EP2004875A1 - Anode for cathodic protection - Google Patents
Anode for cathodic protectionInfo
- Publication number
- EP2004875A1 EP2004875A1 EP07701806A EP07701806A EP2004875A1 EP 2004875 A1 EP2004875 A1 EP 2004875A1 EP 07701806 A EP07701806 A EP 07701806A EP 07701806 A EP07701806 A EP 07701806A EP 2004875 A1 EP2004875 A1 EP 2004875A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- conductive material
- anode body
- anode
- electrically conductive
- ionically conductive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000004210 cathodic protection Methods 0.000 title claims abstract description 19
- 239000004020 conductor Substances 0.000 claims abstract description 159
- 239000000463 material Substances 0.000 claims abstract description 28
- 239000003906 humectant Substances 0.000 claims abstract description 13
- 239000002245 particle Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 23
- 239000011888 foil Substances 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 6
- 239000003513 alkali Substances 0.000 claims description 6
- 230000004888 barrier function Effects 0.000 claims description 4
- 238000009434 installation Methods 0.000 claims description 4
- 239000004567 concrete Substances 0.000 abstract description 25
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 abstract description 11
- 229910000831 Steel Inorganic materials 0.000 abstract description 10
- 239000010959 steel Substances 0.000 abstract description 10
- 229910052725 zinc Inorganic materials 0.000 abstract description 10
- 239000011701 zinc Substances 0.000 abstract description 10
- 230000007797 corrosion Effects 0.000 description 14
- 238000005260 corrosion Methods 0.000 description 14
- 230000006835 compression Effects 0.000 description 10
- 238000007906 compression Methods 0.000 description 10
- 150000002500 ions Chemical class 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000010276 construction Methods 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- 230000009471 action Effects 0.000 description 5
- 239000010405 anode material Substances 0.000 description 5
- 238000004891 communication Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 239000011800 void material Substances 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000011900 installation process Methods 0.000 description 2
- 239000002923 metal particle Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000037237 body shape Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011344 liquid material Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012811 non-conductive material Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 150000003751 zinc Chemical class 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
- C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
- C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
- C23F13/08—Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
- C23F13/10—Electrodes characterised by the structure
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
- C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
- C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F2201/00—Type of materials to be protected by cathodic protection
- C23F2201/02—Concrete, e.g. reinforced
Definitions
- This invention relates to an anode for use in cathodic protection of a cathode in a medium, for example a structural steel member in a layer of concrete or mortar.
- anode for use in cathodic protection of steel members in concrete using sacrificial anodes to generate a current which acts to reduce corrosion of the steel or otherwise to effect restoration of the concrete.
- the anode disclosed is formed of a mixture of zinc powder or particles which are pressed together with a quantity of a humectant which is also in powder form so as to create an anode body which is an intimately mixed structure. This provides a material in the anode itself which acts to enhance the current flow and also forms voids or pores where corrosion products can be absorbed.
- An allernative manufacture technique is also disclosed in which the powder is applied on one side of a sheet or between sheets of the zinc foil which is or are rolled to form the anode body.
- the anode is shaped into a suitable body shape for use in concrete which can be a puck shaped body or strips or flat elements as required. These bodies form a particular exterior surface of a prescribed surface area which is in ionic contact with the medium. Some shapes have been designed which may increase the surface area in contact with the concrete, but even the most complex shapes have an increased contact ratio only of the order of 2, that is, the surface area is twice that of a more simply formed body.
- the present applicant also has the following issued patents and pending applications in USA, the disclosures of which may be referred to for further details of cathodic protection systems with which the present invention is concerned:
- the improvement of the above Bennett application relates to the application of a humectant in free-flowing form which is positioned at the interface between the zinc anode coating and the concrete surface. It has been found and is disclosed in this application that the provision of the humectant in free-flowing form acts to absorb moisture from the area above the surface.
