EP0564546A1

EP0564546A1 - Method of repairing building constructions with metal parts embedded in them

Info

Publication number: EP0564546A1
Application number: EP92902455A
Authority: EP
Inventors: Sten Henning V Litalo; Hans Oppitz
Original assignee: Eltac Nogler und Daum KG; Coating AS
Current assignee: Eltac Nogler und Daum KG; Coating AS
Priority date: 1990-12-18
Filing date: 1991-12-18
Publication date: 1993-10-13
Also published as: NO905454D0; WO1992011399A1; AU9133191A

Abstract

La présente invention décrit un procédé pour la rénovation d'ouvrages (1) avec des éléments métalliques (5) insérés dans ces derniers et reliés à une source de tension continue (10), dont le potentiel positif est en contact avec une couche protectrice électriquement conductrice disposée à la surface de l'ouvrage (1), et dont le potentiel négatif est relié à la terre et/ou à des parties métalliques (5). Une partie de la surface de l'ouvrage (1) est munie de la couche protectrice conductrice. A cette dernière est appliquée une tension effective maximale de 0,2 à 4 V, de préference 1,5 V, laquelle présente une courbe de tension pulsatoire.The present invention describes a method for renovating structures (1) with metallic elements (5) inserted therein and connected to a DC voltage source (10), the positive potential of which is in contact with an electrically protective layer. conductive disposed on the surface of the structure (1), and whose negative potential is connected to the ground and / or to metallic parts (5). Part of the surface of the structure (1) is provided with the conductive protective layer. To the latter is applied a maximum effective voltage of 0.2 to 4 V, preferably 1.5 V, which has a pulsating voltage curve.

Description

Process for the renovation of buildings with all parts embedded in them

The invention relates to a method as described in the preamble of patent claim 1.

Electrical corrosion protection systems for metal parts or structural parts embedded in protective sleeves are already known - according to Ing. Taschenbuch Hütte 28th edition, IV, B, pages 1482 to 1487. In this method, the negative pole of a direct current source is connected to a pipeline laid in the ground. So-called protective anodes, for example iron protective anodes with coke coating, are arranged at a distance from the pipeline and are connected to the positive pole of the direct current source. Corrosion protection systems of this type were able to reduce corrosion on pipelines, but in many cases they could not be prevented.

Another known electrically operated (active) corrosion protection system - in accordance with GB-S 2 140 456 - has a DC voltage source whose positive potential is applied to a thin, permanent, non-corrodible anode made of strips, rods, wires or nets. These anodes are fixed to the concrete surface with an epoxy adhesive and then coated with a conductive paint. The negative potential of the direct voltage source is due to the reinforcement formed by metal parts. The electrical field formed between the anode and the cathode is intended to prevent corrosion of the metal parts, ie the reinforcement, for example in bridges, with the protective current flowing in the field. Furthermore, according to this device, electrodes are provided in the area of the reinforcement, with which the voltage in the electrical see field in the area of the reinforcement is monitored in order to automatically monitor the current flow in the electrical field via a control device connected to the electrodes. With this known device it is thus possible to reduce the susceptibility to corrosion of reinforcements, in particular metal parts in reinforced concrete components. A satisfactory solution to the corrosion problems in reinforced concrete components is not possible with this device either.

In a further known corrosion protection system - according to WO / 8604099 - the positive potential of a DC voltage source is contacted over a large area with the surface of the structure, while the negative potential is applied to the reinforcement material embedded in the structure. With this method, which has proven itself well, remedial measures on the surface of the structure are necessary to achieve an intensive field structure in order to produce a corresponding conductivity.

