[0001] This invention relates to cathodic protection systems and has particular reference
to cathodic protection systems used to protect iron or steel reinforcement bars in
concrete structures.
[0002] Impressed current cathodic protection systems are well known in use to protect structures
immersed in water, particularly sea water. In such a system the object to be protected
is made a cathode whilst the counter electrode is made an anode. Negatively charged
ion species are attracted towards the anode where they tend to concentrate, unless
sufficient diffusion of ions occurs in the region of the anode to disperse them. In
free sea water, the movement of the negatively charged ions occurs freely and readily,
such that there is a minimal buildup of ions around the anode.
[0003] Reinforced concrete essentially comprises a series of steel reinforcing bars (commonly
referred to as rebars) surrounded by a concrete mixture.
[0004] It is well known that steels are not corroded in alkaline media. Reinforcing bars
are very frequently covered with an adherent "rust" layer when embedded in concrete,
which experience has shown improves the adhesion between concrete and steel. With
time, as may be shown by removing the concrete cover, the rust changes chemically
allowing the formation of a dark, protective, film well adherent to concrete. This
is the very satisfactory usual situation that exists.
[0005] Concrete, by various mechanisms, is porous to water, albeit very slowly, and even
after so called full curing, will allow a slow uptake with some kind of equilibrium
being established with the surrounding environment. This again is a normal situation.
However, if salt water is present on the surface, then the salt and its contained
chloride ions may penetrate into the concrete. It is not immediately obvious why salt
contamination is more of a problem to some concrete than others, because concrete
is widely used as a constructional material for use in seawater. The design of the
concrete structure and thickness of the outer concrete layer may be particularly important.
[0006] In the case of chloride contaminated concrete, a risk exists that chloride ions will
enhance the corrosion of the steel. The resultant corrosion product formed by the
enhanced reaction occupies a greater volume than the space occupied by components
prior to chemical reaction, eventually creating intense local pressure that brings
about cracking of the concrete and eventual spalling of the concrete cover to expose
rebars directly to the atmosphere.
[0007] A great deal of reinforced concrete has been used in building and in road construction
and particularly in the fabrication of support pillars, cross beams and road decks
for bridges. Over the years increasing amounts of common salt, sodium chloride, has
been used in winter to prevent ice formation on the road. The melted snow or ice and
sodium chloride solution tends to seep down into the concrete, and it has been found
that the presence of the chloride ion penetrating to the rebars can give rise to corrosion.
In some cases, calcium chloride has been added to the concrete as a setting agent,
or the water used to make the concrete contained naturally high levels of chloride
ions and this also increases the rate of corrosion of the rebars. Further, some structures
are exposed to salt-laden atmospheres, particularly in marine locations.
[0008] Electrode potential mapping of the outside surface of concrete rebars is used as
a means of assessing the state of corrosion of embedded rebars and by inference the
depth of penetration and concentration of salt. Around a concrete cross bar to a motorway
bridge, the variation in electrode potential may be 0.5 volts or more. It might be
logical to expect that salt contamination from the bridge roadway would leak onto
the top surface of the cross beams and hence lead to more rapid penetration to rebars
lying near the top surface than on the bottom surface, and this is exactly what is
found.
[0009] The problem of corrosion of the rebars in bridges has become so significant that
much effort is being expended in an attempt to slow down or halt the corrosion before
the concrete structures in the bridges fail.
[0010] By cathodic protection is meant the application of an electrolytic system whereby
the electrode potential of the steel is depressed to a cathodic (negative) potential
to stop or significantly decrease corrosion.
[0011] The cathodic protection of steel in concrete represents an especially challenging
problem for application of cathodic protection for a variety of reasons. An obvious
difference between cathodic protection in concrete and seawater is the difference
in ionic mobility of species within the electrolyte. Although there is an electrolytic
path in concrete, otherwise application of cathodic protection would be impractical,
nevertheless the level of diffusion between anode and cathode is many orders of magnitude
lower than in the seawater case, and the distance between the anode and the cathode
to be protected cannot usually exceed 15 to 30cms.
[0012] Another difference between the seawater and concrete example relates to the change
in pH surrounding the electrodes. It is well known that media surrounding a cathode
will tend to alkalinity, and around an anode will tend to acidity. Alkalinity around
a rebar in concrete, which is already alkaline, is no problem. Indeed additional alkalinity
could be helpful towards the stabilisation of the steel from corrosion.
