Concrete Library 157

Guidelines forElectrochemical Corrosion Control Methods

October 2020

Japan Society of Civil Engineers

Contents
Common Part
Chapter 1 General .............................................................................................................................................. 1
1.1 Scope ............................................................................................................................................................... 1
1.2 Principles of Electrochemical Corrosion Control Methods ............................................................................. 4
1.3 Terms and Definitions...................................................................................................................................... 7

Chapter 2 Investigation.................................................................................................................................... 12
2.1 General........................................................................................................................................................... 12
2.2 Investigation Plan .......................................................................................................................................... 122.2.1 General ............................................................................................................................................................ 122.2.2 Selection of Investigation Items ...................................................................................................................... 13
2.2.3 Determination of Investigation Methods ......................................................................................................... 16

2.3 Implementation of the Investigation .............................................................................................................. 17

Chapter 3 Design ............................................................................................................................................. 18
3.1 General........................................................................................................................................................... 18
3.2 Selection of Electrochemical Corrosion Control Method .............................................................................. 19
3.3 Implementation Plan in Design ..................................................................................................................... 27
3.4 Maintenance Plan .......................................................................................................................................... 27
3.4.1 General ............................................................................................................................................................ 27
3.4.2 Inspection ........................................................................................................................................................ 28
3.4.3 Evaluation........................................................................................................................................................ 29
3.4.4 Remedial measures .......................................................................................................................................... 29

3.5 Design and Maintenance criteria for corrosion prevention ............................................................................ 30
3.6 Materials and Equipment ............................................................................................................................... 31
3.6.1 General ............................................................................................................................................................ 31
3.6.2 Materials Composing Members Subject to Corrosion Control ........................................................................ 32
3.6.3 Materials and Equipment used in Electrochemical Corrosion Control Methods ............................................. 33
3.6.4 Material Characteristics ................................................................................................................................... 34

3.7 Load ............................................................................................................................................................... 34
3.7.1 General ............................................................................................................................................................ 34
3.7.2 Loads to be considered in the Design .............................................................................................................. 35

3.8 Verification of Steel Corrosion ...................................................................................................................... 36

Chapter 4 Implementation ............................................................................................................................... 38
4.1 General........................................................................................................................................................... 38
4.2 Implementation Plan ...................................................................................................................................... 38

4.3 Implementation .............................................................................................................................................. 39
4.4 Inspection....................................................................................................................................................... 40

Chapter 5 Maintenance .................................................................................................................................... 42
5.1 General........................................................................................................................................................... 42

Chapter 6 Records ........................................................................................................................................... 43
6.1 General........................................................................................................................................................... 43

Chapter 1 General Provisions

1

Chapter 1 General
1.1 Scope(1) This publication provides standard guidelines (hereinafter referred to as “the Guidelines”) for the design,
implementation, and maintenance of electrochemical corrosion control applied to newly constructed and existing
concrete structures. The Guidelines are applicable to the following four methods: cathodic protection, desalination, realkalization, and electrodeposition.
(2) The Guidelines cover steel corrosion, among other factors used to verify the durability of structures, based on thefact that the purpose of electrochemical corrosion control is to prevent steel corrosion.
(3) The Guidelines can be used as a means to ensure the durability specified in the "Standard Specifications forConcrete Structures [Design]" published by the Japan Society of Civil Engineers (JSCE).
(4) The Guidelines can be used as a means to repair deterioration due to steel corrosion specified in the “Standard
Specifications for Concrete Structures [Maintenance]” published by the JSCE.
(5) For matters not described in this document, refer to the "Standard Specifications for Concrete Structures [Design]and [Maintenance]" and other relevant guidelines.
[Commentary](1) Electrochemical corrosion control is used proactively to improve or ensure the durability of concrete structures andalso during in-service maintenance to repair deterioration due to steel corrosion and progressive cracking that occurs overtime. The Guidelines herein provide standards to ensure that the investigation, design, implementation, and maintenanceof corrosion control systems are performed in a rational and appropriate manner. The Guidelines are applicable to concrete
structures of maintenance categories A and B as defined in the “Standard Specifications for Concrete Structures[Maintenance]”. The Guidelines can be used as a guide to restore or improve the durability of existing structures, and canbe incorporated into maintenance planning during the design stage to ensure the durability of newly constructed structures.
Electrochemical corrosion control uses an electrochemical reaction that occurs on the surface of steel or insideconcrete when a direct current is applied between an anode installed on the surface or outside the concrete and the steel
inside the concrete, thus preventing corrosion. Despite ongoing technological developments, only a limited number oftechniques are available as a practical method that provides the means to assess the effectiveness of corrosion prevention
during installation and to perform the in-service inspection required for maintenance. Therefore, the Guidelines cover thefollowing four types of methods that have proven to be reasonably effective and practical as a measure to maintain, restore
and improve the durability of concrete structures, or as a means to prevent deterioration due to steel corrosion:
Cathodic protection
It electrochemically controls the corrosion reaction of steel and prevents the progress of corrosion by supplying direct
current to the steel in concrete from an anode system installed on the concrete surface.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

Desalination
It electrochemically reduces chloride ions present in concrete by supplying direct current to the steel in concrete from a
temporary anode system installed on the concrete surface.
Re-alkalization
It electrochemically permeates alkaline solution by supplying direct current to the steel in concrete from a temporary
anode system installed on the concrete surface, thus restoring the pH level (re-alkalization).
Electrodeposition
It electrochemically deposits inorganic electrodeposits on cracks and the concrete surface by supplying direct current tothe steel in concrete through electrolyte solution from a temporary anode system installed on the concrete surface to close
cracks, cover concrete surfaces, and densify surface layers.
As shown in Table 1.1.1, because each of these methods has its own characteristics in terms of the duration andamount of energization, and the methods for measuring effectiveness, the investigation, design, implementation, andmaintenance procedures for each method differ. In addition, different methods may be used in combination whereappropriate. Therefore, for matters common to all four methods, follow the Common part of the Guidelines; and formethod-specific details, follow the Method-Specific Standards part. Note that the Guidelines may be applied to anelectrochemical corrosion control method that may be developed in the future, provided that it provides a means tomeasure the corrosion prevention effect during implementation and to perform the required maintenance inspections, andthat it is shown to be sufficiently effective by actual results or appropriate experiments.
Table 1.1.1 Electrochemical Corrosion Control Methods

Duration
EnergizationofCurrent density*
Current-carrying
voltage
Electrolyte
solution
How to measureeffectiveness
When to check
effectiveness

Cathodic protection
methodContinued
duringcorrosion
prevention
period0.001-0.03A/m2
1-5V－
Measurement of electric
potential or potentialchangeSeveral times per 1-5
years

Desalination method

Re-alkalization method

Electrodeposition
methodAbout eight weeks

About one to two weeks

About six months

1A/m2

1A/m2

0.5-1A/m2

5-50V

5-50V

10-30V

H3BO3
and
K2CO3
Mixed solution, etc.

Na2CO3
aqueoussolution, etc.
Measurementof
carbonation depth of
concrete
After energization iscompleted

Measurement of chloride
ion content in concrete
After energization
completedisSeawater, etc.
Measurement of physicalproperties related tosurface layer quality
After energization iscompleted* Current density: the amount of current flowing per unit area (concrete) to be protected(2) Durability is a performance indicator that comprehensively determines whether a structure can maintain its
performance requirements such as safety, serviceability, and restorability at or above a required level over the planned
service period. This means that if the time-based change in these performance factors can be verified with sufficientaccuracy, there would be no need to use durability as a performance indicator during the maintenance stage. However,
the techniques to predict deterioration or evaluate performance are not practically mature at present. The "Standard
Specifications for Concrete Structures [Maintenance]" states that durability, which has been generally used in Japan, hasbeen designated as a parameter that comprehensively indicates these performance factors during the planned service

Chapter 1 General Provisions

3

period, and that verifying durability is considered to serve as an alternative to verifying whether performance requirements
are met or not in terms of safety, serviceability, and restorability during the planned service period. From the same
viewpoint, the Guidelines consider durability verification as an alternative to verifying performances of structures. In
addition, since electrochemical corrosion control methods are designed to prevent steel corrosion to restore or improvethe durability of structures, the Guidelines focus on steel corrosion, among other aspects of durability verification forstructures. Note that in this document, corrosion control means controlling the state of steel corrosion so that theeffectiveness of corrosion prevention is maintained as intended during the design period. Typically, the methods herein
are used to control corrosion so that it does not occur or progress, but in some cases they may also be used to prevent
corrosion cracking.

(3) To ensure the durability of new concrete structures, it is necessary to design structures that satisfy the durability
requirements over the design service period, considering the importance of the structures, the maintenance categories,
and the economics in terms of life cycle costs. However, it is sometimes difficult to predict all the factors that may affectthe durability of the structures at the design stage. When it is not possible to identify the factors affecting durability in thedesign stage, or when concrete alone may not be resistant enough to the deterioration factors, it is important to provide
redundancy to prevent the deterioration factors from degrading the performance of the structure by implementing backup or multiple protection measures. In the “Standard Specifications for Concrete Structures [Design]”, electrochemicalcorrosion control is presented as a standard protection measure to be taken at the design stage for structures that are
expected to deteriorate due to steel corrosion. In this regard, the Guidelines assume that electrochemical corrosion control
methods may be used as a protective measure to be taken at the design stage of new structures. In such cases, it is important
to include possible maintenance scenarios predicted during the design stage in a maintenance plan so that maintenancework can be done accordingly. If an unexpected scenario occurs during maintenance, the maintenance plan must be
reviewed and appropriate action taken.

(4) Existing concrete structures must be maintained so that the performance requirements for structures such as safety,
serviceability, and restorability are maintained at or above a required level over the planned service period. When
deterioration of a structure is apparent and it is determined that measures should be taken in accordance with theapproaches described in the "Standard Specifications for Concrete Structures [Maintenance]", it is necessary to define
what performance should be achieved, considering the importance of the structure, the maintenance category, theremaining planned service period, the deterioration mechanism, the degree of performance deterioration and other factors;
and to determine appropriate measures to be taken, considering the ease and economy of maintenance and environmental
friendliness, and then to implement them accordingly. The Guidelines describe how to apply electrochemical corrosion
control methods, following the concept presented in the "Standard Specifications for Concrete Structures [Maintenance]"
as a way to deal with structures that show deterioration such as steel corrosion and progressive cracking. When creatinga maintenance plan, it is worth considering the use of electrochemical corrosion control methods while deterioration is
not yet visible, to exclude deterioration factors or prevent the progress of deterioration. Such a preventive practice willsubsequently help to reduce the maintenance burden.

(5) Matters not described in the Guidelines shall be addressed in accordance with the “Standard Specifications for4

C.L. 157 Guideline for Electrochemical Corrosion Control Method

Concrete Structures [General Principles], [Design], [Construction] and [Maintenance]”. Electrochemical corrosion
control methods are intended to prevent deterioration in the performance of structures by preventing steel corrosion, andmay be used independently where deterioration due to steel corrosion is latent or developing. They may also be used in
combination with other repair or strengthening measures at a stage when the deterioration is accelerating. Note that the
Guidelines are applicable in cases where electrochemical corrosion control methods are used to restore or improve thedurability of structures, and when the methods are used in combination with other measures to restore, maintain, or
improve mechanical or other performance, it is recommended to refer to relevant guidelines such as the "Standard
Specifications for Concrete Structures [Design] and [Maintenance]" and the "Guidelines for structural intervention ofexisting concrete structures using cement-based materials (Concrete Library 150)" published by JSCE.

1.2 Principles of Electrochemical Corrosion Control Methods(1) Electrochemical corrosion control methods are used as measures to satisfy the performance requirements of aconcrete structure based on the maintenance category of the structure.
(2) When using the methods, the design corrosion prevention period and the desired effect shall be determinedaccording to the purpose and conditions of the structure.
(3) Electrochemical corrosion control methods must be used with appropriate implementation procedures andworkflows.

