Edo-wms-coe-cor-Int-xxx-014-247-275-Rev-d-methode Statment of Cathodic Protection System _thermal Zinc or Aluminimum Alloys Spraying _ of Concrete Surfaces

A 12.07.2012 ISSUED FOR INFORMATION A.G. E.D. E.D.

Rev. Date Description Prepared Checked Approved

No.

ORIGINATOR

(LISCO ) MISURATA -LIBYA LIBYAN IRON AND STEEL COMPANY

TML CONSTRUCTION CO. INC.

Document Title

METHODE STATMENT OF CATHODIC PROTECTION SYSTEM (THERMAL ZINC OR ALUMINIMUM ALLOYS

SPRAYING ) OF CONCRETE SURFACES PALMIYE MAH. ADNAN MENDERES BULVARI OKTAY SITESI NO: 6 KAT 8 D:17 PK-33100 YENISEHIR –MERSIN –TURKEY Phone :+90.212 643 62 26 Fax :+90.212 643 62 22

Document No.

EDP WMS ECR COR EPC XXX 013 XXX Rev

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Co. Org. Cod

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Disc. Code

Unit Code

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Prj.

NO

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Year DCC

Seq.No Page 32

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Project:(Title) REHABALITASTION PROJECT OF REINFORCED CONCRETE DECK OF HARBOR BULK BERTH NO:1 AT MISRATA

Prj. Identification:

Document Title: (Subject)

METHODE STATMENT OF CATHODİC PROTECTION SYSTEM (THERMAL SPRAYIN ZINC OR ALUMINIMUM ALLOYS ) OF CONCRETE SURFACE

Document No.:

EDO-WMS-COE-COR-INT-XXX-014-247-275-REV-D-METHODE STATMENT OF CATHODIC PROTECTION SYSTEM (THERMAL ZINC OR ALUMINIMUM ALLOYS SPRAYING ) OF CONCRETE SURFACES

Revision: A Date: 13.07.20130.

TABLE OF CONTENTS

1 KAPSAM .............................................................................................................................................. 3

2 STANDARTLAR ................................................................................................................................ 6

3 CORROSION OF REINFORCED CONCRETE AND ITS CATHODIC PREVENTION AND PROTECTION .......................................................................................................................................... 8

3.1 CONCRETE ......................................................................................................................................... 8 3.2 CORROSION OF STEEL REINFORCEMENT IN CONCRETE ............................................................... 8 3.3 THE SOURCE OF CHLORIDE IN CONCRETE ..................................................................................... 9 3.4 CHLORIDE THRESHOLD FOR REBAR CORROSION ........................................................................ 10 3.5 CATHODIC PREVENTION AND CATHODIC PROTECTION .............................................................. 11 3.5.1 CATHODIC PROTECTION IN AQUEOUS MEDIA ................................................................................ 11 3.5.2 CATHODIC PREVENTION AND PROTECTION IN CONCRETE ............................................................. 12 3.5.3 CATHODIC PREVENTION ................................................................................................................ 13 3.5.4 BEHAVIOR OF CONCRETE DURING CATHODIC PREVENTION AND PROTECTION ............................. 14 3.5.5 CATHODIC PREVENTION VERSUS CATHODIC PROTECTION ............................................................ 14 3.6 SACRIFICIAL ZINC ANODES FOR THE PROTECTION OF STEEL REINFORCEMENT IN CONCRETE

15 3.7 CATHODIC PREVENTION AND PROTECTION CRITERIA ................................................................ 16 3.8 REFERENCES ................................................................................................................................... 17

4 THERMAL SPRAYED ZINC/ALUMINIUM COATING AS ANODES .................................... 19

5 CATHODIC PROTECTION SYSTEM SITE SURVEY AND ENGINEERING WORKS ....... 21

5.1 CONCRETE REPAIR STRATEGY (EN ISO 12696:2012 SECTION 5 AND OTHERS) ......................... 21

6 THERMAL SPRAYED ZINC/ALUMINIUM COATING APLLICATION .............................. 27

7 PROCEDURE USED IN WORK SHOP TEST ............................................................................. 34

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1 KAPSAM

Bu döküman, PMAC - Port & Maritime Affairs Corporation. tarafından işletilen ve Hodeidah Limanın iskele çelik kazık ayakları , betonarme yapılarının korozyonu ve mevcut durumunun tespiti için hazırlanacak yapılacak olan inceleme sürecini , raporlama metodolojisini detaylandırmak için hazırlanmıştır

Limanın özellikleri aşağıda verilmiştir.

The port of Hodeidah consists of 8 berths to accommodate vessels up to a maximum draft of 32 feet ( 9.75 mtrs ) and an LOA of 200 mtrs. The port provides 11 sheds totaling 21000 sq.mtrs., 1 million sq.mtrs open storage and 300,000 sq.mtrs. for the container terminal.

The port is equipped with 1 x 3500 hp tug, 3 x 2500 hp tugs for the assistance in berthing of vessels plus 2 line boats of 750 hp. There are fresh water facilities alongside but no bunker facilities. Diesel oil bunkers can be arranged via road tanker.

Berths numbered 1 to 5 are the general cargo and bulk grain berths. These berths are equipped with 6 rain mounted shore cranes of 3 tons swl.

