JP2013537261A - Anode for cathodic protection and method for producing the same - Google Patents

Abstract

A metal anode for cathodic protection in the form of a mesh ribbon with holes having a rhombus mesh is described, the anode having a rhombus arranged such that the holes have a main diagonal oriented along the length of the ribbon And having no cut protrusions on the side edge along the longitudinal direction of the ribbon. A method for obtaining such an anode is also described.
[Selection] Figure 1B

Description

  The present invention relates to the field of cathodic protection of reinforced concrete structures, and in particular to anode designs that are particularly efficient in terms of electrical resistance and flexibility per unit length, and in particular anode designs that are safe for installation and handling. The invention also relates to a method of manufacturing such an anode.

  Reinforced concrete structures affected by the phenomenon of corrosion are well known in the art. Steel reinforcements that are inserted into cementitious structures to improve their mechanical properties are usually used in passivating conditions induced by an alkaline concrete environment. However, after a considerable amount of time, the migration of ions across the porous surface of the concrete causes local erosion of the protective passivating membrane. Of particular concern is chloride erosion, which is practically present in all types of environments where reinforced concrete structures are used, and is particularly large in salt water (bridges installed in the ocean). , Pillars, buildings), salt for antifreeze (bridges and road structures in cold climate areas), and even in environments exposed to seawater, for example in the case of piers and docks. The critical value for exposure to chloride is considered to be about 0.6 kg per cubic meter of concrete, beyond which the passivating state of the reinforcing steel is not guaranteed. Another form of concrete collapse is indicated by the phenomenon of carbonation, which is the formation of calcium carbonate by the reaction of the cementitious mixture of lime with atmospheric carbon dioxide. Calcium carbonate lowers the alkali content in the concrete (from pH 13.5 to pH 9) and produces unprotected iron. The presence of chloride and the simultaneous carbonation represent the worst conditions for the preservation of the reinforcing bars of the structure. The corrosion products of steel are larger in volume than the steel itself, and the mechanical stress caused by their formation may lead to delamination and fracture phenomena of the concrete, which is enormous from an economic standpoint besides safety. It is interpreted as damage. For this reason, the most effective method for indefinitely extending the life of reinforced concrete structures exposed to agents in the atmosphere, even at appropriate salt concentrations, is the cathodic polarization of steel reinforcements. It is known in the art to consist of In this way, the steel reinforcement becomes the position for the cathodic reduction of oxygen, so that anode corrosion and dissolution reactions are suppressed. Such a scheme, known as reinforced concrete cathodic protection, is carried out by associating various types of anode structures with concrete, in which case the reinforcement to be protected acts as a cathode counter electrode, which is accompanied by external The current maintained by the current rectifier passes across an electrolyte consisting of porous concrete partially impregnated with salt solution.

  An anode commonly used for cathodic protection of reinforced concrete consists of a titanium substrate coated with a transition metal oxide or other type of catalyst for the generation of oxygen at the anode. Other valve metals (as pure metal or as alloys) can be used as the substrate, but pure titanium is a fairly preferred choice from a cost standpoint.

  European patent EP 458951 discloses a grid-type electrode structure for cathodic protection consisting of a plurality of metal ribbons (metal strips) with an electrocatalytic coating, the metal ribbons having various geometries. It has a geometrically shaped void.

  This type of ribbon can be produced by extruding an integral metal ribbon, or more generally by a conventional method by stretching the metal, in which case the metal sheet is pressed. The metal sheet is expanded by punching through a series of knives arranged perpendicular to the direction of travel of the ribbon itself. By this first step, an expanded metal sheet can be obtained. The sheet is then subjected to a second step in which a suitable cut is made to obtain the desired size ribbon. This expanded metal ribbon has a mesh shape with rhombus voids having a main diagonal oriented perpendicular to the longitudinal direction of the ribbon.

  This manufacturing method has the disadvantage that metal ribbons with a mesh with cut side projections that are automatically formed during the cutting operation are manufactured, thereby handling these anodes. Is therefore difficult and therefore dangerous at the stage of installation.

  A metal ribbon with smooth side edges is disclosed in Canadian Patent Application CA 20786616 (A1), and according to the method described in this document, the resulting ribbon extends in a continuous longitudinal direction having a constant width. It has an integral part that is necessarily formed in the manufacturing process, and that part can be used only for spot welding. However, in today's cathodic protection systems, it is not entirely desirable to weld the ribbon anode, rather it is preferable to place a plastic spacer in between and directly overlay the ribbon on the reinforcement. In this case, the integral part extending in the longitudinal direction is exactly a loss of material, in particular because this integral part is always covered with precious metal when applying the catalyst layer. However, such a catalyst layer cannot function properly on a nonporous structure and affects the calculation of the actual current density applied to the anode structure, and thus the overall cathodic protection system. Complicate design.

European patent EP 458951 Canadian patent application CA20786616 (A1)

  Various aspects of the invention are set out in the accompanying claims.

  In one aspect, the present invention relates to an anode in the form of a mesh (mesh) ribbon for a cathodic protection system (eg, cathodic protection of reinforced concrete structures), which eliminates the disadvantages of the prior art. And there is substantially no discontinuity in the form of a cut projection at the edge, which has a sinusoidal shape.

  In the context of the present specification, for the sake of simplicity, reference will be made to cathodic protection of reinforced concrete structures, although the invention is practiced in the field of general cathodic protection, for example, including cathodic protection at the bottom of a metal tank. It will be understood that it can be done.

  In another aspect, the invention relates to a method for manufacturing the anode.

  In a further aspect, the present invention relates to a cathodic protection device comprising at least one anode in the form of a mesh ribbon that is substantially free of cut protrusions at the edges.

