TECHNICAL
GUIDELINES
Prepared by the International Concrete Repair Institute
June 2013
Guideline No. 510.1-2013
Copyright ©2013 International Concrete Repair Institute
Guide for Electrochemical Techniques
to Mitigate the Corrosion of Steel for
Reinforced Concrete Structures
TECHNICAL
GUIDELINES
Prepared by the International Concrete Repair Institute
June 2013
Guide for Electrochemical
Techniques to Mitigate
the Corrosion of
Steel for Reinforced
Concrete Structures
Guideline No. 510.1-2013
Copyright © 2013 International Concrete Repair Institute
All rights reserved.
International Concrete Repair Institute
10600 West Higgins Road, Suite 607, Rosemont, IL 60018
Phone: 847-827-0830 Fax: 847-827-0832
Web: www.icri.org
E-mail: info@icri.org
About ICRI Guidelines
The International Concrete Repair Institute (ICRI) was
founded to improve the durability of concrete repair
and enhance its value for structure owners. The identification, development, and promotion of the most
promising methods and materials are primary vehicles
for accelerating advances in repair technology. Working
through a variety of forums, ICRI members have the
opportunity to address these issues and to directly
contribute to improving the practice of concrete repair.
A principal component of this effort is to make carefully
selected information on important repair subjects
readily accessible to decision makers. During the past
several decades, much has been reported in the liter­
ature on concrete repair methods and materials as they
have been developed and refined. Nevertheless, it has
been difficult to find critically reviewed information on
the state of the art condensed into easy-to-use formats.
To that end, ICRI guidelines are prepared by sanctioned
task groups and approved by the ICRI Technical
Activities Committee. Each guideline is designed
to address a specific area of practice recognized as
essential to the achievement of durable repairs. All
ICRI guideline documents are subject to continual
review by the membership and may be revised as
approved by the Technical Activities Committee.
Technical Activities Committee
Kevin A. Michols, Chair
James E. McDonald, RC
Mark Hughes, Secretary
Frank Apicella
Jorge Costa
Andrew S. Fulkerson
Fred Goodwin
Gabriel A. Jimenez
Ralph C. Jones
Peter R. Kolf
David Rodler
Lee Sizemore
Aamer Syed
David Whitmore
Producers of this Guideline
ICRI Committee 510, Corrosion
Matt Sherman, Chair
Peter DeNicola, Secretary
Randal M. Beard
Jorge Costa
Timothy Gillespie
Fred Goodwin
Graeme Jones
Richard R. McGuire
Jessi Meyer
Brian J. Stratman
Paul G. Tourney
Gerard J. Vaerewyck
Frank Verano
Robert Walde
David Whitmore, Subcommittee Chair
Acknowledgments
The members of the committee thank the many
ICRI members who, through their review of the
guideline, offered many insightful and meaningful suggestions.
Synopsis
This guideline is intended to provide information
on electrochemical techniques used to mitigate
the corrosion of steel in atmospherically exposed
concrete structures. The information presented is
based on testing and the experience of owners,
engineers, contractors, and suppliers. This guideline includes information on impressed current
and galvanic cathodic protection, electrochemical
chloride extraction, and realkalization.
Keywords
cathodic protection; concrete; corrosion; corrosion
control; corrosion prevention; electro­chemical
chloride extraction; electrochemical treatment;
galvanic; impressed current; realkalization
This document is intended as a voluntary guideline for the owner, design professional, and
concrete repair contractor. It is not intended to relieve the professional engineer or designer
of any responsibility for the specification of concrete repair methods, materials, or practices.
While we believe the information contained herein represents the proper means to achieve
quality results, the International Concrete Repair Institute must disclaim any liability or
responsi­bility to those who may choose to rely on all or any part of this guideline.
510.1–2013
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
Contents
1.0 Introduction........................................................................................................................................ 1
1.1 Purpose........................................................................................................................................ 1
1.2 The Economic Case for Using Electrochemical Corrosion Mitigation Systems................................ 1
1.3 History......................................................................................................................................... 2
2.0 Safety Considerations........................................................................................................................ 3
3.0 Developing a Corrosion Management Plan....................................................................................... 3
3.1 Project Document Review............................................................................................................. 3
3.1.1 Original Design and Contract Documents............................................................................ 3
3.1.2 Original Construction Submittals......................................................................................... 4
3.1.3 Other Construction Documentation...................................................................................... 4
3.1.4 Repair and Maintenance Documentation............................................................................. 4
3.1.5 Historic Standards............................................................................................................... 4
3.2 Condition Surveys........................................................................................................................ 4
4.0 Corrosion of Steel in Concrete........................................................................................................... 5
4.1 Corrosion Process of Steel in Concrete......................................................................................... 5
4.2 Environmental Conditions............................................................................................................. 6
4.2.1 Exterior Exposure................................................................................................................ 6
4.2.2 Interior Exposure................................................................................................................. 6
4.2.3 Industrial Exposure.............................................................................................................. 6
4.2.4 Urban and Rural Exposure................................................................................................... 6
4.2.5 Coastal Exposure................................................................................................................ 6
4.3 Service-Life Expectations............................................................................................................. 6
4.4 Economics that Affect Decision Making........................................................................................ 7
5.0 Corrosion Mitigation Techniques: Cathodic Protection (CP) and Electrochemical Treatments....... 7
5.1 Introduction.................................................................................................................................. 7
5.2 General Mechanism and Common Requirements.......................................................................... 8
5.2.1 Electrical Continuity............................................................................................................. 8
5.2.2 Electrical Connections to the Reinforcing Steel.................................................................... 8
5.2.3 Electrical Connections to Anodes......................................................................................... 8
5.2.4 Short Circuits...................................................................................................................... 8
5.2.5 Hydrogen Embrittlement...................................................................................................... 8
5.3 Cathodic Protection...................................................................................................................... 9
5.3.1 Mechanism of Protection (ICCP).......................................................................................... 9
5.3.2 Mechanism of Protection (GCP)........................................................................................... 9
5.3.3 Additional Components...................................................................................................... 10
5.3.4 Design Process................................................................................................................. 10
5.3.5 Distributed Anode Systems for ICCP.................................................................................. 11
5.3.5.1 Conductive Coatings............................................................................................. 11
5.3.5.2 Conductive Overlays.............................................................................................. 11
5.3.5.3 MMO Titanium Anode Systems.............................................................................. 11
5.3.6 Discrete Anode Systems for ICCP...................................................................................... 12
5.3.7 Localized Galvanic Systems.............................................................................................. 12
5.3.8 Distributed Galvanic Systems............................................................................................ 13
5.3.8.1 Zinc Installed Inside Protective Jackets in Marine Environments............................ 14
5.3.8.2 Spray-Applied Galvanic Anodes............................................................................. 14
5.3.8.3 Embedded Galvanic Strip Anodes.......................................................................... 15
5.3.8.4 Self-Adherent Galvanic Sheet Anodes.................................................................... 15
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013
Contents
5.4 Electrochemical Treatments........................................................................................................ 15
5.4.1 Mechanism....................................................................................................................... 15
5.4.2 Electrochemical Chloride Extraction (ECE).......................................................................... 15
5.4.3 Electrochemical Realkalization (ERA)................................................................................. 16
6.0 Performance and Longevity of Mitigation Systems........................................................................ 16
6.1 Performance Management......................................................................................................... 16
6.2 Post-Installation Considerations.................................................................................................. 17
7.0 Summary........................................................................................................................................... 17
8.0 References and Standards............................................................................................................... 18
8.1 Referenced Standards and Reports............................................................................................. 18
8.2 Cited References........................................................................................................................ 20
510.1–2013
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
1.0 Introduction
1.1 Purpose
The primary purpose of this guideline is to provide information on electrochemical techniques
used to mitigate the corrosion of reinforcing steel
in atmospherically exposed concrete structures.
This document is not intended to limit the corrosion mitigation techniques to those mentioned
herein, but rather to provide basic information
about those that are commercially available at
the time of this document’s publication. This
guideline is not intended to validate or confirm
performance for any of the systems described.
The information presented is based on testing
and experience performed and acquired by
owners, engineers, contractors, and vendors
engaged in the rehabilitation and protection of
reinforced concrete structures affected by corrosion of the reinforcement.
This guideline includes information on
impressed current and galvanic cathodic protection, electrochemical chloride extraction, and
realkalization. The guideline does not include
information on coatings, overlays, and other
strategies to waterproof and protect that may also
provide corrosion protection benefits. This document also does not include information on
electro-osmotic pulse, which is an electrochemical technique primarily intended as a concrete
drying method that also provides benefits in
mitigating corrosion. This document also does
not include information on electrokinetic nano­
particle treatment, which is an electrochemical
technique that is primarily intended as a method
to improve the physical properties of concrete,
nor does it include information on electrochemical lithium impregnation, which is primarily
intended as a treatment for alkali-silica reaction.
These electrochemical techniques also provide
benefits in mitigating corrosion.