[0013] The formation of acidity around anodes in concrete is a major issue. Acidity cannot
readily diffuse away from the anode either by diffusion under a concentration gradient,
or by field transport to the cathode (ie H
+ to the cathode) brought about by the applied cell voltage. Concrete is readily attacked
by acid, even at very low levels of acidity. Attack is significant at pH 6, and while
some concretes may be more acid resisting than others, attack at pH's down to 2 or
1 (common in some cathodic protection situations) is extremely rapid.
[0014] Hence in practical terms, the problem of cathodic protection of rebars in concrete
is not the ability to arrest the corrosion of steel by depressing the electrode potential,
but the problem of acidity surrounding anodes. Indeed the longevity of cathodic protection
systems applied to concrete may well not be related to the durability of the electrode
materials involved, but be related to the acid attack on concrete surrounding anodes.
In this respect the cathodic protection of rebars in concrete is very different to
cathodic protection of steel in seawater.
[0015] US-A 4 255 241 describes a cathodic protection system for concrete structures which
utilizes plati- nized niobium wire or like metal anodes positioned adjacent the concrete
in a matrix of of conductive carbonaceous material. In this system the wire anode
can be installed directly in a conductive asphaltic coke breeze overlay or inserted
into a slot cut directly into a concrete surface. Likewise EP-A 85 582 describes a
cathodic protection system using conductive polymer concrete in which anodic materials
are positioned adjacent a concrete surface. Polymers are described as desirable because
of their resistance to acid attack. US-A 4 422 917 discloses an electrode material
of the formula TiO
x, wherein x is from 1.55 to 1.95. The material may be used in a cathodic protection
system in which the material forms the anode.
[0016] By the present invention there is provided a cathodic protection system for the protection
of iron or steel reinforcement bars in concrete which includes a source of electrical
current connected to the reinforcement bars and to an anode, so that, in use, the
reinforcement bars are connected as a cathode, wherein the anode is a hydraulically
porous material permeable to water in the liquid state, which is bonded to the concrete
so as to make electrical contact therewith and exposed to the environment over part
of its surface area.
[0017] A preferred material for the anode is porous TiO
x where "x" is in the range 1.67 to 1.95. Preferably "x" is in the range of 1.75 to
1.8. The porous TiO
x material is preferably in the form of a tile grouted to the exterior of the concrete.
A liquid mortar may be used as the grout. The porous TiO
x material may have a thickness in the range 2-3 mm. The density of the material may
be in the range 2.3 to 3.5. The porous TiO
x material may be in the form of a tube passing into a hole in the concrete structure.
[0018] The porous material may be graphite or porous magnetite, porous high silicon iron
or porous sintered zinc, aluminium or magnesium sheet.
[0019] The porous material may be in the form of a tile bonded to the concrete, the tile
having a projecting ear to which electrical contact can be made. The ear may be provided
with a hole or slot. The ear may be connected to a power supply cable having an electrically
conducting core and a lead metal exterior in electrical contact with the core, the
lead being deformed by the action of being pushed into the slot to make electrical
contact therewith.
[0020] The titanium may be anodically passivated and may be coloured. The anodically passivated
layer may be removed where the titanium is in contact with the TiO
x material anodes.
[0021] The titanium may be in the form of strips having sections cut and bent out of the
plane of the strips to form tabs to which the anodes are connected. The anodes may
be connected to the titanium strips by nuts and bolts of titanium or by a titanium
rivet. The strips may mechanically locate the anodes on the concrete. The strips may
be provided with slots.
[0022] There may be a plurality of strips with the strips being bolted, riveted, welded
or otherwise electrically joined together.
[0023] By way of example embodiments of the present invention will now be described with
reference to the accompanying drawings, of which:
Figure 1 is a schematic view in section of a road bridge;
Figure 2 is a schematic view of a support member of a bridge wired with a series of
anodes;
Figure 3 is a cross-section of a support member showing anodes and reinforcement bars;
Figure 4 is a perspective view of one form of anode;
Figure 5 is a perspective view of an alternative form of anode;
Figure 6 is a schematic view of a concrete cross beam and pillars;
-- Figure 7 is a schematic perspective view of an anode connected to a portion of
a strip;
Figures 8 and 9 are schematic views of tabs formed in titanium strip;
Figure 10 is a schematic view of a connection between two titanium strips incorporating
an anode at the connection;
Figure 11 is a plan view of a strip with an anode embedded in concrete;
Figure 12 is a perspective view of an anode and strip; and
Figure 13 is a sectional view of an anode and strip.
