Volume 9 Preprint 15
The application of impressed current cathodic protection to historic listed reinforced concrete and steel framed structures
J. P. Broomfield
Keywords: Impressed current cathodic protection, anodes, historic<br>buildings, conservation, corrosion control
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Volume 9 Paper 15
The application of impressed current cathodic
protection to historic listed reinforced concrete
and steel framed structures
J. P. Broomfield
Broomfield Consultants, 30b Vine Road, East Molesey, Surrey KT8 9LF,
This paper describes some case studies of historic buildings and other
structures treated with impressed current cathodic protection to
provide long term corrosion control that is consistent with the
requirements of conservation of listed buildings and monuments.
Keywords: Impressed current cathodic protection, anodes, historic
buildings, conservation, corrosion control.
Galvanic cathodic protection was invented by Sir Humphrey Davy in
1824 [#01]. Impressed current systems started being used in earnest
on ships and pipelines early in the 20th century.
The first major steps to electrochemical corrosion control treatment of
reinforced concrete occurred in the USA as early as 1959 when Richard
Stratfull applied impressed current cathodic protection (ICCP) to a
This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science
and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at
http://www.umist.ac.uk/corrosion/jcse in due course. Until such time as it has been fully published it
should not normally be referenced in published work. © UMIST 2004.
bridge deck [#ref02].
Between 1973 and 1989 a total of 287 systems
were installed on US interstate highway bridges, predominantly on
structures suffering from deicing salt attack. Many more systems were
applied to other structures as well as to other bridges owned by the
states, counties and cities in the USA and Canada.
The first trials and full scale ICCP systems in UK and Australia were
undertaken in the mid to late 1980s [#ref03]. These were done on
buildings suffering from the deliberate addition of calcium chloride as
a set accelerator in the UK, and on jetties due to marine exposure and
a cement works due to sea salt exposure in Australia. Since then over
1 million m2 of impressed current cathodic protection has been
applied to reinforced concrete structures worldwide.
The Requirements for Conservation of Listed Structures in the UK
In 1967 the civil amenities act introduced conservation areas.
meant that all buildings in a certain area had conservation practices
applied to their maintenance and modification.
In 1988 English Heritage started to list 20 th century buildings of
historic and architectural importance. This means that a number of
steel framed, stone and brick clad buildings have been listed, as well
as reinforced concrete structures. The recent development of the
Heritage Lottery Fund also gave the owners of listed buildings a
financial resource support them in their desire to conserve their
While there is no simple formula for conservation of listed buildings,
there is a number of guidance rules for their maintenance and repair.
Were possible conserve as found
Minimise all intervention
Like for like repairs
Repairs should be reversible
Repairs and changes should be sympathetic
All fabric is important (including later changes and not just
what looks nice)
Application of Impressed Current Cathodic Protection to Listed
Impressed current cathodic protection is a valuable tool in the
conservation of early 20th century steel framed stone, brick and
terracotta clad buildings and later reinforced concrete historic
structures. Anodes can be installed either within the building to
preserve the façade or externally in the mortar between bricks and
stones causing minimal disturbance or damage
The application of impressed current cathodic protection minimises
the amount of repair required. It is also reversible, as anodes, wiring
and power supplies can be removed if later technology provides
improved protection. The monitoring system means that a “health
check” is regularly carried out on vulnerable steelwork. The down side
is that regular monitoring and maintenance of the system is required
Case History 1 Reinforced Concrete University Buildings
Churchill College Cambridge was designed by architect Richard
Sheppard of Robson and partners, and built from 1959 to 1968. The
construction is of low level (mainly 2 storey) buildings with main
elevations of structural precast concrete beams connected to a
concrete frame and supporting glasswork. Investigation of cracking
and spalling of the concrete beams in past few years has revealed
sufficient levels of chloride in the concrete to cause reinforcement
corrosion on some of the buildings with precast facia beams. This is
almost certainly due to the use of calcium chloride as a set accelerator
in the casting yard to speed production rates. Figure 1 shows typical
Figure 1- Typical elevations of Churchill College showing precast
panels at 1st floor and roof level.
After a detailed survey showing above corrosion threshold levels of
chloride in most beams, it was agreed to investigate the feasibility of
applying impressed current cathodic protection to the panels which
have a white stone (quartz or marble) chip revealed aggregate in white
The main constraints on such an installation were as follows:
The campus is occupied 24 hours a day 356 days per year.
Noise, dust and general disturbance must be minimised
Access to the rooms behind the beams should be minimised.
All cables and anodes should be installed with minimum
disturbance to the architectural faces.
Some beams could be accessed from below with long probe anodes
installed vertically to provide protection. However, others could not.
A cathodic protection trial was therefore designed with probe anodes
installed vertically in a panel where there is access to the soffit. The
panel above had two zones, one with a row of anodes installed
horizontally on the centre line, the other with a row of horizontal
anodes below a row of angled anodes as illustrated in Figure 2.