For the purpose of this guideline, the word
“structures” includes buildings, bridges, tunnels,
piers, parking garages, and similar types of
construction. Corrosion mitigation is taken to
mean the reduction or stoppage of corrosion in
the structure.
This guideline is intended to help familiarize
owners, engineers, contractors, suppliers, and
other interested parties with the procedures,
equipment, materials, and other aspects of the
evaluation and selection of corrosion mitigation
techniques for reinforced concrete structures.
None of the information presented herein is
intended to supersede sound judgment exercised
by engineers or other qualified licensed designers
in the selection and implementation of appropriate
corrosion mitigation countermeasures for affected
concrete structures. Furthermore, corrosion
evaluation and design of electrochemical mitigation techniques requires specialized knowledge
and experience, and the procedures discussed
vary considerably in their features, benefits,
limitations, service life, and disruption to the
normal activities of the structure. In addition,
site-specific conditions may require variations
and/or modifications of the techniques described
herein for adequate corrosion protection. As such,
the ultimate selection of the most appropriate
countermeasure should follow a thorough assessment of the root causes that have resulted in
corrosion of the reinforcement and should be done
by qualified personnel with established credentials and experience in this field. Typical qual­
ifications include Professional Engineering
Registration, National Association of Corrosion
Engineers (NACE), Cathodic Protection Specialist Certification, and other qualifications by
virtue of education and experience as may be
acceptable to owners and end-users of these
technologies. In the drafting of this guideline, the
authors have attempted to avoid undue repetition
of information available from other sources such
as ASTM International, NACE, and European
standards. Guidance is provided such that the
reader can readily source these complementary
documents and, where relevant, an explanation
is provided of the issues arising with the use of
corrosion mitigation solutions for reinforced
concrete and masonry structures. Also, this
document does not attempt to duplicate or supersede previous publications and refers to other
documents from NACE, the UK Concrete
Society, and the Comité européen de normalisation (CEN) standards, where applicable.
1.2 The Economic Case
for Using Electrochemical
Corrosion Mitigation Systems
Corrosion is a multi-billion-dollar problem in the
United States and other countries (FHWARD-01-156). Corrosion cost studies carried out
in the U.S. (NACE), the UK, and Japan have
shown that a cost figure of 3 to 4% of their gross
national product can be attributed to the direct
and indirect cost of overall corrosion, including
reinforced concrete structures. In 2002, the
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 1
Fig. 1-1: Bridge beam corrosion
Fig. 1-2: Reinforcing steel corrosion in a parking
garage slab
FHWA/NACE Cost of Corrosion Report suggested a figure of $1 to $3 trillion as the cost to
rehabilitate all reinforced concrete structures in
the U.S. suffering from corrosion-related distress
(FHWA-RD-01-156). Examples of reinforce­
ment corrosion damage to a bridge support beam
and the soffit of a parking garage are shown in
Fig. 1-1 and 1-2.
Because of the magnitude of this problem,
both the public and private sectors have ongoing
activities aimed at reducing or eliminating corrosion damage to concrete structures. Many
technologies and materials have been developed
for prevention and repair of corrosion-induced
damage. The challenge is to select durable, costeffective technologies and materials from the
numerous choices available.
1.3 History
The technique with the most traceable history is
cathodic protection (CP). The other technologies
2 - 510.1–2013
outlined in this guideline mainly evolved from
that method. CP dates from the 1800s, when Sir
Humphrey Davy used a form of galvanic cathodic
protection (GCP) in seawater environments to
protect the hulls of Royal Navy ships.
Impressed current cathodic protection
(ICCP) has been widely used to protect underground structures such as pipelines and storage
tanks since the 1950s. The earliest aboveground
reinforced concrete ICCP systems were reported
in the late 1950s for the protection of bridge
decks. They used high-silicon cast-iron anodes
with a conductive backfill of coke breeze.
Many such systems were installed between
1973 and 1980.
Some of the ICCP systems installed on reinforced concrete bridge decks in the 1980s used
a design consisting of a series of platinum-clad
niobium wires embedded in conductive polymer
mounds. This type of CP system was installed
prior to the installation of a concrete overlay.
These systems are no longer used due to performance issues.
Many of these systems predated the use of
conductive coating and mixed metal oxide
(MMO) titanium anodes that entered the market
and have been used for parking and bridge structures from circa 1980. MMO-coated titanium
anodes for use in ICCP systems for reinforced
concrete structures were introduced around 1985.
These systems are available in ribbon, tubular,
and expanded mesh-type anode formats and are
embedded in slots in the concrete, overlaid with
mortar, or cast directly into the concrete (SHRPS-372; SHRP-C/UWP-92-618).
It was not until the mid-1990s that the discrete
anode form of ICCP was developed with options
existing with activated titanium (tubular and
mesh forms) and conductive ceramic-type
anodes. Discrete anodes have been used to provide specialized targeted protection (to bridge
and parking structure joints, for example) or used
holistically for the protection of bridge support
beams, thick concrete sections, and historic
steel-frame buildings (ETL 1110-9-10(FR)).
Electrochemical treatments were developed
in the mid-1980s to treat corroding structures by
removing contaminants and changing the chemistry of the concrete around the reinforced steel.
There are two principal electrochemical treatments: electrochemical chloride extraction and
electrochemical realkalization. The first commercial application of realkalization was in 1987
to increase the pH of carbonated concrete in the
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
façades of a building in Tromso, Northern
Norway (Kennedy et. al. 1993; Whitmore 1996).
The first commercial applications of electrochemical chloride extraction were in 1988 in the
Norwegian towns of Trondheim and Stavanger,
where chloride-contaminated concrete was
treated (Miller 1989).
In 1988, field and laboratory trials of electrochemical chloride extraction were instigated as
part of the Strategic Highway Research Program
in Ontario, Canada (SHRP C-620) and in Ohio,
USA (SHRP S-669). Since then, over 5,000,000 ft2
(460,000 m2) of concrete surface area have been
treated on hundreds of structures using these
methods. Treated structures can be found in
Europe, North America, the Middle East, Australia, and Asia. Over time, the use of electrochemical mitigation methods to protect concrete
has seen a variety of structures protected,
including apartment and office buildings, bridges,
parking structures, retaining walls, and industrial
buildings (Kennedy et. al. 1993; Velivasakis et.
al. 1998; NACE 01101; NACE 01104).
2.0 Safety
Considerations
Reinforced concrete construction consists of steel
reinforcement (uncoated or coated) placed in a
mixture of cement, aggregate, and water of various formulations. The concrete cover can
weather, crack, spall, and deteriorate due to a
combination of forces such as environmental
conditions over time, internal stresses, and
external loading. Damage may be in the form of
broken pieces of concrete, cracks, corrosion,
efflorescence, staining, delamination, or spalling
of areas of concrete cover. Given the threat of
falling objects before and during the evaluation
and repair of the structure, these conditions pose
a potential safety hazard.
Repair work may require access to the exterior of the structure via ground-supported frame
or system scaffold, mast climbers, or suspended
scaffolding. The design, erection, and usage of
the designated access equipment must be carefully planned and executed. During construction
activities, all personnel engaged in the work
should be outfitted with the appropriate personal
protective equipment and fall protection equipment as required. All safety equipment must
meet applicable Occupational Safety & Health
Association (OSHA) standards. Refer to ICRI
Technical Guideline 120.1, “Guidelines and
Recommendations for Safety in the Concrete
Repair Industry,” for guidance on safe work
practices in the concrete repair industry.
3.0 Developing
a Corrosion
Management Plan
Prior to starting an investigation or repair project,
a plan should be developed to align the expectations of all parties and to guide the work in an
efficient and orderly manner. This plan should
include a review of available documents, documentation of the environmental conditions, and
a definition of service-life expectations, as
described in the following.
3.1 Project Document Review
The first step in developing a corrosion management plan is a review of available project documents, including the following:
1. Original design and contract documents;
2. Original construction submittals;
3. Other construction documentation;
4. Repair and maintenance documentation; and
5. Historic standards.
The primary purpose of the document review
is to gather background information on the
original construction, performance, and repair of
the structure to aid in the thorough understanding
of its materials, configuration, and behavior.
The process of specifying a mitigation option
should include interviews with the owner, property manager, structural engineer, or other individuals who have been actively involved with the
construction and maintenance of the structure
over a period of time or who are intimately
familiar with the focus of the project. Such contacts can provide a living history of the structure
that might only be discovered otherwise through
time-consuming review of existing written documentation and drawings.
3.1.1 Original Design and
Contract Documents
These documents include drawings and specifications for the original construction of the structure.
Structural drawings will often show loads, performance criteria, and the strength of the materials
specified for use in the construction. Architectural
drawings may also show materials and the relationships among structural components. Mechanical and electrical drawings sometimes show
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 3
openings and embedded items that could be
important. Documents identified with the latest
issue date will generally provide the most accurate information and criteria for the structure’s
original construction. Ideally, “as built” or
“record set” drawings, if available, should be
reviewed. However, these documents are not
always comprehensive or accurate in their representation of the actual built structure. They
should be carefully compared with other documentation and observed conditions.
