reference electrode.

Step-down transformer.

The measuring instruments.

Full bridge- full control.

The electric protection devices.

Accessories.

All these equipment will be mounted inside a metallic cubicle, suitable for indoor/outdoor

installation.

Working Conditions:

The oilimmersed transformer-rectifiers will be designed to meet the cathodic protection

requirements.

A.C Supply: 380+10% V three phase 50 Hz, single phase 50 Hz 220 V DC Output: adapted to

requirement

Cooling:

The regulation unit, the step-down transformer and the bridge diodes will be oil-immersed in a

special tank formingthe interior part of the T/Rectifier.

Location:The transformer-rectifiers will be suitable for indoor and outdoor installation, in non-

Hazardous areas.

Cubicle:The transformer-rectifier equipment will contain two parts in a cubicle composed of:

An oil tank where the step-down transformer, the regulating unit and the bridge rectifier will

be located.

A control unit fixed on the oil tank with all commands, Electrical circuits, measuring

instruments, protective devices, fuses and terminals.

The cubicle will be:

Waterproof and dustproof.

Designed for mounting on a concrete plinth.

Fitted with a hinged lockable door.

Externally painted with two layers of antirust undercoat and one final layer of paint suitable

with the specified environment.

Input Unit:

The transformer-rectifiers will be connected through ON/OFF fuses - switch lockable

either in ON or OFF position.

The power outage and the insulation will be conforming to the IEC standard.

Output Regulation Device:

Output regulation device shall be provided to allow for a load variation of the output. The

variation can be done incontinues method by manual volumes. Manual regulation

control shall be easily accessible on control panel.

Bridge Rectifier:

The bridge rectifier will be of SCR which reverse tension must be of 1200 V as minimum.

Measuring Instruments:

The measuring instruments will be having built - in type, different dimensions.

The range of measuring instruments will be such that the maximum working value is

indicated at 70% of full scale deflection.

The ammeter will mounted in parallel to a calibrated to a suitable shunt.

The voltmeter will be protected withsuitable fuses.

A red line will indicate the maximum output value. The measuring instruments will be

located inside thecontrol part of T/R cubicle in front face.

Electrical Protection Devices:

Against Over Voltages

Resistance capacitor circuit will be connected in parallel to the bridge rectifier. An

arrester will be connectedbetween the plus and minus poles of the T/Rectifier.

Against Over intensities

Ultra-fast fuses suitably dimensioned in 12.t will protect the A.C. and D.C. circuits.

Personnel Safety

PVC caps will avoid direct contact with the different poles and instruments.

Earthing

All metallic parts will be electrically continuous and one earthing terminal will allow their

connection to an externalcircuit.

Accessories:

The transformer - rectifiers will be supplied complete with all necessary accessories for

installation, control and operation.

Oil control

The oil tank part will be fitted with a dial thermometer calibrated in degree centigrade

and located in a pocket at thenormal oil level.The oil level inside the tank will be

controlled tanks to a sight glass gauge externally located in thefront of the cubicle

which will be protected against the shocks by a hinged flipper marked "LEVEL"

6 7

Fittings

For handling, two lifting rings will be foreseen at the top of the cubicle.To maintain a dry

atmosphere in the T/Rectifier, an external and removable silicagel cartridgewill be mounted on the

tank inside the control part. For incoming and outgoing cables, weatherproofpacking glands will be

foreseen just in front of the terminals on the control part.

Time Switch:

This equipment is intended to measure interferences between two pipelines catholically protected

or not and coatingresistance value of the pipeline.The time switch will be composed of:

Two adjustable time relays. a selector switch connected to the mains supply.The time switch will

enable a continuouscycle of 2 minutes ON and 3 minutes OFF. It will be dimensioned according to

the T/R characteristics.

Factory Tests:

The transformer - rectifiers will be tested according to the IEC standards tests method. The

following routine testsshall be carried out on each unit.

Measurement of inherent regulation.

Insulation test.

Power loss measurement.

Power faction measurement.

Temperature rise test.

Load test at different steps.

Ratio and polarity test.