Berths numbered 6 and 7 are the container terminal berths equipped with two rail mounted gantry cranes of maximum 30 tons capacity.

Berth No. 8 - is a general cargo berth however has limitations in draft forward and LOA.

Tanker berths: Yemen Petroleum Co berth - this is a dolphin berth for the discharge of clean products only. This berth is situated within the port itself and is limited to tankers of maximum

15000 dwt and an LOA of 150 mtrs and beam of 23 mtrs. The draft alongside the berth is dredged to 10 mtrs however the tanker's draft is limited to 9.75 meters for the channel

Çalıimada , limanın betonarme yapısının rehabilitasyonu için uygulanması gerekli çalışmalar , mevcut durumun tespiti , çelik kazık ayakların mevcut durumunun

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tespiti , mevcut varsa katodik koruma sistemine dair ölçümler yeni sistemlerin nasıl nasıl uygulanacağına dair metodoloji içerecektir.

Dökümanda deklare edilen süreç , ffilen sahada yapılacak çalışmalara sırasında değişiklikleri de içerebilir.

Limanın koordinatları

Latitude: 14° 55' 0" N Longitude: 42° 53' 59" E

Ve aşağıdaki sorulara cevap verilmiştir.

Şekil 1: View of Hodeidah Port

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Şekil 2:View of Hodeidah Port

Şekil 3:VieW of Hodeidah Port

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Şekil 4:View of Hodeidah Port

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2 STANDARTLAR

Bu döküman hazırlanırken aşağıdaki standartlardan yararlanılmıştır.

BS-7361 Part 1:1991 Cathodic Protection Standard DET NORSKE VERITAS (DNV ) recommended practice det norske veritas

dnv-rp-b401 cathodic protection design BS EN 12495 Cathodic Protection for Fixed Steel Offshore Structures NACE RP0387-99 Metallurgical and Inspection Requirements for Cast

Sacrificial Anodes for Offshore Applications. DIN EN ISO 2063- Thermal spraying .Metallic and other inorganic

coatings .Zinc, aluminum and their alloys ISO 12696-2012- Cathodic protection of steel in concrete BS EN 1504-9 Products and systems for the protection and repair of

concrete structures - Definitions, requirements, quality control and evaluation of conformity.

EN ISO 14919 Wires, rods and cords for flame and arc spraying BS EN 12696: 2000 Cathodic Protection of Steel in Concrete BS EN 12954: 2001 Cathodic Protection of Buried or Immersed Metallic

Structures-General Principles and Applications for Pipelines EN 13509: 2003 Cathodic Protection Measurement Techniques NACE TM 0190 Standard Test Method for Impressed Current Test Method

for Laboratory Testing of Aluminium Anodes ASTM B418 Anodes (Cast/wrought galvanic zinc)

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3 CORROSION OF REINFORCED CONCRETE AND ITS CATHODIC

PREVENTION AND PROTECTION

3.1 Concrete

Concrete and steel are ideal combination to withstand both “tensile” and

“compressive” forces as well as to prevent the corrosion of steel embedded in it.

Concrete is a mixture of cement and aggregate and has been efficiently used in

construction industries for centuries [3.1]. Concrete, beside the aggregate it

contains, is composed of hardened unhydrated and hydrated Portland cement.

Hardened cement (cement paste) is not only micro porous (pore size in 2 nm

region with about %28 porosity) but also composed of pore solution which is

alkaline in nature. Hydration of cement is a continuing process and with time,

hydrated cement fills the macro voids between aggregate particles. However if the

ratio of “mixing water” to “cement” is high, some voids (capillary pores) still

remains in the concrete. Therefore two main type of porosity could be defined in

concrete:

a) the pore space that exist as ultra-fine gel pores in the hydrated cement

b) Capillary pores, larger voids, in the cement paste.

Water, liquids, air and the other gases diffuses through the pores of the concrete

if concrete is surrounded with such an environment. However if the pores are

filled with stagnant solutions (water or others) diffusion of gases are partially

prevented [3.2]

It is well documented that the pH of the gel solution in concrete is close to 13.

Concrete pH is influenced by several factors such as alkali content of the cement,

and the richness of the cement in concrete.

3.2 Corrosion of Steel Reinforcement in Concrete

Structural steels when buried in concrete are exposed to high pH environment in

which they easily passivity and are covered with a protective layer [3.3]. Until the

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protective layer is destroyed, steel reinforcement in concrete is protected against

the corrosion by the passive layer covering its surface. As it is well known, in

neutral and alkaline aqueous environment, oxygen dissolved in water is

responsible from the corrosion of metals. For rebar in concrete environment,

water reaching the surface of rebar following its diffusion through the concrete

cover does not cause corrosion if rebar surface is in passive state.

Passivity of steel is destroyed either by acidification of the concrete around the

rebar (for example by carbonation) or by some ions; among them chloride ions

being the most prominent.

Several theories exist on how the passive layer is destroyed by chloride ions [3.4].

The end result is the exposing of the metal surface to the corrosive action of the

dissolved oxygen in solution filling the concrete pores. Anodic areas on the steel

surface further attract the negatively charged chloride ions hence increasing its

local concentration. Corrosion products (oxides and oxyhyroxides) with their

increased volume crack the concrete cover permitting further ingress of chloride

ions as well as the oxygen containing water into the concrete.

