WO2017042387A1

WO2017042387A1 - Method for laying an anode system for cathodic corrosion protection

Info

Publication number: WO2017042387A1
Application number: PCT/EP2016/071458
Authority: WO
Inventors: Detlef Koch; Majid Mahjoori
Original assignee: Koch GmbH
Priority date: 2015-09-10
Filing date: 2016-09-12
Publication date: 2017-03-16
Also published as: DE102015115297A1; EP3347507B1; EP3347507A1; US20190119819A1

Abstract

It is intended that an anode system (8) for cathodic corrosion protection can be laid particularly easily, quickly and inexpensively. For this purpose, a method with the following steps is provided: - laying a bundle of carbon fibre filaments (10) over a surface area; - laying at least one primary anode strip (12) in such a way that the primary anode strip (12) is connected to the bundle (10) in an electrically conducting manner in a number of contact regions (18); - connecting the primary anode strips (12) to a primary anode wire (26).

Description

description

Method for laying an anode system for cathodic corrosion protection

The invention relates to a method for laying an anode system for a cathodic protection against corrosion and the use of a non-metallic tape anode in a two-dimensional anode system for cathodic corrosion protection.

Reinforced concrete structures are an integral part of the infrastructure in almost every country in the world. In addition to residential and working buildings, many busy structures made of reinforced concrete are built, e.g. Parking garages, garages, highways, bridges, tunnels etc. A large number of these structures will be used for 50 to 100 years (and sometimes even longer). However, apart from the mechanical stress, it is above all de-icing salts that are added to the reinforced concrete structures. The deicing salts are usually chloride-containing. Therefore, in combination with water, solutions are created which cause corrosion in the structures. For many structures, therefore, substantial, cost-intensive repair work on the reinforcement must be carried out after only 20-25 years.

For this purpose, the contaminated overlay concrete is usually removed, the reinforcing steel cleaned and provided with a new corrosion protection (for example on a polymer or cement basis). However, the repaired area often lasts only a few years (due to mechanical, thermal, and / or hygric incompatibilities), requiring prompt further repair, even when the cover concrete is heavily stressed. This causes high costs, represents a significant intervention in the structure and not least leads to usage restrictions during the repair

One possibility of suppressing corrosion and ideally preventing it is the cathodic corrosion protection (PPS) of buildings. As one of the major As part of a non-destructive repair method, cathodic corrosion protection is becoming increasingly important as an economic repair method for components that are at risk of corrosion or damage.

The principle of electrochemical protection (cathodic protection) is to electrically influence the corrosion process of unalloyed or low alloy steels (e.g., reinforcing steel) in an extended electrolyte (soils, seawater, when used in reinforced concrete: concrete) by introducing direct current. The application of this direct current (protection current) causes a shift of the electrochemical potential of the metal to be protected in the negative direction, whereby the metal surface is cathodically polarized and damaging corrosion is prevented.

To impress a protective current, a permanent and corrosion-resistant anode must first be coupled to the concrete and attached to the positive pole of a rectifier serving as a voltage source. The negative pole of the DC voltage is connected to the steel to be protected (with reinforced concrete to the reinforcement). After switching on the DC voltage to be protected steel is cathodically polarized and the steel corrosion largely prevented.

With the help of an inserted reference electrode, the condition of the building, the structure or the pipeline or the corrosion of the steel can be monitored remotely.

For the most uniform and safe corrosion protection, it is desirable that the anode system as large as possible in the vicinity of serving as a cathode steel element, for example, the reinforcing steel, is designed. However, this is hardly feasible with the anode systems used hitherto, for example when using rod anodes or titanium tape anodes, or it is very difficult to install, as for example when using a reticulated titanium anode. In particular, the application of a reticulated titanium anode for the protection of a reinforced concrete structure on the concrete is due to the inflexibility of the material particularly laborious and time consuming.

The invention is therefore based on the object of specifying a method for laying an anode system for cathodic corrosion protection, which can be carried out in a particularly simple, fast and cost-effective manner.

This object is achieved according to the invention by the method comprising the following steps:

- surface laying of a bundle of carbon fiber filaments;

Laying at least one primary anode tape such that the primary anode tape is electrically connected in a number of contact areas with the bundle;

- Connection of the primary ribbons to a primary soda wire.