[0024] It is necessary to understand the causes of acidity to understand the present invention.
In any electrolytic system involving anodes and cathodes, the overall reaction is
the summation of component parts, which includes specific electrochemical reactions
at both electrodes. In the case of an anode in concrete, the predominating reactions,
albeit at very slow rate compared with most cathodic protection systems, is either
the oxidation of chloride ions to release chlorine gas, or the oxidation of water
to release oxygen and leave behind H
+ ions. This latter reaction is the particularly important one, 2H
20 - 4e → O2 + 4H
+.
[0025] For every 96,540 coulombs of electricity passed involving this reaction, 1g H
+ will be produced. Such H
+ concentration (which is, of course, acidic) will react with concrete, in a volume
depending upon the available calcium hydroxide accessibility within the concrete.
Thus a simple model can be considered. Hydrogen ions generated by the reaction set
out above may:
a) react with all the calcium compounds in the volume of concrete immediately surrounding
the anode;
b) depress the pH of the surrounding concrete to a low pH;
c) migrate towards the OH- near the cathode;
d) pass through the porous anode to be oxidised by the air; or
e) pass through the porous anode and be diluted by the moisture from the atmosphere
or rainwater.
[0026] Short term (seven day) practical tests with a single anode passing 25mA suggests
that the volume of concrete attacked will be 12cm
3, and the pH depressed to a value of O. Assuming normal porosity, density and Ca(OH)
2 content of concrete, the amount of H
+ ion produced required to react with 12cm3 of concrete will be 0.036gH
+.
[0027] At a pH of O the H
+ concentration will be 1 g/I H
+ so that the H
+ requirement to depress the pH of available moisture will be 0.012gH
+. Therefore the total H
+ generated to the anode over seven days would approximate to 0.036 + 0.012 = 0.048gH
+.
[0028] The number of coulombs of electricity passed in seven days is 15,120 coulombs. Assuming
30% current efficiency for oxygen evolution, the reaction 2H
20 - 4e - 0
2 + 4H
+ will result in 0.047gH
+ ion generation. Hence it appears that a 25mA anode will produce between 0.05 to 0.1
gH
+ per week. At 1 mA/anode the corresponding figure would be 0.002 to 0.004gH
+ per week. At this rate it would take eighteen weeks to react all Ca(OH)
2 in 12cm
3 zone of concrete per week, and, of course, correspondingly longer time periods the
lower the current passed or the volume of concrete affected.
[0029] The calculations involved are approximate but while advanced at no detriment to the
claims of the patent, are advanced as an indication of the magnitude of the problem
of acid attack around anodes in concrete.
[0030] Some indication of the effect of porous anodes in removing acidity has been obtained
from laboratory experiments in which porous anodes were cemented to a reinforced concrete
block and were kept saturated with water artificially by means of a surrounding shallow
rim. With application of current to rebars within the concrete, acidity develops on
the outer surface of the porous anode and after five hours of operation at 80mA at
8 volts the pH of the distilled water fell to 2.7.
[0031] It should be noted that H
+ ions generated at the anode/concrete interface diffused away from the cathode into
water to the outer side of the anode, presumably because of the favourable concentration
gradient.
[0032] In a further experiment, hydraulically porous T
J40
7 material was used to divide the volume of a glass beaker into two approximately equal
volumes. In one side was placed sodium chloride solution and a titanium metal strip
cathode. In the other (representing the atmosphere side in the bridge deck) was put
distilled water. With the hydraulically porous Ti
40
7 separator connected as an anode and anodically polarised with respect to the titanium
cathode, acidity developed with time in the initially distilled water compartment.
Such acidity develops in spite of the good diffusivity of H+ ions in the sodium chloride
side, ie H
+ ions diffused in the "wrong" direction away from the cathode.
[0033] Referring now to the drawings, as illustrated schematically in Figure 1, many road
bridges are based on a series of upstanding pillars 1, 2 supporting a cross member
3. Members 1, 2 and 3 are formed of reinforced concrete. The cross members 3 carry
a plurality of substantially rectangular section steel girders 4, 5 which carry the
actual road bed 6.