3.3 The Source of Chloride in Concrete

The sources of chloride in concrete may vary; mixing water and chloride

containing aggregates are two most important ones. However the chloride in the

environment is another most important source. Part of the chlorides present

during concrete mixing may be chemically bound and become inactive. Chloride

entering the concrete from the surrounding environment following solidification

stays always free and causes the depassivation of steel.

Therefore diffusion and or entry of chloride and oxygen containing water are the

two most important processes that control the corrosion of rebar in concrete.

Diffusion of chloride in concrete is quite well documented [3.5]. Recently works on

modeling of chloride ion, oxygen and water movement are also attracting attention

[3.6, 3.7],

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3.4 Chloride Threshold for Rebar Corrosion

Depassivation of steel in concrete starts if its chloride content is more than a

“threshold” level. However there are not universally agreed threshold values.

Chloride that causes depassivation is free, namely water soluble chloride.

However because acidification may release chemically bound chloride also, some

codes specify not only water soluble but acid soluble chlorides levels.

It is well known that the effect of chloride on passive layer depends on the

alkalinity (OH-) of the concrete. Hausman [3.8] claimed that Cl-/OH- greater than

0.6 depassivates steel. However based on data of Gouda [3.9], Diamond [3.10]

had claimed that at high pH threshold level is approximately 0.3.

Various national codes had given various chloride threshold values as a

percentage of cement in both reinforced and pre-stressed concrete. The threshold

chloride level varied widely from code to code .

Figure.3,1 shows the result of a quite recent investigation [3.11] regarding the

chloride threshold values for reinforced concrete.

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FIGURE 3.1 : Risk of corrosion initiation in reinforced concrete as a function of chloride concentration [3.4].

3.5 Cathodic Prevention and Cathodic Protection

Among the several approach to either prevent or stop the corrosion of steel

reinforcements in concrete the most successful and the sure method appears to

be “the cathodic protection” [3.12]. However steel being embedded in a high

resistivity media such as concrete and concrete embedded in again high

resistivity soil bring forth the problem of ”how one can be sure that the steel is

protected catholically?”

3.5.1 Cathodic protection in aqueous media

Corrosion is a complex phenomenon governed not only by the properties of

corroding metal and corrosion inducing environment but also by cathodic and

anodic reactions taking place at the metal surface and the thermodynamic and

kinetic parameters influencing the corrosion process [3.13]. Additionally, all those

parameters could change with time, making the system even more complex.

Although for a steel piece immersed in an aqueous solution a simple

measurement of the potential of the metal can accurately indicate the degree of

cathodic protection, for “pre-stressed steel embedded in concrete mortar buried in

high resistivity soil” no simple answer exists.

In aqueous solutions the potential of a corroding metal could be changed in two

directions. It can be made more negative or more positive. By moving the

potential of dissolving metal towards more negative values, the rate of dissolution

could be decreased. Because dissolution of metal (anodic reaction) is usually

controlled by the electron exchange rate at the metal-solution interface, the

relation between the anodic (corrosion) current and the potential change follows

logarithmic Tafel Law.

Therefore if the potential of a corroding metal is shifted towards negative values

for one Tafel slope, the rate of reaction decreases by %90. Further decrease of

the potential for another Tafel slope decreases the corrosion rate by only another

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%9. One to two Tafel slope shift of the corroding metal potential towards negative

values decreases the rate of corrosion between %90 and %99.

3.5.2 Cathodic prevention and protection in concrete

The Tafel slope of steel in freely corroding and passive state varies between 60

mV and almost infinity [3.14]. Therefore there is no single Tafel slope for a

repassivating steel surface in concrete to guide us to decrease the corrosion rate

by shifting the potential of corroding steel towards more negative (more cathodic)

potentials.

This is because corrosion of rebar in concrete is different than steel corrosion in

aqueous solution. Steel is passive in concrete.

Corrosion of rebar in an alkaline concrete media occurs if the protective passive

layer on rebar is destroyed by chloride ions and rebar is exposed to the corrosive

action of aqueous dissolved oxygen. Steel bar corrodes by pitting (see Figure 3.2)

(3.19). Increasing the chloride ion concentration at the rebar-concrete interface

shifts pitting potential towards more negative values. Applying a cathodic current

to corroding rebar shift its potential to passive region where either pitting initiation

stops but initiated pits still propagates, or to still more negative values where both

pit initiation and propagation stop completely.

Figure 3.2 Schematic illustration of the anodic behavior of steel in the presence of chloride (3.19)

Passive region

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The first case is called “cathodic prevention” and the second “cathodic protection”.

Increasing the applied current further brings the potential of steel into immunity

zone where other reactions such as the reduction of hydrogen ions start.

3.5.3 Cathodic Prevention

The idea of cathodic prevention is extensively investigated by P. Pedeferri and his

co-workers (3.19) and the technique is recognized by “BS EN 12696-2000

Cathodic protection of steel in concrete”.

Figure 3.3 schematically describes both “cathodic prevention” and “cathodic

protection”.