- an anode for use in cathodic protection of a cathode in a medium
- an anode body comprising: an anode body; the anode body being shaped and arranged such that it can be installed with at least one exterior surface in contact with a medium which is in contact with a cathode to be protected; the anode body comprising an electrically conductive material and an ionically conductive material; an electrical connecting lead electrically connected to the electrically conductive material of the anode body for connection to the cathode; the electrically conductive material and the ionically conductive material being intermixed through at least a part of the interior of the anode body; the electrically conductive material being arranged in the anode body to define at least one electrically conductive path in the anode body and communicating to the connecting lead; the ionically conductive material being arranged in the anode body to define at least one ionically conductive path extending from the at least one exterior surface of the anode
- an anode for use in cathodic protection of a cathode in a medium
- an anode body comprising: an anode body; the anode body being shaped and arranged such that it can be installed with at least one exterior surface in contact with a medium which is in contact with a cathode to be protected; the anode body comprising an electrically conductive material and an ionically conductive material; an electrical connecting lead electrically connected to the electrically conductive material of the anode body for connection to the cathode; the electrically conductive material and the ionically conductive material being intermixed through at least a part of the interior of the anode body; the electrically conductive material being arranged in the anode body to define at least one electrically conductive path in the anode body and communicating to the connecting lead; the ionically conductive material being arranged in the anode body to define at least one ionically conductive path extending from the at least one exterior surface of the an
- This construction has the advantage that ions can flow through the ionically conductive path or paths between the medium and the surface of the electrically conductive material within anode the body so that these paths significantly increase the surface area of the electrically conductive material at which ions can be formed from a nominal surface area of exterior surface of the anode body by a contact ratio of at least 5.
- the contact ratio can be greater than 10 or even greater than 100, so that the amount of current is dramatically increased. This is orders of magnitude greater than can be achieved by shaping the surface or forming the surface using different techniques.
- the medium can be any material which allows corrosion of steel or other structural members in the medium.
- the present invention is particularly concerned with concrete or mortar materials and steel members therein since this is a well known problem area leading to corrosion of the steel and consequential breakdown of the concrete.
- the same principles may be used in other media and for protecting other cathodes.
- the medium usually is separate from the ionically conductive material in the anode body in that it is not intended that the medium enter the anode body to form the paths therein.
- the ionically conductive material can be formed at least partially from salts or polymers which can be humectant in nature and can be alkali. It will be appreciated therefore that the ionically conductive material can be formed from a cementitious material.
- the principles disclosed herein are primarily but not necessarily concerned with sacrificial systems where there is no impressed current since these systems have more limitations due to a limited level of current output from an anode. However the principles can also be used with impressed current systems particularly in applications where space availability for installation of the anodes is limited.
- the ionically conductive path or paths include at least portions thereof which extend laterally relative to the exterior surface within the anode body into connection with the electrically conductive material. That is, in general the paths extend in two or three dimensions in the body. Depending on the method of manufacture, the paths may be random or may be generally parallel to and at right angles to the exterior surface.
- the ionically conductive paths have interconnecting portions within the anode body.
- the anode body is shaped and arranged to be embedded in the medium with a plurality of exterior surfaces arranged for contacting the medium.
- the invention can also be used with anodes intended for surface mounting so that the anode has in effect only one exterior surface intended to contact the medium.
- the ionically conductive material is coated onto surfaces of the portions of the electrically conductive material at voids in the anode body so that the ionically conductive material extends from one void to the next to form in effect a continuous path from the exterior surface to the location within the anode body where it connects with the electrically conductive material. If the paths are broken they cannot of course communicate the ions between the medium and the electrically conductive material within the anode body and thus do not contribute to the available surface area. In some cases this forms an anode body with voids which are not filled and therefore are free from the ionically conductive material.
- a continuous ionic path or series of paths need to be created from the exterior of the anode body into these interior locations.
- This arrangement can be obtained by the ionically conductive material being deposited from solution so that it extends from one space to the next by the solution wicking between the spaces during the manufacture until the solvent is dried leaving the ionically conductive material deposited.
- other techniques may be used for generating continuity in the ionically conductive material paths in the anode body. For example this can be done by causing migration of the ionically conductive material or by application of an ionic gel or paste directly to the sheet. Void areas which remain can provide areas for containing the corrosion products which are greater in volume than the sacrificial metal.
- the ionically conductive material is a humectant and has a pH greater than 12 since these are known to enhance the current level.
- the ionically conductive material has a pH less than 4.5 and is contained within the anode body such that the outer surface of the anode body acts as a pH barrier.