For type tests, factory test report may be

acceptable.

Ultra-fast fuses suitably dimensioned in

12.t will protect the A.C.and D.C. circuits.


High silicon Iron Anode

Silicon iron anodes are designed for the effective protection of steel structures and pipelines

from corrosion by the impressed current method. They are manufactured from high silicon

cast Iron alloy, one of the most important anode materials used by the corrosion engineer to

protect steel in a variety of situations. Three types of this anode are available, according to

standard ASTM A518 M.

Chemical Composition

Consumption Rate

Chemical Composition (Wt %)

1 0.65-1.1 0.5 Max 0.5 Max 0.5 Max Reminder

2 0.75-1.15 3.25-5.0 0.4-0.6 0.5 Max Reminder

3 0.7-1.1 3.25-5.0 0.2 Max 0.5 Max 1.5 Max. Reminder

Grade

C Si Cr Mo Cu Mn Fe

14.20-14.75

14.20-14.75

14.20-14.75

EnvironmentCurrent DensityA/M2 ConsumptionRate

Kg/A.Year

Fresh Water 10 0.11

Sea Water 15 0.31

Sea Water 200 F 10 0.41

Buried Sea Water/Sand 8 0.68

Carbonaceous Backfill 15 0.1

1.5 Max.

1.5 Max.


8 9


Physical Property of Silicon Iron

Properties Unit Test Method (ASTM)

Density g/cm3

Approved Method

Hardness (Min) HB E 10

Compressive Strength (Min) Mpa A 256

Electrical Resistivity (Max) µΩ.cm

B 193

Impact Resistance (Min) J A 327 (Charpy Type)

Re quire ment

7-7.05

500

650

72

0.1

Silicon Iron anodes are cast in several shapes and size to meet a variety of requirements.

The following table shows details of the range available.

Size of Anode:

Rod Type

Diameter (mm) Head Diameter(mm) Net Weight (kg)

51 76

14.5

51 76 19

51 76 22.5

76 102

29

76 102 38

Lengh (mm)

915

1220

1525

915

1220

76 102 1525 49

Tubular Type

Inside Diameter(mm) Outside Diameter(mm)Length(mm)

67 47

1067

56 36 2134

67 47 2134

95 75

2134

121 100 2134

Thickness(mm)

10

10

10

10

10

121 86 17 2134

14

21

29

39

50

79

Net Weight(kg)

2.1Mixed Metal Oxide (MMO) Anode

Mixed Metal Oxide Ribbon Anodes (Protection For Above Ground Tank Bottoms)

Cathodic protection is an economical method for controlling corrosion on aboveground storage

tank bottoms. While sacrificial systems can be used, impressed current designs have proven to

be more cost effective and easier to install. The anodes are composed of a titanium ribbon

substrate coated with a mixed metal oxide catalyst. Because the titanium substrate is naturally

passivized by an oxidizing film, the ribbon anode remains dimensionally stable over time.

Direct current transfer is accomplished through the mixed metal oxide catalyst which is highly

conductive, and fully oxidized so that higher current outputs are possible.

This two part composition allows for a

maximum current density of 5.0mA/ft to

achieve a 50 - 100 year design life. Spacing

between the metal anode strips can be

adjusted to achieve various design life

requirements. The anodes can also be easily

cut so that placement may be made under all

areas of the tank. Because the strips are

electrically continuous, multiple paths are

available for current flow. This in turn lowers

the driving voltage required for protection, and

provides the anode with redundant electrical

connections for increased reliability. Greater

dependability is also achieved through the

elimination of field splices.

They are manufactured from cross-linked polyethylene and shrink fitted over the anode. The

dielectric strength of the end caps is 10 kV per mm.

Anode Cap

Anode caps may be factory fitted to cabled anodes. They are designed to counteract, and

effect, when single end anode connections are specified. The caps have protective

polymeric lining capable of withstanding corrosive environmental conditions including

chlorine and Sulphate attack.