At the region “A” pits initiate because of chloride contamination, at region “B”

initiation stops but pit propagation continues (cathodic prevention region), at

region “C” both pitting initiation and propagation stop (cathodic protection region)

and finally at region “D” which is also an immunity zone for steel, hydrogen starts

to form (overprotection, hydrogen embrittlement region).

Figure 3.3 Schematic illustration of steel behavior in concrete as a function of the

chloride content.

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In a sound concrete with no chloride contamination, rebar potentials are less

negative than -200 mV (SCE). By shifting the potential of rebar from “1” to “2”

pitting initiation is completely stopped (Figure 3.3). The potential of rebar is now

more negative than the pitting potential, namely it is in the passive area (Figure

3.2). However this passivity is imperfect; in other words if a pit already exists in

this region it will propagate but even if the chloride content of the concrete

increases (arrow towards direction”3”) the metal will still be passive and pitting

initiation will not be allowed. All these factors increases the chloride threshold

value at the rebar surface hence prevents its corrosion. Based on the extensive

experience and the tests carried out by P. Pedeferri and his co-workers he claims

that “.. the increase in the chloride threshold brought about by cathodic prevention

in practical application is expected to be sufficient to avoid corrosion initiation

throughout the entire service life” (3.19).

3.5.4 Behavior of concrete during cathodic prevention and protection

Shifting the rebar potential to more negative values also increases the rate of

cathodic reaction around the same area. Cathodic reaction is the reduction of

dissolved oxygen in solution filling the concrete pores and voids and it produces

alkaline OH- ions which further stabilizes the passive film. Because of the excess

negative charge at the surface of the rebar during both cathodic prevention and

protection, negatively charged chloride ions are repulsed from the passivated

metal surface. Using high cement content and low mixing water and therefore

decreasing the pores in concrete substantially decrease and slow down the

ingress of chloride contaminated water into the concrete. Passive protection of the

concrete surface, namely coating it with appropriate paints (example: coal tar

epoxy) further decreases the rate of chloride penetration. All these precautions

further help fulfill cathodic prevention its role of eliminating the danger of rebar

corrosion, if the technique is immediately applied to rebar in sound concrete

before chloride contamination starts.

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3.5.5 Cathodic prevention versus cathodic protection

Cathodic prevention, compared to cathodic protection is achieved with lesser

current densities applied to rebar in concrete. Presently there are no limits for

cathodic prevention current for pre-stressed wires of PCCP buried in soil.

Cathodic prevention current densities given in “BS EN 12696-2000 Cathodic

protection of steel in concrete”(Annex A, A3) is for “atmospherically exposed

concrete”. The works of P. Pedeferri quoted in this report (3.19) is also for

atmospherically exposed concrete which is subject to periodic drying and wetting

hence the penetration of both oxygen containing water and chloride ions are

easier. For example when the same concrete is immersed in sea water, once the

pores are filled with sea water, its high chloride content locally depassivates steel

and corrosion of rebar starts. However once the oxygen around the rebar is

consumed, because the supply of oxygen to rebar surface is quite slow,

corrosion progresses at very low rates. That is why spalling of concrete cover on

rebar is almost never seen in completely sea water immersed reinforced concrete

structures.

The cathodic prevention current densities, 0,2 to 2 mA/m2, quoted in BS EN

12696-2000 is similar to oxygen diffusion limiting current densities for reinforced

concrete structures immersed in sea water (2.20).In the same section (Section

A3) it is clearly stated that: “cathodic protection” current density is approximately

one order of magnitude lower than that required for cathodic protection.” This is

why BS EN 12696-2000 suggests as cathodic protection current densities 2 – 20

mA/m2 for steel surfaces embedded into atmospherically exposed concrete.

3.6 Sacrificial Zinc Anodes for the Protection of Steel Reinforcement in

Concrete

The use of zinc as sacrificial anode to protect the rebar in concrete had both

advantages and disadvantages. Because the free corrosion potential of zinc is

lowest among the existing sacrificial anodes it can hardly shift the potential of pre-

stressed rebar in concrete to negative values where atomic hydrogen is produced

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causing the embrittlement of rebar, more dangerous than metallic corrosion.

However because its driving potential is limited, it may not overcome the

resistance in high resistivity environment hence could not produce sufficient

electrons to decrease the corrosion of protected metal. The recommended soil

resistivity's for zinc sacrificial anodes application are below 15 ohm.m.

3.7 Cathodic Prevention and Protection Criteria

Initially proposed in the fifties the recommendation to shift the potential for 100

mV towards negative values efficiently decreased the rebar corrosion and since

extensively used as “criteria for cathodic protection in concrete”.

Especially laboratory investigations on the validity of 100mV potential shift (or

decay) indicate that the amount of the potential shift for protection is related to the

level of chloride contamination of concrete at the rebar level. Following laboratory

experiments in very heavily contaminated concrete, protection potentials going to

-150 mV or more are recommended [3.16].

In spite of these recommendations extensive survey of cathodically protected

concrete structures indicated that -100 mV potential shift is fully satisfactory[3.17,

] and even in some bridge application, much lower potentials than -100 mV

effectively protected the rebar in concrete [3.18].

Today, there is no single answer to the “protection criteria” question. The aim of

cathodic prevention and protection is to shift the potential of corroding steel

towards more cathodic (more negative) potentials where passive film is stable and

initiation of pits is eliminated hence corrosion is either slowed down extensively or

stopped completely. Therefore “criteria for cathodic protection” should secure

desired decrease or elimination of corrosion of protected metal.