- the ionically conductive material may be a mixture of a first ionically conductive material which is both a humectant and which is selected to maintain a high level of anodic activity at the surface and one or more ionically conductive or non-conductive materials which are selected not to maintain a high level of anodic activity at the surface.
- the anode body has a core connected to the lead which core is formed substantially wholly of the electrically conductive material so as to be free from the ionically conductive material. This can be used to ensure that the required electrical connection to the lead is properly maintained during the life of the anode and is not affected by the presence of the ionically conductive material which is not electrically conductive.
- the anode body is formed from overlying layers of conductive material, such as foil, with the ionically conductive material between the layers, which layers and the ionically conductive material are rolled around an axis and optionally compressed. This ensures effective electrical connection through the structure since the sheets or layers are continuous and yet provide the necessary spaces and paths through the body for the ionically conductive material. After rolling the layers may be compressed either axially or in other directions.
- conductive material such as foil
- the layers are perforated so as to define some of the paths through the layers.
- the anode body may be formed from particles of the electrically conductive material and the ionically conductive material. These materials may then be compressed together. Other techniques can also be used using different starting material such as flakes, ribbons, wires, or sheets of the electrically conductive material.
- the anode is preferably a member formed in advance for application into or onto the medium as a finished anode so that its structure and construction is completed prior to installation. In this case it generally will have a thickness of the anode body from the at least one exterior surface to an opposed surface of at least O. ⁇ cms.
- the principles of the invention can be applied to either sacrificial or impressed current systems.
- the electrically conductive material is formed of a non-sacrificial material such that the current is applied as an impressed current
- the ionically conductive material may have the property of providing an alkali environment to buffer acid given off by the electrically conductive material.
- a method for cathodic protection of a cathode in a medium comprising: providing an anode body; installing the anode body with at least one exterior surface of the anode body in contact with a medium which is in contact with a cathode to be protected; the anode body comprising an electrically conductive material; connecting an electrical connecting lead from the electrically conductive material of the anode body to the cathode; the electrically conductive material being arranged in the anode body to define at least one electrically conductive path in the anode body and communicating to the connecting lead; intermixing with the electrically conductive material of the anode body through at least a part of the interior of the anode body an ionically conductive material; arranging the ionically conductive material in the anode body to define at least one ionically conductive path extending from the at least one exterior surface of the anode body into the interior of the anode body ; and arranging
- the ionically conductive material is intermixed with the electrically conductive material prior to the installing of the anode body in the medium.
- the ionically conductive material may be infused or leached into the anode body as part of or subsequent to the installation process.
- the ionically conductive material is arranged to form the at least one ionically conductive path in the interior of the anode body to contact the interior locations on the at least one electrically conductive path prior to the installing of the anode body in the medium.
- the ionically conductive material may be present in the anode body prior to installation, it may be caused by wetting to diffuse through the body as part of or subsequent to the installation process.
- the anode body is formed by providing interconnected voids between the electrically conductive material; locating the ionically conductive material in the voids; and causing some of the ionically conductive material to migrate through the voids so as to define the at least one ionically conductive path.
- the ionically conductive material is conveniently in solution while migrating such that the solution coats the surface of the voids and wicks through the voids leaving the ionically conductive material in the voids when the material comes out of solution.
- the ionically conductive material can be supplied in any form such as gel or semi-liquid material which can migrate to ensure complete paths through the anode body rather than merely pockets of ionically conductive material which are not connected and thus cannot conduct the ions through the body to the medium at the surface.
- the porous body is pre-formed of the electrically conductive material such as zinc with the ionically conductive material omitted and subsequently the ionically conductive material is infused or leached in solution into the paths and spaces in the body.
- the electrically conductive material such as zinc with the ionically conductive material omitted and subsequently the ionically conductive material is infused or leached in solution into the paths and spaces in the body. This is preferably done as a manufacturing technique before the body is installed but in some cases it may be done in situ in or on the medium.
- Figure 1 is a schematic illustration of a cathodic protection system utilizing a sacrificial anode.
- Figure 2 is a schematic illustration of a cathodic protection system utilizing an impressed current.