3.1.2 Original Construction
Submittals
The submittals include shop drawings, product
literature, material data sheets, test reports,
installation instructions, mockup reports, and
warranties. While not generally retained by
owners or easily obtained, these documents
supplement the original design and contract
documents and may contain detailed information
about the fabrication, installation, and warrantable performance of components:
• Shop drawings: Shop drawings may contain
specific details of construction, including
element shapes, support components, structural steel, penetrations and embedded items,
or anchorage systems; and
• Material submittals: Material submittals can
be useful to determine or confirm the strengths,
sizes, and standard details of the materials
used in the construction. Additionally, know­
ledge of proprietary products can assist in
obtaining in-kind replacement materials.
3.1.3 Other Construction
Documentation
These documents include change orders, bulletins, directives, meeting minutes, correspondence, test reports, photographs, and other
documentation during construction of the structure. These documents often clarify or modify
the design documents, but they are usually not
available after usage of the structure has begun.
3.1.4 Repair and Maintenance
Documentation
Repair and maintenance are sometimes performed
by the facility personnel without creating any
technical documents or contract. Sometimes, these
repairs or maintenance can alter the original function of the construction. There are other maintenance and repairs that are performed during the
life of the structure by a professional consultant
or contractor. Typically, the repairs and mainte4 - 510.1–2013
nance provided by these professionals are documented on as-build drawings and field reports.
These documents should be reviewed because
they may provide vital information regarding the
history and construction of the structure.
3.1.5 Historic Standards
Sources for building specific documents can
include the owners, design professionals, permitting authorities, contractors, key subcontractors,
testing agencies, and building managers. Documentation for historic structures may also reside
in preservation societies, local libraries, and uni­
versities. Professional societies, building trade
organizations, and publishers catering to the
construction industry have numerous documents
on current and historic construction details and
materials. The building codes in effect at the time
of the construction also describe key standards
in effect at the time of the construction. Conditions that are of particular interest may include:
• Prestressed/post-tensioned elements and duct
types;
• Isolated metal details;
• Anchorage details;
• Structural steel details;
• Reinforcement type, especially the presence
and type of coatings on reinforcing steel; and
• Stray electrical currents.
3.2 Condition Surveys
The term “condition survey” describes assessment of the deterioration mechanisms and causes
of the associated damage that is designed to lead
to the selection of the appropriate corrosion
mitigation technique(s). To provide future low
maintenance and long-term protection, specific
information on the condition of the structure is
needed. The survey documents that are useful to
review include property reports; engineering
evaluations; occupant surveys; post-construction
inspection reports; bridge inspections; and other
reports providing historical information on the
condition, problems, and performance of the
structure. Comparison of observed conditions
with previously reported conditions can be used
to develop a service history and determine causes
and rates of deterioration.
Technology and scientific methods are available to evaluate corrosion of reinforcing steel
(and other embedded metals) and the associated
damage. These techniques are designed to determine the extent of damage, define the corrosion
state of steel in undamaged areas, evaluate the
cause(s) of corrosion, and determine the prob-
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
ability of the steel to corrode in the future. After
this information is obtained, a suitable repair and
corrosion protection strategy can be developed.
It is important to point out that concrete itself
can deteriorate regardless of the condition of
embedded reinforcement. Examples of this
include freezing-and-thawing deterioration and
alkali-silica reactions. Although these damage
mechanisms are not caused by corrosion, they
can result in accelerated corrosion by compromising the passive protective environment provided by the concrete.
The most important reason for investing in
such a survey is to provide valuable data to ensure
the correct technical solution(s) are devised and
the owner can anticipate the best value for the
money for achieving the service-life extension of
the structure. The assistance of a professional
engineer or corrosion specialist is recommended
to conduct the condition survey. In addition, it is
common to undertake a physical condition survey
for reinforced concrete structures by assessing
and quantifying the nature of the problem with:
• Visual inspection (ACI 201.1R);
• Acoustic sounding (ASTM D4580);
• Concrete cover (ACI 228.2R);
• Corrosion potential (ASTM C876);
• Chloride content (ASTM C1152/C1152M,
C1218/C1218M); and
• Carbonation (EN 14630).
Other advanced techniques that can be used
include corrosion rate assessment (normally
using linear polarization resistance or galvanostatic pulse), petrographic analysis (ASTM
C856), thermography (ASTM D4788), and
concrete resistivity (ASTM G57).
The survey data are essential to determine
quantities for repair cost estimation purposes to
evaluate the root cause of the problem and to
develop a corrosion-management strategy that
offers the correct mitigation options. It is not
uncommon to adopt more than one mitigation
option to develop a holistic approach to protect
a structure.
4.0 Corrosion of Steel
in Concrete
4.1 Corrosion Process of Steel
in Concrete
It is not the intent of this guideline to provide a
detailed description of the science of the corrosion process but instead to provide an overview
of the issues normally encountered with reinforced concrete structures. For additional information on the corrosion of steel in concrete, refer
to ACI 222.2R.
The high pH normally present in the concrete
surrounding the reinforcing steel naturally passivates the steel surface to provide a durable and
versatile material. The passivated surface can be
compromised by several factors, such as chloride
or carbonation, which allows initiation of corrosion. To initiate corrosion on the steel surface,
oxygen and water need to be present to provide
a cathodic reaction.
It is important to note there are two distinctly
separate reactions: anodic (where corrosion actually happens) and cathodic (where corrosion is
prevented). Steel can and often does corrode in
oxygen-deficient areas as long as oxygen is
present in other (cathodic) areas. The typical
reactions occurring at anodic and cathodic areas
of steel in concrete are as follows:
At the anode, iron dissolves to form iron ions.
(Anode) Fe
Fe 2+ + 2e– (oxidation/corrosion reaction)
At the cathode, oxygen combines with water and
electrons to form hydroxyl ions (Lowenstein 1995).
(Cathode) 1/2 O2 + H2O + 2e–
20H– (reduction reaction)
The corrosion process is facilitated by depassivating agents, such as chloride, other corrosive
ions, and reduced pH. Chloride and other corrosive ions disrupt the formation of the passive
iron oxide layer that is generally stable under
alkaline conditions. This situation can lead to
corrosion that, under normal oxygen availability,
forms corrosion products that occupy up to eight
to 10 times the volume of the original steel. This
volume change causes expansive forces that
exceed the tensile strength of the concrete
resulting in spalling, delamination, and cracking
of the concrete cover.
Concrete quality is arguably a main factor in
the corrosion process, as poor-quality concrete
can reduce the timeline to corrosion initiation
and may provide little or no protection once the
corrosion process has begun. Formation of cracks
due to restrained shrinkage, loading, or other
factors can also reduce the time to initiation of
corrosion by providing pathways for corrosive
agents to reach reinforcing steel. Successful corrosion mitigation methods address at least one
of the processes that cause depassivation of the
steel reinforcement and hence mitigate the prop­
agation of corrosion.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 5
4.2 Environmental Conditions
The external and internal environments are
important factors affecting the performance of
reinforced concrete structures. Structural deteri­
oration is much more likely in an environment
with excessive moisture, elevated temperatures,
aggressive chemicals, or excessive loading. Any
of these factors can contribute to deterioration and
requirements for rehabilitation with or without
corrosion mitigation techniques being used. When
analyzing the cause of the deteri­oration of a
structure, it is critical to include an examination
and evaluation of the environmental conditions
surrounding the structure. For a successful rehabilitation and for defining future performance
expectations, envi­ronmental influences on the
deterioration must be considered.
4.2.1 Exterior Exposure
Exterior climate, especially exposure to moisture, wide temperature variances, chloride ions,
and aggressive chemicals, must be considered.
Freezing of critically saturated concrete can lead
to freezing-and-thawing damage. High temperatures and moisture can lead to the acceleration
of corrosion, and the resultant expansion could
result in premature cracking. Exposure to acid
rain and carbon dioxide can lead to carbonation
and corrosion.
4.2.2 Interior Exposure
A controlled interior climate is typically less
aggressive than an exterior, non-climate controlled
environment. However, humidity and condensation may result in premature corrosion and deterioration of steel reinforcing, resulting in loss of
structural integrity of the structure. Additionally,
the differential pressure between exterior and
interior envelopes of buildings can result in water
infiltration. Typically, thorough investigation,
including exploratory openings in the structure,
may be required to determine potential structural
and serviceability issues in these exposures.
4.2.3 Industrial Exposure
Industrial environments may cause premature
deterioration of reinforced concrete structures.
Aggressive chemicals, high humidity, and high
carbon-dioxide levels can lead to premature
deterioration of the concrete and the reinforcing
steel. Corrosion mitigation of structures in an
industrial environment requires a thorough
understanding of the processes and chemicals
and their potential to cause premature deterioration of the structure components.