10 11

To obtain the highest level of protection from an impressed current cathodic protection system, you need

an anode with a very low consumption rate and high current capacity. With tubular mixed metal oxide line

of anodes, you get powerful protection and unsurpassed stability. The anodes are made using tubular

titanium substrates which are coated with a mixed metal oxide catalyst.

The catalyst is thermally applied to the titanium to form an extremely chemical resistant bond. This

special composition brings together the stability of titanium with the conductive properties of the mixed

metal oxide catalyst to achieve superior performance. In soil and fresh water applications, the anodes 2have a recommended current density approximately 100Amp/m , and can be operated over 500Amp/

2m in sea water environments. Even at these relatively high discharge levels, the anodes will be

consumed at less than 1.0 mg/A.year.


Chemical Composition

Substrate

ASTM B-265 Grade 1 Titanium

Catalyst

IrO +Ta O2 2 5

Nominal Dimensions

Anode Ribbon

Component

Anode Ribbon

Conductor Bar

0.25 6.4

12.7

12.7

0.5

0.5

0.025

0.025

0.40

0.6

0.6

1.0

mmInchInch mm

Width Thickness

Mixed Metal Oxide Tubular Anodes (Dimensionally Stable in All Environments)

The tubular style also means lead wire

connections can be made in the center of

the anode. With tubular anodes, this

connection consists of a brass wedge

connector which grips firmly to the internal

circumference of the anode.

This connection is protected from moisture

intrusion by a waterproofing sealant which

fills the entire anode tube. One end of the

anode is then covered with shrink tubing

for a completely sealed electr ical

connection. Anodes are then tested for

quality assurance.

Standard Dimension and Shipping Weughts

Anode Type

Nominal Dimension Nominal WeightCurrent

Rating*Diameter Length Bare Packaged

KPK 01

KPK 02

KPK 03

KPK 04

Inch mm Inch mm oz/ft g/m Ibs kg Amper

Based on 20 year design life in calcined petroleum grade coke

2.6

5.1

11.1

16.9

10.5

11.7

11.4

12.3

23314

317

351

538

25

25

27

3.4

3.4

3.8

3.8

610

1219

1000

1219

2.0

4.0

3.3

4.0

10.10.75

19.10.75

25.41.0

31.81.25

The tubular design of these anodes also

allows for numerousperformance benefits.

The tubular configuration provides a larger

surface area which in turn permits greater

current output and lower anodetoearthe

resistance.

Mixed metal oxide ribbon anodes are designed for use on

both newly constructed aboveground storage tanks with

secondary containment liners, and existing tanks utilizing

double bottom construction. Unlike other impressed

current tank bottom anodes, ribbon anodes do not require

coke breeze. They can be used in sand with various levels

of moisture and salt content, and can be designed to

provide effective protection for 50 years or more.


12 13


Sacrificial Anode Cathodic Protection

Type1 Less than 10mm 100%

Greater than 1 mm 90%

Type 2 Less than 3 mm 100%

Greater than 0.5 mm 90%

Type 3 Less than 1.0 mm 100%

Less than 0.6 mm 80%

Greater than 0.4 mm 90%

Greater than 0.15 99%

mm

Coke Breeze .2.1

Coke breeze is used for backfill in vertical, horizontal and well ground bed.

Advantages of backfill are:

Preventing from direct contact anode with soil (a

Increase anode dimension to decrease anode resistance (b

Decreasing resistively around anode (c

Providing uniform environment around anode (d

Physical Property of Silicon Iron

Properties of coke Type 1 Type 2 Type 3

Carbon Content (%Min.)

Moisture Content (%Max.)

Ash Content (%Max.)

Sulphur Content (%Max.)

Volatiles Content (%Max.)

3Density (kg/m )

80

5

15

1

5

650-800

90

5

5

5

5

700-1100

95

1

3

1

1

1050-1200


14


3.1. Sacrificial Magnesium Anode

Magnesium anodes are used seldom in cathodic protection with more than 10 years life design.

These anodes are not used in soils with high resistivity because drain of necessary current density

needs large amount of magnesium and it is not economic.

Chemical Composition (According to ASTM B 843)

Capacity = 1230 Ahr/kg

Anodes used in land shall be backfilled to reduce resistance and moisture absorption.