The invention is based on the consideration that a particularly simple and rapid installation of the anode system can be achieved if the inflexible titanium tapes or reticulated titanium anodes can be dispensed with as far as possible or if the tapes only have to be laid linearly. Since it is not necessary to dispense with a planar laying of the anode system, a second material is used in addition to the titanium tapes, which can be laid particularly easily and flexibly. It was recognized that a linear bundle of several carbon fiber filaments, a so-called carbon fiber multifilament, both has sufficient flexibility for the areal laying, as well as a sufficiently high electrical conductivity has, in order to come as an anode system for the cathodic protection in question. In addition, such a carbon fiber multifilament as a meter is inexpensive and easily available, whereby a significant cost savings in the construction of an anode system is possible.

To act on the flat-laid bundle with the protection current, this is electrically connected to a plurality of contact areas with a linearly laid titanium anode band, for example, and this primary anode band to a Primary rattan wire connected. This primary anode wire can then be connected to the positive pole of a voltage source as already explained above.

In addition to the use of cathodic corrosion protection in steel structures (such as docks) or pipelines and pipelines, this can also be used in the context of reinforced concrete structures. It is subsequently to equip the reinforced concrete structures with a cathodic corrosion protection or to consider this directly in a new building.

Both for the refurbishment of reinforced concrete structures, when parts of the concrete layer are reapplied and also in the new building is laid for a particularly simple installation of carbon fiber multifilament this in a preferred embodiment on or in the fresh concrete. However, in order to avoid a short circuit between the carbon fiber multifilament as the anode and the reinforcing steel as the cathode because, for example, the carbon fiber multifilament rests on the reinforcing steel, sufficient spacing of the carbon fiber multifilaments from the reinforcing steel is achieved by means of an insulating intermediate layer, for example a glass fiber composite reinforcement ,

In particular, when retrofitting an existing reinforced concrete structure with a cathodic corrosion protection, slits are cut or milled in an advantageous embodiment in the concrete into which the Karbonfasermultifilament can be placed. Further increase or enlargement of the concrete layer to cover the anode system is thus avoided.

In alternative or additional preferred embodiment, the carbon fiber multifilament for fixing to the concrete can also be glued to this. For this purpose, a conductive adhesive can be used, with which the carbon fiber element is fixed in individual points or over the entire area on the concrete. This method can be used in particular in the renovation of old concrete surfaces. The adhesive used in this case comprises especially preferred embodiment ionic additives and water to conduct yourself electrolytically.

For particularly good contact between the carbon fiber multifilament and the primary anode belt, the carbon fiber multifilament is wound in the contact regions around the primary anode belt in a particularly advantageous embodiment. This creates a large number of contacts in these areas, via which the current can be transferred from the primary anode band to the carbon fiber multifilament.

In order to best protect the contact areas and at the same time to connect the carbon fiber multifilament and the primary anode tape better electrically together, the contact areas are enclosed in a preferred embodiment with epoxy resin. Due to the shrinkage of the epoxy resin after application, the contact between the carbon fiber multifilament and the primary anode tape is further improved. The shrinkage of the epoxy resin is thus used specifically to enhance the contact between the carbon fiber multifilament and the primary anode tape. In the case of a primary metallic anode, it is preferably isolated so as not to act as a current supplying anode itself. The insulation thus prevents current from being conducted directly into the electrolytes and too little current entering the actual anode. In a preferred embodiment, therefore, the epoxy resin used is not conductive or insulating.

Overall, the attachment of a carbon anode to a primary anode and the subsequent copper cabling has heretofore been very difficult and a major problem. Unlike other anode materials, carbon can not be welded or brazed to the primary anode or copper cabling. However, by using linear and flexible bundles of carbon fibers, it is now possible to wrap the primary anode tape in order to increase the contact surfaces. In addition, there is the possibility of a mechanical connection or a bond with a conductive adhesive. For a fixation of the entire anode system or even only parts of the reinforced concrete, this is advantageously covered with a conductive mortar. So it is best protected from external influences.

The carbon fiber multifilament is designed meandering in an advantageous embodiment, so as to achieve a particularly uniform distribution and to allow over the meandering bows a particularly simple contact with the primary anode belt. Alternatively, however, other installation patterns can be used which are adapted to the place of use. For example, a laying in individual strips is possible, which are designed parallel to each other and connected to each other via the anode tape.

In addition to the use of such cathodic corrosion protection in reinforced concrete structures, it is also possible to protect the corrosion of steel structures, such as pipelines, port facilities.