[Commentary](1) and (2) Electrochemical corrosion control methods are used to prevent steel corrosion and subsequent progressive
cracking and are implemented to maintain, restore or improve the durability of a concrete structure according to thescenario defined in the maintenance plan based on the maintenance category of the structure. The methods can be applied
to both new and existing structures. When using the methods to ensure the durability of a new structure, be sure to define
the design corrosion prevention period and the desired effect based on the design service life and the limit state of thestructure. When using the methods for repair purposes, be sure to define the design corrosion prevention period and thedesired effect based on the target period and performance level specified in the maintenance plan for the structure.
Examples of objectives are: “Steel corrosion will not progress during the design corrosion prevention period”, or “Steelcorrosion may progress, but harmful cracking due to steel corrosion will not occur during the design corrosion prevention
period (or the remaining planned service period).

(3) The electrochemical corrosion control method should be implemented with appropriate investigation, design,
implementation, and maintenance to achieve the desired effect over the design corrosion prevention period. It is also
necessary to thoroughly examine the organizational, personnel, material, and budgetary requirements in advance. With
appropriate implementation procedures in place, the investigation, design, implementation, and maintenance must follow
the flowchart shown in Figure 1.2.1. It is also important to follow the PDCA (Plan-Do-Check-Act) cycle for all of thesemaintenance activities.
As shown in the figure, there are two paths in the flowchart: one path is followed when the method is used as aChapter 1 General Provisions

5

repair measure in the maintenance of existing structures based on the approaches described in the "Standard Specifications
for Concrete Structures [Maintenance]" and the "Guidelines for structural intervention of existing concrete structuresusing cement-based materials (Concrete Library 150)"; and the other path is followed when the use of the method is
considered in the maintenance planning at the design stage to ensure the required durability of a new structure. In bothcases, the design, verification, implementation, and maintenance should be carried out according to the specific details
given in the Method-Specific Standards section. After the method is implemented, it is important to incorporate methodspecific maintenance considerations into the maintenance plan of the structure.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

Standard Specifications for Concrete Structures [Maintenance]
Maintenance plan
Inspection

mechanism
Prediction
Performance evaluation

Are remedial
measures required?

(when used to ensure durability of a
new structure)

Assessment

RecordingIdentification of deterioration

Remedial measures(when used for repair)

Guidelines for structuralintervention of existing concrete
structures using cement-basedmaterials [Concrete Library 150]
Repair/ strengthening plan

Common Part of this document
Plan (Chapter 1)
Investigation (Chapter 2)

Survey of existing structure

Design (Chapter 3)

Design of repair/strengthening

Implementation (Chapter 4)

Fail

Method-Specific Standards
section of this document
Cathodic protection method
Desalination method
Re-alkalization method
Electrodeposition method

Maintenance (Chapter 5)
Performanceverification
OK

Maintenance

Recording (Chapter 6)( ) Related Chapter

Figure 1.2.1 Structure of the Guidelines and Flowchart of Electrochemical Corrosion Control Procedures

Chapter 1 General Provisions

1.3 Terms and Definitions
In the Common part and the Method-specific Standards part of the Guidelines, terms are defined as follows:(1) Terminology used in the Common part
Tidal zone: The area between high and low water levels, or between respective shoreline positions. For
reference, the definitions of levels in the marine environment used in the Guidelines are shown below.
Atmosphere at sea
Splash zone
(Wave height)
Mean high water level
Average water level

Tidal zone

Mean low tide level
Submerged zone
Ocean floor
Submarine groundDefinitions of levels in the marine environment
Design corrosion prevention period: The period of time estimated in the design process during which theintended corrosion prevention effect must be maintained.
Electrolyte solution: A generic term for electrically conductive solutions containing electrolytes. It constitutes a
temporary anode in desalination, re-alkalization, and electrodeposition methods.
Professional engineer of electrochemical corrosion control methods: An engineer who has comprehensive, highlevel knowledge and extensive experience in concrete structures and is able to make appropriate technicaljudgments in the application and maintenance of electrochemical corrosion control methods. Defined for eachof the four methods: cathodic protection, desalination, re-alkalization, and electrodeposition.
Corrosion prevention: In a narrow sense, it means the prevention of corrosion of steel in concrete. In the
Guidelines, it means controlling the state of corrosion prevention of steel reinforcement to achieve theintended corrosion prevention effect over the design corrosion prevention period. In most cases thepractice is used to control corrosion so that it does not occur or progress, but in some cases it is used
to prevent corrosion-induced cracking from occurring.
Maintenance criteria for corrosion prevention: Indicators and their levels used in verification during
design, quality control during implementation, inspection after implementation, and diagnosis during

7

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

maintenance, to determine whether the intended corrosion prevention effect can be achieved over thedesign corrosion prevention period. The indicators are quantitative values such as the amount ofpolarization of the steel or the grade of appearance, or a combination of both. The corrosion control
index is used for cathodic protection, the desalination target for desalination, the re-alkalization target
for re-alkalization, and the electrodeposition target for electrodeposition.
Intended corrosion prevention effect: The condition or degree of deterioration (the grade of appearance)of steel that is specified during design and must be maintained for the design corrosion prevention
period. In general, it means a state in which corrosion is not occurring or progressing. Based on thiscondition, appropriate control standards for corrosion prevention are specified for each method.
Anode and anode materials: An electrode and its materials connected to the positive electrode of the DC
power supply.
(2) Terminology used in the Method-Specific Standards part(i) Terminology common to all methods
Anode: An electrode at which an electric current flows toward the electrolyte and an oxidation reaction
occurs. In electrochemical corrosion control, the anode is connected to the positive electrode of the DC
power supply. In steel corrosion, it is the part where corrosion progresses.
Anodic reaction: Oxidation reactions that occur around steel or anode materials in concrete. Major anodic
reactions include:
Fe → Fe2+ + 2e－ (reaction that occurs on the corroded part of the steel)
4OH － → 2H2O + O2 + 4e － (reaction that occurs around the anode material due toenergization)
2Cl－ → Cl2 + 2e－ (reaction that occurs around the anode due to excessive current flow)

Cathode: An electrode at which current flows from the electrolyte and a reduction reaction occurs. Inelectrochemical corrosion control, it refers to the steel inside the concrete, and it is connected to thenegative electrode of the DC power supply. In steel corrosion, reduction occurs at the cathode.
Cathodic reaction: Reduction reaction that occurs on the surface of the steel in concrete. Major cathodic
reactions include:
2H2O + O2 + 4e－ → 4OH－ (reaction that occurs on the surface of corroded steel materials
when the power is applied. )2H2O + 2e－－→ H2 + 2OH(reaction that occurs around steel due to excessive current
flow)

Hydrogen embrittlement: Reduction in toughness of steel materials due to absorbed hydrogen.
Hydrogen generation potential: The potential at which hydrogen gas is generated at the cathode.
Exhaust current: The return of direct current supplied by the DC power supply from the steel materials tothe power supply.
Drain terminal: A terminal attached to the steel to connect the negative side of the DC power supply inelectrochemical corrosion control.

Chapter 1 General Provisions

Drain point: The point of contact between the steel and the wiring when the direct current returns to the DC
power supply in electrochemical corrosion control.
(ii) Cathodic protection method”Instantaneous OFF” potential: The potential of the anode or the steel inside the concrete measured
immediately after the cathodic protection current is stopped in a test to verify the corrosion prevention
effect. This potential approximates to the true potential without voltage drop (IR drop). Abbreviated as Eio.
Off potential: The potential of the anode or the steel inside the concrete measured after sufficient time has
elapsed since the cathodic protection current was stopped. Abbreviated as Eof.
On potential: The potential of the anode or the steel inside the concrete when the cathodic protection current
is applied. This potential includes a voltage drop (IR drop). Abbreviated as Eon.
Cathodic polarization: To change the potential of a metal in the negative (base) direction by supplying aprotective current (direct current) to the metal.
Cathodic protection: A method of controlling corrosion of steel by changing the potential of the steel to beprotected in the negative (base) direction (cathodic polarization) by supplying a protective current (direct
current).
Surge absorber: A device that absorbs overvoltage caused by lightning and protects equipment such as DC
power supplies.
Backfill material: A material added to the outer surface of the anode to reduce the contact resistance of theanode material or to maintain the performance of the galvanostatic anode system and to facilitate thedissolution of the sacrificial anode.
Anode coating material: A material that protects the anode material and also acts as a backfill material.
Cement-based mortar is commonly used.
Sacrificial anode: Anode used in the galvanic anode system. A metal (such as zinc) having greater ionization
tendency than the steel inside concrete is used as an anode.
Contact resistance: Resistance generated at the interface between the reference electrode or anode and theanode coating material, and at the interface between the reference electrode and concrete.
Energizing point: Contact point between the wiring and the anode system in cathodic protection.
Constant voltage method: A cathodic protection method in which a constant voltage is applied from a DC
power supply to prevent corrosion.
Constant potential method: A cathodic protection method that prevents corrosion by maintaining thepotential of steel at a constant level.
Constant current method: A cathodic protection method that prevents corrosion by applying a constantcurrent from a DC power supply.
Voltage drop (IR drop): Voltage drop due to resistance of concrete, anode and wire materials. It is equal tothe difference between the on-potential and the ”Instantaneous OFF” potential.
Professional engineer of cathodic protection method: An engineer with specialized knowledge of cathodic
protection methods. Refers to an engineer who has comprehensive, sophisticated knowledge andextensive experience in concrete structures, is familiar with the use and maintenance of the cathodic

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

protection systems, and can make appropriate technical judgments. In the area of cathodic protection
system maintenance, it also refers to an engineer who has been involved more than once as a leader in thedesign, implementation, or maintenance of a cathodic protection project.
Measuring terminal: A point of contact between wiring and steel to measure the potential of the steel in acathodic protection system. No protective current passes through this wiring.
Distributor: Current distribution material used to ensure electrical continuity between anode materials.
Generally made of titanium.
Depolarization: A phenomenon in which a change in the potential of the steel occurs when the supply ofprotective current is stopped.
Depolarization quantity: This is one of the indices of corrosion control in a cathodic protection system andrefers to the amount of potential difference between the ”Instantaneous OFF” potential Eio and the off
potential Eof of the steel (ΔEd = Eof - Eio).
Polarization: A phenomenon in which a change in the potential of the steel occurs when a protective current
is supplied.
Polarization quantity: This is one of the indices of corrosion control in a cathodic protection system andrefers to the amount of potential difference between the natural potential E0 and the ”Instantaneous OFF”
potential Eio of the steel (ΔEp = E0 - Eio).
Corrosion control index: An item and level for controlling the corrosion prevention condition of the steel
inside concrete. It corresponds to the maintenance criteria for corrosion prevention defined in the
Common part of the Guidelines.
Protective potential: The electric potential required to prevent corrosion of the steel.
Protective current: The electric current supplied to the steel to maintain the corrosion prevention condition.
(iii) Desalination method, re-alkalization method, and electrodeposition method
Liquid-phase reaction: The reaction of ions present in a solution, depending on the stability of the bond. In
particular, in the electrodeposition reaction, positive and negative ions in the solution shows a reaction of
precipitating and precipitating as poorly soluble salts.
Temporary energizing system: A system consisting of temporary anodes, DC power supplies and wiring
materials.
Temporary anode: Collectively refers to anode materials, electrolyte solution and holding materials.
Temporary anode system: A system in which a temporary anode is fixed to the concrete surface.
Characteristics vary depending on the materials used and the method of fixing.
Professional Engineer of re-alkalization method: An engineer with specialized knowledge of the realkalization process. Refers to an engineer who has comprehensive, sophisticated knowledge andextensive experience in concrete structures, is familiar with the use and maintenance of the re-alkalization
process, and can make appropriate technical judgments.
Professional Engineer of desalination method: An engineer with specialized knowledge of the desalination
process. Refers to an engineer who has comprehensive, sophisticated knowledge and extensive experiencein concrete structures, is familiar with the use and maintenance of the desalination process, and can makeChapter 1 General Provisions

11

appropriate technical judgments.
Professional Engineer of electrodeposition method: An engineer with specialized knowledge of theelectrodeposition process. Refers to an engineer who has comprehensive, sophisticated knowledge andextensive experience in concrete structures, is familiar with the use and maintenance of theelectrodeposition process, and can make appropriate technical judgments.
Electrodeposits: Inorganic substances such as insoluble calcium carbonate and magnesium hydroxide
deposited by cations such as calcium and magnesium ions in electrolyte solution in a temporary anode,seawater, or groundwater.
Crack closure rate: Percentage of crack length blocked by electrodeposit to total length of crack before
countermeasure.
Surface coverage: Percentage of the area covered by electrodeposits to the area to be repaired.
Holding material: A material used to hold an electrolyte solution on the concrete surface.
[Commentary]
The above is a list of terms and definitions used in the Guidelines. The explanations are intended to be as
simple and understandable as possible for those civil engineers who may not be familiar with electrochemicalterms.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

Chapter 2 Investigation
2.1 General
An investigation plan shall be developed by considering the investigation items, methods and the implementation
system that will serve the purpose of the investigation. The investigation shall be properly conducted according to theplan.