[0034] As shown in Figures 2 and 3 there is provided a mechanism for cathodically protecting
the rebars in the structure 3. The rebars 7 (more clearly shown in Figure 3) are connected
to a source of electrical current 8 as cathodes. A series of hydraulically porous
TiOx tiles 9, 10 are grouted to the exterior of the concrete structure 3 and an electrical
connection is made to the tiles in a suitable manner. The preferred value for x is
1.75, but tiles where x is predominantly in the range 1.75 to 1.8 are acceptable.
Electrodes of this material are described in US Patent 4 422 917, the description
of which patent is incorporated herein by way of reference.
[0035] As the TiOx material will conduct electricity as an anode it may be used to pass
an electrical current through the moisture in the concrete into the rebars 7. During
operation anions such as CI- are attracted to the anodes and by using porous TiO
x material the anions can diffuse through the TiO
x to be oxidised by the air in the atmosphere or to be washed away by the irrigation
of the anodes which will occur from rain water washing over the surface of the support
structures, or by applied water irrigation.
[0036] It will be appreciated that tubular anodes can be used. If necessary water could
be directed through the anodes from gulleys on the road deck.
[0037] By irrigating the anodes, excessive anion buildup in the concrete can be reduced.
[0038] One method of connecting the anodes to the electrical conductor line is shown with
reference to Figure 4. In Figure 4 the anode plate 11 is provided with an upstanding
ear 12 integral with the plate. A hole 13 exposed through the ear 12. Electrical contact
is made by bolting or clamping a suitable wire through the aperture 13.
[0039] An alternative method of making a connection is illustrated in Figure 5. In the design
of Figure 5 a tile 14 of circular or eliptical shape is provided in the centre with
three up-standing ears 15, 16 and 17. The ears are provided with slots 18, 19 and
20. It will be seen with the slots 18 and 20 face in the opposite direction to the
slot 19.
[0040] A lead coated wire having a copper core is threaded around the ears 15, 16 and 17
and the slots are so positioned that tightening of the lead covered wire causes the
wire to bite into the slots 18, 19 and 20 to make an electrical contact.
[0041] An alternative mode of operation may be used containing TiOx as the electrical conducting
constituent formed by packing powder into grooves in the concrete back-filled into
grooves in the concrete.
[0042] The current density which needs to be applied to the anodes is very low. Typically
a current density of the order of 20 milliamps/m
2 will protect the steel rebars. Thus for concrete structure 11/
2 m2 by 14 m long, a total current number across being 1-2
1/
2 amps would be sufficient. Operating 15 cm x 15 cm tiles at 5 amps/m
2 would permit each tile to pass 0.1 amp so that 15-20 tiles per cross-beam would be
sufficient.
[0043] It will be appreciated that the number of tiles used would be determined by the required
cathodic protection throwing power. Each anode would be electrically connected to
the power source used for the impressed current cathodic protection system.
[0044] The hydraulically porous TiO
x material, particularly material having a density in the range 2.3 to 3.5 g/cc is
readily bonded by cement to concrete and has the distinctly advantageous property
of not being effected by water freezing within the pores of the material. As the material
is hydraulically porous water as a liquid (rather than merely as a vapour) can pass
through it; for example material of 3 mm thickness with a head of water of 30 cm will
pass one litre of water per 5 cm
2 of exposed surface area per day.
[0045] Instead of using lead coated wires as connectors titanium strips may be used. The
titanium strips may themselves have a coating to restrict corrosion of the strips
in which case an oxide film formed by ano- dising is preferred. This arrangement is
shown more clearly in Figures 6 to 13.
[0046] Referring to Figure 6 this shows the concrete cross beam 3 supported on the pillars
1, 2. The beam is a conventional steel rebar reinforced concrete structure. The pillars
1 and 2 are also conventional concrete with steel rebars. Extending along the length
of the beam 3 is a titanium strip 21 and extending vertically from the strip is a
plurality of strips, two of which are shown at 22, 23. The entire length of the concrete
beam 1 will be covered by strips 22, 23. The strips 5, 6 are spot welded, riveted,
bolted or otherwise connected to the strip 21 and a vertical strip 24 is connected
to the strip 21. Strip 24 is connected to a suitable source of electrical current
as an anode and a suitable connection is made to the steel reinforcement within the
beam 3 as a cathode. Thus electricity can be conducted along strips 24 and 21 to the
plurality of vertically extending titanium strips 22, 23. A plurality of Tid.75 anodes
are bolted to the strips 22, 23 as shown in Figure 7. The anode 25 are of a ceramic-like
material and are bolted to tabs formed integrally in the strip 26. The tabs are shown
in more detail as 27 and 28 in the strips 29 and 30 shown in Figures 8 and 9.