Therefore either the monitoring of the potential change of the protected metal or

the anodic current decrease of the same metal could be used as to control the

effectiveness of cathodic protection. The monitoring of potential being easier it is

a preferred method of monitoring.

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3.8 References

3.1 Mehta, P.K. and Monteiro, P.J.M., Concrete: Structures, Properties, and Materials. Prentice Halls 1993 3.2 Bentur, A., Diamonds S. and Berke, N.S., Steel Corrosion in Concrete: Fundamentals and Civil Engineering Practice, E and FN Spon (Chapman and Hall), London, 1997). 3.3 Pourbaix, M., Atlas of Electrochemical Equilibrium in Aqueous Solutions, Pergamon Press Limited, London, 1976 3.4 ACI 222R-96, Corrosion of Metals in Concrete, ACI Committee 222 3.5 Glass, G.K. and Buenfeld, N.R., Chloride Induced Corrosion of Steel in Concrete, Prog. Struct. Engng. Mater. 2, (2000), 448-458 3.6 Thoft-Christensen P., Deterioration of Concrete Structures , First International Conference on Bridge Maintenance, Safety and Management, IABMAS 2002, Barcelona, 14-17 July 2002 3.7 Maruya T., Hsu K., Takeda H. and Tangtermsinukul S. Numerical Modelling of Steel Corrosion in Concrete Structures due to Chloride Ion , Oxygen and Water Movement. Journal of Advanced Concrete Technology, 1.2. (2003) 147-160 3.8. Hausman. D.A., Steel Corrosion in Concrete, Materials Protection, 6, 11 (1967) 19-22 3.9. Gouda. V.K., Corrosion and Corrosion Inhibition of Reinforcing Steel, I: Immersed in Alkaline Solutions. British Corrosion Journal, 5,9, (1970), 198-203 3.10. Diamond. S., Chloride Concentration in Concrete Pore Solutions Resulting from Calcium and Sodium Chloride Admixtures. Cement, Concrete and Aggregates 8, 2 (1986) 97-102 3.11. BRE Centre for Concrete Construction. Corrosion of Steel in Concrete, Part 2, Investigation and assessment. BRE Digest 444. Watford, UK:Building Research Establishment. February, 2000. 3.12 Chess. P. Gronvold and Karnov, Editors, Cathodic protection of Steel in Concrete, E and FN Spon, London, 1998, pp187 3.13 Jones. D.A., Principles and Prevention of Corrosion, Prentice Hall, NJ, 2.nd Ed. 1996, pp 572 3.14 Glass. G.K., Hassanein. A.M. and Buenfeld. N.R., Monitoring the Passivation of Steel in Concrete Induced by Cathodic Protection, Corrosion Science, 39, 8 (1997) 1451-1458 3.15 Krasnoyarskii. V.V., parameters of Cathodic Protection (Development of the Theory), Protection of Metals, 38, 2 (2002) 157-160

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3.16. Vennett. J. and Broomfield. J:P:, Analysis of studies on Cathodic Protection Criteria for Steel in Concrete, Materials Performance, December 1997, 16-21 3.17 Bennett. J. and Turk. T., Criteria for the Cathodic Protection of Reinforced Concrete Bridge Elements, SHPR-3-359, Strategic Highway Research Program NRC, Washington DC, 1994, pp 14 3.18 Haldeman CH. And Schreyer. A., 10 Years of Cathodic Protection in Concrete in Switzerland, Eurocorr 97, European Federation of Corrosion Event No 208, Trondheim, Norway, 22-25 september 1997, Volume I, pp 533-563 3.19. Bertolini L., Bolzoni F., Pedeferri P., Lazzari L., and Pastore T., Cathodic Protection and Cathodic Prevention in Concrete: Principles and Applications, J. of Appl.Electrochemistry, 28,(1998), 1321-1331.

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4 THERMAL SPRAYED ZINC/ALUMINIUM COATING AS ANODES

In principle, sprayed zinc /aluminum coating can be applied in two different

cathodic protection systems:

1-As galvanic corrosion protection by sprayed zinc/aluminum coating with

reprofilling: The application of the zinc/aluminum coating is possible when either

no spalling of the concrete has occurred or spalling have been repaired. This

variant allows the flow of current between the electrodes to be determined. A

conditional currents regulation is also possible through the arrangement of

resistances. A reduces protection of the reinforcement, however is possible in

case of too low concrete conductivity. That is the reason why system of this type

only works in atmospheres offering sufficient humidity and a high temperature.

This variant , however offers the option of a retrofit with an artificial current supply

so that installation of this type can also be operated as impressed current system

2- As impressed current system with sprayed zinc /aluminum coating : In

such a system the concrete repro filling is the first step . The cathodic corrosion

protection effect does not arise from the potential difference between the zinc

/aluminum anode and the protected reinforcing steel but from the feeding of and

electric potential by means of an appropriately arranged power supply.

The substantial differences of the three above -mentioned system are compared

in table -4.1

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Table-4.1 Characteristics of difference cathodic corrosion protection concepts..