6 - 510.1–2013
4.2.4 Urban and Rural Exposure
Urban and rural environments are typically less
aggressive than industrial environments. As a
result, corrosion mitigation systems typically can
be designed to minimize the current density
requirements for impressed current cathodic
protection (ICCP) and galvanic cathodic protection (GCP) systems to provide longevity and a
suitably optimized economic solution.
4.2.5 Coastal Exposure
Coastal environments are generally highly corrosive. Coastal environments are subject to wind
and rain, along with direct exposure to saltwater
and salt-laden mist. The combination of moisture
and salt can cause severe corrosion of the reinforcing steel. Therefore, evaluation of structures
in coastal regions should consider the highly
corrosive nature of the coastal environment.
4.3 Service-Life Expectations
Many structures exposed to a corrosive environment have been deteriorating for years; therefore, the service life remaining is one of the key
factors to assess. To choose the most important
techniques or a combination of techniques to
best suit the remediation of the structure, the
owner needs to agree with the service-life extension period. The ability of each mitigation
technique to achieve the agreed upon service-life
extension should be assessed by the corrosion
specialist for the project and be justified during
the detailed design.
A schematic derived from Tuuti’s model
(Fig. 4-1) illustrates the effect of intervention
on phases of corrosion development with
respect to service life and theoretical level of
maximum permissible corrosion. Corrosion
progresses over a structure’s service life, as
shown in Fig. 4-1. Initially, no corrosion takes
place until ingress of chlorides, carbonation, or
other aggressive species cause corrosion initiation. Proactive intervention during the corrosion
initiation phase is very cost-effective and results
in both a delay of corrosion propagation and an
extension of service life. With early intervention, it is likely that the time to reach maximum
permissible corrosion will be extended; thus,
the service-life extension is increased. It is also
likely that the longer the propagation phase has
progressed, the more robust the corrosion
mitigation technique must be to sufficiently
reduce the corrosion rate to achieve a servicelife extension.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
Corrosion of Steel
Reinforcement
Maximum Permissible Corrosion
Intervention Point
(Reactive maintenance)
Intervention Point
(Proactive maintenance)
Time
Corrosion Initiation Phase
Corrosion Propagation Phase
Ingress of aggressive species
through cover concrete
e.g. chlorides, carbonation
Accelerated degradation of
steel reinforcement
Service Life without Maintenance
Extended
Service Life
Fig. 4-1: Impact of various intervention stages on service-life extension
4.4 Economics that Affect
Decision Making
The economic constraints on any project can
dictate the choice of mitigation techniques. However, even low-cost solutions must be technically
justified or there is a risk that the desired servicelife extension will not or cannot be met. In addition, it should be recognized that it is possible for
lower-cost interventions to result in higher lifecycle costs if the resulting corrosion mitigation
is less effective or the service life is shortened.
Value engineering can be advantageous if a more
economical approach is devised that still meets
the technical requirements of the project.
5.0 Corrosion
Mitigation Techniques:
Cathodic Protection (CP) and
Electrochemical Treatments
5.1 Introduction
The following section describes the various
electrochemical techniques that are commonly
used to protect steel reinforcement from corrosion. These include:
• Impressed current cathodic protection
(ICCP);
• Galvanic cathodic protection (GCP);
• Electrochemical chloride extraction (ECE);
and
• Electrochemical realkalization (ERA).
This guideline outlines the mechanisms of
protection and does not advocate any particular
technique. As stated previously, the mechanisms used will be dictated by the technical
and economic merits as they relate to the specific problem with a specific structure. In addition, a coating system may be a beneficial
component of a mitigation technique as either
a technical requirement of the system or as an
aesthetic consideration. Selection of a coating
should be made carefully to ensure compatibility with the electrochemical technique and
durability of the entire system. A typical system
selection flowchart is outlined in Fig. 5-1. This
chapter also provides guidance on the performance characteristics of each technique and
the management requirements following
their use.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 7
5.2.2 Electrical Connections to the
Reinforcing Steel
The electrochemical system must be electrically
connected to the reinforcing steel to be protected.
The electrical connections to the reinforcing steel
must be durable and should be confirmed by field
testing. The number and location of electrical
connections to the reinforcing steel should meet
or exceed manufacturer’s recommendations.
5.2.3 Electrical Connections
to Anodes
Fig. 5-1: System selection flowchart
5.2 General Mechanism and
Common Requirements
Cathodic protection and electrochemical treatments involve passing direct current from an
anode to the reinforcing steel within the concrete.
The amount of current and the duration the
current is applied to the structure will vary
depending on the type of system. There are a
num­­­­ber of general requirements that apply to all
electrochemical techniques used to mitigate the
corrosion of steel in concrete. Some of the general requirements are outlined in the following.
5.2.1 Electrical Continuity
For steel to be protected, it must be electrically
connected to the electrochemical system. Unconnected (discontinuous) metallic elements will
not receive any protection from the installed
system. In addition, discontinuous metal sections
may inadvertently be forced to corrode by the
operating system if they are located within the
area of influence of the system. This is sometimes
referred to as “stray current corrosion” and
should be avoided. Generally, it is desirable to
confirm that all embedded metallic (steel) conductors within the area of influence of the electrochemical technique are electrically inter­
connected. Any unconnected (discontinuous)
metal should be electrically connected to the rest
of the steel to be protected.
8 - 510.1–2013
The electrochemical system must be electrically
connected to the installed anode(s). These electrical connections have an increased risk of
corrosion compared to reinforcing steel connections; therefore, additional care must be taken to
specify and install durable electrical connections
to the anodes. For impressed current anode connections, there is a risk the connection wire may
corrode if it is not completely sealed from the
environment or if it is not made from a corrosionresistant material. For galvanic system anode
connections, the anode is corroding over time so
care must be taken with the anode connection
detail to ensure the connection between the anode
and the connection wire is not lost due to corrosion of the anode material itself. The use of
multiple connections is recommended to ensure
redundancy in the installed system.
5.2.4 Short Circuits
In the case of ICCP and electrochemical treatments, it is important that there are no electrical
short circuits between the anode and the reinforcing
steel to be protected. If a short circuit is present,
it will not be possible to energize the system and
the reinforcing steel will not be protected.
5.2.5 Hydrogen Embrittlement
Some electrochemical techniques that apply
higher potentials can result in the hydrolysis
(decomposition) of water. If this occurs,
hydrogen may be generated at the steel/concrete
interface. Electrochemical techniques that are
likely to operate above this potential include
ECE, ERA, and ICCP.
Certain types of steel, including some hightensile, high-carbon steels used for post-tensioning and prestressed tendons in concrete, are
sensitive to the presence of hydrogen such that
they may lose ductility and become brittle. For
this reason, the use of electrochemical techniques, which may result in the generation of
hydrogen, is generally not recommended on
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
portions of structures that may contain highcarbon steel, such as prestresssing or post-tensioning steel, which may be adversely affected
by hydrogen embrittlement (Enos et. al. 1996).
Conventional reinforcing steel is not adversely
affected by the presence of hydrogen and does
not experience embrittlement.
5.3 Cathodic Protection
Cathodic protection refers to the process of
delivering a direct current using an anode to
counteract the corrosion current of steel within
a conductive electrolyte (Pedeferri 1996; Scannell and Sohnghpurwala 1993). For the purposes
of this document, the electrolyte is generally the
water and ionically conductive materials within
concrete. This method in effect moves the anodic
reaction from the steel to another artificial anode
where the passage of current can occur without
damage to the concrete. CP systems can be
grouped into two basic types: impressed current
(that requires an external power supply) and
galvanic or sacrificial systems (that generate
their own current via the bimetallic coupling of
dissimilar metals). In both cases, the current
polarizes and protects the reinforcing steel,
making it function as a cathode—hence, the
name cathodic protection.
The prerequisite for a material to be regarded
as a durable ICCP anode is that it must be conductive and stable. Testing ICCP anode materials
in accordance with NACE TM 0294 will verify
their durability and functionality. The following
sections describe the generic anode materials on
the market at time of printing that have a significant track record for protecting steel in concrete by the ICCP and GCP methods. It is noted
that over-polarization of tensioned (prestressed
or post-tensioned) steel by cathodic protection
may present a risk of hydrogen embrittlement.
While this may not be as significant a risk with
galvanic systems, if an ICCP system is used, it
is essential for the designer to ensure that polarization controls are available within the management system to prevent over-polarization.
5.3.1 Mechanism of Protection (ICCP)
Impressed current cathodic protection forces a
direct current from an external power supply to
flow from an anode through the concrete to the
reinforcing steel, as shown in Fig. 5-2. A current
of sufficient magnitude and direction is necessary
to overcome the natural flow of electrons
resulting from the corrosion process. The direct
Fig. 5-2: Impressed current cathodic protection system
Fig. 5-3: Galvanic (sacrificial) anode protection
current is supplied from an external source, most
often an AC/DC (transformer) rectifier (NACE
SP 0290).