Furthermore, it has been found in the past that reinforced concrete structures are considerably damaged, particularly by the penetration of acid gases into the concrete. This is mainly due to the amount of CO2 in the air. This proportion of CO2 is constantly increasing due to the increasing consumption of fossil fuel. These gases are able to penetrate into the pore system of the concrete through open-pore lacquer films. As a result, the previously alkaline environment in the concrete is changed by a process, which is generally referred to as carbonization, into an acidic environment by the formation of calcium carbonate. If this acidification penetrates into the depth of the concrete in which the reinforcements or other reinforcing steels or reinforcing iron are arranged, the film which is initially passive and which prevents rust on the iron due to the alkaline environment in the soil is destroyed and corrosion occurs. It is then necessary to repair the concrete, very often protecting the surfaces with CO2-inhibiting coatings that are applied to the concrete. Repairs to the concrete are usually removed by removing the damaged concrete parts by manual chiseling or with high-pressure water and filled in by injecting cement or concrete, which is subsequently coated. In another known method - according to NO-PS 160 696 for the electrochemical realcalization of carbonized concrete surfaces, an electrical direct voltage is applied between a reinforcing element in a carbonized area of the concrete and an electrode in an area which exhibits alkaline behavior. In the method according to the Norwegian patent in particular, the acidified area of the concrete is realized by the transport of a basic liquid to the acidic area, the lye-like liquid being supplied by an internal or external lye supply via the direct current. According to this Norwegian patent, this lye supply exists in a certain area in the concrete, provided that the wall or the object formed by the concrete is double-reinforced and that this reinforcement is not in direct contact with the reinforcement in the acidic position that should be protected. In practice it has been found that this is rarely or never the case. It is usually always a contact between a possible inner and outer reinforcement in such a construction. Furthermore, these alkalines can be provided in alkaline electrolytes on the outside of the concrete wall or surface. From the outside, the liquid is transported in the direction of the reinforcements, which are then surrounded by the alkali with a rust-proof coating. In practice, the latter alternative is used. However, this method is also very expensive to carry out. It is very labor-intensive, with many and complex work operations. In addition, the result is questionable and involves a safety risk due to the high voltage and direct current. Furthermore, it causes high costs, combined with the risk of expenditure of time, since this method has to be part of a major maintenance.

According to the prior art, according to NO-PS 160 696, an electrode is used in a wet alkaline environment, which is arranged on the outside of the concrete structure to be realized. This environment is an electrolytic medium which is applied to the surface of the structure and an electrolyte can be used as the electrolytic medium, in the form of an aqueous solution of calcium, soda and / or potassium salts in liquid form or incorporated in a porous medium such as mineral wool, sawdust, sand or clay alongside other porous media. In practice, in these known methods, an outer, thin reinforcement grid is applied to the concrete surface, which acts as an electrode. Then an alkaline wet cardboard pulp is sprayed onto the entire wall in such a thickness that the net is completely covered. This process takes place after the repa-

2 rature of the concrete as previously described. This slurry can comprise approximately 50 l / m of wall surface. Then a direct current source with an output power between 500 and 700 amperes and a voltage of 10 to 50 V is connected to the electrode network and the reinforcements. According to this Norwegian patent, the external electrode is to be connected to the negative potential of the direct voltage source, while the reinforcements in the carbonized zone in the concrete are connected to the positive potential. In the known method, the current changes to an electrolysis current and that is the actual energy consumer. The power is turned on to cause the liquid to quickly enter the wall (2-3 days). The cardboard porridge must be checked and improved continuously to prevent it from drying out. Security checks must be carried out in order to prevent the high current intensity from coming, for example, with internal power systems of the building object, which could lead to injury to people and to the burning of underground cables and the like. Furthermore, problems arise in the wet alkaline area with short-circuits between the reinforcements through breaks, cracks, nails, binding wires for reinforcements, fittings and the like. This causes problems since no realization can occur since it is known that the electrical current is always is looking for the simplest way and therefore the desired reaction does not take place. After the end of the treatment period, the cardboard pulp and the remnants of the electrode network, which is badly corroded during the treatment period, must be removed and removed. The alkaline deposits are very strong and thorough cleaning must therefore be carried out. Rust deposits are often created by the external reinforcement network and these deposits are located on the concrete wall and must therefore be removed. Finally, a protective layer must be applied to prevent the concrete from carbonizing again. Due to the previous penetration of alkaline liquids into the concrete, a Drying of the surface must be made possible and the type of coating must in many cases be selected very carefully in order to enable sufficient adhesion.

The object of the present invention is to create a method for metal parts embedded in structures and to protect them from corrosion, in particular by means of concentration elements, that is to say galvanic elements, and in which a field which is uniform in all areas of the structure comes into effect . In addition, it should be possible to use an electromechanical process which is simple, cheap and safe and which enables the reinforcing inserts to be re-passivated in carbonated concrete.

The object of the present invention is achieved by the features specified in patent claim 1. The advantage of this solution is that by using a very low operating voltage, which is applied to the electrodes, the energy supplied via the electrodes is not sufficient to trigger dissociation. In conjunction with the pulsating voltage curve, this now enables the salts, which are heteropolar compounds, not to disintegrate into their ions. This keeps them in a state of limbo as they are neutral. This prevents the types of cations other than hydrogen ions and at least one type of anions different from hydroxide ions present on the crystal lattices of the salts from being separated electrolytically only to a small extent and thus almost no salt residues being produced, which is usually the case after dissociation their polarity to the anode in the case of anions or to the cathode in the case of cations. However, this also avoids that in the landfill area of these salt residues can react with other elements present there to form new compounds, and thus compounds with chlorine ions for the formation of acids are avoided.