Anode Layout for inaccessible beam soffit
Anode Layout for accessible beam soffit Zone 1
Figure 2 – Schematic of anode layout with approximate anode
The anodes were 500mm CPI™ rod anodes with a balance resistor in
the head, with a mixed metal oxide coated titanium (MMO/Ti) rod
embedded in a proprietary carbonaceous backfill.
Given the internal arrangement behind the beam it is not possible to
drill from inside. Therefore through hole were drilled from the outside
and the anode installed with the cabling inside the building. The
external surface finish of a quartz revealed aggregate and white
cement made repair of the beam and reinstatement of the anode holes
quite straight forward to achieve an aesthetically acceptable finish that
should not change with weathering.
Trials of the anode arrangements showed adequate polarization in
zones 1 and 2 but inadequate polarization at the top of zone 3 with 5V
constant voltage applied to all zones.
An anode layout was therefore determined as conforming to zone 1 in
Figure 1 where the soffit of the beam can be accessed, and as for zone
2 where the anodes cannot be inserted vertically. There will be further
discussion as to whether the titanium cables connecting the anodes
need to be run internally or whether chases can be cut in the outer
surface for all work to be done externally. This will be considered if
the Conservation officer and College officials are convinced that the
repairs using new white cement and quartz aggregate will be
Case History 2 New Zealand National War Memorial
New Zealand’s National War Memorial is located in Wellington and
consists of the Carillon, completed in 1932, and the Hall of Memories,
which was consecrated in 1964. The memorial commemorates the
New Zealanders who gave their lives in the South African War, in the
First and Second World Wars, and in the wars in Korea, Malaysia and
Vietnam; it also honours the NZ men and women who served in those
Figure 3 – The New Zealand
National War Memorial
Carillon is a 50 metre high
structure that contains 74
bells which each range in
weight ranging from 10kg
to 12.5 tonnes. Their total
weight of 70.5 tonne and 6
octave range makes it the
third largest carillon in the
A survey identified that the reinforcement corrosion was limited to the
mullions and the area around the openings as the Carillon faces the
bay. Trails of anode spacings were conducted. An impressed CP
system was installed consisting of 570 discrete internal anodes. There
were 3 mm diameter MMO/Ti rods in carbonaceous backfill at 600 mm
The anodes were 100 mm or 150 mm long as required from the
results of the trial. There were 25 zones each with it’s own embedded
Ag/AgCl reference electrode to permanently protect approximately
170 square metres of at-risk structural concrete. 12mm diameter
holes were drilled on the required 600 mm centres. Holes were
checked with a “down hole cover meter” to ensure they were not too
close to reinforcement. They were then filled with the carbonaceous
backfill and the anode rod inserted. A titanium wire was connected
between the anodes and wired into a junction box and then connected
back to the power supply. A remote monitoring system was installed
to monitor the 25 zones. The system was commissioned in June 1999
Case History 3 Balcony of a small building in St Martin’s Lane London
Next to the recently renovated Coliseum Theatre is a small building
originally part of Architect Frank Matcham’s 1904 theatre building. It
has an elaborate terracotta stone balcony at the second floor level. At
all levels the terracotta was cracking due to corrosion of the steel
frame. Upper levels were dismantled, steelwork repaired and
stonework replaced or renewed. However the second floor level was
considered to be too intricate so impressed current cathodic
protection was installed using MMO/Ti ribbon anodes.
Figure 4 shows the balcony with horizontal cracks in the terracotta
stones due to corrosion of the steel beam. Two vertical steel columns
have also caused cracking of the terracotta columns. Figure 5 shows
the installation of ribbon anode in the joints between stones and a
reference electrode being installed.
Figure 4 – The balcony showing damage
Figure 5 – Close up of ribbon in joints, new stone and installation of a
The ICCP system consists of a single zone running across the front of
the building at 2nd or level and up the columns of the balcony. The
system was commissioned in October 2005 and is running at less than
10V D.C. and a few tens of milliamperes.
Case History 4 A small brick building in St Martin’s Lane London
Just up the road from Case History 3 there is and ICCP system on an
office building. This consists of four zones running from the bottom
of the first floor to parapet level on the four exposed corners of the
building. The system was installed and commissioned in September
2005. It was a subcontract package to control the vertical cracking of
external brickwork around the vertical steel columns at four corners of
the building. Typical damage is shown in figure 6. Each column is a
separate zone running at less than 10V D.C. and a few tens of
milliamperes per zone.
Each zone consists of a MMO/Ti expanded metal ribbon in the mortar
joints running down one side and up the other side of the column.
The ribbon is 10mm wide by 0.9mm thick with a current rating of
3mA/m length. There is a reference electrode approximately 1/3 and
2/3 of the way down each zone. There is a ring conduit behind the
roof parapet to collect the wires from the anode, the steel column and
the reference electrodes and connect them to the monitoring system
situated in a steel cabinet inside the cupboard beside the lift motor
room on the roof.