5.3.2 Mechanism of Protection (GCP)
Galvanic (or sacrificial) anode cathodic protection of steel in concrete requires the steel to be
connected to a more electronegative (more
active/less noble) metal such as zinc. Because of
their different electrochemical potentials, electrons flow from the anode to the cathode. Electron
loss at the anodes causes the anodes to cor­rode
(oxidize). The electrons provided by the galvanic
anode protect the steel (cathode) from corroding.
GCP is similar to ICCP in that a current of
sufficient density is required to protect the target
steel. This can be provided either locally or in a
distributed manner (see Performance and Longevity of Mitigation Techniques, Section 6).
There is no external power supply required as
the galvanic cell set up between the steel and the
more base metal (for example, zinc) drives the
current naturally, as shown in Fig. 5-3 (UFGS-26
42 13.00 20).
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 9
5.3.3 Additional Components
In addition to the anode system, there is a requirement for other components to make up the full
CP system. For ICCP systems, these include:
• Cathode (steel) connections;
• DC cabling (positive [anode] and negative
[steel] circuits);
• Junction boxes;
• Monitoring devices (reference electrodes and
corrosion rate probes) with wiring;
• Power and control units (transformer-rectifier)
with environmentally protected boxes;
• Monitoring measurement electronics (optional);
and
• Network and central control unit (optional).
For GCP systems, these include: (a) cathode
(steel) connections; and (b) monitoring measurement electronics (optional).
Cabling for DC and monitoring circuits is
detailed in the standards documentation and
should also comply with national building codes.
These are normally color-coded for ease of
identification and labeled according to the design
requirements. If networks are used for distributed
management systems, then typically these should
comply with protocols such as the American
National Standards Institute (ANSI) EIA709.1
for open network communication. Junction
boxes and zonal electronic enclosures for
housing external connections and components
should be environmentally protected for the
conditions prevalent to that site, which may
include dust and water protection, such as
National Electrical Manufacturers Association
(NEMA) 4x or IP65.
5.3.4 Design Process
After all information is gathered, the next step
is designing a plan for repair and mitigation
(NACE SP 0187). A formal repair design is
helpful in estimating costs and the effects of the
work on the structure. A formal design is necessary for ICCP systems due to their complexity.
A formal design may not be required with the
localized use of galvanic anodes within the
repair, where the target steel is typically the steel
that extends from within the repair to the area
directly adjacent to the perimeter as a method of
controlling ring (or incipient) anodes.
In some cases, electrochemical techniques
may be avoided; and the use of techniques such
as the application of coatings, sealers, and waterproofing membranes may provide sufficient
longevity for structures that are not currently
10 - 510.1–2013
corroding or are in less aggressive environments.
Suitability and future maintenance issues should
be considered within the design phase.
With all electrochemical techniques that pass
a current into a structure, the layout of the steel
reinforcement should be known and the electrical
continuity of the steel should be confirmed. The
effectiveness and design of a CP system will
depend on environmental conditions such as
moisture and chloride content of the concrete;
environmental exposure conditions; and the
presence of coatings, sealers, and other highresistance layers.
The localized use of galvanic anodes within
the repair is a possible exception to the need for
electrical continuity. In this case, the target steel
is typically the reinforcing steel that extends from
within the repair to the area directly adjacent to
the perimeter as a method of controlling ring (or
incipient) anodes. In this instance, the electrical
continuity of the reinforcing steel should still be
tested, but the risk of isolated steel within the
local area is limited. However, for distributed
galvanic systems, distributed and discrete ICCP
systems, and electrochemical treatments, it is
important that the steel is electrically continuous
to avoid the risk of stray current corrosion.
The design process requires knowledge of the
following features of the structure in question:
• Steel configurations and dimensions;
• Construction layout and geometric features;
• Site layout; and
• Code compliance.
This should lead to development of a detailed
design document that may include the following
sections:
• Design life expectancy;
• Steel surface area calculations;
• Anode details;
• Cathode (steel) connections and circuit
details;
• Electrical wiring/circuit diagrams (especially
ICCP);
• Monitoring instrumentation details;
• Method to ensure all embedded metal is
electrically connected;
• Power, control, and management systems
(with or without remote capability); and
• Future maintenance requirements.
The design documentation may be a document that evolves to an installation and commissioning document (archive of the installation
including as-built information and drawings or
proof of correct design implementation) and to
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
an operations and maintenance document that
details the future management of the corrosion
mitigation to that structure (NACE SP 0390).
Cementitious
conductive
overlay
5.3.5 Distributed Anode Systems
for ICCP
Three main types of distributed anode ICCP
systems are typically used. These are: 1) con­
ductive coatings; 2) conductive overlays; and
3) mixed metal oxide (activated) titanium mesh.
5.3.5.1 Conductive Coatings
One type of conductive coating anode system
consists of carbon as the main anode component
within an organic vehicle, such as polyurethane
or acrylic or an inorganic vehicle such as silicate.
These systems can be applied using normal
methods of spray, brush, or roller to cover a
prepared (typically grit-blasted) concrete surface. Because carbon is not as inert as some other
anode materials, it is consumed over time, has a
lower anodic current density capability (maximum of 20 mA/m2), and is generally not suitable
for structures with higher steel densities. Generally, these systems have been installed on balconies and the soffits of parking garage slabs.
Another type of conductive coating is surfaceapplied, arc-sprayed zinc metalizing. Zinc is also
not an inert anode material and will be consumed
over time as the system operates. When connected to an AC/DC transformer rectifier, arcsprayed zinc or carbon-filled conductive coatings
can be used as an ICCP anode.
Fig. 5-4: Cementitious conductive overlay on
a concrete-paneled college building
5.3.5.2 Conductive Overlays
Conductive overlays, as shown in Fig. 5-4, are
similar to conductive coatings in that they generally depend on carbon as the anode but, in this
case, within a cementitious or asphaltic vehicle.
The anode is spray-applied, poured, or otherwise
applied to the surface of the concrete that has
been prepared typically by grit-blasting to
improve the bond of the overlay. Electrical connection is made between insulated cable and a
titanium or cast iron plate that acts as the primary
anode. Current passes from the primary anode
to the conductive overlay where it is distributed
over the treated surface of the structure.
5.3.5.3 MMO Titanium Anode Systems
These anodes typically consist of titanium coated
with a mixed (precious) metal oxide (MMO)
film. These anodes come in many forms suitable
for varied applications, such as mesh, ribbon,
and tapes. Mesh and ribbon are generally used
for aboveground installation to decks, soffits,
Fig. 5-5: MMO titanium anode mesh installation
and walls. MMO titanium anode mesh being
installed on the grit-blasted concrete surface of
a reinforced concrete support beam beneath a
marine jetty is shown in Fig. 5-5.
MMO-coated titanium anode mesh can tolerate higher current outputs than carbon-based
anodes with a maximum normal operating current density of 110 mA/m2. Anode connection is
made by crimping an insulated cable to a titanium rod and spot-welding to the mesh or ribbon
(Fig. 5-6). In North America, a titanium conductor bar is generally used and is welded to the
titanium anode. The titanium conductor bar
extends out of the concrete and all connections
to copper wire and cabling are made in junction
boxes (external to the concrete).
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 11
Anode mesh is embedded within a cementitious overlay and used for protecting large
surface areas such as bridge or parking decks.
A ribbon anode is also available for grouting
into slots cut into the concrete (Fig. 5-7).
Cementitious materials used for overlays or
filling slots should have a documented track
history or should be tested to ensure compatibility and long-term performance. These anodes
are generally expected to have a life expectancy
of over 40 years.
Fig. 5-6: Anode mesh installed to beam with positive
DC feed connection spot welded in position
Fig. 5-7: Anode ribbon mesh installed into
parking deck within slots in the concrete
5.3.6 Discrete Anode Systems for ICCP
Discrete anode systems tend to be either MMO
titanium ribbons “rolled” to form a rod shape, a
coated solid rod, or conductive titanium suboxide ceramic. Discrete anodes vary considerably with regard to their current outputs. MMO
titanium anodes are typically designed based on
a maximum current density of 110 mA/m2. Conductive ceramic discrete anodes (Fig. 5-8) can
be operated at higher current densities (up to
900 mA/m2) (Sergi et al. 2008) or they may be
operated at lower current densities similar to
MMO titanium anodes.
All forms of discrete anodes are drilled into
the structure and installed in a designed array.
For reinforced concrete structures, the spacing
between the anodes is typically between 8 and
20 in. (200 and 500 mm), depending on the steel
configurations and concrete resistivity, which
affect the ability of the anode to “throw” current
in three dimensions (Whitmore 2002). The
discrete anode array is interconnected with
titanium wire (often insulated to ensure no
contact with any steel reinforcement) by
crimping a titanium crimp to an anode lead wire
by spot welding or by a screw-thread arrangement within a titanium casing, depending on
the anode type.
Discrete anodes installed within a bridge joint
arrangement to protect the prestressed anchor
positions at the ends of the beams are shown in
Fig. 5-9. A historic bridge suffering from chloride-induced corrosion accelerated by runoff
from the road above is shown in Fig. 5-10. The
reinforced concrete half-joints and support
beams for suspended and cantilevered sections
were protected with a discrete anode system.