[0047] As can be seen in Figure 10 the tabs can be formed as connectors for adjacent strips
31, 32 and also to connect in an anode 33. The anodes are secured by means of titanium
nuts and bolts 34.
[0048] The anodes may be embedded into holes drilled into the concrete and are grouted into
position as shown in Figure 11. The anode 35 is surrounded by grout 36 located in
the concrete structure 37. The anode is bolted to titanium strip 38.
[0049] By this system the permanently connected anodes can be distributed over the surface
of the beam 3 and of course, if required, over the surface of the upright pillars
1, 2. Any other structure can simultaneously be protected.
[0050] Because the concrete grout securing the anodes may well become weak during operation,
even if it is one chosen for its acid resistance such as a high alumina cement, it
is probably desirable to use mechanical means to hold the anodes in situ in addition
to the grout. The titanium strips can carry out both functions of supplying current
to the anodes and holding the anodes in situ. When such a system is used, slotted
strips 39 (Figures 12 and 13) can be used. To install such a system, initially the
position of the shear (longitudinal) rebars in the material is located, marked out
with chalk, and thus enabling the location of the hydraulically porous tile anodes
to be marked in approximate position. The hydraulically porous tile used measured
50 mm x 50 mm and had a hole drilled in one location to take a titanium metal nut
40 and bolt 41. The connector strip 39 of slotted titanium had a width of 20 mm and
was 0.5 mm thickness. By means of a self tapping screw, the strip is located at its
upper end, leaving slot locations for the anode and defining positions for the self
tapping holding screws 42. Because of large aggregate in the concrete cover, it is
difficult to drill holes exactly in the concrete, thus the use of the slots facilitated
installation. Then the anode tiles are grouted at locations down the strip and the
titanium nuts 40 screwed loosely in position and the self tapping screws 42 screwed
into position while the acid resisting cement is still soft. This sequence is progressed
along the side of the beam.
[0051] When the electrically conducting and chemically resistant grout has hardened, the
nuts to the anodes are tightened, and a horizontal linking titanium strip connector
applied.
[0052] The horizontal connector will also be attached to the concrete structure, but only
after all other positioning had been completed. The system can then be used to protect
the rebars.
[0053] Obviously the cathodic protection system could be used to protect rebars in concrete
in any situation, for example car parks, foundations, marine structures etc. In the
case of bridges the system can be installed on the underside of the bridge deck itself
to protect the bridge deck. This installation can be done without interfering with
the traffic flow.
1. A cathodic protection system for the protection of iron or steel reinforcement
bars in concrete which includes a source of direct electrical current connected to
the reinforcement bars and to an anode, so that, in use, the reinforcement bars are
connected as a cathode, wherein the anode is a hydraulically porous material permeable
to water in the liquid state, which is bonded to the concrete so as to make electrical
contact therewith and which is exposed to the environment over part of its surface.
2. A cathodic protection system as claimed in claim 1 wherein the anode is a hydraulically
porous ceramic material.
3. A cathodic protection system as claimed in claim 1 or claim 2 in which the hydraulically
porous material is directly bonded to the concrete by cement.
4. A cathodic protection system as claimed in claim 1 or claim 2 in which the hydraulically
porous material is embedded in a conducting backfill.
5. A cathodic protection system as claimed in any one of claims 1 to 4 in which the
hydraulically porous material for the anode is TiOx where "x" is in the range 1.67 to 1.95.
6. A cathodic protection system as claimed in claim 5 wherein "x" is in the range
of 1.75 to 1.8.
7. A cathodic protection system as claimed in claim 5 or claim 6 in which the porous
TiOx material has a thickness in the range 2-3 mm.
8. A cathodic protection system as claimed in any one of claims 5 to 7 in which the
density of the porous material is in the range 2.3 to 3.5.
9. A cathodic protection system as claimed in any one of claims 5 to 8 in which the
porous TiOx material is in the form of a tube passing into a hole in the concrete
structure.
10. A cathodic protection system as claimed in any one of claims 1 to 4 in which the
hydraulically porous material is selected from the group consisting of graphite, porous
magnetite, porous high silicon iron and porous sintered zinc sheet.