Specifications of anode backfill are as follow:

Powdered Gypsum: 75%

Granular Bentonite: 20%

Sodium Sulphate: 5%

Also cables for anode connection shall be made from copper and XLPE or PVC insulation coat.

3.2. Sacrificial Aluminum Anode

Aluminum anodes are one type of sacrificial anodes in cathodic protection systems that are

used generally in offshore industries for metals corrosion protection.

CHEMICAL COMPOSITION

The chemical composition of anodes is as follow according to DNV RP B401 standard:

ELECTROCHEMICAL BEHAVIOR

According to DNV RP B 401 standard, the electrochemical properties of aluminum anode

shall be as follow:

Minimum Electrochemical Efficiency: 2500 Ahr/kg. ·

Minimum Open circuit potential: -1.05 V respect to Ag/AgCl Reference Electrode. ·

Minimum closed circuit potential: -0.8 V respect to Ag/AgCl Reference Electrode. ·

WEIGHT PERCENTELEMENT

Al

Zn

Cu

Si

Fe

Mn

Pb

Mg

Other impurities, each

Total other impurities

5.3-6.75

2.5-3.5

0.08 Max

0.3 Max

0.005 Max

0.25 Max

0.03 Max

Reminder

----

----

Element

Fe

Si

Cu

Zn

In

Others

Al

Weight Percent

0.09 max

0.12 max

0.003 max

2.5-5.0

0.015-0.040

0.02 max

Remainder

These are used when necessary current is low, soil

has low resistivity, and or when input current source

for transformer rectifier is not available.

Magnesium anodes have an advantage and it is

better and simpler current distribution than

impressed current system due to current drain in

small field.

There is over protection near drain point that is

causes current lose. Consequently, Current lose

can be minimized by proper control


16 17

Natural potential deference between zinc and steel produces an electrochemical cell and naturally

corrosion protection consequently. Zinc metal in this process is as an anode. Zinc anodes are used

generally in offshoreindustries due to protection voltage that is produced between zinc and steel.

These anodes are used in tankersand floaters generally.

Zinc anodes are produced in Karpira Kavir Company in deferent sizes and shapes.

Chemical Composition (According to DNV RP B 401)

Electrochemical Properties: (According to DNV RP B 401)

Cathodic Protection Equipment

Element Weight Percent

Aluminum

Cadmium

Iron

Lead

Copper

Zinc

0.1-0.5

0.07 Max

0.005 Max

0.006 Max

0.005 Max

Reminder

Zn-basedseawater 780 -1.00

sediments 700 -0.95

Recommended design electrochemical capacity and design closed circuit

potential for anode materials at seawater ambient temperatures

Anode MaterialType

Environment Electrochemical Capacity(Ah/kg)

Closed Circuit Potential(V)


3.3. Sacrificial Zinc Anode


18



4.1. Positive and Negative Bond Boxes

The standard bond box is designed for basic cable connections that do not require shunts or resistors,

and contains only terminallugs. They are provided in various sizes to accommodate numerous types

of wires. The non-conductive panels are resistant towarpage and weathering. Positive and negative

bond boxesshall be as per standard and meet the requirements of climatic conditions.The boxshall be

made of 3 mm thickness sheet steels and the degree of protection shall beIP-55.After assembly of test

box to mounting pipe & prior to installation, all steel partsshall be painted with following procedure:

a) Surface preparation to sa2 1/2.

b) One red lead primer (70microns).

c) One intermediate coat of alkyd paint (100 microns at least)

d) One finishing coat of alkyd glossy yellow color paint (100 microns)

(Total thickness of painting 270 microns at least)

4.2. Cathodic Protection Cables

CONDUCTOR

The conductors shall be plain annealed stranded copper. Stranding shall be circular(noncompacted).