- Figure 3 is a top plan view of a sheet of foil which is arranged for use in manufacturing an anode according to the present invention.
- Figure 4 is a side elevational view of the sheet of Figure 3.
- Figure 5 is a side elevational view similar to that of Figure 4 showing a further step in the process.
- Figure 6 is a side elevational view similar to that of Figures 4 and 5 showing a rolled anode structure.
- Figure 7 is a schematic illustration showing the compression of the anode structure of Figure 6.
- Figure 8 is a schematic side elevational view of an alternative construction of anode for use in a cathodic protection system.
- Figure 9 is a cross sectional view through an anode according to the present invention formed using an alternative technique.
- Figure 10 is a view showing a small portion of the anode of Figure 9 on an enlarged scale showing the electrically conductive paths and the ionically conductive paths.
- like characters of reference indicate corresponding parts in the different figures.
- FIG. 1 a cathodic protection system for a medium 10 in which is embedded a cathode 11 and an anode 12.
- the anode 12 is of a sacrificial material which is electro-negative relative to the cathode 1 1 and is connected to the cathode 11 by a lead 13.
- the present invention is concerned with the protection of reinforced concrete where the medium 10 is a layer of concrete and the cathode
- 1 1 is a steel element which is within the concrete medium, is partly embedded in the concrete medium or is in contact with the concrete medium
- the surface of the sleel which is in contact with the concrete medium can corrode for reasons well known to persons skilled in the art
- the anode 12 is embedded in the medium so that it is in ionic contact with the medium so that ions within the medium transfer between the anode and the cathode while electrons form a current passing through the electrical lead 13
- This circuit therefore as is well known protects the steel and reduces or prevents corrosion of the steel
- the arrangement of the present invention provides an anode which has generally a series of electrically conductive paths within the body of the anode which are interspersed with ionically conductive paths within the anode so that there is a dramatically increased surface area between these paths through which the current can pass
- FIGS 3 through 7 One technique for manufacturing an anode of this type is shown in Figures 3 through 7
- a sheet of a suitable sacrificial anode material such as zinc is laid flat and is coated over a first area 15 of the sheet 14 with a layer of particles 16 of an ionically conductive material
- Sheet 15 is formed with perforations 17 which can be in the form of slots or holes
- the slots or holes cover at least the portion 15 of the sheet 14
- a further portion 18 of the sheet 14 is free from the particles 16 so that the sheet consists solely of the sacrificial anode material in the area 18.
- a first action water, or other solvent such as a water based solution, from a spray nozzle 20 is applied onto the layer of the particles 16 so as to wet those particles.
- This has two effects. Firstly it assists in adhering the particles to the sheet 14. Secondly it supplies a solvent which acts to dissolve part of the ionically conductive material which is generally soluble in water.
- a layer 16A on the surface of the sheet 14 which forms a solution of the ionically conductive material from the particles 16.
- This layer 16A extends over the area 15 and is prevented from entering the area 18 so that the area 18 remains bare.
- the water or solvent may be applied first and the salts second.
- the salts may be in the solution, gel or paste and applied as a single application.
- the edge 21 of the sheet is turned upwardly and rolled in the form of a spiral roll to form the construction shown in Figure 6.
- a first portion or core of the spiral roll as indicated at 22 is free from the ionically conductive material in the layer 16A.
- This forms a core 22 of the spiral roll which wraps around one or more wires 23 of the anode structure with the wire or wires 23 being applied at the edge 21 prior to the rolling to form the lead 13 of the anode body.
- the lead 13 as defined by the wire or wires 23 projects outwardly from one end or both ends of the rolled structure.
- the lead extends into the rolled structure and lies along the edge 21 so as to form a electrical contact with the edge 21 and the portion of the sheet 14 wrapped around that wire.
- the wire 14 may be a bare conductor or may carry a surrounding layer of the sacrificial anode material which thus forms part of the core 22.
- the wire or the layer of the sacrificial anode material may be welded or otherwise attached to the edge of the sheet for improved electrical connection.
- the core 22 defined by the wire and by the surrounding layer of anode material in the absence of the ionically conductive material thus forms a body around the wire 23 which is wholly of electrically conductive material so as to provide an effective initial communication of current from the wire 23 into the body of the anode.