[Commentary]
In order for the application of electrochemical corrosion control to maintain its intended effect for the intended duration,
appropriate investigation results are essential for the applicability assessment and method selection, as well as for thedesign, implementation, and maintenance of the corrosion control system. It is necessary to develop an appropriate
investigation plan by selecting investigation items and methods appropriate to the purpose of the investigation andestablishing a feasible implementation system. The results of the investigation should be properly recorded and retained
as they can be used at every stage of the design, construction, and maintenance of the structure.

2.2 Investigation Plan
2.2.1 General
The overall work plan should be prepared after selecting the investigation methods, considering the investigation items
according to the purpose and field conditions. In addition, the implementation system should be determined, taking
into account issues such as safety and health management.

[Commentary]
An investigation plan should be prepared with an appropriate selection of investigation items and methods to determine
the applicability of electrochemical corrosion control and to obtain information needed for the design and implementation
phases. The overall work plan should then be prepared and the implementation system established, taking into accountissues such as site safety and hygiene control.
After selecting investigation items, it is necessary to determine the investigation methods and procedures thatwill efficiently and adequately obtain the required information, and then develop an overall work plan. It is important todevelop a plan along with its implementation system by evaluating the environmental conditions in which the concrete
structures and the members will be placed, determining if the investigation can be performed while the structures are inservice, and investigating if there are any time restrictions on the investigation.
The investigation plan is basically made before the execution of each investigation, but in order to carry out theinvestigation efficiently, it is important to grasp the investigation items and the investigation method necessary for theChapter 2 Survey

13

implementation of an electrochemical control method as early as possible. Therefore, during the evaluation of theapplicability of an electrochemical corrosion control method, it is better to start preparing an investigation plan, including
the investigation for the selection of the method and the investigation for the design and implementation, based on theconditions of the target structure and its deterioration mechanism, and so on.

2.2.2 Selection of Investigation Items
Investigation items should be selected appropriately to achieve the purpose of each investigation.

[Commentary]
For electrochemical corrosion control methods, different types of investigation are required: prior investigation todetermine the applicability of an electrochemical corrosion control method (hereinafter referred to as the “Prior
investigation”); investigation to select an appropriate electrochemical corrosion control method according to the purposeof corrosion prevention (“Investigation for method selection”); and investigation to obtain information necessary for thedesign and implementation of the selected method (“Investigation for design and implementation”). As shown in Table
2.2.1, these investigations are conducted at different stages. When planning an investigation at each stage, it is importantto select the necessary investigation items according to the purpose of the investigation.
The purpose of the Prior investigation is to obtain the information necessary to determine whether
electrochemical corrosion control is applicable to the target structure. Such information includes: whether electrochemicalcorrosion control is applicable to the deterioration mechanism assumed for the structure; whether the supply of direct
current to the target steel will not be inhibited; and whether the direct current will not cause any other deformations of theconcrete. Therefore, it is necessary to investigate into issues such as the structural types and the materials used for thetarget members, the environmental conditions in which the members are placed, the main deterioration mechanism, thedeterioration conditions such as the grade of appearance, the history of remedial measures, and the methods and materials
used in the previous repairs. Examples of causes that inhibit direct current to the steel are the use of corrosion resistantsteel (e.g., epoxy-resin coated reinforcing bars) and the application of surface coating materials or surface penetrants tothe surface of the structure. In the case of concrete structures in which alkali silica reaction (ASR) may occur, adequate
investigation is required because ASR may be promoted by the electrochemical corrosion control. For newly constructedconcrete structures, it is desirable to assume the deterioration mechanism. Table 2.2.2 shows examples of Prior
investigation items.
The purpose of the Investigation for method selection is to obtain the information necessary for the selection of
the method to be applied to the target structure or its members. For this investigation, in addition to the Prior investigation
items, it is necessary to select investigation items needed to examine the expected effects of applying the electrochemicalcorrosion control method, and the persistence of the effects, the service condition of the structure when the method isapplied, the scope and numerical data of the implementation (e.g., area to be applied), environmental constraints andconsiderations, and the economic efficiency such as life cycle cost. Table 2.2.3 shows examples of investigation items.
The information already obtained from the Prior investigation can be used for this investigation.
The purpose of the Investigation for design and implementation is to obtain the information necessary for the14

C.L. 157 Guideline for Electrochemical Corrosion Control Method

design and implementation of the selected electrochemical corrosion control method. For this investigation, in addition
to the investigation items of the previous stages, the investigation items suitable for the selected electrochemical corrosion
control method shall be selected. For existing concrete structures, it is also necessary to obtain information such as theexact location, area and size of cracks or delamination, and measures taken in the past, to determine the pretreatment of
concrete and steel required prior to the application of electrochemical corrosion control method. This investigation is
generally carried out at the detailed design stage of each method, but it is often appropriate to carry out some additional
investigations during the implementation stage, such as an investigation to determine the extent and amount of degradation.
Table 2.2.4 shows examples of investigation items for this investigation. The information already obtained from theinvestigations performed during the previous stages can be used for this investigation.

Table 2.2.1 Purpose and Timing of the Investigation
Name of Investigation

1) Prior investigation

PurposeInvestigation performed during

To gather information necessary to evaluate theapplicability of electrochemical corrosion control
methods

applicability
determination
examination) stage(preliminary

2)
Investigation
method selectionforTo gather information necessary to selectelectrochemical corrosion control methods

method selection (basic design) stage

3)
Investigation
designimplementation

for
and

To gather information necessary for detailed design
and implementation of selected electrochemicalcorrosion control methods

detailed design stage for each method (someinvestigations are additionally conducted during
the implementation stage)

Table 2.2.2 Examples of Prior Investigation Items

Implementation conditions
Hazards for third party
State of deterioration

Investigation items
Type of structure
Shape and dimensions of members
Shape and type of steel
Site conditions
History of remedial measures (type of remedial measures,
etc.)
Schedule, duration, and time of implementation
Presence of hazards for third party
Deterioration mechanism, grade of appearance, etc.

○:Investigation required△:Investigation recommended

Structure

New construction○○○○

Existing
○
○
○
○

－

○

○
○
△

○
○
○

Remarks-:Investigation not possible or not necessary

Table 2.2.3 Examples of Investigation Items for Method Selection

Structure

Service life
Implementation
conditions
Hazards forthird party

Investigation items
Type of structure
Shape and dimensions of members
Shape and type of steel
Site conditions
History of remedial measures (type of remedial measures, etc.)
Planned service period
Remaining planned service period
Presence or absence of commercial power supply
Locations of DC power supplies and enclosures
Schedule, duration, and time of implementation
Impact on third parties

New construction
○
○
○
○
－
○
－
○
○
○

Existing
○
○
○
○
○
－
○
○
○
○

○

○

Remarks 1)

Prior

Prior

Chapter 2 Survey

State ofdeterioration
Economy15

Deterioration mechanism, grade of appearance, etc.

△○

Material costs, replacement costs, renewal costs, etc.

○○○:Investigation required△:Investigation recommended-:Investigation not possible or not necessary
1) The "Prior" in the remarks column indicates that the information obtained from the Prior investigation may be used.

Table 2.2.4 Examples of investigation items for design and construction

Investigation items

Targetstructures

Service life
Environmental
conditions

Implementation
conditions

Hazards forthird party

DefectHistory ofremedial
measures
Deposits/ Incidents

Quality ofconcreteStateofdeterioration

State of steel

Type of structure
Shape and dimensions of members
Shape and type of steel
Site conditions
History of remedial measures (type of remedial
measures, etc.)
Load conditions (traffic volume, upper load,
etc.)
Planned service period
Remaining planned service period
Details of environmental conditions
Spraying of anti-freeze materials

Cathodic
protection
New
const Exist
ructi
ing
on
○
○
○
○
○
○
○
○

Desal
ination

Realkalizat
ionElectrod
epositio
n

○
○
○
○

○
○
○
○

○
○
○
○

－

○

○

○

○

△

△

△

△

△

○
－
○
○

－
○
○
○

－
○
○
○

－
○
○
○

－
○
○
○

Presence of commercial power supply

○

○

○

○

○

Locations of DC power supplies and enclosures
Water quality of electrolyte solution(concentration of Ca or Mg ions in seawater,brackish water and groundwater, etc.)
Schedule,
duration,
and
time
of
implementation.

○

○

○

○

○

－

－

－

－

○

○

○

○

○

○

Impact on third parties

○

○

○

○

○

－

○

○

○

○

－
－
－
－
－
－
－
－

○
○
○
○
○
○
○
－

○
○
○
○
○
○
○
－

○
○
○
○
○
○
○
－

○
○
○
○
○
○
○
○

－

○

○

○

○

○1)

○1)

○1)

○1)

－
○
－
－

－
○
－
－

○1)

○1)

○
－
－

○
－
－

○1)
－
○
△
△

△

○

○

○

○

－
－

△
△

○
△

－
○

△
△

－

△2)

△2)

△2)

△2)

○1)
○1)
○1)

○1)
○1)
○1)

○1)
○1)
○1)

○1)
○1)
○1)

○1)
○1)
○1)

Delamination, Spalling, Honeycomb, Scaling,etc. (Position, Area)
Cracks (Shape, Width, Length)
Strain of Rust (Position, Area)
Water leakage / Water splash (Position, Area)
Exposed metal (Position, Size)
Surface treatment (Position, Area, Type)Patching (Position, Area, Type)Strengthening (Position, Area, Type)
Deposits of marine organisms (Type, Quantity)
Incidental
equipment(Existingpipes,
Inspection passages, etc.)
Materials (Type of cement, etc.)
Water to cement ratio
Electrical resistivity
Water permeability
Porosity
Deterioration mechanism, grade of appearance,
etc.
Chloride ion concentration
Carbonation depth
Degree of deterioration due to alkali-silica
reaction, etc.
Position of steel (Cover)
Arrangement and quantity of steel
Shape and type of steel

Remark 4)

Prior

Selection

Selection

Prior

Prior

16

C.L. 157 Guideline for Electrochemical Corrosion Control Method

EconomyType and arrangement of sheath
Corrosion conditions of steel
Electrical continuity between the steel
Polarization of steel (Cathodic polarization)
Material costs, replacement costs, renewal
costs, etc.

○1)
－
○
－

○
○
○
△3)

○
○
○
－

○
○
○
－

○
○
○
－

○

○

○

○

○

Selection○:Investigation required△:Investigation recommended-:Investigation not possible or not necessary
1) Verify with design and implementation documents.
2) Conduct this investigation when deterioration may be caused by ASR.
3) Conduct this investigation when deemed necessary during the design phase, such as when determining the current density forthe cathodic protection method or determining the anode arrangement.
4) "Prior" in the Remarks column indicates that the information from the Prior investigation may be used. Similarly, "Selection"
indicates that the information obtained from the Investigation for method selection may be used

2.2.3 Determination of Investigation Methods
Investigations and their implementation system shall be determined based on site conditions and other considerations
for the investigation items selected according to the purpose of each investigation.

[Commentary]
It is important to appropriately determine the investigation methods based on the site conditions for the investigation
items selected according to the purpose of the investigation at each stage. There are various methods, such as one basedon design and relevant documents, one based on on-site measurement, and one based on samples taken from the site.
They can be classified into the following five types:(i) Document searchInformation appropriate to the selected electrochemical corrosion control method is obtained from documents such as
design and completion documents, maintenance plans, maintenance records, and interviews with related parties.
(ii) Environmental survey
Information on the site conditions of the structure is obtained. It includes environmental conditions, construction
conditions, hazards for third parties, and interviews with related parties.
(iii) Appearance inspection
Information on the target existing structure is obtained from documents or site inspection. It includes concrete surface
defects such as delamination, spalling and metal exposure, history of remedial measures, and the location, size, area andtype of ancillary equipment.
(iv) Inspection of concrete
Information on the quality of the concrete and the cause of deterioration of the target structure is obtained from documents
and site inspection.
(v) Inspection of steel
Information on the condition of steel in concrete is obtained by inspecting the design and site conditions.