The advantages achieved by the invention are, in particular, that a particularly simple and inexpensive surface application of an anode system is made possible by the use of a carbon fiber multifilament. A recourse to a laying less flexible fabric or a mat as an anode system can thus be avoided. The current continues to be conducted via linearly laid primary sands, for example made of titanium strip, and then passed on via the contact areas to the carbon fiber multifilament and thus distributed over a wide area.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

1 a reinforced concrete cutout with a cathodic corrosion protection,

2 shows a cross section through the primary anode belt in a contact region in various design variants, FIG. 3 laying of carbon fiber multifilaments with glass fiber composite reinforcement, FIG.

4 shows a schematic sequence of the method for laying an anode system.

Identical parts are provided with the same reference numerals in all figures.

In the embodiment of FIG. 1, a reinforced concrete structure 1 is shown, wherein the steel reinforcement or the reinforcing steel 2 is protected by means of an applied voltage 4 from corrosion. Such cathodic corrosion protection becomes necessary because, due to various processes such as carbonation and, in particular, the action of chlorides, the passivation of reinforcing steel 2 can be locally canceled. As a result, anodic regions that result in metal dissolution and cathodic regions in which O 2 is formed result in overall formation of localized corrosive foci. In cathodic corrosion protection, an electrical voltage is applied between the corroding reinforcement and an anode connected to the component.

The primary protective effect is based on the polarization shifting the electrochemical reaction equilibria enough to suppress the material dissolution in the anodic regions in favor of the cathodic partial reaction.

Another primary protective effect is that even the passive areas of the corroding reinforcement are cathodically polarized, so that the driving force for the corrosion process is missing. While the primary protection effects are very fast, the secondary protective effects, such as the increase in the OH concentration at the surface of the reinforcement and the depletion of oxygen near the reinforcement, are due to the cathodic reaction and the migration of the negatively charged Cl ions in the direction of the anode, effective later, but then lead to a reduction of the protective current density. In the embodiment of FIG. 1, an anode system 8 was applied to the existing concrete 6 with reinforcing steel 2. In this case, the anode system 8 comprises a bundle of carbon fiber filaments, a so-called carbon fiber multifilament 10, which is arranged in meandering fashion on the concrete 6. In the edge region of this carbon fiber multifilament 10, ie in the region of the meandering arcs, two primary anode ribbons 12 in the form of titanium ribbons are arranged. The meandering bends of the 14 Karbonfasermultifilaments 10 wrap around the titanium strips 12 to allow an electrical connection. The titanium strips 12 are connected via a primary anode wire, not shown, to the positive pole of the voltage source 4. This voltage can be controlled via a remote monitoring system, not shown, so that the state of the building or the reinforced concrete structure can be detected and continuously monitored. The anode system 8 arranged on the concrete is covered in the exemplary embodiment by a conductive mortar 16 so as to be protected against external influences and access.

In the exemplary embodiments of FIG. 2, the primary anode tape 12 is shown in cross section in a contact region 18 in various embodiments.

In Figure 2a, the primary sorbent tape 12 wrapped by the carbon fiber multifilament 10 lies in a previously milled or cut slit 20 of the concrete 6. This slit 20 has been filled with a grout 16 in a further operation so as to protect the primary sands belt and also the carbon fiber multifilament 10 ,

Also in Figure 2b, the primary anode tape 12 wrapped by the carbon fiber multifilament 10 is placed in a slot 20 in the concrete. In contrast to Figure 2a, however, the primary anode tape 12 and the carbon fiber multifilament 10 are enclosed by an epoxy resin 22 in this embodiment. In principle, the use of other resins or even mortar is possible. This additionally protects the primary anode belt 12 and the carbon fiber multifilament 10 and provides 22 due to the shrinkage of the epoxy resin after application for a particularly close contact. To fill the slot and thus to fix the primary anode belt 12, a grout 16 is also used here.

By contrast, the primary sorbent tape 12 wrapped in the carbon fiber multifilament 10 in FIG. 2 c rests directly on the concrete 6. The anode system in this case is covered with a layer of conductive mortar 16 so that it is fixed on the concrete. In contrast to Figure 2c, the primary anode tape 12 wrapped by the carbon fiber multifilament 10 in Figure 2d, before being covered by the conductive mortar, is fixed to the concrete with a conductive adhesive 24.

The attachment options for the primary anode belt shown here can also be transferred to the carbon fiber multifilament. Again, this can be in slots in the concrete, covered with epoxy resin, glued to the concrete or covered with a layer of conductive mortar.