- the core does not corrode and therefore electrical connection to the wire is maintained more effectively during the corrosion of the anode body in the areas outside the core.
- the sheet 14 is rolled into the area 15 thus rolling into the structure in spiral form the layer 16A.
- the core 22 is surrounded by alternate layers of the sheet and the layer 16A which are rolled into a spiral. These alternate layers can communicate through the sheet by way of the perforations 17 so that each layer of the ionically conductive material defined by the 16A is in communication with the next adjacent layer through the space provided in the sheet 14 by the perforations 17.
- An optional reinforcement layer 24 can be provided which is engaged onto the outside surface of the sheet 14 in the area of that sheet approaching the opposite end edge 25 which forms the outermost portion of the sheet 14 when rolled.
- the reinforcing layer 24 has a width equal to that of the sheet and a length sufficient so that it wraps around at least one or two of the turns of the spiral when formed as shown in Figure 6.
- the spiral so formed is placed into a press 28 which contains the cylindrical form of the spiral with a cylindrical wall 29 and includes compressing pistons 30 and 31 which are moved inwardly by suitable compression actuators 32 so as to compress the spiral axially to reduce the length of the spiral. It will be appreciated that this compression distorts the layer 14 so that it becomes distorted out of its spiral pattern and can fold and crease to form generally random patterns.
- the particles 16 are retained within the structure by the solvent.
- the solution containing the ionically conductive material and the particles, if any, of the ionically conductive material remain in a layer on one surface of the sheet 14. These materials are therefore compressed into the interstices between the portions of the electrically conductive material as they are folded and creased during the compression action.
- air may be present in some of the locations between the portions of the sheet so as to form voids. All of the air or some of the solution may be expelled during the compression. However in the resultant compressed product there will be in most cases some particles, some air and some solution.
- the electrically conductive material or metal will be compressed at places so that it contacts other portions of the metal through the structure forming a myriad of little paths through the structure from the external surface through to the wire. In between these little paths will be some solution, some voids and some particles, in most cases. The solution is free to migrate through the interstices so that it will tend to wick into the interstices filling or partly filling most or all of the interstices. This movement is of course assisted by the compression.
- the ionically conductive material will tend to deposit out of solution onto the surfaces of the interstices thus coating all of the surfaces and providing a path through those interstices onto substantially all or most of the metal surfaces within the interior structure of the anode body.
- the ionically conductive material which has been deposited out of solution and the remaining particles of ionically conductive materials.
- the finished anode body has within its structure a series of electrically conductive paths in communication with a series of ionically conductive paths defining between them a surface area which is significantly greater than the simple exterior surface of the structure itself.
- This increase in surface contact through the series of internal passages and paths can be greater than 100 times the simple exterior surface of the anode body and certainly will be greater than 10 times or greater than 5 times, depending upon the method of construction.
- the surface area depends upon the thickness of the foil so that thinner foil will generate for a certain volume a much larger number of interstices and surface area since the surface area of the initial foil from which the structure is formed is much greater.
- Foil of different thicknesses can be used and the thickness of the foil may lie in the range 0.001 to 0.050 inch and more preferably in the range 0.003 to 0.020 inch.
- the ionically conductive material may contain or consist of materials which enhance the effectiveness of the current from the anode.
- materials which are humectants can assist in the generation of current since they tend to absorb and maintain moisture in the area of the surfaces concerned.
- the whole of the ionically conductive material may therefore be formed from a humectant material of which many examples are known in the prior art or the material may consist of a mixture of humectant and other non- humectant materials.
- a further characteristic which enhances current is that of providing a material which has a relative high pH generally greater than 12.
- the ionically conductive material may be chosen in order to provide such a high pH within the anode body.
- Other enhancement materials may also be provided as part of or a characteristic of the ionically conductive material.
- the material may have a relatively low pH since the material may be contained within the anode and thus the outer surface of the anode acts as a pH barrier. The provision of the perforations within the sheet 14 ensures that the ionically conductive paths are also formed from separate path portions within the anode body which are interconnected by the perforations and thus pass through the layer defined by the sheet 14 back and forth.