A further embodiment is described in claim 2, whereby the local elements formed between the areas of the metal parts which are exposed to the different pH values are switched off by the superimposed electrical field and in turn a continuous one anodic protection of the metal parts is achieved.

In the embodiment according to patent claim 3, it is advantageous that the possible water vapor diffusion allows gases or water vapor to pass through the plastic layer, as a result of which the structure can dry out or gases or the like present in the structure can be broken down is possible.

However, a procedure according to claim 4 is also possible, as a result of which the plastic layer can be protected from external influences, in particular conductive deposits and dirt and the like, and nevertheless an unimpeded gas exchange between the interior of the concrete body to be protected in the ambient air is possible.

The measure according to claim 5 prevents the occurrence of dissociation between the metal parts and the carbonized concrete parts, whereby, above all, an oxyhydrogen gas formation can be reliably prevented.

The procedure according to claim 6 above all ensures depolarization of the anode.

It is also advantageous according to claim 7 that the cathode is supplied with the same voltage at the same time, as a result of which the salts or the conductive salt residues are reached between the components present at the positive and negative potential of the DC voltage source.

However, an embodiment according to claim 8 is also advantageous because good conductivity and low contact resistances and thus a low continuous output for the supply system for maintaining the electrical field are achieved.

However, an embodiment is also possible, as a result of which the boron salt is deposited on the reinforcing material acting as an anode as a result of the ion transport to the reinforcement material acting as anode, and thus any loose iron particles are solidified on the reinforcement material is reached.

However, an embodiment according to claim 10 is also advantageous because it prevents the molecules of the heteropolar compounds from disintegrating into their ions and thus prevents acidic or basic compounds from forming at the anode or cathode.

An advantageous embodiment is described in patent claim 11, whereby a resistant and long-term coating of the buildings is achieved.

An embodiment according to claim 12 is possible because the negative voltage component eliminates the substances formed by the electrolytic decomposition, in particular the unfavorable gases in a reverse reaction.

However, a method according to claim 13 is also advantageous because it raises the mean voltage potential to the positive range without the need for additional switching and / or regulating devices.

However, training according to claim 14 is also possible because very inexpensive supply devices can be used which can easily achieve a medium, positive potential via control elements.

An advantageous development describes claim 15, whereby a large and a spatially intensive electric field is built up, in which the field strength can be kept low. Likewise, a low contact resistance is achieved, as a result of which lower power output is sufficient for the effective operation of the method and thus an economical method for protecting such a structure is achieved.

Finally, however, a method according to claim 16 is also advantageous because it means costly periodic renewals or sanitation. The corrosion protection devices used are avoided.

The procedure according to claim 17 prevents the build-up of contaminants favoring corrosion.

If one proceeds according to claim 18, the advantage is achieved that the multilayer structure of the electrode arranged on the surface of the component ensures good adhesion and thus overall a distributed introduction of energy in the electrical field. This prevents the occurrence of voltage peaks and thus the occurrence of dissociations or electrolysis phenomena.

The measures according to claim 19 are also advantageous, since this avoids the current density or voltage peaks in the region between the two electrodes.

If one proceeds according to claim 20, a uniform electric field is created, the current density of which is sufficient to switch off the local elements in the area of the reinforcements, thereby protecting the metal parts which form the reinforcement of the structures.

The measures according to claim 21 prevent the occurrence of electrolysis phenomena by exceeding the wetting tension of water, whereby damage to the structure or aggressive decomposition of the concrete and, above all, the dreaded detonating gas formation can be prevented.

Furthermore, it is also advantageous to proceed according to claim 22, since this provides additional security for avoiding voltage peaks or excessive current densities.

Claim 23 describes an embodiment which is very advantageous for the renovation of concrete structures, since the electrode arranged on the outside can thereby be produced in a simple manner, which is also environmentally friendly through the use of a water-based lacquer. For a better understanding of the invention, it is explained in more detail below with reference to the exemplary embodiments shown in the drawings.