When laying the filaments 10 in fresh concrete care must be taken that the filaments 10 do not touch the steel reinforcement 2 or are too close to it, so that a short circuit between the filaments 10 as an anode and the steel reinforcement 2 as a cathode can be avoided. In the embodiment according to FIG. 3, therefore, the filaments 10 are arranged on an insulating glass fiber composite reinforcement 28. In this case, first the filaments 10 are fastened with binders 30 to this glass fiber composite reinforcement 28 and then also the composite of filament and glass fiber composite reinforcement 28 with other binders 32 on the steel reinforcement 2. Thus, even in fresh concrete, for example in new-clay structures, a sufficient spacing of the filaments 10th to reinforcing steel 2 are ensured.

In Fig. 4, the individual process steps in the order ung an anode system 8 with a carbon fiber multifilament 10 are shown in schematic illustrations. As can be seen in FIG. 4a, the carbon fiber multifilament 10 is applied meander-shaped onto the concrete 6. For this purpose, it is possible that in an upstream step slits are cut or milled into the concrete into which the carbon fiber multifilament 10 can be inserted. When laying the carbon fiber multifilament 10, the meandering bends 14 are intentionally extended so that a loose loop of carbon fiber multifilament 10 is formed. The slots can then be filled with grout to already have a fixation of the carbon fiber multifilament on the concrete 6 for the further steps.

In a next step (Figure 4b), the titanium strips 12 are laid as a primary anode in the area of the meandering arches 14. Due to the laid down carbon fiber multifilament 10, it is now possible to design the titanium strips 12 linear. Thus, a complex and complicated deformation of the titanium strips 12 can be dispensed with. Again, it is possible that previously appropriate slots are introduced into the concrete 6, in which the titanium strips 12 can be sunk.

Subsequently (Figure 4c) or during the laying of the titanium strips 12, the loops of the carbon fiber multifilament are wound around the titanium strips 12 in the area of the meandering curves 14. This results in contact areas 18 in the region of the meandering arches 14, via which an electrical connection between the titanium strip 12 and the carbon fiber multifilament 10 is formed. These contact areas can now be enclosed, for example, with epoxy resin, so that on the one hand the contact areas 18 are protected and the shrinkage of the epoxy resin results in a higher and secure bond between the carbon fiber multifilament 10 and the titanium strip 12. The possibly existing slots of the titanium strips 12 can then be filled with grout, whereby the anode system 8 is fixed on the concrete 6.

Finally, (Figure 4d), the titanium strips are connected via a primary anode wire 26 to the positive pole of a voltage source, not shown. In this way, a particularly simple, quick to install and cost-effective planar anode system for cathodic corrosion protection in reinforced concrete structures is achieved.

LIST OF REFERENCE NUMBERS

1 reinforced concrete

2 reinforcing steel

4 voltage source

6 concrete

8 anode system

10 bundles as carbon fiber filaments

12 primary anode belt

14 meander arch

16 mortars

18 contact areas

20 slot

22 epoxy resin

24 glue

26 primary soda wire

28 fiberglass composite reinforcement

30 binders

32 binders

Claims

150465 claims

1 . A method of laying an anode system (8) for cathodic corrosion protection, comprising the following steps:

- laminating a bundle of carbon fiber filaments (10);

- Laying at least one primary anode belt (12), such that the primary anode belt (12) in a number of contact areas (18) to the bundle (10) is electrically connected;

- Connecting the primary anode bands (12) to a primary soda wire (26).

2 method for laying an anode system (8) according to claim 1, characterized in that in the case of the protection of reinforced concrete structures, the bundle (10) is laid in prepared slots in the concrete.

3 method for laying an anode system (8) according to claim 1 to 2, characterized in that the bundle (10) by means of an adhesive (24) is attached.

4 method for laying an anode system (8) according to claim 1, characterized in that in the case of the protection of reinforced concrete structures, the bundle (10) is laid in fresh concrete or mortar.

5 method for laying an anode system (8) according to claim 1 to 4, characterized in that the bundle (10) in the contact areas

(18) is wound at least partially around the primary anode belt (12).

A method for laying an anode system (8) according to claim 1 to 5, characterized in that for connecting the bundle (10) and the Primary-anode tape (12) at the contact areas (18) epoxy resin (22) is used. Method for laying an anode system (8) according to Claims 1 to 6, characterized in that the bundle (10) and / or the primary anode tape (12) are covered with conductive mortar (16). Method for laying an anode system (8) according to claim 1 to 7, characterized in that the bundle (10) is designed meandering. Use of a non-metallic band anode (10) in a two-dimensional anode system (8) for cathodic corrosion protection (1). Use according to claim 9, characterized in that the

Bandanode (10) comprises a carbonaceous filament.