  Some of the most important results obtained by the inventors are presented in the following description, which is provided by way of example only and is not intended to limit the invention.

  The anode according to the invention consists of an expanded metal ribbon, which is characterized by a mesh with rhombus cavities with a main diagonal oriented along the length of the ribbon. In one embodiment, the side edges of the ribbon have a sinusoidal profile, where there are no cut protrusions.

  The inventors have surprisingly found that the anode for cathodic protection described herein has a significantly lower ohmic resistance per unit length, for example four times lower than prior art anodes. .

  Low electrical resistance can reduce the number of electrical connections (eg, in the power grid), thereby saving significant material and installation time.

  In one embodiment, the metal mesh ribbon comprises titanium.

  In another embodiment, the metal mesh ribbon is coated with a catalytic coating comprising a noble metal or oxide thereof.

  In one embodiment, the ribbon dimensions have a width in the range of 3 mm to 100 mm, a thickness of 0.25 mm to 2.5 mm, and a length of 1 m to 150 m.

In order that the present invention may be better understood, reference is made to the following drawings, which are intended to depict some preferred embodiments and are not intended to limit the scope of the invention.
FIG. 1A shows a top view of a conventional expanded metal anode. FIG. 1B shows a top view of an expanded metal anode according to the present invention.

  Specifically, FIG. 1A shows a top view of a conventional anode, characterized by the presence of protrusions 1 cut by a manufacturing method including a cutting step, and a rhombus oriented in the direction of the ribbon width. A rhombus geometry having a main diagonal 3 of the void and a sub-diagonal 4 of the diamond void oriented in the longitudinal direction of the ribbon.

  FIG. 1B shows a top view of an anode according to the invention, characterized by the fact that there are side edges 2 that are not cut and not sharp, and that the diamond-shaped voids are oriented in the longitudinal direction of the ribbon. A rhombus geometry having a main diagonal 3 at the center and a diamond sub-diagonal 4 at the rhombus oriented in the direction of the ribbon width.

  Some of the most important results obtained by the inventors are reported in Table 1. There, the ohmic resistance data of a typical anode of the present invention is compared to a conventional anode. The anodes labeled A and B are rhombus geometric anodes with rhombus main diagonals oriented perpendicular to the longitudinal direction of the ribbon, similar to that shown in FIG. It is the conventional one obtained by extending vertically with respect to the moving direction of the integral metal ribbon. The anodes labeled C and D are geometrically shaped anodes according to one embodiment of the present invention, similar to that shown in FIG. 1B.

  The anodes C and D are stretched in a direction perpendicular to the direction of movement of the unitary metal ribbon that traveled along the parallel rows of knives in the device, thereby pressing the unitary ribbon in the direction orthogonal. It is manufactured by punching out and expanding. The production of this ribbon is completed by the last row of knives, which have blades of a predetermined length that are larger than the blades of the previous knife, on the side of the ribbon shown in FIG. 1B. Appropriate pressure is applied to form the edge. In addition to the advantages already described with respect to conductivity due to the anode geometry, this method provides an expanded metal ribbon without a single piece extending in the longitudinal direction, which is not cut afterwards. It has the advantage that it is not accompanied at all by the edges and is therefore considerably safer and easier to handle during installation. Furthermore, this method advantageously allows to obtain a desired length of metal ribbon immediately after the expansion is completed. Furthermore, this manufacturing method makes it possible to obtain ribbons that are longer than conventional methods, and therefore the use of large equipment such that the overall integrity of the anode device is reduced because a large number of ribbons need to be connected. To make it easier.

  From the data reported in the table, it can be seen that for a given width, the anode of the present invention exhibits about 60% lower ohmic resistance.

  The above description is not intended to limit the present invention, and the present invention can be used in accordance with various embodiments without departing from the scope thereof, and the scope of the present invention is unambiguously defined by the appended claims. To be confirmed.

  Throughout the specification and claims of this application, the term “comprising” is not intended to exclude the presence of other elements or additions.

Literature considerations, statutes, materials, devices, articles, and the like are included herein for the purpose of merely providing a background for the present invention.
Some of these matters, or all of them, form part of the prior art basis, or they are in the field relevant to the present invention before the priority date of each claim of this application. It has not been suggested or expressed that it was a general consensus.

  1 cut protrusions, 2 non-pointed side edges, 3 main diagonal of rhombus void, 4 sub-diagonal of rhombus void.

Claims (8)

  An anode for cathodic protection in the form of an expanded metal ribbon with a diamond-shaped mesh without a longitudinally extending integral part, said diamond-shaped mesh having a main diagonal parallel to the longitudinal direction of the ribbon Said anode, characterized in that it is arranged geometrically.   The anode according to claim 1, wherein no discontinuity exists in the contour of the side edge along the length of the ribbon.   The anode according to claim 1, wherein the metal is titanium.   The anode according to claim 1, wherein the metal is coated with a catalyst layer.   The anode according to claim 4, wherein the catalyst layer contains a noble metal or an oxide thereof. A method for producing an anode according to any one of claims 1 to 3, comprising the following steps:
Running the metal ribbon through an expansion device comprising a first predetermined length of at least one row of knives arranged parallel to the direction of movement of the metal ribbon;
Expanding the metal ribbon by the action of pressing and punching of the at least one row of knives;
Forming the contour of the side edge of the expanded metal ribbon by the action of pressing and punching on the last row of knives having a second predetermined length blade greater than said first length; ,
Said method.   6. A cathodic protection device comprising at least one anode according to claim 1 embedded in a cementitious structure with a metal reinforcing bar.   A method for cathodic protection of reinforced concrete structures comprising applying an anodic potential to the anode of the cathodic protection device of claim 7.

Images