Show it:

1 is a side view of a building 1 in which the metal parts formed by the reinforcement are arranged in a protective jacket formed of concrete and a surrounding one

Protective layer with the electrical corrosion protection device for performing the method according to the invention;

2 shows the building in front view cut along the lines II-II in Fig.1;

3 shows a part of the protective jacket with metal parts arranged therein in the area of the protective layer applied to its surface, partially cut away in a diagrammatic representation;

4 shows a voltage-time curve for the voltage at the electrodes of the corrosion protection device, which voltage changes between positive and negative potential;

5 shows another embodiment variant of a corrosion protection device for carrying out the method according to the invention in a simplified, diagrammatic representation.

In Fig. 1, a building 1, in particular a bridge 2 is shown, which consists of a prestressed concrete structure.

A protective jacket 4 formed from concrete 3 comprises the reinforcement 6 formed by metal parts 5. To protect the metal parts 5 against corrosion by anodic and cathodic partial reactions occurring in different longitudinal areas thereof due to galvanic elements which are located between anodic and cathodic areas of the metal parts 5 Due to different pH values in the moisture-enriched concrete 3 serving as electrolyte, a corrosion protection device 7 is provided.

The corrosion protection device 7 for preventing the corrosion of the metal parts 5 comprises a voltage supply device 8, e.g. a DC voltage source 10 formed by a battery 9, the positive potential of which is present at a positive pole 11 and the negative potential of which is present at a negative pole 12. The negative pole 12 can either be connected to an earth conductor 13, which anchors in the area 14 surrounding the building 1, e.g. is buried and / or connected to the reinforcement 6 via a line 15.

The positive pole 11 of the DC voltage source 10 is connected to an arranged, electrically conductive plastic layer 16 of the protective jacket 4 via a line 17. This plastic layer 16 is on its surface facing away from the protective jacket 4 18 with a protective layer 19, for. B. provide a varnish 20 which preferably has a pore size which also enables water vapor diffusion.

A preferred embodiment of the plastic layer 16 is the use of acrylic polyester. The plastic layer 16 or the protective layer 19 or the lacquer 20 can be formed, for example, in a conductive plastic, for example in the manner of a thermoset with a macromolecular structure, for example in an acrylate with at least partially crosslinked polymers. The advantage of such a conductive plastic for the plastic layer 16 or possibly the protective layer 19 or the lacquer 20 is that it contains synthetic resin dispersions, synthetic resin solutions or synthetic resins with metal or semimetal compounds or their solutions in an amount, so that a synthetic resin molecule comes approximately to a metal or semimetal atom and which, after mixing and adding reducing agent in a slight excess or by known thermal decomposition, contains metal or semimetal atoms and in which the ions formed or still present are washed out and the dispersions , Solutions or granules with graphite or carbon black are further processed. What is surprising with that Use of such plastics that they are much more resistant to mechanical and thermal stresses, since the conductivity is independent of the free-floating conductor particles embedded in the plastic - as schematically shown over part of the plastic - ie the conductive connection in the plastic is not achieved via the conductor particles, but rather through the adherence of the silver ions in the cavities of the large plastic molecules, the semiconductor taking on properties by reducing the silver ions. This makes it possible to make do with a graphite powder content in an amount of 40%, based on the plastic, in order to adjust the properties of the conductive plastic to the field of application in distribution lines according to the invention.

The details of such a plastic are described in Austrian Patent No. 313 588.

Such plastics are not only resistant to chemical and electrochemical influences, but also have a high resistance to aging, since they contain no ions and hardly change as a result of the action of electrical currents.

The plastics described above can be used advantageously in conjunction with the cathodes and / or anodes or electrodes shown in the various exemplary embodiments and have proven extremely useful in practical tests. Another advantage of these plastics is that they have high surface adhesion and surface roughness. Furthermore, the plastic layer 16 is preferably mixed with a reducing agent, in particular a boron salt, as a result of which oxygen reduction occurs in the area of the protective layer or, through boron ions which may be detached, in the concrete structure itself, which improves the invention Process and the chemical reactions taking place. To reinforce the plastic layer 16 or the protective layer 19, it is also possible to use these nets 21, grids, knitted fabrics, nonwovens made of high-strength fibers or threads or only fibers or threads made of high-strength materials such as glass, plastic, Graphite, metal or the like, in particular use of electrically conductive materials 22.

As can be seen more clearly from FIG. 2, the electrical plastic layer 16 of the protective jacket 4 can also be arranged from a surface 24 facing away from a roadway 23, which in particular form side walls 25 and an underside 26 of a bridge. Of course, however, it is also possible to coat the entire surface of a building, in particular also in the case of houses, the surrounding outer walls, continuously with the electrically conductive plastic layer.

