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182 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
Cathodic protection for concrete structures
its negative pole to the steel reinforcement to be protected. The
anode system, whose function is to supply a uniform current distri-
bution to the steel reinforcement, is made of a high lifetime conduc-
tive material plus an overlay, embedded in the concrete or applied
on the concrete surface. With such a system, the current can easily
be adjusted in order to maintain the steel/concrete potential at a
desired level. This is done by setting the rectifier output potential.
For atmospheric structure, the most used anode systems are:
n activated titanium mesh coated with noble metal oxides (Ti/
MMO) with a low resistivity mortar overlay. The Ti/MMO mesh
is fixed to the surface of the concrete structure and is encap-
sulated with mortar that usually is applied by projection (see
Figure 4);
n conductive coatings or organic paints applied directly on the
concrete surface;
n probe shape anodes with different lengths and diameters, de-
pending on the concrete structure to be protected. The anode ma-
terial can be titanium covered by electroplated platinum; Ti/MMO
or conductive ceramics in tubular, tape or rod form. The anodes
are inserted in holes made in the concrete containing conductive
fillers such as a graphite gel or a low resistivity mortar;
n mesh type Ti/MMO tapes with different thicknesses. The tapes
are installed in shallow grooves made on the concrete surface
and then covered by low resistivity mortar applied by spraying
(see Figure 5);
n conductive coatings sprayed on the concrete surface. These
are essentially cementitious material containing nickel coated
carbon fibers;
n thermal sprayed metallic coatings (mainly pure zinc). This type
of anodes are also used in the galvanic cathodic protection
method (see item 6).
Figure 6 shows the possible electrochemical reactions that can oc-
cur on an anode surface and on a cathode (steel reinforcement)
surface. If the anode material does not oxidize, which is the case
C B
Figure 5 – Mesh type Ti/MMO tape (a). Titanium tapes installation and welding (b). Final visual aspect (c)
A
Figure 6 – Schematic representation
of impressed current cathodic protection