Figure 6 – Example of
cracking of brick
work due to the
of the corner steel
This is reflected on all
four corners of the
Figure 7 Zone and reference electrode locations – Front elevation
Figure 7 shows the new mortar in the joints after the installation of the
Case History 5 University of East Anglia Biology Tower
The main campus buildings of the University of East Anglia were
designed by Sir Denys Lansdun and built in the 1960s. The original
main buildings, which are Grade II listed, include the iconic “ziggurats”
which form the main accommodation blocks (featured on the English
Heritage website) and the “teaching wall” consisting of a linear 5 storey
block of offices research and teaching spaces punctuated by lift and
stair towers rising to eight storeys.
In 2002 a contract was let to carry out an overall concrete protection
plan, with an immediate priority to repair the Biology Tower due to the
construction of a new extension to the Biosciences School. The
original building showed low concrete cover to the reinforcement,
carbonation induced spalling a patchwork of old repairs of vary colour
and texture and old trials of anticarbonation coatings which were
unacceptable to English Heritage.
It was agreed that ICCP was the best way of guaranteeing a repair in
keeping with the listed status and capable of ensuring that concrete
does not spall onto the glass atrium of the new extension. In this case
probe anodes were used installed from the inside of the building. On
the outside conventional low shrinkage patch repair materials were
used and then an architectural coating with anticarbonation properties
(Keim Concretal Lazur™) was applied to blend in repairs with the old
concrete, retaining original board markings and other features
considered to be important features of the building.
Probe anodes of MMO/Ti and conductive ceramic were installed in the
stair wells and the roof level plant rooms. Figure 8 shows the probe
anodes in the roof level plant room where the cables were kept at
surface level for easy identification and repair. Figure 9 shows “before
and after” photographs from the back of the Biotower.
The silicate based penetrating sealer type coating blends in the repairs
to the original concrete and should weather in such a way as to
minimise the risk of the patchwork appearance developing with time.
Figure 8 – Biotower Plant Room showing Anode wires on surface
Figure 9a – Biotower before repair showing coating trials and exposed
Figure 9b - Biotower after Concrete repair and coating
application minimising “patchwork” appearance.
Discussion and Conclusions
Cathodic protection of steel in concrete is a mature technology
which is now being applied to structures of historic and
architectural importance. It is successfully being applied to
early 20th century steel framed buildings and monuments as
well as mid to late 20 th century reinforced concrete structures.
The development of mixed metal oxide coated titanium rod,
tube and ribbon anodes, as well as the conductive ceramic
tube anodes has facilitated the installation of anodes in a
sympathetic way with minimal disturbance to the fabric and to
the aesthetic appearance of structures.
Systems can be very large with 50 or more zones all remote
monitored and controlled, or simple manually controlled
systems with very few zones. However, they all require
maintenance on a regular basis.
At the moment there is very little guidance on the application
of ICCP to steel framed and historic structures. On of the few
is produced by Historic Scotland [#ref06]. The revision of the
European Standard on cathodic protection of steel in concrete
is underway and there is consideration of including
information on steel framed buildings. However, some
practitioners advocate a separate document for such
structures. This is unlikely to occur in the foreseeable future.
However, the National Association of Corrosion Engineers has
a Task Group on the subject which may produce a state of the
art report and ultimately a standard in a few years time.
The author would like to acknowledge the kind permission to
publish information about their buildings and contracts as
Jennifer Rigby, Bursar Churchill College Cambridge.
Owner of 55/56 and of 36 St Martin’s Lane Shaftsbury Covent
Garden Ltd., Contract Administrator Robert Say, Fresson and
Tee Chartered Surveyors.
University of East Anglia Estates and Building Division, Neil
Jackson (Project Director), Martin Lovatt (Project Manager),
Structural engineer Andrew Brown Jacobs Babtie, London
!ref01 ‘The beginnings of cathodic protection’, H. Davy, Phil. Trans. Of
the Royal Soc. London, 1824.
!ref02 ‘Progress report on inhibiting the corrosion of steel in a
reinforced concrete bridge’ Stratfull. R.F. Corrosion. 15(6):331t to
334t, Jun 1959
!ref03 ‘Cathodic Protection for Reinforced Concrete: It's application to
buildings and marine structures’ Broomfield, J.P. Langford, P.E. and
McAnoy, R. Corrosion 87. 1987 Mar 9-1987 Mar 13; Corrosion of
Metals in Concrete Proceedings of NACE Conference. NACE Houston,
!ref04 “Concrete Building Pathology” Ed Susan MacDonald, Publ.
Blackwells,Oxford, pp 288-293.
!ref05 Gibbs, P. Corrosion in masonry clad early 20th century steel
framed buildings. Technical Advice Note 20. 2000; Publ. Historic