- Figure 9 and 10 is shown an alternative construction of the anode body which is defined by compressing particles of the electrically conductive material and the ionically conductive material.
- a wire 23A which extends into a core 22A of a cast portion of the metal
- a body 35 which is defined by compressed particles as; indicated at 36.
- the particles may be generally amorphous or may have a shape such as a flake or small piece of sheet since it will be appreciated that the compression of any such object will provide the necessary interstices containing the ionically conductive material in solid, gel or solution form.
- Figure 10 shows schematically a series of metal particles 36 between which are interstices 37.
- the ionically conductive material is shown in cross hatch and includes particles 38 and deposited materials 39 which coats on the surfaces of the particles 36. Some of the interstices are filled with a particle and some have voids as indicated at 40.
- the voids can accommodate expansion of the anode body caused by the corrosion of the individual particles. It will be appreciated that the corrosion occurring due to the sacrificial nature of the metal particles 36 takes place at the surface of each particle causing that particle to expand as corrosion occurs. The corrosion materials which are of a greater volume than the original material can thus expand into the voids 40 thus avoiding significant expansion of the anode body itself at its exterior surface.
- the content of the anode body may have a range as follows:
- the ionically conductive material has a pH less than 4.5 and is contained within the anode body such that the outer surface of the anode body acts as a pH barrier.
- the use of low pH material in the anode body can provide a significant enhancement of the flow of current but is normally unacceptable in view of its detrimental effect on the concrete surrounding the anode.
- the low pH material is contained within the anode body and thus is prevented from accessing and degrading the concrete.
- FIG 8 there is shown an alternative embodiment which is formed by individual layers 50, 51 , 52 etc. of the electrically conductive material. In between each layer and the next is provided a layer 53, 54 etc. of the ionically conductive material. Each sheet of the zinc or other material is perforated as indicated at 55.
- the provision of the perforations 55 ensures that there are a series of ionically conductive paths from the exterior of the body through the interior of the body communicating at a plurality of separate locations within the body with the electrically conductive path or paths through the body leading to the wire 56.
- Each of the ionically conductive paths communicates with the exterior of the body through the perforations 55. It will be appreciated that it is necessary for the ionically conductive paths to communicate with the exterior surfaces as indicated at 57 and 58 of the anode body in order that the ions can flow through the medium
- the reinforcement element 11 is a rebar within the concrete.
- the metal element 1 1A is a structural member which extends from contact within the concrete to a position outside the concrete such as a deck rail or the like so that the portion buried in the concrete can be protected from corrosion.
- the perforations in the sheets are not essential and the sheets may be imperforate.
- the ionically conductive paths to itie separate locations in the interior of the body must pass along the sheets to the ends of the sheets. While this increases the distance, the selection of an ionically conductive material which reduces the resistance to current flow to a level significantly below that of concrete (or the medium) will reduce the deleterious effect of this increased distance.
- anode body in a further alternative arrangement including a medium and a reinforcing steel member can be laid on a top surface of the medium or concrete and is covered by a floor covering layer.
- This arrangement can be used with the other types of structure previously described but is particularly applicable to the layer arrangement of Figure 8 where a construction of multiple layers or thin foil may result in an anode body of the order of 0.05 to 0.25 inches in thickness.
- FIG. 2 An impressed current system is shown in Figure 2 where the anode body is connected through the wire 13B to a power supply generally indicated at 13C.
- the anode body is formed from a conductive material which is not sacrificial but is intended to be maintained.
- Such anode bodies are typically of titanium since there is little or no corrosion of such material within the system.
- the same arrangement of paths of electronically conductive material and paths of ionically conductive material provide a significantly increased surface area within the anode body for the communication of the current through the anode body.
- the anode used in the impressed current system is particularly of advantage in a situation where a limited volume anode is required.
- the amount of current can be controlled by the voltage from the power source 13C.
- the highly concentrated anode structure of the present invention can be used in an impressed current system.
- the ionically conductive material used with the impressed current system can advantageously be selected so that it provides an alkali environment to buffer acid given off by the electrically conductive material and to allow gas generated to diffuse away. It is well known that impressed current systems used with non-sacrificial anodes give off as part of the electrolytic action an acid at the anode which can cause localized breakdown of the concrete where the acid interferes with the alkali nature of the concrete. Thus the provision of an alkali in the ionically conductive material which is arranged to buffer the acid production is advantageous in preventing these problems.