The three variants are suitable for use under humid conditions , e.g. in changing

water and spray water zones. In principle, an investigation has to be made for

every application whether an external power supply is required. Optimal condition

for the operation without impressed current is in regions without long dry periods,

such as coastal areas or tropical regions.

The decision whether or not a galvanic system with/without electrical insulation

between both electrodes has to be designed depends on the area of spalling on

the concrete structure.

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5 CATHODIC PROTECTION SYSTEM SITE SURVEY AND ENGINEERING

WORKS

Söz konusu projede , beton yüzeyine galvanik anotlu bir katodik koruma sistemi

termal zinc/aluminyum kaplama yapılması metoduna göre uygulanacaktır. Bu

uygulamada dizayn aşağıda metotlara göre yapılacaktır.

Dizayn yapılırken , katodik koruma sisteminin hangisinin seçileceğine ancak

aşağıdaki çalışmalar yapıldıktan sonra karar verilecektir.

İskele bütün yüzeylerinin , donatı /beton yapı potansiyelleri ölçülecektir.

Beton yapının bütün bölgelerinde standartlara uygun olarak, elektriksel

iletkenlikleri (resistivities), ve pH değerleri ölçülecektir.

Bütün iskelenin bir potansiyel, rezistivivet haritası çıkarılacak , ve her

bölge için uygulanacak olan metot (1,2, tespiti yapılacaktır.

Özellikle deniz yüzeyine bakan kısımlarda potansiyel ve direnç

ölçümlerinin mevsim şartları dikkate alınarak uygun zamanda yapılması

dikkate alınmalıdır

İskele betonarme tamirinde kullanılacak olan tamir harcina , kesinlikle bu

çalışmalar yapıldıktan sonra karar verilmelidir. Tamir harcinin elektriksel olarak

iletken olmaması , yüksek dirence sahip olması durumunda uygulanacak olan

katodik koruma sistemini değiştirecektir. Bütün yapılarda aynı sistemin

uygulanması söz konusu olmayabilir. . Bu tür yapılarda tamir harci olarak

polimerik yapıda malzemelerin kullanılması, eğer yüzeye daha katodik koruma

uygulanacak ise katiyen tavsiye edilmez. Tamir metodu ENISO 12696:2012 ye

göre aşağıdaki şekilde önerilmiştir.

5.1 Concrete repair strategy (EN ISO 12696:2012 Section 5 and others)

One of the most important parameter to consider before planning “sprayed metal

galvanic anode cathodic protection” of an old and corroded concrete structure is

the resistivity of the remaining sound concrete, previously repaired parts and

delaminated, cracked and damaged sections requiring repair.

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The term “repair” signifies reinstatement of the damaged/deteriorated concrete to

provide an uninterrupted path for the flow of cathodic protection current prior to

the installation of cathodic protection, as well as reinstatement at locations where

concrete hasbeen removed to provide access to reinforcement and other steel, to

install cable connections and monitoring sensors, etc.

The driving potential of sprayed aluminum or zinc is only 0.25 V. Therefore if the

concrete resistivity is high anode cannot produce sufficient current to protect

rebar's.

Hence the impact of variations in concrete resistivity on the cathodic protection

system is very important.However thereis no firm guidance on limits of electrical

resistivity with respect to cathodic protection, but the designer shallconsider

whether full protection can be achieved where required for the ranges and

absolute values of concreteresistivity found on the structure.

All repair materials from previous installations with significantly different electrical

resistivity from the parentconcrete shall be broken out. Typically, these repair

materials with an electrical resistivity outside the range of approximately half to

twice that of the parent concrete, when measured under the same conditions as

the parent concrete, will be removed in orderto allow relatively uniform current

distribution to reinforcement. For example, predominantly epoxy-based repair

materialswill have very high resistivity values and may shield reinforcement within

or behind them from cathodic protection.. Physically sound chloride-contaminated

or carbonated concrete will not be removed prior to applying cathodic protection.

Concrete shall be reinstated using cementations materials. The electrical

resistivitycharacteristics and mechanical properties of the repair materials shall be

compatible with the original concrete.

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Humectants, moisture retaining material could be applied to the surface of a

galvanic anode to keep the concrete-anode interface moist.

To protect the surface of the sprayed metal from atmospheric corrosion a

polymeric coating may be applied to the surface of a galvanic anode. SicaCor

6630 is a candidate coating for this purpose.

Katodik koruma dizayn parametrelesi , ISO 12696-2012- Cathodic protection of

steel in concrete " nolu standartta belirtildiği gibi karma galvanik sistem olabilir.

Bu standartta "" 6.2.1.2 Thermally sprayed metallic coatings" ," The anode system

shall comprise a thermally sprayed metallic coating of Zn, Al-Zn, Al-Zn-In or Ti."

The coating thickness of the zinc/aluminum anode is variable and usually ranges

between 300 and 500 micron. The thickness is regularly controlled with test

strips. The adhesion of zinc/aluminum coating normally ranges above 1.5 MPaA

Special appliances and methods of measurements also permit the inspection of

the mechanical stability of the zinc coating on concrete.