Note that the required or applicable investigation differs depending on the time of the investigation and thecondition of the target structure. The Prior investigation and the Investigation for method selection primarily require (i)Chapter 2 Survey17

and (ii), while the Investigation for design and implementation requires (i) through (v). Items (i) and (ii) are primarily
required for newly constructed structures, while items (i) through (v) are required for existing structures.
When planning an investigation, it is necessary to examine the whole work schedule of the investigation andestablish an appropriate implementation system that can perform a reliable investigation. Especially, it is important that
the Investigation for design and implementation should be carried out by professional engineers who specialize in theselected electrochemical corrosion control method. An on-site investigation must be planned with work safety andenvironmental considerations in mind. For more details on investigation methods, refer to the Method-Specific Standards
part and Appendix 1 (outline of the investigation methods).

2.3 Implementation of the Investigation
The investigation should be conducted as planned to ensure that information is obtained according to the purpose ofeach investigation.

[Commentary]
The investigation shall be conducted efficiently according to the plan. On-site investigations shall be carried out withwork safety and environmental protection measures in place. After each investigation, ensure that the intended
information is obtained. Based on the results, review the content of subsequent investigations and, if necessary, revise theinvestigation plans before proceeding.
Based on the results of the Prior investigation, determine the applicability of an electrochemical corrosion
control method. If it is determined to be applicable, conduct the Investigation for method selection, and determine anappropriate electrochemical corrosion control method. The results of the Investigation for design and implementation
should be used during the design and implementation stages so that the expected effects of each method can be fully
demonstrated. All investigation results shall be recorded and stored.

18

C.L. 157 Guideline for Electrochemical Corrosion Control Method

Chapter 3 Design
3.1 General(1) An electrochemical corrosion control method shall be selected considering the purpose of corrosion prevention,
the expected main effects, and the deterioration mechanism of the concrete structure to be protected.
(2) The applicability of an electrochemical corrosion control method to a newly constructed concrete structure shallbe examined in accordance with Chapter 3 “Structural Planning” of the "Standard Specifications for Concrete
Structures [Design: General Requirements]".
(3) The applicability of an electrochemical corrosion control method to an existing concrete structure shall be
examined based on the "Standard Specifications for Concrete Structures [Maintenance]" and the "Guidelines forstructural intervention of existing concrete structures using cement-based materials (Concrete Library 150)".

[Commentary](1) When designing an electrochemical corrosion control method, select an appropriate method based on the results of
the Investigation for method selection, taking into account the purpose of corrosion prevention, the expected main effects,
and the deterioration mechanism of the concrete structure, as shown in Table 3.1.1.
The cathodic protection method can be applied to structures where steel corrosion may occur or has occurred
due to chloride attack or carbonation or other causes. It can also be used when steel corrosion has occurred due to multiple
deterioration mechanisms and the cause of corrosion has not yet been identified.
The desalination method can be applied to structures suffering from chloride attack in anticipation of the effectof reducing the chloride ion concentration in concrete.
The re-alkalization method can be applied to structures suffering from steel corrosion due to carbonation, in
anticipation of the effect of restoring alkalinity in concrete.
The electrodeposition method, which is expected to improve the migration resistance of corrosion factors, canbe applied to structures subject to chloride attack and carbonation and structures with nonprogressive cracks.

Table 3.1.1 Purpose of corrosion prevention, expected effects, and applicable deterioration mechanisms
Electrochemical corrosion
control method
Cathodic protection
Desalination
Re-alkalization
Electrodeposition

Purpose of corrosion
prevention
To suppress
reaction

Expected main effect

Major deterioration mechanism ordeformation to which the method
appliescorrosion Reduction of corrosion reaction
Chloride attack*, carbonation*
rate

Reduction of chloride ion
To improve the corrosive concentration
environment of steel
Recovery of alkalinity
To suppress the supply of Improving the migration
corrosion factors
resistance of corrosion factors

Chloride attack
Carbonation
Chloride attack**, carbonation**,Non-progressive Cracking*** Includes cases where the main cause of steel corrosion is assumed to be chloride attack or carbonation at the stage of method

Chapter 3 Design19

selection.
** Can be used as surface coating after the application of desalination method or as crack repair or surface treatment in special
working environments.

(2) and (3) With regard to durability, as stated in Section 3.2 (Studies on performance requirements) of Chapter 3(Structural Plan) of “Standard Specifications for Concrete Structures [Design: General Requirements]”, if a highly
corrosive, severe environment makes it difficult to ensure the required durability using the permeation resistance ofconcrete materials, it is recommended to consider the use of a cathodic protection method or an electrodeposition method.
In this case, the design corrosion prevention period and the intended corrosion prevention effect should be appropriately
determined based on the design service life and the required performance of the structure, and the use of anelectrochemical corrosion control method that satisfies these requirements should be examined.
In addition, as described in Section 3.4 (Studies on Maintenance) of the Specifications mentioned above, if it isanticipated that an electrochemical corrosion control method will be used during the in-service stage in order to reduce
the life cycle cost of the structure, it is advisable to consider ways to facilitate the use of the method at the time of structuralplanning. In such a case, refer to the descriptions relating to existing concrete structures in the Guidelines.
When an existing concrete structure requires repair as part of maintenance and an electrochemical corrosion
control method is deemed applicable, an appropriate method shall be selected according to the “Standard Specifications
for Concrete Structures [Maintenance]” and “Guidelines for structural intervention of existing concrete structures using
cement-based materials (Concrete Library 150)”. The design corrosion prevention period and the intended corrosion
prevention effect shall then be determined based on the target period and the target performance level defined in themaintenance plan of the structure, considering the present conditions of the structure, implementation conditions, ease ofmaintenance, and other requirements.

3.2 Selection of Electrochemical Corrosion Control Method(1) To achieve the intended corrosion protection effect, an appropriate electrochemical corrosion control methodshould be selected, taking into account the implementation process, maintenance procedure, environmental
friendliness, and economic efficiency.
(2) As a measure against chloride attack, it is basic to use the cathodic protection method, the desalination method or
the electrodeposition method.
(3) As a measure against carbonation, it is basic to use the cathodic protection method, the re-alkalization method or
the electrodeposition method.
(4) As a measure against cracking, it is basic to use the electrodeposition method.

[Commentary](1) When selecting an electrochemical corrosion control method, consideration should be given to the requirements ofthe corrosion control method necessary to achieve the intended corrosion prevention effect based on the deterioration
state of the target structure, the structure type, and environmental conditions. Consideration should also be given to
matters related to the implementation procedure, ease of maintenance, environmental restrictions, economic efficiency,
and so on. Examples of these considerations are shown in Table 3.2.1. Since the importance of each item differs for each20

C.L. 157 Guideline for Electrochemical Corrosion Control Method

structure, it is important to select a corrosion control method considering these issues comprehensively. For a detailed
examination of these considerations, it is necessary to refer to Method-Specific Standards part. As a reference, Appendix
2 outlines the method selection flow for each structural manager, Appendix 3 shows the LCC/LCCO 2 calculation method
and sample calculations, and Appendix 4 provides a case study of the design, implementation, and maintenance of thecathodic protection method.
An appropriate electrochemical corrosion protection method should be selected to maintain the intended
corrosion prevention effect on the structure or its members, whether new or existing, over the design corrosion prevention
period. For newly constructed structures, the cathodic protection method and the electrodeposition method are used.

Table 3.2.1 Examples of considerations when selecting an electrochemical corrosion control method
Category

Subcategory1) Deterioration state

Deterioration
Structural
condition
Performanceassurance2) Occurrence of complex
deterioration
3) Structural type4) Environmental conditions
5) Expected effects6) Sustainability of the effects
7) State of service

Implementation
methodMaintainability
Environmental
friendlinessEconomic
efficiency

Points to note
Deterioration process and appearance grade in the main deterioration
mechanism when the method is applied
Presence or absence of complex deterioration (possibility of multiple
deterioration mechanisms) and its status
Structural type of applicable member (PC member/RC member)
Environmental conditions in which applicable components are placed
Expected effects of using the corrosion control method (including recovery ofmechanical performance)
Durability of effect vs. design corrosion prevention period (service life)9) Ease of maintenance

Necessity and feasibility of implementation while the structure is in service
Work process (efficiency) based on the amount of work (including
pretreatment), procurement of materials and equipment, necessity of temporary
scaffolding, ease of installation, time available for work, etc.
Ease of maintenance after implementation

10) Environmental constraints

Restrictions on the generation of dust, noise, etc.

11) Cost

Life cycle costs, etc.

8)
Efficiency
implementationof(2) For chloride attack, the cathodic protection method, desalination method or electrodeposition method is used basedon the results of the durability verification of the structures or the results of the inspection, evaluation, and judgment forthe structures. When selecting an electrochemical corrosion control method as a measure against chloride attack on
concrete structures, it is necessary to consider various points as shown in Table 3.2.1.
Regarding the 1) Deterioration state, the applicable method differs depending on the deterioration process andthe grade of appearance. The applicable method also differs for different 5) Expected effects, such as restoration andimprovement of durability, and restoration of mechanical performance. Therefore, it is necessary to consider these factors
when selecting an electrochemical corrosion control method. Table 3.2.2 shows examples of appearance grades andapplicable methods for chloride attack prevention. Regarding 4) Environmental conditions, the scope of each method
differs depending on the environment, such as land, inland, and marine, as shown in Table 3.2.3.

Table 3.2.2 Examples of appearance grades and applicable methods (measures against chloride attack)
Structures

Appearance Grade

Deterioration
process

Newly
constructed－－

Expected effectRestoration and improvement ofRecovery of mechanicaldurability
performance
Surface treatment 1), cathodic－
protection 1)

Chapter 3 Design

21

structure
Grade I
Grade II
Existing
structures

Grade III-1
Grade III-2
Grade IV

Surface treatment 1), desalination 1),－
and cathodic protection 1)
Surfacetreatment,
desalination,
Propagation stage－
cathodic protection
First half of the Repair of cross section, desalination,－
acceleration stage and cathodic protection
2)
Second half of the Repair of cross section, desalination , Cross section repair
acceleration stage and cathodic protection 2)
necessary)
Deterioration
Desalination 3), cathodic protection 3) Cross section repair
stage
Initiation stage(if1) Preventive measure.
2) Consider using it in combination with other methods (such as external cabling) if necessary.
3) Can be used in combination with other methods (such as external cabling).
Note: Electrodeposition method can be used for the same purpose as the surface treatment shown in the table.