The protective layer 19, in particular the lacquer 20, is arranged on the plastic layer 16 on the side facing away from the surface 24.

The plastic layer 16 is connected via the line 17 to the positive pole 11 of the voltage supply device 8. The negative pole 12 of the

Voltage supply device 8 is connected via line 15 to grounding conductor 13, for. B. connected to a band 27, which, for. B. in Er¬ erection of the building 1 in the area of a footprint 28 of the building 1 is arranged in the field. The line 15 can, however, also be loaned or connected in an electrically conductive manner to the metal parts 5 forming the reinforcement 6. In this case, a voltage between 1 V and a maximum of 10 V is fed into the lines 15 and 17 via the voltage supply device 8. Due to the different transmission losses in the lines or between the plastic layer 16 and the structure, e.g. the bridge 2 to an effective voltage between the plastic layer 16 and the metal parts 5 of 0.2 V to 4 V, in particular 1.5 V.

At the same time, a current density between the individual contacts

2 cycle areas or points of the plastic layer 16 0.5 to 5 mA / m.

2 At least 3 to 10 are preferred over an area of 100 m

Contact connections between the line 17 and the plastic layer

16 provided.

As can further be seen from FIG. 2, the reinforcement 6 is the one that forms it Metal parts 5 embedded in the concrete 3. When the cement binder sets and hardens, potassium hydroxide, Ca (OH) 2 is formed and a strongly alkaline solution with pH values greater than 12.5 forms in the pore water of the concrete. In this environment, metal parts, in particular made of steel, are protected against corrosion by a thin oxidic cover layer. The concrete 3 forms a protective jacket 4, ie a secondary mechanical protection against injuries to this cover layer and at the same time also prevents - at least in the case of dense concrete - the penetration of aggressive substances up to the reinforcement 6.

Is it now z. B. to a carbonization of the concrete 3, inter alia by the action of carbon dioxide from the air, the pH value in the area of the reinforcement 6 penetrates through the carbonized surface additionally aggressive substances, such as chlorides by salt scattering or , the oxidic cover layer of the steel is dissolved and there is between those areas of the reinforcement 6 or the metal parts 5 in which this oxidic cover layer is dissolved and those where the oxidic cover layer is still very high due to the strongly alkaline solution has a pH value to form a galvanic element, the moisture in the concrete forming the electrolyte.

This corrosion of the reinforcement 6 by the galvanic element takes place through a separate oxidation in the area of the undamaged metal parts 5 lying in the alkaline area and to a reduction in the area of those parts of the metal parts 5 in which the oxidic covering layer has been destroyed by the action from outside.

The fact that now with the corrosion protection device 7 to prevent corrosion, the electrically conductive plastic layer 16 positive or the entire remaining areas are kept negative, can now due to the electric field of the positive potential of the voltage supply device 8 anode and do not set an oxidation process at the reinforcement 6 present at the negative potential, the galvanic elements being neutralized, since the metal parts 5 are each clearly at the negative potential and therefore none between different areas of these metals Potential difference can arise more.

This type of galvanic elements made of similar metals in different electrolytes - which are actually formed by the same electrolyte, namely moisture in concrete 3, but with a different pH value - do not arise from the potential difference of different metals according to the voltage series. but rather by heterogeneous composition of the electrolytes, essentially as a result of concentration differences which can occur in the case of similar electrolytes. These elements are usually referred to as concentration elements. By applying a directed electric field with precisely defined positive and negative potentials, the corrosion current that is generated by galvanic elements is superimposed and thereby ineffective or compensated. The field 29 built up by the voltage supply device 8 to prevent corrosion, or the currents flowing in this field - symbolically represented by thin lines - should usually be higher than the corrosion currents generated by the concentration elements.

The currents 30 flowing in the field 29 - also referred to as protective currents -

2 are relatively small in the present case, e.g. 0.5 - 5 mA / m because there is a high conductivity of the electrolyte formed by the moisture in the concrete 3, a cathodically controlled corrosion. The low electrolyte resistance thus results in a protective current requirement which can only be approximately the corrosion current of the galvanic elements acting in the absence of an electrical field.