The material shall be copper of such quality and purity that the finished product shall have the

properties and characteristics prescribed in IEC Publication 228 Class 2, or ASTM specification B8

Class B. Conductor sizes, as will be specified by the Purchaser, shall be in accordance with one of the

designations listed in Table 1 to achieve the resistance value required:

TABLE 1 – Physical Properties of XLPE/PVC Cables

The size, cross-sectional areas, and direct

current resistance of the conductor in the

completed cable is conformed the minimum and

maximum values al lowed by the above

referenced standards.

Single Core Plain annealed copper conductor,

XLPE insulated / PVC extruded bedded / steel

wire armoured / PVC sheathed. 600 / 1000 volts

grade to BS5467.

TABLE 2 – Physical Properties of XLPE / PVC / SWA / PVC Cables

Nominal CrossSection

Nominal InsulationThickness

Nominal SheathThickness

Approx. OverallDiameter (mm) Approx. Weight Maximum Resistance Of

Conductorat 20°C

4 mm²

6 mm²

10 mm²

16 mm²

25 mm²

35 mm²

50* mm²

70 mm²

95 mm²

0.7 mm

0.7 mm

0.7 mm

0.7 mm

0.9 mm

0.9 mm

1.0 mm

1.1 mm

1.1 mm

1.4 mm

1.4 mm

1.4 mm

1.4 mm

1.4 mm

1.4 mm

1.5 mm

1.6 mm

1.6 mm

6.8 mm

7.4 mm

8.3 mm

9.3 mm

11.0 mm

12.2 mm

14 mm

16 mm

18 mm

77 kg/km

100 kg/km

144 kg/km

207 kg/km

305 kg/km

406 kg/km

560 kg/km

770 kg/km

1015 kg/km

4.52 Ω/Km

3.02 Ω/Km

1.79 Ω/Km

1.13 Ω/Km

0.712 Ω/Km

0.514 Ω/Km

0.379 Ω/Km

0.262 Ω/Km

0.19 Ω/Km

Nominal Cross-Sectional Area

Number of StrandsApproximate

Overall DiameterApproximate

Weight (Kg/Km)

16

25

35

50

70

95

120

7

7

7

7

19

19

19

13.5

15.3

17.4

19.1

21.1

23.4

26.3

435

575

805

1010

1210

1620

2100

INSULATION

Cable insulation shall be made from materials chemically and physically resistant to the

environmental effects to be anticipated in buried or submerged service. It shall provide

continuous coverage, adequate dielectric properties, and have a high resistance to

abrasion, stress cracking and notch propagation. The insulation shall be one of the types

listed asbelow. The insulation shall be applied tightly to the conductor without adhering to it

and shall form a compact and homogeneous body.

The sheath (jacketing) shall be an extruded layer of the types listed as below. The sheath

shall be continuous having a thickness as uniform as possible and not less than the values

specified. It shall be possible to remove the sheath of the cable without damaging the

insulation of the conductor. Cable insulation (primary insulation and sheath) shall be

completely free of cracks, nicks, scratches, or other discontinuities. Cable insulation shall

have a voltage rating of 600/1000 Volts in accordance with National Electrical Code.

The types of insulation and sheath compound covered by this Part of Standard specification

are listed below.

20 21

Polyvinylchloride (PVC)

Insulation and sheath compound based on polyvinylchloride or copolymer of vinyl chloride and vinyl

acetate conforming to ASTM specifications D 2219 (as Insulation) and D 1047 (as Jacketing).

High molecular weight polyethylene (HMWPE)

Insulation and sheath compound based on thermoplastic polyethylene conforming to ASTM

specifications D 1351 (as Insulation) and D 2308 (as Jacketing).The polyethylene before application

to the conductor (or cable) shall comply with the requirements of ASTM specification D 1248 for

type I, Class A, B, or C; category 5; grade E5 or J3.

Cross-Linked polyethylene (XLPE)

Insulation compound based on chemically cross-linked polyethylene conforming to ASTM

specification D 2655. The base polymer of this insulation consists substantially of polyethylene or a

polyethylene copolymer.

Polyvinylidene fluoride (PVDF)

Insulation compound based on especially chemical-resistant modified polyvinylidene fluoride

conforming to ASTM specification D 3144.