Table 3.2.3 Scope of application for different environments (measures against chloride attack)MethodEnvironment
Land and inland areas
Atmosphere at sea
Marine environment

Electrochemical corrosion control method
Cathodic protection
Electrodeposition
Desalination method
methodmethod
○
○
△
○

○

△

Splash zone

○

○

△

Tidal zone

△

△

△

Submerged zone

△

△

○

○: Applicable △Careful consideration is required

Table 3.2.4 provides an example of items to consider when selecting a method to restore or improve durability
as a measure against chloride attack. The table shows the applicability and considerations of the cathodic protection
method, desalination method, and other methods with reference to the items listed in Table 3.2.1. The Guidelines focus
on the appropriate selection of an electrochemical corrosion control method, but for reference purposes, the table also
provides characteristics of the surface treatment method and the cross section repair method in the other methods column,
in comparison with the cathodic protection method and the desalination method. A case where a structure has ASR (alkalisilica reaction) concerns is shown as complex deterioration. It should be noted that the considerations described in thistable may not always apply to structures in special conditions; the considerations are intended for concrete structures,such as bridges, which have many proven implementations of electrochemical corrosion control methods.
The cathodic protection method can be applied to both new and existing concrete structures, and can be used
for structures in environments ranging from land to inland, and from the atmosphere at sea to underwater. However, when
it is applied to existing structures after the acceleration stage, it is necessary to consider using it in combination with othermeasures such as cross section repair or external cabling, depending on the degree of deterioration of mechanicalperformance such as cracks and cross section defects of steel. In addition, when it is applied to members in the tidal zoneof the marine environment, design considerations such as separating the corrosion prevention circuit from the atmosphere
are necessary. When applied to the structure in which ASR is a concern, it is advisable to refer to the Method-SpecificStandards part and decide the applicability and implementation procedures. In terms of maintainability, the cathodic
protection method has the advantage that the corrosion prevention effect can be quantitatively assessed by appropriate
inspections. In addition, when used in conjunction with a remote monitoring system, it can provide continuous monitoring

22

C.L. 157 Guideline for Electrochemical Corrosion Control Methodand data collection from remote locations, allowing for more sophisticated, simplified and streamlined maintenance.
The desalination method can be applied to existing concrete structures, but when used after the acceleration
stage, it is necessary to consider using it in combination with other measures such as cross section repair and external
cabling, just as with the cathodic protection method. When used in the tidal zone, it is necessary to assess the applicabilityby thoroughly examining the field conditions, because the temporary energizing system can be easily damaged by external
forces such as waves. It is common practice to use the surface treatment method together when desalination is applied toconcrete structures that are affected by external chloride ions. Even if the desalination treatment is properly performed,
experience shows that it is impossible to completely remove chloride ions, and it is common for chloride ions to remain
in concrete. The applicability of the desalination method is basically evaluated from the perspective of whether theintended corrosion prevention effect can be maintained over the design corrosion prevention period. When thedeterioration of the structure is at or after the propagation stage, it is very important to investigate and evaluate the chloride
ion concentration and the state of steel corrosion, which significantly affect the sustainability of the effect. When applying
the desalination method to structures where ASR is a concern, consult the Method-Specific Standards part to determine
applicability and implementation method.
With its expected effectiveness, the electrodeposition method is applicable to both new and existing structuresin the initiation and propagation stages as a measure against chloride attack. As described above, the electrodeposition
method can also be used as a surface coating after the desalination method has been used. However, unlike general surface
treatment methods, there is not enough quantitative data available on salt shielding effects, making it impossible toquantitatively assess the duration of the effect.

Table 3.2.4 Examples of considerations in the selection of electrochemical corrosion control methods for restoration andimprovement of durability (measures against chloride attack)
Cathodic protection method *Desalination method*

1) State of deterioration

A standard method for all
deterioration processes (Table
3.2.2)

Same as on the left

2) Possibility of ASR

Carefulrequired.

Same as on the left

3) Structural type

Under general conditions,applicable to both PC members
and RC members.

4)
Environmental
conditions

5) Expected effect6) Sustainability of effectconsiderationis

It can be used in land and inland
areas, atmosphere at sea, andsplash zones. Studies required
for use in the tidal zone (Table
3.2.3).
Corrosion reaction rate can be
reduced.
Mechanicalperformancecannotbe
expected to recover.
Long-term
corrosion
prevention effects can be

Same as on the left

Other repair methods**
Surface treatment methods are
often
used
beforethepropagation stage, and the crosssection repair method is often
used during and after theacceleration stage (Table 3.2.2).
Carefulconsiderationisrequired for the surface
treatment method and the crosssection repair method (seeConcrete Library 119 of theJapan
Societyof
Civil
Engineers).
Carefulconsiderationisrequired when applying thecross section repair method to
PC members.

It can be used in land and inland
areas, atmosphere at sea, andsplash zones. Studies required
for use in the tidal zoned (Table
3.2.3).

Depends on repair methods andmaterials used (see Concrete
Library 119 of the Japan
Society of Civil Engineers)

Chloride ions can be removed.
Mechanicalperformancecannot be expected to recover.

The cross section repair method
is also expected to recovermechanical performance.

Long-term
prevention

The surface treatment method
and the cross section repair

effects

corrosion
can beChapter 3 Design

maintained
maintenance.

7) State of service

8)
Efficiency
implementation

properNoneof9) Ease of maintenance

10)Environmental
constraints11) Cost

with

Pretreatment and repair (ofcracks and cross section) ofmembers with a lot ofdelamination and spalling areoften time consuming.
The linear/dotted anode method
is easy to visually inspect.
Corrosion prevention effect canbe confirmed quantitatively bymonitoring. Inspection byprofessional engineers on thismethod is required.
Usually, dust, vibration, andnoise associated with chipping
operations are rarely a problem(unless the chipping area islarge).
Depends on the remaining
planned service period. If thearea of delamination andspalling is small, the initial
repair cost is lower and the LCC
is also likely to be lower thanthat of the cross section repair
method.

maintained
maintenance.

23

with

properSame as on the left

Same as on the left

Normalinspection
andmaintenance are possible.
When used with in combination
with the surface treatment
method, maintenance of surface
treatment is necessary.

Same as on the left

Same as on the left

method are expected to beeffectiveinpreventing
corrosion for the period
corresponding to the design
conditions.
Because the use of the crosssectionrepairmethodtemporarily
reducesthemechanical performance of thestructure, prior examination isnecessary.
Same as on the left for the crosssection repair method (seeConcrete Library 119 of theJapan
Societyof
Civil
Engineers).
Surface treatment method andcross section repair method:same as the desalination
method.
Same as on the left for the
cross section repair method (seeConcrete Library 119 of theJapan
Societyof
Civil
Engineers).
Depends on the remaining
planned service period. If thearea of delamination andspalling is large, the initial costof the cross section repair
method is less than that of thecathodic
protection
ordesalination methods, and the
LCC is likely to be lower.

*

For further details, refer to the Method-Specific Standards part (cathodic protection method and desalination method) andappendices.
** Other methods here mean the surface treatment method and the cross section repair method. The cross section repair method
involves repairing all cross sections (partial cross section repair is not applicable). The table shows only points to be noticed
in comparison with the electrochemical corrosion control methods. Note that the electrodeposition method is applicable forthe same purpose as the surface treatment method.

(3) As a measure against carbonation, the cathodic protection method, re-alkalization method or electrodeposition method
is used based on the result of the durability verification of the structure or the result of the inspection, evaluation andjudgment for the structure. When selecting an electrochemical corrosion control method as a measure against carbonationof concrete structures, it is essential to consider various points shown in Table 3.2.1.
Regarding the 1) deterioration state, the applicable method differs depending on the deterioration process andthe grade of the appearance. The applicable method also differs for different 5) expected effects, such as restoration andimprovement of durability, and restoration of mechanical performance. Therefore, it is necessary to consider these factors
when selecting an electrochemical corrosion control method. The table 3.2.5 shows examples of grades of appearance
and applicable methods for carbonation prevention. Regarding 4) environmental conditions, the scope of each method
differs depending on the environment as shown in Table 3.2.6.
The Table 3.2.7 provides an example of points to consider when selecting a method to restore or improve
durability as a measure against carbonation. The table shows the applicability and considerations of the cathodic
protection method, re-alkalization method, and other methods with reference to the items listed in Table 3.2.1. The

24

C.L. 157 Guideline for Electrochemical Corrosion Control Method

Guidelines focus on the appropriate selection of an electrochemical corrosion control method, but for reference purposes,
the table also provides characteristics of the surface treatment method and cross section repair method in the other methods
column, in comparison with the cathodic protection method and the re-alkalization method. A case where a structure has
ASR (alkali-silica reaction) concerns is shown as complex deterioration. It should be noted that the considerations
described in this table may not always apply to structures in special conditions; the considerations are intended for
concrete structures, such as bridges, which have many proven implementations of electrochemical corrosion control
methods.

Table 3.2.5 Examples of grades of the appearance and applicable repair methods (measure against carbonation)
Expected effect
Structures

Appearance
Grade

Deterioration process

Newly constructedstructures－－

Grade I

Initiation stage

Grade II

Propagation stage

Existing structures
Grade III-1
Grade III-2
Grade IVFirst half of theacceleration stage
Secondhalfofacceleration stage
Deterioration stage

Recovery ofmechanicalperformance

Restoration and improvement of
durability
Surface treatment 1) (including antispalling 1))
Surface treatment 1) (including antispalling 1)),Re-alkalization 1)
Surface coating (including antispalling),
Cross
sectionrepair2),
realkalization, and cathodic protection
Cathodic protection, re-alkalization,and cross section repair
Cross section repair, cathodic
protection3), and re-alkalization 3)
4),
Cathodic
protection
realkalization 4)

－
－

－

－
Cross section repair (ifnecessary)
Cross section repair

1) Preventive maintenance method.
2) Select this method when the steel corrosion rate is high or the amount of corrosion is large.
3) Consider using it in combination with other methods (such as external cabling) if necessary.
4) Can be used in combination with other methods (such as external cabling).
Note 1: In all deterioration processes, the additional use of water treatment is effective in preventing the progress of steel corrosion.
Note 2: Electrodeposition method is applicable for the same purpose as surface treatment and surface coating shown in the table.

Table 3.2.6 Scope of application for different environments (measure against carbonation)
MethodEnvironment
Land and inland areas
Marine environment (atmosphereat sea)Electrochemical corrosion control method
Cathodic protection
Electrodeposition
Re-alkalization method
methodmethod
○
○
△
○

○

△

○ Applicable △Careful consideration is required

Table 3.2.7 Examples of considerations in the selection of electrochemical corrosion control method for restoration andimprovement of durability (measure against carbonation)
Cathodic protection method*Re-alkalization method*

1) State of deterioratedstate

A standard method used during
and after the propagation stage(Table 3.2.5)

A standard for all deterioration
processes (Table 3.2.5)

2) Possibility of ASR

CarefulSame as on the left

considerationis

Other methods**
Surface treatment is often used
before the propagation stage,
and cross section repair is often
used during and after the
propagation stage (Table 3.2.5).
CarefulconsiderationisChapter 3 Design

required.

3) Structural type

Under general conditions,applicable to both PC members
and RC members.

Same as on the left

4)
Environmental
conditions

Applicable to land, inland areas
and atmosphere at sea (Table
3.2.5)

Same as on the left

5) Expected effectCorrosion reaction rate can be
reduced.
Mechanicalperformance cannot be expected
to recover.

6) Sustainability
effectof7) State of service

8)
Efficiency
implementation

None

of

9) Ease of maintenance

10)Environmental
constraints11) Cost*

Long-term corrosion prevention
effects can be maintained withproper maintenance.

Pretreatment and repair (ofcracks and cross section) ofmembers with a lot ofdelamination and spalling areoften time-consuming.
The linear/dotted anode method
is easy to visually inspect.
Corrosion prevention effect canbe confirmed quantitatively bymonitoring. Inspection byprofessional engineers on thismethod is required.
Usually, dust, vibration, andnoise associated with chipping
operations are rarely a problem(unless the chipping area islarge)
Depends on the remaining
planned service period. If thearea of delamination andspalling is small, the initial
repair cost is lower and the LCC
is also likely to be lower thanthat of the cross section repair
methodCarbonation depth is set to 0 or
progress of steel corrosion is
reduced.
Mechanicalperformance cannot be expected
to recover.
The corrosion prevention effectcan be maintained for a longterm. However, when thesurface treatment method isused together in environmental
conditions where re-carbonation
is a concern, the effect depends
on the sustainability of thecorrosion prevention effect of
the surface treatment method.

Same as on the left

Same as on the left

Normalinspection
andmaintenance are possible. Whenused with the surface treatment
method, maintenance of surface
treatment method is necessary.

Same as on the left

Same as on the left

25

required for the surface
treatment method and crosssection repair method (seeConcrete Library 119 of theJapan
Societyof
Civil
Engineers).
Carefulconsiderationisrequired when applying thecross section repair method PC
members.
Depends on repair methods andmaterials used (see Concrete
Library 119, Japan Society of
Civil Engineers)
The cross section repair methodis
expectedtorecovermechanical performance.

The surface treatment method
and cross section repair method
are expected to be effective inpreventing corrosion for theperiod corresponding to thedesign conditions.
Because the use of the crosssectionrepairmethodtemporarily
reducesthemechanical performance of thestructure, prior examination isnecessary.
Same as on the left for crosssection repair method (seeConcrete Library 119 of theJapan
Societyof
Civil
Engineers).
Surface treatment method andcross section repair method:same as re-alkalization method.
Same as shown on the left forthe cross section repair method(see Concrete Library 119 of theJapan
Societyof
Civil
Engineers).
Depends on the remaining
planned service period. If thearea of delamination andspalling is large, the initial costof the cross section repair
method is less than that of thecathodic protection method or
the re-alkalization method, andthe LCC is likely to be lower.