5.3.7 Localized Galvanic Systems
Fig. 5-8: Cylindrical and fluted type conductive
ceramic anodes
12 - 510.1–2013
Localized galvanic systems are typically targeted toward protecting a newly repaired area
of concrete with the aim of delaying the onset
of ring (incipient) anode formation around the
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
perimeter of the repair. Ring anodes can form
as a result of the newly formed repair acting as
a macro-cathode relative to the original concrete around it due to differences in alkali­
nity or chloride content. The natural processes
arise where an anode is formed locally that
balances the reduction reaction by forming an
oxidation, or corrosion site. The severity of the
ring anode formation will be dictated by the
level of chloride, degree of carbonation, and
moisture condition that prevails in the neighboring parent concrete. The more corrosive the
environment, the greater the demand will be on
the galvanic anode.
Localized galvanic anodes are usually in the
form of zinc encased in a mortar shell that is
admixed with an activator to ensure continual
activation of the anode surface. Activators
should be used in such a manner as to provide
long-term protection to the structure and should
not be detrimental to the structure. The anode
assembly is strapped to the reinforcement steel
using integral steel tie wires in an array around
the perimeter of the repair (Fig. 5-11) (ACI RAP
Bulletin 8; Whitmore and Abbott 2000). Anodes
may also be supplied in rod form and cored into
the concrete on a grid pattern and connected to
the reinforcing steel at a designed spacing
similar to discrete ICCP anode systems (Whitmore 2002).
Localized (discrete) galvanic anodes have a
maximum current capacity based on their size
and efficiency. Manufacturers supply guidance
on anode spacing and required density for different applications. These systems do not require
any external power supply and are not typically
monitored, as discussed in Section 6.
Discrete
anode
locations
Fig. 5-9: Discrete anodes installed to protect prestressed anchor positions
Discrete anodes
installed to protect
leaking half joints
Fig. 5-10: Discrete anode system installed for protection of a historic bridge structure
5.3.8 Distributed Galvanic Systems
Distributed galvanic systems use the same concept of dissimilar metals, but they distribute the
galvanic metal over the entire repair area rather
than using discrete anodes (NACE 01105). Distributed galvanic systems are found in various
forms, such as:
• Zinc installed inside protective jackets in
marine environments;
• Spray applied to the concrete surface;
• Strips embedded in concrete encasements or
concrete overlays; and
• Self-adherent sheet applied to the concrete
surface.
Preparation of the element being protected is
important and usually involves typical concrete
repair procedures, including removal of delami-
Fig. 5-11: Localized (discrete) anode installation in a
localized repair
nated concrete, repair of cracks, cleaning steel,
and placement of repair material prior to the
installation of the mitigation system.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 13
5.3.8.1 Zinc Installed Inside Protective
Jackets in Marine Environments
For galvanic jacket systems, the anode is normally a zinc mesh or activated zinc strips, which
are electrically connected to the steel reinforcement using multiple connections for redundancy
and installed around the structural element,
typically a marine concrete pile. A protective
fiberglass casing or jacket is then installed
(Fig. 5-12), and the annular space between the
external jacket and concrete pile is filled with
mortar to provide an electrolytic path for current.
A completed repair is shown in Fig. 5-13. The
natural bimetallic coupling forms the driving
voltage and electrons pass to the steel to protect
it from corrosion. In turn, the zinc is consumed
(NACE 01105; Whitmore 2004).
5.3.8.2 Spray-Applied Galvanic Anodes
Fig. 5-13: Typical view of completed galvanic
jacket system
During the arc-spray application method, wires
of the desired material are melted together and
sprayed onto the prepared concrete surface, as
shown in Fig. 5-14. High-purity zinc is the most
common galvanic alloy used on concrete structures. Other zinc or aluminum alloys are used in
some cases. Arc-sprayed coatings have been used
as anodes in both galvanic and ICCP systems.
The majority of arc-sprayed coatings are
installed as galvanic anodes. In marine environments, pure zinc functions well as a galvanic
anode (SHRP-S-405; Sagues and Powers 1996).
In non-marine environments, zinc alone may
not provide sufficient current to protect the
reinforcing steel. There are two options available
for applications in these environments. One
option is to apply a humectant to the arc-sprayed
coating to promote corrosion of the arc-sprayed
galvanic coating, as shown in Fig. 5-15 (Bennett
1998; Covino et al. 1999). Another option is to
change the composition of the coating to an
alloy, which remains active in less humid conditions. Monitoring of these anode systems is
discussed in Section 6.
Fig. 5-14: Application of arc-sprayed coating
Fig. 5-15: Humectant activated arc-sprayed zinc anode
being installed on the substructure of the Garden City
Skyway, ON, Canada
Fig. 5-12: Jacket system positioning prior to connection
and grouting
14 - 510.1–2013
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
5.3.8.3 Embedded Galvanic
Strip Anodes
For large-area CP applications, activated galvanic
strip anodes can be designed and installed on the
concrete surface and embedded in a concrete
overlay or encasement, as shown in Fig. 5-16.
These systems are effective for structures with
significant concrete damage, where it may not be
practical to remove all of the chloride-contaminated concrete, and it is more practical to form
and recast the concrete surface. Embedded galvanic strip anodes may be used in marine and
non-marine applications and contain activators to
keep them active over time. Due to their larger
size and distributed nature, these systems can be
designed to provide CP current densities (Ball and
Whitmore 2005).
5.3.8.4 Self-Adherent Galvanic
Sheet Anodes
Self-adherent galvanic sheet anodes are surfaceapplied systems installed using discrete connections to the reinforcing steel in the area of the
anode installation. They comprise a zinc sheet
combined with an ionically conductive adhesive
(NACE 01105). The adhesive contains activators
to keep the zinc surface active. Typical applications include the soffit of concrete balconies and
concrete decks, as shown in Fig. 5-17.
Fig. 5-16: Distributed galvanic strip anodes are
embedded in a concrete encasement of a chloride
contaminated bridge pier cap, Montreal, QC, Canada
5.4 Electrochemical Treatments
Electrochemical treatments (electrochemical
chloride extraction and realkalization) use the
passage of current for a short period of time from
a temporary anode to the reinforcing steel to
move ionic species (such as chloride, hydroxide,
and alkali) within the concrete with the intent of
changing the chemistry of the concrete surrounding the reinforcing steel.
5.4.1 Mechanism
Both processes increase the alkalinity at the
concrete/reinforcing steel interface and aid in
restoration of the passive oxide film that is normally found on the surface of the reinforcing
steel when embedded in concrete. This restores
the natural protection offered by the concrete to
the steel, protecting it from corrosion and future
chloride attack or carbonation.
5.4.2 Electrochemical Chloride
Extraction (ECE)
ECE (sometimes referred to as desalination)
increases the alkalinity of the concrete surrounding the reinforcing steel and reduces the
Fig. 5-17: Self-adherent galvanic sheet anodes being
installed on the soffit of a parking garage slab, Oklahoma
quantity of chloride ions in contaminated concrete by attracting negatively charged chloride
ions to a positively charged temporary anode
applied to the surface of the concrete (NACE
01101). An electric field is applied between a
temporary external anode and the embedded
reinforcement, which temporarily becomes a
cathode during treatment. In the case of chloride
extraction, the application of the electric field
results in the migration of chloride ions away
from the embedded reinforcing steel and toward
the externally mounted anode where they collect
in the electrolyte (usually tap water) and are
removed, as shown in Fig. 5-18 (Allies and
Whitmore 1999; Buenfeld et al. 1998).
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 15
Fig. 5-18: Schematic diagram depicting components
used with ECE and the mechanism of operation
Fig. 5-20: ERA schematic illustrating components and
operation mechanism
Fig. 5-19: ECE installation of a cellulose fiber overlay
on the temporary anode system
Fig. 5-21: Realkalization of concrete façade, Ronald
Reagan National Airport
Chloride extraction is most effective at
removing chlorides present in the concrete cover
(Hassanein et al. 1998; Said-Shawqi et al. 1998).
In a typical reinforced concrete structure,
approximately three times as much chloride will
be removed from the concrete cover compared
to the concrete between the first and second mats
of reinforcing steel. When the chloride extraction
process is completed, the reinforcing steel will
repassivate, as it will be in a low-chloride, highpH concrete environment (NACE SP 0107; Glass
et al. 2003; Harrington-Hughes 1993).
Figure 5-19 shows the installation of an ECE
system consisting of a sprayed cellulose fiber
with a temporary anode on a bridge pier cap in
Virginia, USA (SHRP S-2033). This arrangement
is very similar for the realkalization process.
5.4.3 Electrochemical Realkalization
(ERA)
Realkalization is used to restore the alkalinity
(pH) of concrete structures suffering from
carbonation (NACE 01104). Realkalization is
similar to chloride extraction, but it uses an
alkaline solution, usually a potassium carbonate
16 - 510.1–2013
solution as the electrolyte. The alkaline electrolyte is drawn into the concrete because of the
applied electric field (as well as capillary absorption, diffusion, ion migration, and hydroxyl gen­
­­eration), thus raising the concrete pH (Fig. 5-20).