- these anodes give off gas as part of the electrolytic action.
- the provision of a porous ionically conductive medium and anode structure is beneficial in allowing the gas generated to diffuse away.
- the anode body be embedded within the structure.
- Such embedded anodes as indicated in Figures 1 and 2 thus provide a number of exterior surfaces which contact the medium since both the top and bottom surfaces and any side surfaces contact the medium.
- the anode body generally has a thickness which is greater than 0.5 centimetres and can be as much as 3 centimetres or greater to provide sufficient volume and sufficient internal contact surface to generate the currents required in the system and to maintain those currents over an extended period of time.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Prevention Of Electric Corrosion (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002538949A CA2538949A1 (en) | 2006-03-07 | 2006-03-07 | Anode for cathodic protection |
PCT/CA2007/000260 WO2007101325A1 (en) | 2006-03-07 | 2007-02-21 | Anode for cathodic protection |
Publications (3)
Publication Number | Publication Date |
---|---|
EP2004875A1 true EP2004875A1 (en) | 2008-12-24 |
EP2004875A4 EP2004875A4 (en) | 2009-12-30 |
EP2004875B1 EP2004875B1 (en) | 2019-09-11 |
Family
ID=38468987
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP07701806.7A Active EP2004875B1 (en) | 2006-03-07 | 2007-02-21 | Anode for cathodic protection |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP2004875B1 (en) |
AU (1) | AU2007222909B2 (en) |
CA (1) | CA2538949A1 (en) |
WO (1) | WO2007101325A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7967971B2 (en) | 2008-03-11 | 2011-06-28 | Nigel Davison | Discrete sacrificial anode assembly |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5292411A (en) | 1990-09-07 | 1994-03-08 | Eltech Systems Corporation | Method and apparatus for cathodically protecting reinforced concrete structures |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4957612A (en) * | 1987-02-09 | 1990-09-18 | Raychem Corporation | Electrodes for use in electrochemical processes |
GB9015743D0 (en) * | 1990-07-17 | 1990-09-05 | Pithouse Kenneth B | The protection of cementitious material |
US6033553A (en) * | 1996-10-11 | 2000-03-07 | Bennett; Jack E. | Cathodic protection system |
US5968339A (en) * | 1997-08-28 | 1999-10-19 | Clear; Kenneth C. | Cathodic protection system for reinforced concrete |
US6572760B2 (en) * | 1999-02-05 | 2003-06-03 | David Whitmore | Cathodic protection |
US7276144B2 (en) * | 1999-02-05 | 2007-10-02 | David Whitmore | Cathodic protection |
US7767330B2 (en) * | 2005-05-04 | 2010-08-03 | Gm Global Technology Operations, Inc. | Conductive matrices for fuel cell electrodes |
-
2006
- 2006-03-07 CA CA002538949A patent/CA2538949A1/en not_active Abandoned
-
2007
- 2007-02-21 AU AU2007222909A patent/AU2007222909B2/en active Active
- 2007-02-21 WO PCT/CA2007/000260 patent/WO2007101325A1/en active Application Filing
- 2007-02-21 EP EP07701806.7A patent/EP2004875B1/en active Active
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5292411A (en) | 1990-09-07 | 1994-03-08 | Eltech Systems Corporation | Method and apparatus for cathodically protecting reinforced concrete structures |
Non-Patent Citations (2)
Title |
---|
See also references of WO2007101325A1 |
VRABLE J.B.: "Cathodic protection for reinforcing steel in concrete", ASTM STP 629, 1977, pages 124 - 149, XP003030740 |
Also Published As
Publication number | Publication date |
---|---|
EP2004875A4 (en) | 2009-12-30 |
EP2004875B1 (en) | 2019-09-11 |
AU2007222909B2 (en) | 2012-05-03 |
WO2007101325A1 (en) | 2007-09-13 |
CA2538949A1 (en) | 2007-09-07 |
AU2007222909A1 (en) | 2007-09-13 |
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