A further advantage which is achieved by the establishment of a directed electric field is that the negative ions of the negative chlorides or salts through the electric field in the direction of the electrically conductive plastic layer acting as anode 31 and acting as anode 16, hike and bloom there. In order to enable these negative chloride ions to bloom and to prevent the anode 31 from being blown off from the protective jacket 4 by this blooming of the salts, the conductive plastic layer has 16 pores, the pore size of which is sufficient to permit water vapor diffusion and thus an outflow. flowering of the negative ions, that is to say the salts and the like. The cations, i.e. the positive metal ions such as B. K +, NA +, Ca2 +, on the other hand, migrate to the negatively charged metal parts 5 and form an effective protective coating 32 with the oxidation products of the metal parts 5.

The protective layer 19, in particular made of an acrylic polyester, applied to the plastic layer 16, like the plastic layer 16, has pores which allow water vapor diffusion.

3 shows another embodiment for building up an electrical potential for carrying out the method. The electrically conductive plastic layer 16 is arranged as a protective layer on the surface 24 of the protective jacket 4 made of concrete 3 with the metal parts 5 of the reinforcement 6 embedded therein.

In order to achieve a uniform, large-area field, band-shaped lines 33, for. B. pure silver strips 34 are embedded, which are connected via line 17 to the positive pole 11 of the voltage supply device 8. The band-shaped lines 33 and

Pure silver strips 34 are either fully integrated into the plastic layer 16 or at least 3 to 10 contact areas per 100 m surface 24 of the protective jacket 4 are connected or contacted with the plastic layer 16 in a highly conductive manner.

The negative pole 12 is connected to the grounding conductor 13 via the line 15. The voltage supply device 8 is connected via lines 35 to a supply device 36 and is supplied with alternating current from the latter, the voltage supply device 8 having a rectifier element 37, by means of which a pulsating direct current is generated, the positive potential of the positive pole 11 and the latter negative potential is present at the negative pole 12.

The plastic layer 16 has pores 38, the size of which enables water vapor diffusion and is mixed with a reducing agent, in particular a boron salt - schematically represented by crosses 39. On The surface 40 facing away from the surface 24 of the protective jacket 4 is arranged on the plastic layer 16, the protective layer 19 also provided with pores 41, whereby water vapor diffusion is also possible through this.

This configuration produces a large-area electrode which, even in the event of vibrations or interruptions of individual line connections, provides a flat voltage supply and thus the occurrence of current and voltage peaks in the area of the electrode or the electrical field 29 built up by the electrode, which is shown schematically by field lines 42 is indicated, avoids.

As shown in FIG. 4, with this pulsating voltage, the voltage with a positive potential is greater than that with a negative potential, or the time of the voltage applied with a positive potential is greater than that with a negative potential.

The positive sine curve 43 of a correspondingly transformed down mains voltage is obtained, while the negative part 44 of the sine curve is cut off in the lower voltage range, so that as long as the negative

Proportion of the original sine curve does not exceed a certain voltage, there is no voltage and only when the sine voltage exceeds the predetermined voltage limit, the voltage exceeding this voltage limit is applied to the electrodes.

If the use of the mains frequency also offers particular advantages, the method according to the invention is not restricted to sinusoidal voltages of 50 or 60 s. When passing through a zero value 45, the anode present at the positive potential over the longer period of time is applied to negative potential, while the cathode present at the negative potential over the longer period of time is connected to positive potential.

This preferred form of the voltage-time curves can be achieved, for example, with a voltage supply device described in FIG. 6 of EP-PS 0 100 845. 5 shows a component 46 of a concrete structure with reinforcing elements 47. There is an acidified zone 48 between the reinforcing elements 47 and the surface of the component 46, which causes the reinforcing elements 47 to corrode. In order to prevent this corrosion of the reinforcement elements 47 and to produce an alkaline rust protection layer on the reinforcement elements 47, these reinforcement elements 47 are connected to a direct voltage source 50 via a line 49. This potential or connection acts as a cathode.

An electrically conductive coating 52 is applied to the outside or a surface 51 of the component 46 and is in direct contact with the open pores in the concrete and the pore water therein. This connection or coating 52 serves as an anode.

The coating 52 can consist of a current-conducting, synthetic and / or cement-based permanent coating. For example, For such a coating, an electrically conductive paint can be used, which is commercially available under the trade name ELK-82 or similar other water-based paints or lacquers.

This coating 52 is contacted with a low current via contact areas 53 via various lines 54, for example also running parallel to one another.