For further details, refer to the Method-Specific Standards part (Cathodic protection method and Re-alkalization method)
and appendices.
** Other methods here mean the surface treatment method and the cross section repair method. The cross section repair method
involves repairing all cross sections (partial cross section repair is not applicable). The table shows only points to be noticed
in comparison with the electrochemical corrosion control methods. Note that the electrodeposition method is applicable forthe same purpose as the surface treatment method.

26

C.L. 157 Guideline for Electrochemical Corrosion Control Method

The cathodic protection method can be applied to both new and existing concrete structures located in the land and inland
areas and in the atmosphere at sea, which are susceptible to carbonation. However, when it is used for existing structuresduring and after the acceleration stage, it is necessary to consider using it in combination with other methods such as the
cross section repair method and the external cabling method, according to the degree of deterioration of mechanicalperformance based on cracks and cross-sectional defects of steel, and so on. Application to the structure that may beaffected by ASR requires considerations similar to those for chloride attack. In terms of maintainability, the cathodic
protection method has the advantage that the corrosion prevention effect can be quantitatively assessed by appropriate
inspections. In addition, when used in conjunction with a remote monitoring system, it can provide continuous monitoringand data collection from remote locations, allowing for more sophisticated, simplified, and streamlined maintenance.
The re-alkalization method can be applied to existing concrete structures, but when it is applied to existing
structures during and after the acceleration stage, it is necessary to consider using it in combination with other methods
such as the cross section repair method and the external cabling method, just as with the cathodic protection method. The
applicable environmental conditions are the same as for the cathodic protection method. The re-alkalization method
generally does not require any surface treatment after application, but it is recommended to perform surface treatment inenvironments where constant exposure to water may cause the electrolyte solution to leak. The applicability of the realkalization method is basically evaluated from the perspective of whether the intended corrosion prevention effect canbe maintained over the design corrosion prevention period. The evaluation is made by investigating and checking thecarbonation depth of the concrete structure. If the deterioration of the structure is at or after the propagation stage, special
attention should be paid to the degree of carbonation depth and steel corrosion, which significantly affect the sustainabilityof the effect. When applying the re-alkalization method to structures where ASR is a concern, consult the Method-SpecificStandards part and determine if the method is applicable.
With its expected effectiveness, the electrodeposition method is applicable to both new and existing structuresin the initiation and propagation stages as a measure against carbonation. However, unlike general surface treatment
methods, there is not enough quantitative data available on the effectiveness of the method in controlling carbon dioxide
and carbonation, making it practically difficult to quantitatively assess the duration of the effect, and thus prior researchand investigation is essential.

(4) The electrodeposition method is applicable to non-progressive cracks, for the purpose of improving the migration
resistance of corrosion factors, based on the results of inspection, evaluation, and judgment for the structures.
Electrodeposition is expected to fill cracks and densify the concrete surface, and produce the side benefit of providing
better surface quality and surface coating effect. It can also be used to repair cracks generated during the construction of
concrete structures. It is possible to use the method to repair cracks or perform surface treatment on structures located in
special environments with many work constraints, such as structures located underwater or underground, and structures
located in hot spring environments or radiation controlled areas. However, it is difficult to quantitatively evaluate theduration of the effect of the method, because there is not enough quantitative data available on its effectiveness in
improving the resistance to the permeation of materials in cracked closures and surface layers, and thus prior researchand investigation is essential.

Chapter 3 Design27

3.3 Implementation Plan in Design
The designer shall prepare an implementation plan based on the results of the Investigation for design andimplementation. The plan should consist of an outline of the implementation method and procedure, taking into accountthe characteristics of the materials and equipment to be used.

[Commentary]
The implementation plan prepared by the designer is intended to present the implementation method and procedures thatwill be the basis for Section 3.8 (verification of steel corrosion) of this document. The plan will be the basis for the
execution plan prepared by the executing party, but should not prevent the executing party from proposing safe, rational,
and efficient execution methods and procedures. When preparing an implementation plan, the designer should consider
issues such as the overall process and the implementation method based on the results of the Investigation for design andimplementation, taking into consideration the characteristics of the materials and equipment to be used.

3.4 Maintenance Plan
3.4.1 General
In order to maintain the effectiveness of corrosion control for an intended period of time, a maintenance plan shall be
formulated. The plan should include information such as appropriate inspection items and methods, timing andfrequency of inspections, the evaluation method, and actions to be taken if deterioration is observed.

[Commentary]
This section describes the method-specific maintenance plan to be formulated and incorporated into the maintenance planfor the structure, and Section 3.8 (Verification of steel corrosion) assumes that maintenance is conducted according to themethod-specific maintenance plan.
Even in structures to which the electrochemical corrosion control method is applied, steel corrosion may
progress due to the penetration of chloride ions from the outside, diffusion of endogenous chloride ions, lowered pH of
the steel surface caused by carbonation, or other reasons. Therefore, it is necessary to pay special attention to thepenetration of chloride ions, movement of residual chloride ions, and changes in the alkaline atmosphere around the steel
when preparing a maintenance plan specific to the electrochemical corrosion control method. Attention should also be
paid to indices and their levels that are used as criteria for maintaining structures against corrosion or checking theeffectiveness of corrosion control. These indices are sometimes not monitored in the maintenance of ordinary structures,but it is important to focus on them when preparing a method-specific maintenance plan.
In the structure to which the cathodic protection method is applied, it is necessary to ensure that the cathodic
protection system is maintained in good condition throughout the design corrosion protection period and that the intended
corrosion prevention effect can be achieved. Polarization quantity and depolarization quantity are indices used as criteria

28

C.L. 157 Guideline for Electrochemical Corrosion Control Method

for corrosion control according to Section 3.5 (Design and Control Standard for Corrosion Prevention) , but if it is assumed
that the corrosion prevention effect cannot be properly evaluated with these indices, other corrosion control indices may
be used instead. In such cases, it is necessary to adjust the maintenance plan accordingly (e.g., more frequent inspections).
For structures using desalination, re-alkalization, or electrodeposition methods, it is sufficient to ensure that theintended corrosion prevention effect can be achieved over the design corrosion prevention period.

3.4.2 Inspection(1) Inspection of structures to which the cathodic protection method is applied shall ensure that the cathodic protection
system is in good condition and the intended corrosion prevention effect is maintained.
(2) Inspection of structures to which the desalination, re-alkalization, and electrodeposition methods are applied shallensure that the intended corrosion prevention effect is maintained.

[Commentary](1) When inspecting structures to which the cathodic protection method has been applied, it is necessary to confirm thatthe cathodic protection system is in good condition and that the intended corrosion prevention effect is maintained.
Inspections are performed to determine the soundness of the cathodic protection system and remote monitoring system,
as well as the corrosion prevention effect. The cathodic protection system should be visually inspected and measured todetermine the operating condition of the DC power supply equipment, the condition of the storage box such asenergization and monitoring terminals, the anode system, the reference electrode, and the condition of the piping. The
integrity of the remote monitoring system is verified by its operating condition. Standard methods for confirming thecorrosion prevention effect include measuring the polarization or depolarization of the steel potential and visuallyinspecting for deformation such as cracking of the concrete surface. If the remote monitoring system is integrated withthe cathodic protection system, the operating status of the DC power supply and the corrosion prevention effects can bechecked on a daily basis using the readings from the remote monitoring system.

(2) For the desalination, re-alkalization, and electrodeposition methods, inspections are performed to determine whether
the intended corrosion prevention effect is achieved. As part of the design, implementation, and maintenance specified in
the Method-Specific Standards, items related to the corrosion control indices may also be investigated. In particular, it isimportant to obtain the initial values of the indices during the initial inspection, since the indices are required in Section
3.4.3 (Evaluation) to verify the corrosion prevention effect.
For structures where the surface treatment method is used in addition or where the electrodeposition method isused, also refer to the section describing the inspection of the surface treatment method in the "Recommendation forConcrete Repair and Surface Protection of Concrete Structures (Concrete Library 119)" published by JSCE.

Chapter 3 Design29

3.4.3 Evaluation
The structures to which the electrochemical corrosion control method has been applied shall be evaluated to determine
whether the intended corrosion prevention effect can be maintained over the design corrosion prevention period. The
evaluation shall be based on the information obtained from the inspections.

[Commentary]
The structures or their members shall be evaluated after the application of the electrochemical corrosion control method
to confirm that the corrosion prevention effect is maintained. If the effect decreases over time, due consideration shall begiven to ensure that the intended corrosion prevention effect is maintained over the design corrosion prevention period.
The structures to which the cathodic protection method is applied shall be comprehensively evaluated based on the resultsof the inspections to confirm that the operating condition of the cathodic protection system satisfies the requirements toachieve the intended corrosion prevention effect and that the materials and equipment constituting the system are in asound condition to satisfy the predetermined criteria.
The evaluation of structures to which the desalination, re-alkalization, or electrodeposition methods have been
applied shall confirm that the intended corrosion prevention effect is maintained over the design corrosion prevention
period. The evaluation shall be performed using items related to the indices defined as the maintenance criteria forcorrosion prevention in the design, implementation, and maintenance of the Method-Specific Standards.

3.4.4 Remedial measures(1) If periodic remedial actions are anticipated for the structure after the electrochemical corrosion control method isapplied, the plan for such actions shall be reflected in the maintenance plan.
(2) If the evaluation indicates that the desired corrosion prevention effect has not been achieved, the maintenance planfor the structure shall be reviewed.

[Commentary](1) The externally powered cathodic protection system requires periodic maintenance, including replacement of the DC
power supply and its components, replacement of anode materials and sacrificial anode materials (in the case of thegalvanic anode method), and surface treatment method used in conjunction. These activities should be included in themethod-specific maintenance plan as well as the maintenance plan for the structure.

(2) If the desired effect has not been achieved on the structure or its members after the application of the electrochemicalcorrosion control method, the maintenance plan for the structure should be reviewed. In some cases, repeated remedialactions only on the parts and members to which electrochemical corrosion control has been applied may be sufficient forthe performance of the structure at the end of its planned service life to exceed the maintenance control limit or therequired performance; while in other cases, some other actions on other parts or members may be necessary. Therefore,

30

C.L. 157 Guideline for Electrochemical Corrosion Control Method

it is necessary to select appropriate remedial measures according to the "Standard Specifications for Concrete Structures[Maintenance]" by referring to the inspection and evaluation results.
If the required performance of the structure can be satisfied by the implementation of remedial measures, thefollowing should be considered: repair and renewal of the cathodic protection system, review and adjustment of theenergization quantity, improvement of the energization system, and review of the corrosion prevention management, etc.

3.5 Design and Maintenance criteria for corrosion prevention(1) Each method shall be designed appropriately to achieve the intended corrosion prevention effect throughout thedesign corrosion prevention period.
(2) In a design process, the maintenance criteria for corrosion prevention shall be determined as needed based on thedesign corrosion prevention period and the intended effects.

[Commentary](1) Based on the results of various surveys described in Chapter 2 (Investigation), the design of the electrochemicalcorrosion control method shall basically take into consideration such issues as the deterioration state and structural
condition of the concrete structure, the expected effects, the methods of implementation, effect verification, andmaintenance methods. For the design details given in the Common Part of this document should be followed. The structure
or its member to which the electrochemical corrosion control method is applied shall be designed to achieve the intended
corrosion prevention effect during the design corrosion prevention period.
A cathodic protection system must be designed based on the condition of the structure as determined by theinvestigation. Issues that should be considered include: the characteristics and scope of a cathodic protection method(constant voltage, constant potential, or constant current method) and post-implementation activities such as maintenanceinspection and equipment replacement. Based on these considerations, the appropriate method, and anode and otherrequired materials should be selected and the energization system and monitoring system should be designed.
A desalination, re-alkalization, or electrodeposition process should be designed based on the condition of thestructure as determined by the investigation. The design process includes determining the energization conditions,selecting the materials and equipment to be used (e.g., anode materials and electrolyte solutions), and arranging the layoutof the temporary anode system. The temporary anode system should be designed considering the characteristics and scopeof each system.