Realkalization is a process that generally takes
3 to 7 days to complete for typical concrete cover
depth and is effective to the depth of reinforcing
steel that is used as the cathode. Installation of
the steel anode for realkalization of a concrete
façade at Ronald Reagan National Airport,
Washington, DC, is shown in Fig. 5-21.
6.0 Performance
and Longevity of
Mitigation Systems
6.1 Performance Management
Only ICCP typically requires monitoring of performance to be conducted as it is described within
the U.S. and European standards (NACE SP
0290). If desired, however, other electrochemical
techniques outlined within this document can be
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
monitored for electrochemical changes to the
steel within the structure in the same manner as
ICCP systems. However, these would require
different acceptance criteria, depending on the
technique and the desired level of protection.
For example, GCP systems are required to
polarize the steel in the negative direction in a
similar manner to ICCP systems. As such, a
significant measure of polarization (that is,
>100 mV if required to meet NACE cathodic
protection guidelines [NACE SP 0290; Whitmore 2004]) would signify CP is being
achieved. The measurement of output current
can confirm the current density being provided
and that the anode has not been consumed
(NACE 01105). Similarly, galvanic corrosion
prevention or corrosion control can be monitored using the available acceptance criteria
such as a current density of 0.2 to 2.0 mA/m2
for corrosion prevention (EN 12696; Ball and
Whitmore 2005).
ECE and ERA treatments rely on the ability
of the process to re-establish corrosion passivation to the steel reinforcement and, therefore,
should affect both a change in corrosion potential
and the corrosion rate as a consequence of completing the treatment (NACE SP 0107; NACE
01101; NACE 01104).
If required, all electrochemical techniques for
mitigating corrosion can be monitored for performance. Typical monitoring includes half-cell
and corrosion rate testing. These can be accomplished using either temporary field equipment
or permanently installed equipment. The selection of manual or permanently installed equipment will depend on access, location, size of the
protected area, and other factors.
Typical acceptance criteria for corrosion
management systems are shown in Table 1.
6.2 Post-Installation
Considerations
ICCP requires on-going evaluation and monitoring because it depends on electronics and
wiring for power and control (UFC 3-570-06).
Furthermore, monitoring is necessary because
circumstances, such as changes in concrete
moisture content, can require adjustment to
maintain current density and because anodes will
eventually be consumed (SHRP-S-670). Finally,
changes in building management and operations
personnel creates the potential for lost knowledge on the system’s operation and monitoring,
and even its existence. Some monitoring is also
needed for GCP systems because of their finite
life until the anodes are consumed and can no
longer provide protection.
The design document formulated prior to
implementation may be supplemented to create
an as-built Installation and Commissioning
Report complete with record drawings of the
installation. Archived management facilities
provide electronic storage and ready access to
the reports, plans, and specifications.
A monitoring schedule with the Owner should
be agreed on during the design phase such that
the specialist costs for the on-going performance
evaluation have been established. It should be
noted that an ICCP system, once installed, tends
to require evaluation over the lifetime of the
building (in a similar manner to management of
fire alarm systems).
7.0 Summary
There is a strong economic case for including
some form of corrosion mitigation technique
with concrete repair projects to ensure the condition of the structure in question is controlled
and assured. Several electrochemical techniques
are available and the appropriate method may
be selected depending on the problems that
prevail and the desired objectives of the owner
and designer.
All systems should be considered in conjunction with the structural design of the repair
scheme with ICCP systems requiring careful
design and arrangement of components.
Management of the systems at present is
required mainly on ICCP projects but all electrochemical techniques may be monitored if desired
to verify the performance of the installed system.
Table 1: Typical Acceptance Criteria for Corrosion Management Systems
Cathodic protection
Steel polarization of 100 mV or greater if corrosion potentials
≤ -200 mV cse
Corrosion control
Current density to steel of 1-7 mA/m2
Corrosion prevention
Current density to steel of 0.2 to 2.0 mA/m2
Corrosion passivation
Passive corrosion potentials (≤ -200 mV cse)
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 17
8.0 References
and Standards
8.1 Referenced Standards
and Reports
The standards and reports listed as follows were
the latest editions at the time this document was
prepared. Because these documents are revised
frequently, the reader is advised to contact the
proper sponsoring group if it is desired to refer
to the latest version.
American Concrete Institute
201.1R, “Guide for Conducting a Visual
Inspection of Concrete in Service”
222.2R, “Corrosion of Prestressing Steels”
228.2R, “Nondestructive Test Methods for
Evaluation of Concrete in Structures”
RAP Bulletin 8, “Installation of Embedded
Galvanic Anodes”
American National Standards Institute
EIA709.1, “Control Network Protocol
Specifications”
ASTM International
ASTM C856, “Standard Practice for Petrographic Examination of Hardened Concrete”
ASTM C876, “Standard Test Method for
Corrosion Potentials of Uncoated Reinforcing
Steel in Concrete”
ASTM C1152/C1152M, “Standard Test
Method for Acid Soluble Chloride in Mortar
and Concrete”
ASTM C1218/C1218M, “Standard Test
Method for Water Soluble Chloride in Mortar
and Concrete”
ASTM D4580, “Standard Practice for Measuring Delaminations in Concrete Bridge Decks
by Sounding”
ASTM D4788, “Standard Test Method for
Detecting Delamination in Bridge Decks Using
Infrared Thermography”
ASTM G57, “Standard Test Method for Field
Measurement of Soil Resistivity Using the
Wenner Four Electrode Method”
European Standards
EN 12696, “Cathodic Protection of Steel in
Concrete”
EN 14630, “Carbonation Depth in Hardened
Concrete by the Phenolphthalein Method”
18 - 510.1–2013
International Concrete
Repair Institute
ICRI Technical Guideline No. 120.1, “Guidelines and Recommendations for Safety in the
Concrete Repair Industry”
NACE International
01101, “Electrochemical Chloride Extraction
from Steel Reinforced Concrete—A State-ofthe-Art Report”
01104, “Electrochemical Realkalization of Steel
Reinforced Concrete—A State-of-the-Art Report”
01105, “Sacrificial Cathodic Protection of
Reinforced Concrete Elements—A State-of-theArt Report”
SP 0107, “Electrochemical Realkalization and
Chloride Extraction for Reinforced Concrete”
SP 0187, “Design Considerations for Corrosion Control of Reinforcing Steel in Concrete”
SP 0290, “Impressed Current Cathodic Protection of Reinforcing Steel in Atmospherically
Exposed Concrete Structures”
SP 0390, “Maintenance and Rehabilitation
Considerations for Corrosion Control of Existing
Steel-Reinforced Concrete Structures”
TM 0294, “Testing of Embeddable Anodes
for Use in Cathodic Protection of Atmospherically Exposed Steel-Reinforced Concrete”
Transportation Research Board
SHRP-C/UWP-92-618, “Cathodic Protection
of Reinforced Concrete Bridge Components”
SHRP-C-620, “Evaluation of NORCURE
Process for Electrochemical Chloride Removal,”
http://onlinepubs.trb.org/onlinepubs/shrp/
SHRP-C-620.pdf
SHRP-S-372, “Cathodic Protection of Concrete
Bridges: A Manual of Practice,” http://onlinepubs.trb.org/onlinepubs/shrp/SHRP-S-372.pdf
SHRP-S-405, “Sprayed Zinc Galvanic
Anodes for Concrete Marine Bridge Substructures,” http://onlinepubs.trb.org/onlinepubs/shrp/
SHRP-S-405.pdf
SHRP-S-669, “Electrochemical Chloride
Removal and Protection of Concrete Bridge
Components—Field Trials,” http://onlinepubs.
trb.org/onlinepubs/shrp/SHRP-S-669.pdf
SHRP-S-670, “Control Criteria and Materials
Performance Studies for Cathodic Protection of
Reinforced Concrete,” http://onlinepubs.trb.org/
onlinepubs/shrp/SHRP-S-670.pdf
SHRP-S-2033, “Guideline for Performing
Electrochemical Chloride Extraction to Concrete
Structures,” http://leadstates.transportation.org/
car/SHRP_products/2033.stm
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
U.S. Army Corps of Engineers
ETL 1110-9-10(FR), “Cathodic Protection
System Using Ceramic Anodes”
UFC 3-570-06, “Operation and Maintenance:
Cathodic Protection Systems,” http://www.
wbdg.org/ccb/DOD/UFC/ufc_3_570_06.pdf
UFGS-26 42 13.00 20, “Cathodic Protection
By Galvanic Anodes,” http://www.wbdg.org/
ccb/DOD/UFGS/UFGS 26 42 13.00 20.pdf
These publications may be obtained
from these organizations:
American Concrete Institute
38800 Country Club Drive
Farmington Hills, MI 48331
www.concrete.org
American National Standards Institute
11th Fl., 1899 L Street NW
Washington, DC 20036
www.ansi.org
ASTM International
100 Barr Harbor Drive
West Conshohocken, PA 19428
www.astm.org
International Concrete Repair Institute
10600 West Higgins Road, Suite 607
Rosemont, IL 60018
www.icri.org
NACE International
1440 South Creek Drive
Houston, TX 77084-4906
www.nace.org
Transportation Research Board
500 Fifth Street NW
Washington, D.C. 20001
http://www.trb.org
U.S. Army Corps of Engineers
Engineering and Support Center
Huntsville, AL 35816
http://www.hnd.usace.army.mil/techinfo/
index/aspx
8.2 Cited References
Allies, J., and Whitmore, D., “Halting Corrosion
Using Electrochemical Methods,” ASCE, 1999.