The present invention is based on the finding that in the event of a corrosive attack on the reinforcing elements 47 in concrete, in practice only care must be taken to create an alkaline environment on the surface of the iron or reinforcing elements 47 in order to prevent corrosion to prevent. Of course, in contrast to the previously patented methods for electrochemical realcalization of the concrete, it is not necessary to realkalize the entire concrete between the reinforcing elements 47 and the surface 51. The electrode, that is to say the anode which is present at the positive potential and which is arranged on the outside or surface 51 of the component 46, namely acts during When the present method is carried out, it is not used as a supply reserve for alkali or as an electrolyte, but merely as a positive potential range. In the reinforcing elements 47, which then represent a negative potential (cathode), OH ions are then produced from the alkalis which are always present in the concrete.

Based on the fact that the present method only functions via the electrical current flow via the path of the pore water and is based on the effect that the system is operated for an unlimited period of time, a lower current density is required in order to achieve the desired effect . Accordingly, when carrying out the present method, it is sufficient to use low voltages and current intensities. An example of such a low voltage is 1 V to 6 V, preferably not more than 5 V and as an example of the

2 low current, the current density should not be more than 0.5 to 5 mA / m. When using the method according to the invention, an immediate change in the corrosion situation after the action of the electrical current is achieved and the long-term build-up of alkaline passivating ambient conditions on the reinforcing elements 47 begins.

It is advantageous for the present method to use permanently installed supply sources which can also be operated using solar elements which are continuously connected to the electrodes throughout the treatment. The length of time that is required can vary between different structures. After a certain treatment time, a check by arranging core bores and potential measurements is possible, on the basis of which it can be decided whether this treatment is to be continued or can be ended. Because of the aforementioned reasons, there are, if at all, only small negative effects if the duration of treatment is continued for a longer period.

Immediately after the application or application of the electrically conductive coating 52, optionally electrically conductive primer 55 and a CO2-repellent coating 56 should also be applied. The

Primer 55 can preferably also be electrically conductive. The As a result of such treatment, uncertainties that can arise with regard to the service life of such concrete structures can largely be eliminated and the structures will allow a considerably longer, non-destructive use.

The process sequence that is usually necessary when the present method for the repassivation of the reinforcing elements 47 in the carbonized concrete is to be carried out as follows:

1. Opening the concrete pores by removing old paint or coating in those areas that are intended to be protected by the present method, e.g. Areas of the concrete structure or the entire surface 51 thereof.

2. Repairs of the blasting with fillers based on cement.

3. Application of the electrically conductive coating 52, the primer 55 and the coating 56.

4. Embedding the contact areas 53 in order to enable sufficient current distribution, for example in a number of 3 to 10, for example 4 contact areas 53 per 100 m ^{2 of} the surface 51.

5. Application of the CO2 resistant coating 56.

6. Attachment of a small stationary DC voltage source 50 and connection of the reinforcing elements 47 with the negative pole and the external outer coating 52 with the positive pole.

The main advantages of the system are:

A) If the electrically conductive coating and the contacts are applied and connected to the DC voltage source 50, further work on the object or component is not hindered, so that time is saved. B) The corrosion of the metal is prevented.

C) Over time, an alkaline environment builds up on the surface of the reinforcing elements 47 or rods.

It can thus be seen that the steps required to carry out the present method are small and extremely simple, compared to the steps that have to be taken if a method is carried out in accordance with the prior art. In comparison, the present method enables harmless, dry electrochemical protection and passivation of the reinforcing elements 47 of the component, while undesirable side effects, such as e.g. the influences of conductive liquids, high current density, the incalculable duration of action, the uncertain result, the cleaning work, the clearing work and the maintenance etc. are avoided.

For various design variants of reinforced constructions, which are to be passivated again by the present method, the expected magnitude of the current density is a few orders of magnitude lower than the current density used in the known method. The voltage used in the method according to the invention is also lower than the voltage used in the known methods.

The present method enables the owner of a building he wants to maintain to stop the corrosion of the reinforcement elements 47 and to build up an alkaline environment in the area of the reinforcement elements.

Finally, the present method is a simple, cost-saving and safe way to passivate and stop the corrosion of reinforcing elements 47 in carbonized concrete.

For a better understanding of the invention, individual parts have been shown disproportionately and to scale in the exemplary embodiments. Furthermore, some of the combinations of features described overall in the exemplary embodiments can also represent independent solutions according to the invention.