(2) The following indicators can be used alone or in combination to determine the maintenance criteria for corrosion
prevention: numerical values such as the chloride ion concentration of the steel surface, the carbonation depth and thepolarization quantity of the steel, any deformation due to corrosion on the surface of the structure, and the grade ofappearance of the cathodic protection system. Depending on the indicators to be used, the inspection items and frequency
of maintenance inspections will differ. Therefore, it is essential to define the maintenance criteria for corrosion prevention
and maintenance plans that can be used to evaluate whether the intended corrosion prevention effect can be maintained
over the design corrosion prevention period. The maintenance criteria for corrosion prevention is an index used to confirm

Chapter 3 Design31that the formula (3.8.1) used in verification of steel corrosion is satisfied. For example, in the cathodic protection method,
the design limit value is set for the corrosion rate of steel (protective current density) and checked by obtaining the design
response value. It is an index used to confirm that the value attains 100 mV or higher using the polarization quantity or
the depolarization quantity as the prescription. Therefore, for different stages of verification for steel corrosion at the timeof design assuming the state immediately after the application of electrochemical corrosion control method, quality
control during construction, confirmation of effect immediately after construction (inspection), confirmation of corrosion
prevention effect in maintenance (evaluation), maintenance criteria for the same corrosion prevention may be used, ordifferent indices and levels may be used. In any case, when establishing maintenance criteria for corrosion prevention, it
is necessary to set appropriate indicators and levels that can confirm that the intended corrosion prevention effect can beachieved over the design corrosion prevention period.
The maintenance criteria for corrosion prevention in the cathodic protection method corresponds to the
corrosion control index defined in Section 3.5 Maintenance criteria for corrosion prevention of the Guidelines for the
Cathodic Protection Method. An appropriate maintenance plan should be developed according to the corrosion control
index to be used, and steel corrosion will be verified on the assumption that maintenance will be performed according to
the plan.
As for the desalination, re-alkalization, and electrodeposition methods, it is common practice to remove thetemporary energization system after implementation, and the conditions of chloride ion concentration, pH, oxygen, water,and other factors that cause steel corrosion in concrete may change over time. Therefore, when designing a temporary
energization system for these methods, it is necessary to set the target to be achieved immediately after implementation,
assuming that the intended corrosion prevention effect will be achieved at the end of the design corrosion prevention
period. The maintenance criteria for corrosion prevention in the desalination, re-alkalization, and electrodeposition
methods are defined in Section 3.5 of the corresponding guidelines for each method. An appropriate maintenance planshould be developed according to the target set for each method and steel corrosion verification will be performed
accordingly. From the above, it is essential to develop a maintenance plan to confirm that the intended corrosion
prevention effects are achieved during the design corrosion prevention period, because in the maintenance of the structure
to which these methods are applied, there are cases where the target set immediately after the construction of the temporary
energization system (maintenance criteria for corrosion prevention used in the design assuming conditions immediately
after application) is no longer satisfied but the intended corrosion prevention effects are still maintained.

3.6 Materials and Equipment
3.6.1 GeneralIn the application of the electrochemical corrosion control method, materials and equipment of the required quality
and performance shall be selected and used to satisfy the intended corrosion prevention effect for the design corrosion
prevention period with the required energization.

[Commentary]

32

C.L. 157 Guideline for Electrochemical Corrosion Control Method

It is important that the materials and equipment used have the required quality and performance to achieve the intended
corrosion prevention effect on the structure or its members to which the electrochemical corrosion control method isapplied, over the design corrosion prevention period. Such materials and equipment include: for new concrete structures,
those used for the members to which the corrosion control will be applied; for existing concrete structures, those used forthe target members and those used for pretreatment; and for both new and existing concrete structures, those used for new
cathodic protection systems and temporary energizing systems. Some members of existing concrete structures may havea history of repairs, and the materials used for such members must also be examined. It is necessary to ensure that thematerials and equipment used in each case retain the required performance to deliver the required direct current to thesteel in concrete.
Materials and equipment specific to the electrochemical corrosion control method include anodes, wiring, andDC power supply equipment, and should be selected based on their characteristics, design values, and environmental
impact. In particular, it is necessary to ensure that the DC power supply equipment is safe for humans and ecosystems,
that it does not cause noise or radio wave interference to the surrounding environment, and that its structure is explosionproof where required.

3.6.2 Materials Composing Members Subject to Corrosion Control
The materials constituting the members subject to corrosion control shall be of a quality that does not significantly
inhibit energization.

[Commentary]
In the electrochemical corrosion control method, the steel in concrete is used as the cathode, and direct current is supplied
from the anode installed on or near the concrete surface. Therefore, it is necessary to ensure that the materials used forthe members do not inhibit energization.
For newly constructed concrete structures, the concrete used for the members should be of quality that does not
significantly inhibit energization.
For existing concrete structures, it is necessary to check the quality of the concrete used for the members andthe materials used in previous repairs, and if the materials are found to interfere with the expected effects of each method,they should be replaced with appropriate materials. Factors that may inhibit energization include steel on the surface(including exposed reinforcing bars), corrosion-resistant steel (e.g., epoxy-coated reinforcing bars), cross section repair
materials and crack injection materials whose electrical resistivity is significantly different from that of the concrete in
the area to be protected from corrosion, covering materials and hydrophobic impregnating materials of the concretesurface layer. In addition, for existing concrete structures, it is necessary to pretreat deteriorated areas such as cracks,
delamination, spalling of the member. The pretreatment materials shall be of a quality that does not significantly inhibit
energization.

Chapter 3 Design33

3.6.3 Materials and Equipment used in Electrochemical Corrosion Control Methods
Materials and equipment used for the electrochemical corrosion control method shall have sufficient durability
according to the energizing conditions of each method such as the energizing period and the energizing current amount,and shall satisfy the intended corrosion prevention effect by the application of each method.

[Commentary]
In the electrochemical corrosion control method, there are specific materials and equipment used for a cathodic protection
system and a temporary energization system. These materials and equipment must not inhibit energization for the design
corrosion prevention period and must satisfy the designed energization conditions.
In the cathodic protection method, continuous protective current supply is required for the design corrosion
prevention period in principle, so the materials and equipment should be selected in consideration of the environment of
the structure and the design corrosion prevention period. The materials and equipment include anode materials,
distributors, anode covering materials, and the DC power supply equipment. Note that the performance of the anodematerial can be verified using the accelerated test described in NACE Standard TM0294-2016, Item No. 21225: Testingof Embeddable Anodes for Use in Cathodic Protection of Atmospherically Exposed Steel-Reinforced Concrete; and thatthe electrical resistivity rate of the repair material used for the anode covering material and pretreatment can be verified
using the test described in the Japan Society of Civil Engineers Standard "Test method of measuring resistivity for
patching repair materials with four electrodes" (JSCE-K 562). For the materials and equipment whose parts can be easily
renewed or replaced, it is effective to perform the renewal or replacement during a periodic inspection based on themaintenance plan for cathodic protection.
In principle, the energization period is limited for the desalination, re-alkalization, and electrodeposition
methods. Therefore, the materials and equipment used for these methods should be selected in consideration of theenvironment of the structure, and the energizing conditions such as the energizing period and the energizing current
amount. The materials and equipment used in these methods include anode materials, anode holding materials, electrolyte
solution, and a temporary DC power supply. For example, alkaline electrolyte solution containing substances such as
H3BO3 and K2CO3 is used in the desalination method, while alkaline electrolyte solution containing Na2CO3, K2CO3, or
Li2CO3 is used in the re-alkalization method. In the electrodeposition method, when the natural water is used as electrolyte
solution, it should contain substances capable of precipitating poorly soluble salts, and when the artificial aqueous solution
is used, it should contain substances such as magnesium acetate.
Repair materials for pretreatment of existing concrete structures and anode covering materials for cathodic
protection should be used with consideration of the aforementioned characteristics and other factors such as usable timeand curing time. These characteristics can be evaluated using the methods specified in the relevant Japanese Industrial
Standards (JIS) and the Japan Society of Civil Engineers standards.

34

C.L. 157 Guideline for Electrochemical Corrosion Control Method

3.6.4 Material Characteristics
For the materials used in the electrochemical corrosion control method and for the constituent materials of the members
to be protected, the characteristic values required for the verification of steel corrosion in each method shall be
determined by an appropriate method.

[Commentary]
The characteristic values required for the verification of steel corrosion in structures to which the electrochemicalcorrosion control method is applied shall be determined appropriately for the materials used for each method and theconstituent materials of the members protected from corrosion, based on the environmental and other conditions.
Verification for steel corrosion of the structure to which the cathodic protection method is applied, the corrosion rate of
the steel in the object member to which the direct current is supplied as an index, for using the protective current density
as an equivalent physical quantity as an index, electrical resistivity such as concrete or repair material used to predict theprotective current density is a characteristic value. In the desalination method, the chloride ion concentration in the vicinityof the steel is used as an index for verification, so the diffusion coefficient of chloride ion after the application of themethod, which is used to predict the penetration of chloride ion, is used as a characteristic value. In the re-alkalization
method, the carbonation depth is used as an index for verification, so the rate coefficient of carbonation after theapplication of the method, which is used to predict the progress of carbonation, is used as a characteristic value. In theelectrodeposition method, the hydraulic conductivity of concrete and the diffusion coefficient of chloride ions after theapplication of the method are used as characteristic values. These characteristic values may be appropriately determinedby thoroughly examining the past test results related to each method. For the characteristic values of ordinary materials
used in each method and their handling, it is recommended to refer to the Method-Specific Standards part.

3.7 Load
3.7.1 General(1) For the verification of steel corrosion, appropriate combinations of loads assumed to occur during theimplementation stage and the design corrosion prevention period shall be taken into account.
(2) The design load shall be obtained by multiplying the characteristic value of the load by the load factor.

[Commentary]
Since the electrochemical corrosion control is intended to prevent steel corrosion, the Guidelines focus on the preventionof steel corrosion, an indicator used to evaluate the durability of structures. Therefore, the verification focuses mainly on
steel corrosion. In the verification for steel corrosion, it is necessary to consider appropriate combinations of all loads thatare assumed to affect the development of rust and corrosion reactions in steel during the construction and design corrosion
prevention period. When designing using maintenance criteria for corrosion prevention, appropriate combinations of allChapter 3 Design

35

assumed loads shall be considered according to the maintenance criteria. In principle, the design loads shall be inaccordance with "Standard Specifications for Concrete Structures [Design]" when electrochemical control is used together
with other methods to maintain, recover, or improve mechanical or other performance and the load factor used in a
multiplication formula to obtain a characteristic value of the load shall be in accordance with Chapter 6 Load of the"Standard Specifications for Concrete Structures [Design: General Requirements]". The load factor for environmental
actions can generally be assumed to be 1.0.

3.7.2 Loads to be considered in the Design(1) Appropriate consideration shall be given to the loads occurring on the structure to be treated and on the part towhich the electrochemical corrosion control method is applied.
(2) If the actual measured value of the load is known, the characteristic value obtained from the measured value
may be used.

[Commentary](1) and (2) The loads to be considered in the design of electrochemical corrosion control methods include those thatremain unchanged from before application and those that are changed or added after application. These loads must be
appropriately considered based on the structure to be protected, and they differ depending on its member, purpose andthe methods of application and implementation. Therefore, it is important that each of the loads on the structure is
examined separately in each state and that their responses are reasonably combined where necessary. In particular, it isnecessary to sufficiently consider the environmental actions likely to occur on the structure and the new actions that may
occur due to the application of the corrosion control method. The former include temperature, solar radiation, humidity,
supply of moisture, supply of various substances and their concentration, and the latter include re-diffusion of chloride
ions and macrocell corrosion, and changes in chemical composition due to energization.
If a more reliable verification or a more rational design is possible by actually measuring the characteristics
acting on the structure, the measured values obtained from statistical processing of multiple measurement results can beused as characteristic values. In such cases, the load factors used in the design load should be defined accordingly. For
the characteristic values of the standard loads used in each method and their handling, it is recommended to refer to the
Method-Specific Standards part.

36

C.L. 157 Guideline for Electrochemical Corrosion Control Method

3.8 Verification of Steel Corrosion(1) Steel corrosion shall be verified by confirming that the desired corrosion prevention effect can be achieved overthe design corrosion prevention period, provided that the established implementation plan and maintenance plans are
implemented.
(2)

In general, steel corrosion of structures to which the electrochemical corrosion control method is applied shallbe verified using the following equation (3.8.1):
γi Sd / Rd ≦ 1.0(3.8.1)

where Sd: Design response value
Rd : Design limit value
γi : Structural factor , generally 1.0 to 1.2 may be used.
(3) The established maintenance criteria for corrosion prevention can be used to confirm that the equation (3.8.1) issatisfied for corrosion prevention for each of the following stages: verification at the time of design (verification
assuming conditions immediately after the application of the method), post-implementation inspections, andmaintenance inspections (confirmation of the corrosion prevention effect).