In the contact of the zinc coating with the reinforcement is intended, either as

galvanic sacrificial anode or for the application with external current , metallic

elements are installed during the concrete repair work which can be electrically

connected with the sprayed zinc/aluminum coating

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The application of the zinc/aluminum sprayed coating is accomplished in several

layers. A mechanical and electrically connected coating (figure 2 ) is generated

with sufficient adhesion to the concrete surface

Şekil 5. 5- Arc sprayed zinc/aluminum coating

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In order to guarantee the monitoring function of the system for future

maintenance and control the monitoring system had to be planned in detail

including

Number of protection and monitoring zone

Number and location of the connection to the steel reinforcement

Number and location of the zinc connections for 1. alternative

Number and location of the reference cells

Location and accessibility of the monitoring systems

Option for impressed current operation

In addition, a design engineer may be influenced by other factors, such as:

Type of construction (i.e., prestressed, post tensioned or

conventionally reinforced concrete)

Cathodic protection design current density (i.e., mA/m2 of steel

surface)

Maximum anode current density (i.e., mA/m2 of anode surface)

Proper zoning and distribution of protective current

Installation methods and feasibility of incorporating the system into

the repair scheme

Electrical continuity of embedded steel

Availability of AC power

Type of transformer rectifier, including control mode, enclosure and

accessories

Remote monitoring system for rectifier

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TREATMENTS APPLIED AND THEIR JUSTIFICATION UNDER EN 1504 EN1504-9 Principal

Method/ Principle EN Standard Elements Treated Materials Used

1 – Protection against ingress 8 – Increasing Concrete Resistivity

Hydrophobic Impregnation, EN 1504 Part 2 Principle 1.1 and 2.1

EN1504 Part 2 EN 1062-3 maximum value

w =0.035 kg/m2

.h0.5

Area below deck level, deicing salts applied & chloride level at rebar below corrosion threshold

Silane compatible with cosmetic coating used to “tone down” repairs

1 – Protection against ingress

Anticarbonation Coating, EN 1504 Part 2 Principle 1.3c

EN 1504 Part 2 EN1062-6 Permeability to CO

2

SD

>50m

Parapets on walkways above deicing salts where chloride levels are very low

Cosmetic coating with anticarbonation properties

1 – Protection against ingress

Waterproofing membrane EN1504 Part 9 Principle 1.7

EN1504 Part 9 Principle 1.7 No membrane tests listed in 1504.

Walkway decks Waterproofing system

3 – Concrete Restoration 7 – Preserving or Restoring Passivity

Hand Applied Mortar, Principle 3.1, 7.2

EN1504 Part 3 Class R4 Compressive Strength >40MPa Adhesive Bond >2 MPa

All Damaged elements

Pre bagged Patch Repair Material

10 Cathodic Protection

Local galvanic Anodes, Principle 10.

Galvanic anodes not covered in 1504 or yet in EN12696

Patch repairs with chloride levels in excess of the corrosion threshold

Zinc anodes encapsulated in a proprietary activating mortar

Cathodic Protection Current Densities for Existing and New Reinforced Concrete Structures from various International CP Standards

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6 THERMAL SPRAYED ZINC/ALUMINIUM COATING APLLICATION

Thermally Sprayed Aluminium-Zinc-Indium. This alloy was developed during the laboratory-testing portion of a Federal

Highway Administration research contract and consists of 80 percent Aluminum,

20 percent Zinc, and 0.2 percent Indium (Al-20Zn-0.2In).8,9 Several installations

have been completed in marine and northern deicing salt environments (Figure

3). The anode has demonstrated in both field and laboratory testing to provide a

degree of cathodic protection that is superior to thermally sprayed zinc.4 Based

on predicted consumption rates and test data, this anode can be expected to

provide a reasonable life expectancy of 10-15 years in a sub-tropical marine

environments and possibly 15-20 years in northern de-icing salt environments.

Şekil 6.1 - Thermally sprayed Al-Zn-In anode for galvanic cathodic protection of a concrete bridge.

These thermal spray coatings provide corrosion protection by excluding the

environment ( or electrolyte) and acting as a barrier coating (like paints,

polymers, and epoxies), but unlike typical barrier coatings they also provide

sacrificial anodic protection.

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Şekil 6

Metalizing kaplama, bir elektrik arkının içine iki metal telinin ergitilmesi ve bu

ergime ile oluşan partiküllerin önceden hazırlanmış yüzeye doğru yönlendirilmesi

ile bir kaplama tabakası oluşturulan bir termal sprey metodudur.

Metalizing Kaplama Prosesi

Sprey sistemi eş zamanlı ve devamlı bir şekilde iki metal telin aynı hız oranıyla

besleyen ekipmandan oluşur. (+) ve (-) yükle yüklenmiş olan teller kesişme

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noktasında temas ettiği zaman bir ark meydana gelir. Oluşan ark sayesinde

teller hızlı bir şekilde ergir. Kurutulmuş hava ile yüzeye püskürtülür.

Kaplanacak yüzeylerin hazırlanması

Yüzey tamamen temizlenmeli ve uygun bir aşındırıcı ile pürüzleri giderilmelidir.

Termal püskürtmeden hemen önce yüzey kurulanmalı ve toz, yağ, tufal, pas ve

diğer kirliliklerden arındırılmalıdır.