Claims

Patent claims

1. Method for the renovation of structures with metal parts embedded in them, which is in contact with a DC voltage source, the positive potential of which is in contact with an electrically conductive protective coating arranged on the surface of the structure, and the negative potential of which is connected to earth and / or the metal parts is present, characterized gekenn¬ characterized in that a part of the surface of the building is provided with the conductive protective coating and on this a maximum effective

Voltage of 0.2 to 4 V, preferably 1.5 V is present, which has a pulsating voltage profile.

2. The method according to claim 1, characterized in that the metal parts are exposed to different pH values over their longitudinal course and are preferably present at the negative potential of a direct voltage source (10).

3. The method according to claim 1 or 2, characterized in that the protective coating consists of a conductive, in particular adhesive plastic layer (16), in which a supply line is embedded and which has a pore size that enables water vapor diffusion.

4. The method according to one or more of claims 1 to 3, da¬ characterized in that at least 50% of the surface of the structure (1) with the conductive plastic layer (16) are coated and on the side facing away from the structure (1) this conductive plastic layer (16) has a protective layer (19), in particular made of lacquer (20), which has a pore size that enables water vapor diffusion.

5. The method according to one or more of claims 1 to 4, characterized in that between the plastic layer (16) and on the metal parts (5) a maximum effective voltage of 0.2 - 4 V, in particular 1, 5 V is present.

6. The method according to one or more of claims 1 to 5, characterized in that the time integral of the voltage present in particular at the anode with a positive potential is greater than the time integral of the voltage with a negative potential.

7. The method according to one or more of claims 1 to 6, characterized in that the time integral of the voltage applied to the cathode is greater with the negative potential than the time integral of the voltage with positive potential.

8. The method according to one or more of claims 1 to 7, characterized in that the supply line is formed by a pure silver band (34) and this is embedded in the electrically conductive plastic layer (16).

9. The method according to one or more of claims 1 to 8, da¬ characterized in that the plastic of the conductive plastic layer (16) is mixed with a reducing agent, in particular a boron salt.

10. The method according to one or more of claims 1 to 9, characterized in that the energy output of the DC voltage source (10) is limited so that almost no electrolytic dissociation arises.

11. The method according to one or more of claims 1 to 10, characterized in that the conductive plastic layer (16) consists of an acrylic polyester.

12. The method according to one or more of claims 1 to 11, characterized in that in the pulsating voltage, the voltage with a positive potential is greater than that with a negative potential.

13. The method according to one or more of claims 1 to 12, characterized in that the time of the voltage applied in particular to the anode with a positive potential is greater than that with a negative potential Potential.

14. The method according to one or more of claims 1 to 13, characterized in that the alternating voltage is a sinusoidal voltage with mains frequency, the voltage of the negative period reduced, in particular the voltage peak of the negative period is cut off.

15. The method according to one or more of claims 1 to 14, characterized in that in the plastic layer (16) or between two layers of the plastic layer at least one layer of e.g. a net (21), grid, knitted fabric, fleece or the like made of high-strength fibers or threads, e.g. embedded in glass, metal, ceramic, plastic or carbon.

16. The method according to one or more of claims 1 to 15, characterized in that the plastic of the conductive plastic layer (16) is chemically resistant to water, aqueous solutions, inorganic salts, acids and alkalis.

17. The method according to one or more of claims 1 to 16, characterized in that the plastic of the conductive plastic layer (16) or the plastic layer (16) receiving layer composite is water-impermeable.

18. The method according to one or more of claims 1 to 17, characterized in that the electrode arranged on the surface of the building (1) consists of a permanent electrically conductive coating, an electrically conductive primer or an electrically conductive impregnation, which is present at the positive potential of the DC voltage source (10).

19. The method according to one or more of claims 1 to 18, characterized in that the electrode is connected via one or more contact areas to the positive potential of the DC voltage source (10) which in the electrically conductive coating, the electrically conductive primer or the electrically conductive impregnation are embedded.

20. The method according to one or more of claims 1 to 19, characterized in that the contacting areas or

Supply line DC voltage is supplied, which is a current density

2 causes between 0.5 and 5 mA / m surface.

21. The method according to one or more of claims 1 to 20, characterized in that a DC voltage with between the metal reinforcing elements den¬ nenden metal parts (5) and the outer electrode

1 to 6 V is applied.

22. The method according to one or more of claims 1 to 21,

2 characterized in that three to ten contact areas per 100 m

Surface can be arranged.

23. The method according to one or more of claims 1 to 22, characterized in that the electrode arranged on the surface is formed by an electrically conductive water-based paint.