11. A cathodic protection system for the cathodic protection of steel reinforcement
bars embedded in concrete, the system comprising a plurality of anodes as claimed
in any one of claims 5 to 9 embedded in spaced location in concrete, the anodes being
electrically interconnected by titanium conductors, the anodes being anodically polarised
relative to the steel reinforcement bars by means of an external source of current.
12. A cathodic protection system as claimed in claim 11 in which the titanium conductors
are in the form of strips.
13. A cathodic protection system as claimed in claim 11 or claim 12 in which the titanium
is in the form of strips having sections cut and bent out of the plane of the strips
to form tabs to which the anodes are connected.
14. A cathodic protection system as claimed in claim 12 or claim 13 in which the anodes
are connected to the titanium strips by nuts and bolts of titanium or by a titanium
rivet.
15. A cathodic protection system as claimed in any one of claims 12 to 14 in which
the titanium strips mechanically locate the anodes on the concrete.
16. A cathodic protection system as claimed in claim 15 in which the strips are provided
with slots.
17. A cathodic protection system as claimed in any one of claims 12 to 16 in which
there is a plurality of strips with the strips being bolted, riveted, welded or otherwise
joined together in electrical contact.
1. Kathodisches Schutzsystem für den Schutz von Eisen- oder Stahl-Bewehrungsstäben
in Beton, welches eine mit den Bewehrungsstäben und mit einer Anode verbundene Gleichstromquelle
aufweist, so daß die Bewehrungsstäbe als Kathode angeschlossen sind, wobei die Anode
ein hydraulisch poröses, für Wasser im flüssigen Zustand durchlässiges Material ist,
das an den Beton gebunden ist, einen elektrischen Kontakt mit diesem herstellt und
über einen Teil seiner Oberfläche der Umgebung ausgesetzt ist.
2. Kathodisches Schutzsystem nach Anspruch 1, bei welchem die Anode ein hydraulisch
poröses keramisches Material ist.
3. Kathodisches Schutzsystem nach Anspruch 1 oder 2, bei welchem das hydraulisch poröse
Material mit Zement an den Beton gebunden ist.
4. Kathodisches Schutzsystem nach Anspruch 1 oder 2, bei welchem das hydraulisch poröse
Material in einer leitenden Hinterfüllung eingebettet ist.
5. Kathodisches Schutzsystem nach einem der Ansprüche 1 bis 4, bei welchem das hydraulisch
poröse Material für die Anode TiOx ist, wobei x im Bereich von 1,67 bis 1,98 liegt.
6. Kathodisches Schutzsystem nach Anspruch 5, bei welchem x im Bereich von 1,75 bis
1,8 liegt.
7. Kathodisches Schutzsystem nach Anspruch 5 oder 6, bei welchem das poröse TiOx-Material eine Dicke im Bereich von 2 bis 3 mm aufweist.
8. Kathodisches Schutzsystem nach einem der Ansprüche 5 bis 7, bei welchem die Dichte
des porösen Materials im Bereich von 2,3 bis 3,5 liegt.
9. Kathodisches Schutzsystem nach einem der Ansprüche 5 bis 8, bei welchem das poröse
TiOx-Material die Gestalt eines Rohres hat, das sich in ein Loch im Beton erstreckt.
10. Kathodisches Schutzsystem nach einem der Ansprüche 1 bis 4, bei welchem das hydraulisch
poröse Material aus der Graphit, porösen Magnetit, Siliziumeisen mit hohem Siliziumgehalt
und poröses gesintertes Zinkblech umfassenden Gruppe ausgewählt ist.
11. Kathodisches Schutzsystem für den kathodischen Schutz von in Beton eingebetteten
Stahl-Bewehrungsstäben, welches eine Mehrzahl von in Abständen im Beton eingebetteten
Anoden nach einem der Ansprüche 5 bis 9 aufweist, wobei die Anoden mittels Titan-Leitern
elektrisch miteinander verbunden sind und bezüglich der Stahl-Bewehrungsstäbe über
eine äußere Stromquelle anodisch vorgespannt sind.
12. Kathodisches Schutzsystem nach Anspruch 11, bei welchem die Titan-Leiter in Form
von Bändern vorliegen.
13. Kathodisches Schutzsystem nach Anspruch 11 oder 12, bei welchem das Titan in Form
von Bändern vorliegt, von welchen durch Einschnitte gebildete Abschnitte zur Bildung
von Lappen für den Anschluß der Anoden aus der Bandebene abgekantet sind.