Her durumda yüzeyin pürüzlülüğü ilgili taraflarca anlaşma sağlanan özelliklere

göre hazırlanan iş parçasına benzer özelliklere sahip bir referans yüzeyle

mukayese yapılarak doğrulanmalıdır

Metalizing Kaplama

Kaplama basınçlı hava ile aşındırıcı kullanılarak yüzey hazırlanmasından belirli

bir süre sonra yüzey tamamen temiz ve kuru olarak yapılmalıdır (kaplama

başladığı zaman).

Bu süre mümkün olduğunca kısa olmalı ve lokal şartlara bağlı olarak 4 saatten

az olmalıdır.

Termal püskürtme ile kaplama yapılacak yüzeyde yoğunlaşmaya sebep olacak

şartlar altında söz konusu püskürtme işlemi yapılmamalı ve yüzey,

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kabarcıklanmayı önlemek için çiğlenme noktasının üstündeki bir sıcaklıkta

muhafaza edilmelidir.

Kaplanacak yüzeyde bir bozulma gözlendiğinde yüzey hazırlama işlemi

tekrarlanmalıdır.

Kaplama işleminde metali ergitmede sadece elektrik kullanılır, eriyen metal

kurutulmuş yüksek basınçlı kurutulmuş hava ile yüzeye püskürtülür. Eriyen

metaller damlacıklar halinde üst üste birikerek kaplamanın oluşması sağlanır.

Metalizing Kaplama Sistemi 1- Püskürtme Tabancası 2- Güç Ünitesi 3- Tel Besleme Ünitesi 4- Kontrol Ünitesi

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Kaplamada en önemli kısım tabancadır. Sürücüler tarafından eşit hızlarda

sürülen teller tabanca içerisinde yüklerle yüklenip iki tel arasında ark meydana

getirilir.

Ark vasıtasıyla ergiyen partiküller Atomize gaz ile kaplama yüzeyine 100 ila 150

m/sn’lik bir hızla püskürtülürler

Elektrik arklarını üretmek için güç ünitesinden genellikle doğru akım kaynağı

kullanılır. Kullanılan voltaj kullanılan sprey (kaplama) malzemesine bağlı olarak

18 ila 40 volt arasındadır.

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Akım istenen birikme hızına bağlı olarak 50 ila 2000 A arasında ayarlanabilir. Ark

sprey için bazı tipik parametreler şu şekildedir.

Ark sıcaklığı : 5000°C Partikül hızı : 100-300 m/sn Sprey Mesafesi : 100-250 mm Elekt. giriş gücü : 6-80 kW Pulverize hava debisi : yaklaşık 60 m3/s Kaplama kalınlığı : 0,05-5 mm Sprey malzemeler : Teller, çapı 1,6 - 3,2 mm Metaller : Al, Zn, Zn/Al,….

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Voltaj Ve Amperin Etkisi Voltaj arttıkça partiküllerin sıcaklığı artacaktır. Buda püskürtme hızını düşürür

Dolgu teller ve kullanım yerleri Analiz Açıklama Kaplama

Sertliği (HV 0,3)

Ergime Derecesi (°C)

Özellikler

Zn 99,99

Çinko 25 420 Korozyondan Koruma

Zn-Al 85–15

Çinko, Alüminyum

35 450 Endüstri ve deniz atmosferinde korozyon koruma, SO2’li atmosferlerde yüksek direnç

Al 99,5 Alüminyum 40 660 Endüstri ve deniz atmosferinde korozyon, 800 °C ve yukarısında yüzeyde çelik ile difüzyon bağı oluşturmasına rağmen yüksek direnç, gıda endüstrisindeki kaplamalar

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7 PROCEDURE USED IN WORK SHOP TEST

Laboratory testing was designed to improve the usefulness of the guide to

STANDART in several basic areas. These were the following:

• Tests on sealer materials, including high solids,

• Testing of the effects of different abrasive mixes on the performance of Standard

to examine the effects of angularity on performance and to examine methods to

measure angularity in the field.

• Evaluation of the spray parameters of standoff distance and application angle on

coating microstructure and performance.

• Testing of the effects of the hardness of the steel substrate on surface

preparation requirements.

• Testing of the effects of high-strength, low-alloy steel versus carbon steel

substrate on standard performance.

Aluminum spraying Zinc spraying

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Tests applied to the objectives

1-HSLA = high-strength, low-alloy.

2 Existing coupons from a previous study and laboratory polarization tests used

to evaluate.

Kaplamanın yüzeye yapışma testleri laboratuvarda yapıldığı gibi , saahda her

500 m2 de bir yapılan uygulamalarda ve denemelerde yapılacaktır.

Yukarıdaki testler , uygulama sırasında hazırlanacak olan bir Inspection Test

planında hangilerinin yapılacağı açıklıkla belirtilecektir. Yukarıdaki tablo bir

örneklemedir.

Uygulama sırasında her 10 m2 lik bir alanca kalınlık ölçümleri , iskelede uygun

olan her m2 de bir potansiyel ölçümü yapılacaktır Bu ölçüm hem koruma

öncesinde hemde koruma sonrasında yapılacaktır.

Edo-wms-coe-cor-Int-xxx-014-247-275-Rev-d-methode Statment of Cathodic Protection System _thermal Zinc or Aluminimum Alloys Spraying _ of Concrete Surfaces

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