DD275487A1 - ANODE FOR THE KATODIC CORROSION PROTECTION OF STEEL OR TENDER CONCRETE - Google Patents

Abstract

The invention relates to an anode for the cathodic corrosion protection of steel or prestressed concrete, in particular for the subsequent installation of protection systems in the context of structural rehabilitation. The aim of the invention is to provide an economically producible and processable anode material with high electrical conductivity. The object of the invention is to provide an anode with a low removal rate, which enables a flat application and thus a uniform current input at a low current density. According to the invention, the anode material consists of a mixture of 1.0 part by weight of a thermosetting binder, 1.0 to 2.0 parts by weight of a graphite dust of the composition 0-0.5 mm and 0.5 to 2.0% by weight. Parting of metal and / or metal alloy dust 0-2 mm.

Description

Field of application of the invention

The invention relates to an anode for the cathodic corrosion protection of steel or prestressed concrete, in particular for the subsequent installation of protection systems in the context of structural rehabilitation.

Explanation of the known prior art

It is known to use the cathodic corrosion protection method for the active corrosion protection of cement-concrete steel, which already exhibits corrosion phenomena. In particular, in the rehabilitation of heavily chloride-containing reinforced concrete structures, the cathodic corrosion protection method has proven to be the only effective long-term protection method.

From the life of the anode material used essentially depends on the effectiveness of the entire protection system. As anode materials, which must have good electrical conductivity, low electrical resistance and low rate of removal due to current flow, it is known:

Iron-silicon alloys (DD PS 206,566)

- Magnetite

- placed titanium (EP PS 0.222.829)

- graphite (DE OS 2,207,061)

Titanium oxide (EP PS 0.186.334)

Carbon-containing thermoplastic cable (US Pat. No. 4,502,929)

Anodes made of iron-silicon alloy, magnetite and graphite are not suitable because of the compact design for the cathodic corrosion protection of reinforced concrete, as they ensure by punctual arrangement not sufficiently uniform current distribution in the protected object as well as due to the locally concentrated current leakage, the pH of the concrete in Lower the environment of the anodes by formation of H ⁺ ions and create an acidic environment, which is capable of greatly reducing the concrete strength. It has been reported that rod-shaped, compact anodes with correspondingly high current densities lower the pH of the concrete from the original 13 to 1 to 2 and that the resulting acid can completely dissolve the concrete (EPC PS 186.334).

Furthermore, it is known that electrically conductive rendered inks (US PS 2,309,171) or made electrically conductive polymer concrete (US PS 346.428) can be used in cathodic protection systems.

Own experiments with graphite-modified pigmented or filler-containing polymer-based binders, however, have shown that the electrical resistance of such materials is very high and that no appreciable current flows. The proportions of not more than 50% by volume of graphite, referred to US Pat. No. 2,309,171, based on the hardened product, are to be estimated as much too low. The other named anode materials are only available for special applications and economically unfavorable.

Object of the invention

The object of the invention is to provide an economically producible anode with good processing properties for steel and prestressed concrete, which has a high electrical conductivity.

Explanation of the essence of the invention

The invention has for its object to provide an anode which has a low removal rate and allows a flat application of a uniform current input at low current density. According to the invention, the object is achieved by applying a layered anode applied to the entire surface of the reinforced concrete structure to be protected, comprising a mixture of a duromeric binder such as epoxy resin, unsaturated polyester resin, methyl methacrylate resin or polyurethane resin with a mixture of electron-conducting substances of different grain size, which have very low removal rates. such as Iron-silicon dust, graphite dust, magnetite dust, exists.

According to the invention, the mixture for the anode material consists of 1.0 part by weight of the duller binder, 1.0 to 2.0 parts by weight of a graphite dust of grain size 0-0.5 mm and 0.5 to 2.0 parts by weight of a metal and / or metal alloy dust the grain size 0-2 mm. As metal and / or metal alloy dust, an electron-conducting dust with low removal rate is used in anodic current flow, for example iron-silicon dust, magnetite dust or platinum dust. These dusts must be homogeneously distributed and solidified in the binder that both their electrical conductivity is maintained as well as advantageous mechanical and processing properties are achieved.