14. Kathodisches Schutzsystem nach Anspruch 12 oder 13, bei welchem die Anoden mittels
Muttern und Schrauben aus Titan oder mittels eines Titan-Niets mit den Titan-Bändern
verbunden sind.
15. Kathodisches Schutzsystem nach einem der Ansprüche 12 bis 14, bei welchem die
Titan-Bänder die Anoden mechanisch am Beton halten.
16. Kathodisches Schutzsystem nach Anspruch 15, bei welchem die Bänder mit Schlitzen
versehen sind.
17. Kathodisches Schutzsystem nach einem der Ansprüche 12 bis 16, bei welchem eine
Mehrzahl von Bändern vorhanden ist, die zur elektrischen Verbindung miteinander verschraubt,
vernietet, verschweißt oder sonstwie miteinander verbunden sind.
1. Installation de protection cathodique destinée à protéger des barres d'armature
de fer ou d'acier, dans du béton, comprenant une source d'un courant électrique continu
connectée aux barres d'armature et à une anode afin que, pendant l'utilisation, les
barres d'armature soient connectées comme cathode, l'anode étant formée d'un matériau
hydrauliquement poreux, perméable à l'eau à l'état liquide, qui est fixé au béton
afin qu'il soit en contact électrique avec lui et qui est exposé au milieu environnant
par une partie de sa surface.
2. Installation de protection cathodique selon la revendication 1, dans laquelle l'anode
est un matériau céramique hydrauliquement poreux.
3. Installation de protection cathodique selon la revendication 1 ou 2, dans laquelle
le matériau hydrauliquement poreux est directement fixé au béton par un ciment.
4. Installation de protection cathodique selon la revendication 1 ou 2, dans laquelle
le matériau hydrauliquement poreux est enrobé dans un matériau conducteur de remplissage.
5. Installation de protection cathodique selon l'une quelconque des revendications
1 à 4, dans laquelle le matériau hydrauliquement poreux de l'anode est TiOx, x étant
compris entre 1,67 et 1,95.
6. Installation de protection cathodique selon la revendication 5, dans laquelle x
est compris entre 1,75 et 1,8.
7. Installation de protection cathodique selon la revendication 5 ou 6, dans laquelle
le matériau poreux de TiOx a une épaisseur comprise entre 2 et 3 mm.
8. Installation de protection cathodique selon l'une quelconque des revendications
5 à 7, dans laquelle la densité du matériau poreux est comprise entre 2,3 et 3,5.
9. Installation de protection cathodique selon l'une quelconque des revendications
5 à 8, dans laquelle le matériau poreux de TiOx est sous forme d'un tube passant dans
un trou formé dans la structure de béton.
10. Installation de protection cathodique selon l'une quelconque des revendications
1 à 4, dans laquelle le matériau hydrauliquement poreux est choisi dans le groupe
qui comprend le graphite, la magnétite poreuse, le fer poreux à teneur élevée en silicium
et une feuille poreuse de zinc fritté.
11. Installation de protection cathodique de barres d'armature d'acier enrobées dans
du béton, l'installation comprenant plusieurs anodes selon l'une quelconque des revendications
5 à 9, enrobées à distance les unes des autres dans le béton, les anodes étant reliées
électriquement par des conducteurs de titane, les anodes étant polarisées anodiquement
par rapport aux barres d'armature d'acier par une source externe de courant.
12. Installation de protection cathodique selon la revendication 11, dans laquelle
les conducteurs de titane sont sous forme de bandes.
13. Installation de protection cathodique selon l'une des revendications 11 et 12,
dans laquelle le titane est sous forme de bandes ayant des tronçons découpés et repliés
en dehors du plan des bandes afin que des pattes auxquelles sont raccordées les anodes
soient formées.
14. Installation de protection cathodique selon la revendication 12 ou 13, dans laquelle
les anodes sont connectées aux bandes de titane par des écrous et des boulons formés
de titane ou par un rivet de titane.
15. Installation de protection cathodique selon l'une quelconque des revendications
12 à 14, dans laquelle les bandes de titane positionnent mécaniquement les anodes
sur le béton.
16. Installation de protection cathodique selon la revendication 15, dans laquelle
les bandes ont des fentes.
17. Installation de protection cathodique selon l'une quelconque des revendications
12 à 16, dans laquelle plusieurs bandes sont présentes, les bandes étant boulonnées,
rivetées, soudées ou raccordées d'une autre manière afin qu'elles soient en contact
électrique.