Cadweld mould

Cadweld mould is in two types of horizontal and vertical connections of cable to the pipe.The

size of mould depends on the size of cable which will be connected.

Ignition Gun

To ignition the powder for beginning of the welding process the operator uses an ignition gun.

The packing material ofthe welding cartridge will prevent the ingress of moisture. The size of

welding cartridge fits into the holder to be used.

Thermit Welding

The complete Thermit welding (Cadweld) kit includes cadweld powder and other accessories like

cadweld mould,ignition gun and…

Cadweld Powder

This part specification covers the minimum requirements for the supplyof Thermit weld(cadweld)

powder for connection of cathodic protection leads to new or in-servicesteel pipes by Thermit welding

process. The Thermit weld powder for all welds of coppercable to steel pipe irrespective of cable size is

variable due to the cable size. Each cartridgepowder charge shall be enclosed in a separate

polyethylene tube with ignition powder atthe bottom or separate. The ignition powder has special

degree for ignition.The materialshall be of such quality and purity that when applied, produces strong

and permanent highconductivity connection. The material shall meet the initial properties after storage

forat least 3 years from the date of delivery at normal storage conditions.

Overall:

Plastic sheet:

Sheet thickness:

Plastic dome:

Adhesive thickness:

Weight

Application temperature

Service temperature

Shelf life

4" x 4"

2.75" x 4" (serrated)

10 mils

1.625" dia, 0.8" height

165 mils

2.1 oz

-20 to +120°F

-40 to + 185°F

Rotate annually

Dim

ensio

ns

22 23

Usage

-Unprotected pipe

-Insulated flange

-Catholically protected pipe

-Insulated copper wires connecting zinc anodes & pipeline

-Two 60" zinc anodes separated by isolation spacers

-Low resistance backfill surrounding zinc anodes

Features

-Two anode units available

-Pre-packaged for easy installation in study cardboard tubes with wood ends

-Zinc anode composition conforms to ASTM B-418-01, Type I & II.

-Low resistivity backfill, 75% gypsum, 20% bentonite, 5% sodium sulfate



PermanentCopper/Copper Sulfate Reference Electrodes

The cell is pre-packaged in a cloth bag containing a low-resistance backfill material, and is completely

assembled and ready for immediate installation.

Plastic positioning pins on the cell assure that a sufficient amount of the backfill will exist around the

cell's electrical contact point. Because of this, a low-resistance groundbed can be created simply by

watering the area surrounding the cell. Lead wire connections to the cell are made, wire containing any

designed cable insulation (mostly 10sqmm PVC insulated). The length of the wire is depending of the

location of cell installation.

Reference electrodes are normally used for measuring structure/electrolyte potentials, or as sensing

electrodes for control system.

Portable Copper/Copper Sulfate Reference Electrodes

Reference electrodes provide accurate and reliable potential measurements on buried metallic

structures. Theirplacement in close proximity to protected structures permits readings which are more

exact and less affected byfluctuating soil conditions than those obtained by portable cells. Long-life

performance is achieved through a ruggeddesign, which includes impact resistant PVC tubing. The

tubing houses a 99.99% pure copper element and a supersaturatedsolution of copper sulfate. The

copper sulfate mixture ensures that the copper element remains electricallystable, so that the cell's

potential value will not fluctuate. From this special composition, the cell achieves a minimumdesign life

of fifteen years, and maintains an accuracy level of ±5 millivolts.

Zinc earthing cell dimension:

TypeDimension of each electrode (mm)

Each electrode

weight(kg)

Approx-gross

weight (kg)

I 1500 40 40 17 60

II 950 50 50 17 60

III 600 20 20 27.3 100

IV 300 50 50 5.5 20

length wide height

Zinc Grounding cells

Pre-package zinc grounding cells

provide positive, long-life protection

wherevervoltages must be limited in

underground metallic systems to

reduce danger of shockor arcing &

burning of insulated joints.Typical

grounding installations include oil, gas

&water pipelines, power stations, oil

storage tanks & transmission line

towers & cables.

24 25

corrosion and cathodic protection phenomena · 2018-03-14 · cathodic protection systems are most...

Documents