Ball, C., and Whitmore, D., “Innovative Corrosion Mitigation Solutions for Existing Concrete Structures,” V. 23, No. 3-4, International
Journal of Materials and Product Technology,
2005, pp. 219-239.
Bennett, J. E., “Chemical Enhancement of
Metallized Zinc Anode Performance,” Corrosion
98, Paper 640, NACE International, 1998.
Buenfeld, N.; Glass, G.; Hassanein, A.; and
Zhang, J., “Chloride Transport in Concrete Subjected to Electric Field,” Journal of Materials in
Civil Engineering, Nov. 1998, pp. 220-228.
Covino, B.; Holcomb, G.; Russell, J.; Cramer,
S.; Bennett, J.; and Laylor, H., “Electrochemical
Aging of Humectant-Treated Thermal-Sprayed
Zinc Anodes for Cathodic Protection,” Corrosion
99, Paper 548, NACE International, 1999.
Enos, D. G.; Williams, A. J.; and Scully, J. R.,
“Understanding the Long-Term Effects of
Cathodic Protection on Pre-Stressed Concrete
Structures: Hydrogen Embrittlement of PreStressing Steel,” Corrosion 96, NACE International Annual Conference, Houston, TX, 1996.
FHWA/NACE Cost of Corrosion Report
FHWA-RD-01-156, 2002.
Glass, G.; Taylor, J.; Roberts, A.; and
Davison, N., “The Protective Effects of Electrochemical Treatment in Reinforced Concrete,”
Corrosion 2003, Paper 03291, NACE International, 2003.
Harrington-Hughes, K., “Treatment Halts
Corrosion in Concrete,” Road and Bridge,
Nov. 1993.
Hassanein, A. M.; Glass, G. K.; and Buenfeld,
N. R., “A Mathematic Model for Electrochemical
Removal of Chloride from Concrete Structures,”
Corrosion, V. 54, No. 4, 1998.
Hoar Report, Department of Trade and
Industry, UK Government, 1971.
Kennedy, D.; Miller, J. B.; and Nustad, G. E.,
“Review of Chloride Extraction and Re-alkalisation of Reinforced Concrete,” UK Corrosion
Society, 1993.
Lowenstein, F., “Electroless Copper Plating,”
Modern Electroplating, third edition, 1995,
pp. 734-739.
Miller, J. B., “Chloride Removal and Corrosion Protection of Reinforced Concrete,”
Swedish Road and Traffic Institute, Sept. 1989.
Pedeferri, P., “Cathodic Protection and Cath­
odic Preventation,” Construction and Building
Materials, V. 10, No. 5, 1996, pp. 391-402.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
510.1–2013 - 19
Sagues, A., and Powers, R. G., “Sprayed-Zinc
Sacrificial Anodes for Reinforced Concrete in
Marine Service,” Corrosion, July 1996.
Said-Shawqi, Q.; Arya, C.; and Vassie, P. R.,
“Numerical Modeling of Electrochemical Chloride Removal from Concrete,” Cement and
Concrete Research, 1998.
Scannell, W., and Sohanghpurwala, A.,
“Cathodic Protection as a Corrosion Control
Alternate,” Concrete Repair Bulletin, V. 6,
No. 4, July/August 1993.
Sergi, D.; Simpson, D.; and Hayfield, P.,
“Long-Term Behavior of Ceramic TubularShaped Anodes for Cathodic Protection Applications,” Corrosion 2008, Paper 08305, NACE
International.
Velivasakis, E.; Henriksen, S.; and Whitmore,
D., “Chloride Extraction and Realkalization of
Reinforced Concrete Stop Steel Corrosion,”
Journal of Performance of Constructed Facilities, V. 12, No. 2, 1998, pp. 77-84.
Whitmore, D., “Electrochemical Chloride
Extraction from Concrete Bridge Elements:
Some Case Studies,” Corrosion 1996, Paper 299,
NACE International, 1996.
Whitmore, D., “Impressed Current and Galvanic
Discrete Anode Cathodic Protection for Corrosion
Protection of Concrete Structures,” Corrosion
2002, Paper 02263, NACE International, 2002.
Whitmore, D., “New Developments in the
Galvanic Cathodic Protection of Concrete Structures,” Corrosion 2004, Paper 04333, NACE
International, 2004.
Whitmore, D., and Abbott, S., “Galvanic
Protection Focused on Concrete Repairs,” Concrete Repair Bulletin, V. 13, No. 4, July/August
2000, pp. 12-15.
8.3 Additional Information
ACI Committee 546, 2004, “Concrete Repair
Guide (ACI 546R-04),” American Concrete
Institute, Farmington Hills, MI, 53 pp.
EM 1110-2-2704, 2004, “Cath­odic Protection
Systems for Civil Works Structures,” U.S. Army
Corps of Engineers, Washington, DC, http://
140.194.76.129/publications/eng-manuals/
em1110-2-2704/entire.pdf, 106 pp.
ETL 1110-3-474, 1995, “Cathodic Protection,”
U.S. Army Corps of Engineers, Washington, DC.
PWTB 420-49-29, 1999, “Operation and
Maintenance of Cath­­­­odic Protection Systems,”
U.S. Army Corps of Engineers, Washington, DC,
http://www.wbdg.org/ccb/ARMYCOE/PWTB/
pwtb_420_49_29.pdf, 131 pp.
20 - 510.1–2013
PWTB 420-49-37, 2001, “Cathodic Protection Anode Selection,” U.S. Army Corps of
Engineers, Washington, DC, http://www.wbdg.
org/ccb/ARMYCOE/PWTB/pwtb_420_49_37.
pdf, 36 pp.
SHRP-S-347, 1993, “Chloride Removal
Implementation Guide,” Strategic Highway
Research Program, Washington, DC, http://
onlinepubs.trb.org/onlinepubs/shrp/SHRP-S347.pdf, 49 pp.
SHRP-S-359, 1994, “Technical Alert: Criteria
for the Cathodic Protection of Reinforced Concrete Bridge Elements,” Strategic Highway
Research Program, Washington, DC, http://
onlinepubs.trb.org/onlinepubs/shrp/SHRP-S359.pdf, 18 pp.
SHRP-S-657, 1993, “Electrochemical Chloride Removal and Protection of Concrete Bridge
Components: Laboratory Studies,” Strategic
Highway Research Program, Washington, DC,
http://onlinepubs.trb.org/onlinepubs/shrp/
SHRP-S-657.pdf, 382 pp.
SHRP-S-671, 1993, “New Cathodic Protection Installations,” Strategic Highway Research
Program, Washington, DC, http://onlinepubs.trb.
org/onlinepubs/shrp/SHRP-S-671.pdf, 128 pp.
TI 800-01, 1998, “Design Criteria,” U.S.
Army Corps of Engineers, Washington, DC,
http://www.wbdg.org/ccb/ARMYCOE/COETI/
ti800_01.pdf, 459 pp.
UFC 3-570-02A, 2005, “Cathodic Protection,” U.S. Army Corps of Engineers, Washington, DC, http://www.wbdg.org/ccb/DOD/
UFC/ufc_3_570_02a.pdf, 62 pp.
UFC 3-570-02N, 2004, “Electrical Engineering, Cathodic Protection,” U.S. Army Corps
of Engineers, Washington, DC, http://www.
wbdg.org/ccb/DOD/UFC/ufc_3_570_02n.pdf,
319 pp.
UFGS-26 42 14.00 10, 2008, “Cathodic Protection System (Sacrificial Anode),” U.S. Army
Corps of Engineers, Washington, DC, http://
www.wbdg.org/ccb/DOD/UFGS/UFGS-26 42
14.00 10.pdf, 30 pp.
UFGS-26 42 19.00 20, 2006, “Cathodic Protection by Impressed Current,” U.S. Army Corps
of Engineers, Washington, DC, http://www.
wbdg.org/ccb/DOD/UFGS/UFGS-26 42 19.00
20.pdf, 34 pp.
Guide for Electrochemical Techniques to Mitigate the Corrosion of Steel for Reinforced Concrete Structures
10600 West Higgins Road, Suite 607
Rosemont, IL 60018
Phone: 847-827-0830
Fax: 847-827-0832
Website: www.icri.org
E-mail: info@icri.org