Surprisingly, it was found that, in contrast to filled with graphite dust thermosets, which have no or only low electrical conductivity, a very electrically conductive mass is obtained when adding electron-conducting particles of different particle size and a correspondingly high proportion in the binder.

The anode composition according to the invention is advantageously applied flat in a thin layer, wherein for the production of the electrical connection a wide-meshed copper wire mesh is embedded in the still plastic mass on all sides, so this is even protected against corrosion. The advantage of an anode produced in this way is the extremely low protective current density due to the large area and thus the prevention of the sharp drop in the pH in the concrete.

embodiments The invention will be explained in more detail with reference to three embodiments. Example 1:

For the cathodic protection einertausalzgeschädigten steel reinforcement of reinforced concrete, an electrically conductive material is applied as a flat anode, according to the invention from

1.0 parts by weight of a cold-curing epoxy resin, and 1.0 parts by weight of graphite dust of grain size 0 / 0.5 mm and 1.5 parts by weight of iron-silicon dust of grain size 0 / 2mm

(All information relative to the liquid binder) and is applied to the previously cleaned and repaired concrete surface. In the not yet cured anode material, a copper wire mesh for the production of the electrical connection is embedded, with a second layer of the same material, the copper wire mesh is completely covered to prevent corrosion.

Example 2:

Corrosion damage to the reinforcement has occurred at the buttress of a reinforced concrete pipe bridge as a result of the sinking of the pH due to carbonation and high humidity.

To remedy this damage, a cathodic protection system with the above-described anode is used. For this purpose, the damaged area is cleaned of rust and loose concrete and repaired by Neubeton. After drying, a flat anode consisting of a mixture of

1.0 part by weight of a saponification-resistant two-component polyurethane resin and 2.0 parts by weight of graphite dust of grain size 0 / 0.5 mm and 0.5 parts by weight of iron-silicon dust of 0/2 mm grain size

(All information relative to the liquid binder) applied.

The advantage of the high graphite content is that the anode mass is very highly viscous and therefore does not run off the vertical column wall. The anodic current carrying capacity is about 100 mA / m ² and thus ensures a functional effectiveness of at least 15 years.

Example 3: A reinforced concrete floor in a fertilizer storage hall is severely corroded due to chloride contamination. A conventional one Refurbishment with the order of Neubeton does not provide long-term efficacy because the corrosive chlorides in the concrete

remain.

The solution to the problem is the application of a cathodic corrosion protection system when commissioned by a patent

described flat anode consisting of

1.0 parts by weight of epoxy resin as well

1.0 parts by weight of graphite dust of grain size 0 / 0.5mm and

2.0 parts by weight of iron-silicon dust of grain size 0/2 mm.

The advantage of the high proportion of iron-silicon dust is due to the very good electrical conductivity. At the same time, however, the workability is degraded, which, however, as in this case, can be easily compensated for vertical surfaces by higher densification.

Claims (3)

1. Anode for the cathodic corrosion protection of steel or prestressed concrete, which consists of a mixture of binder and electron-conducting substances, characterized in that the anode material of a mass fraction of a thermosetting binder such as epoxy resin, unsaturated polyester resin, methyl methacrylate resin or polyurethane, 1.0 to 2.0 parts by weight of a graphite dust of grain size 0-0.5 mm and 0.5 to 2.0 parts by weight of a metal and / or metal alloy dust of grain size 0 to 2 mm. 2. Anode according to claim 1, characterized in that as the metal and / or metal alloy dust an electron-conductive dust with a low removal rate at anodic current flow, such as iron-silicon dust, magnetite dust or platinum dust is used. 3. Anode according to claim 1, characterized in that in the anode mass, a copper wire mesh is embedded.