[Commentary](1) and (2) Electrochemical corrosion control is a method designed to prevent deterioration in the performance ofstructures by preventing steel from corroding. Therefore, the verification focuses on steel corrosion. Steel corrosion isverified by confirming that the intended corrosion prevention effect can be achieved throughout the design corrosion
prevention period, provided that the previously formulated implementation plan and the maintenance plan are followed.
However, since the characteristics of materials and actions required for verification change with the environment andtime, the method or combination of methods and indices used to confirm the intended corrosion prevention effects may
differ depending on when the verification is performed.
In principle, response values are calculated using the established maintenance criteria for corrosion prevention,
based on analytical results using an appropriate analytical model, or empirical rules based on extensive past experienceand results, or experimental evidence, according to the applicable corrosion control method, the condition of structures
or members, and the assumed deterioration mechanism.
Direct indices of these design values are: characteristic values such as the corrosion rate in the cathodic
protection method, the chloride ion concentration around the steel in the desalination method, the pH around the steel inthe re-alkalization method, and the resistance to the permeation of the material of the member after the application of theelectrodeposition method. In the durability verification, these characteristic values will be determined based on thematerials, equipment, and system components to be used in the corresponding corrosion control method, and on thecharacteristics of the materials and members. However, if it is difficult to make future predictions with the required
accuracy, indicators can be adequately determined based on information accumulated from similar environments or
structures, previous research and test results, and then the characteristic values obtained from the indicators can be used.
Note that when it is necessary to ensure the continuity of the corrosion prevention effect on an entire system, as in acathodic protection system, it may be effective to set an indirect index using the potential of the steel. For more details,

Chapter 3 Design37

refer to the relevant sections of the Method-Specific Standards part. When electrochemical corrosion control is used in
combination with other measures to restore, maintain or improve mechanical or other performance, refer to the "Standard
Specifications for Concrete Structures [Design] and [Maintenance]" and related guidelines.

(3) When maintenance criteria for corrosion prevention are used to confirm that the equation (3.8.1) is satisfied, in somecases the same maintenance criteria for corrosion prevention are used, while in other cases different values and levels areused for different stages such as steel corrosion verification at the time of design (verification assuming the conditions
immediately after the application of electrochemical corrosion control method), quality control during implementation,
confirmation of effect immediately after implementation (inspection), confirmation of corrosion prevention effect during
maintenance inspections (evaluation). In both cases, it is necessary to establish appropriate maintenance criteria forcorrosion prevention that can ensure that the intended corrosion prevention effect can be achieved over the design
corrosion prevention period.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

Chapter 4 Implementation
4.1 General
Implementation plans shall be adequately prepared, taking into account such factors as the characteristics of thematerials and equipment to be used and the implementation conditions and constraints. Implementation shall be carriedout in such a way as to ensure the quality assumed in the design.

[Commentary]
Electrochemical corrosion control may not be sufficiently effective as designed if it is not implemented undermanagement and quality control appropriate to the characteristics of the materials and equipment to be used. Prior to
implementation, it is necessary to prepare appropriate implementation plans in accordance with the standards andguidelines related to the materials and equipment. It is also very important to ensure the quality assumed in the design byassigning professional electrochemical corrosion control engineers on site to properly manage the implementation.
When electrochemical corrosion control is used to repair structures, time and space for implementation areoften very limited, requiring detailed implementation plans. When electrochemical corrosion control is used to protect
against chloride attack, it is not necessary to remove the sections of concrete where the chloride ion concentration exceeds
the steel corrosion generation limit (in the cross section repair process, such sections must be removed); however, it isconceivable that if the degradation in the remaining sections is not properly treated, the intended corrosion prevention
effect may not be achieved or deterioration may occur relatively early after the corrosion control is applied. Therefore, it
is important to properly pretreat the damaged sections and repair the concrete as described in the Method-SpecificStandards, and to record details such as the process and areas of pretreatment and repair.

4.2 Implementation Plan
(1) The implementation contractor shall draw up an implementation plan for the electrochemical corrosion control
method specified in the design documents, taking into account the structural and environmental conditions andimplementation requirements.
(2) The implementation plan shall specify the implementation method and procedures appropriate to thecharacteristics of the materials and equipment to be used, and the quality control items and procedures.

[Commentary](1) and (2) In formulating an implementation plan, the entire process, implementation method, materials and equipmentused, quality control plan, safety and health management, environmental protection measures should be examined. The
implementation plan should be consistent with the designer’s plan, as well as with requirements and constraints such as
work period, environmental conditions, safety of work, and economical efficiency. Inspection plans agreed with theChapter 4 Construction

39

contractee must be reflected in the implementation plan. The implementation contractor must fully understand the current
condition of the structure and the implementation constraints, and should conduct additional investigations of the structure
beforehand if the results of the Investigation for design and implementation are not sufficient. Work on structures inservice often presents a different working environment from that of new construction, such as limited time and space,requiring careful consideration to ensure quality and safety.
The implementation plan covers all aspects from the actual work to quality control and implementation
management. Since the characteristics of the materials used and the effects of the equipment used may be affected byenvironmental conditions such as temperature and humidity during implementation, it is necessary to examine appropriate
implementation methods and procedures so that the corrosion prevention effects assumed in the design can be achieved.
Quality control and implementation management procedures should also be prepared for each stage of implementation.
The engineer in charge of each work should have access to the implementation plan.

4.3 Implementation(1) Implementation shall be carried out according to the implementation plan.
(2) Implementation shall be carried out under the supervision of professional engineers specializing in theelectrochemical corrosion control method to be used.
(3) Materials and equipment to be used shall be manufactured, processed, transported, and stored in accordance with
their characteristics.
(4) The contractor shall perform quality control at each stage of the implementation according to the quality control
plan.

[Commentary](1) and (2) Implementation should be executed efficiently and safely according to the implementation plan. In general,the quality of the work depends greatly on the ability of the engineers performing the work, so it is important to appoint
professional engineers specializing in the electrochemical corrosion control method to be applied and have them supervise
the work. It is also necessary to clarify the scope of responsibility and authority of each engineer during theimplementation.

(3) Materials and equipment to be used shall be handled as specified. For example, in the cathodic protection
method, all anode materials installed in a corrosion prevention circuit must be electrically conductive, so the anodematerials and the distributor should be properly connected by spot welding or other method. The anode covering materials,
which are generally made of cement mortar, should be protected from weathering by avoiding storage in rain or highhumidity environments. The DC power supply equipment using an external power supply system, must be installed andgrounded (Class D grounding) in accordance with the "Technical Standards for Electrical Facilities".
In the desalination method and the re-alkalization method, careful consideration must be given to worker safety
and leakage prevention in the supply and storage of high pH electrolyte solution. Temporary DC power supplies should
be grounded and preferably energized at 40 V or less.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

When the electrodeposition method is used and anode materials are installed in the sea, they must be anchored
to prevent damage from external forces such as waves and tidal currents. Electrolyte holding materials, if used, should beinstalled in such a way that the electrolyte solution does not leak.

(4) The contractor implements quality control based on the quality control plan to ensure the quality assumed in the design.
In general, it is important for reasonable quality control to conduct frequent quality control at the beginning of
implementation and to flexibly reviewing the quality control plan as the quality stabilizes. If quality control indicates thatplanned control limits are being exceeded, it is necessary to investigate the cause, take action, and review the quality
control plan. If an abnormality occurs, the operator shall immediately report it to the contractor’s supervising engineer.
The supervising engineer shall stop work, identify out-of-specification areas, and immediately report to the supervising
engineer for appropriate action.

4.4 Inspection(1) The contractee shall provide the contractor with an inspection plan at the time of order placement and shall be
responsible for conducting the inspections.
(2) If the inspection result is deemed unacceptable, corrective action shall be taken.

[Commentary](1) Corrosion prevention can be considered effective as intended if properly conducted inspections at each implementation
phase confirm that electrochemical corrosion control has been implemented as specified in the design documents. The
contractee shall make an appropriate inspection plan after having sufficiently examined the materials proposed by thecontractor and the aspects such as reliability of the implementation process to be used. The inspection plan should include
specific descriptions of inspection items, procedures, frequency, and pass/fail criteria. The contractor shall receive theinspection plan prior to implementation and confirm its contents. The contents must be agreed upon by the contractee andthe contractor. The contractee shall be responsible for performing the inspections in accordance with the inspection plan.
Inspection items for the construction of the cathodic protection method include the following: continuity check
between steels, reference electrode operation check, continuity check between anodes, insulation check between anodeand steel, circuit operation check, and initial energization amount adjustment (polarization quantity test, depolarization
quantity test). In the desalination method, there are inspections such as continuity check between steels, and desalination
quantity check after completion of energization. In the re-alkalization method, there are inspections such as continuity
check between steels and carbonation depth check after completion of energization. In the electrodeposition method, there
are inspections such as continuity check between steels, confirmation of crack closure and coating condition after thecompletion of energization.
The inspection procedures and criteria differ depending on the type of structure, the materials used, and theelectrochemical corrosion control method to be applied, and must be determined to enable efficient, reliable, and objective
inspections. It is common practice in Japan to use the procedures and evaluation criteria specified in the JapaneseIndustrial Standards (JIS), the Japan Society of Civil Engineers standards, and the standards specified by the contractee.

Chapter 4 Construction

41(2) If an inspection reveals unacceptable workmanship or quality, corrective action such as rework or material change
shall be taken. After taking corrective action, verify quality by re-inspection. The maintenance plan formulated in thedesign phase may need to be reviewed.
The purpose of inspections is to ensure the quality assumed in the design. The Implementation section of the
Method-Specific Standards describes ways to confirm the corrosion prevention effect (cathodic protection method) andevaluate the achievement of the objective, but it should be noted that inadequate design may have been the cause of the
failure to achieve the objective assumed in the design.

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C.L. 157 Guideline for Electrochemical Corrosion Control Method

Chapter 5 Maintenance
5.1 General(1) The method-specific maintenance plan shall be reviewed as necessary based on the inspection results, and changes
to the plan shall be reflected in the maintenance plan of the structure.
(2) Based on the maintenance plan of the structure, the structure to which the electrochemical corrosion control
method is applied shall be appropriately maintained.

[Commentary](1) and (2) The principle of maintenance is to formulate and implement a management plan to maintain the performanceof a new or existing structure at or above the required level throughout the design service life of the structure. On theother hand, the electrochemical corrosion control is only one of many methods to prevent steel corrosion in concrete
structures, and simply achieving the desired effect during the design corrosion prevention period does not necessarily
guarantee the performance of the structure for the remainder of its service life. Therefore, after applying anelectrochemical corrosion control method, it is necessary to review the maintenance plan for the method based on the
results of method-specific inspections and update the maintenance plan of the structure accordingly.
For the cathodic protection method, the maintenance of the cathodic protection system shall be appropriately
carried out together with the maintenance of the structure based on the updated maintenance plan of the structure.
For the desalination, re-alkalization, and electrodeposition methods, the maintenance of the structure shall beappropriately carried out based on the updated maintenance plan of the structure.

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Chapter 6 Records
6.1 General(1) The contractor shall record the details of the work performed.
(2) For maintenance purposes, the contractee shall maintain and retain records related to the design, maintenanceplan, implementation, quality control, and inspection of the structure during its service period.

[Commentary](1) The records shall contain the implementation plan and the results of the work conducted in accordance with the plan,and should be retained to contribute to the quality assurance of the structure or its members to which the electrochemicalcorrosion control method is applied and to improve the quality and workability of structures in future projects.

(2) These records contain the information necessary to maintain the structure and can be used as a baseline formaintenance after the electrochemical corrosion control method has been applied. It is important that the records containall the work information necessary for maintenance. In order to clarify the role and position of the engineers involved in
the work, it is desirable that the documentation include the company, name, and other necessary information of the persons
who performed each work. The records should be retained during the service life of the structure.