Manufacture of sacrificial anodes

Abstract

Sacrificial anodes for installing in an ionically conductive medium at an installation site containing metal requiring cathodic protection are formed by locating anode cores in a tray having dividing members defining a row of side by side chambers with each chamber containing a respective one of the anode cores and casting into the receptacle a covering mortar for the anode cores with each anode core receiving a coating at least partly surrounding the anode core with the connecting wire exposed. The mortar is cast to form frangible bridges between each anode and the next. The trays are stacked and transported to the site where the installer separates and individually installs the anodes into the medium.

Claims

1. A method for forming sacrificial anodes for installation in an ionically conductive medium at an installation site which medium contains metal requiring cathodic protection comprising: locating in a receptacle a plurality of anode bodies each comprising a sacrificial material and at least one connecting component for use in making an electrical connection between the anode body and the metal; providing in the receptacle dividing members defining a plurality of chambers with each chamber containing a respective one of the anode bodies; and casting into the receptacle a covering material such that the covering material is in contact with at least a portion of each anode body.

2. The method according to claim 1 wherein the anodes are connected in the receptacle each to the next by a frangible bridge portion of the cast covering material.

3. The method according to claim 1 wherein said at least one connecting component extends outwardly from the anode body and wherein the anode bodies are supported and located in the chambers during said casting by engagement of at least one wall portion of the receptacle with said at least one connecting component.

4. The method according to claim 3 wherein each of the chambers has at least one opening for receiving said at least one connecting component.

5. The method according to claim 3 wherein said at least one connecting component comprises a threaded rod.

6. The method according to claim 3 wherein said at least one connecting component comprises a pair of connecting components-with each connecting component extending outwardly from a respective end of the anode body and said at least one wall portion of the receptacle comprises two end wall portions each engaging a respective one of said pair of connecting components-of the anode body to support the anode body within its respective chamber.

7. The method according to claim 3 wherein said at least one wall portion has a slot for the connecting component.

8. The method according to claim 3 wherein said at least one wall portion has a hole for the connecting component.

9. The method according to claim 3 wherein said at least one wall portion of each chamber engages an end of the anode body and reduces the covering material from engaging the connecting component as the covering material is cast.

10. The method according to claim 1 wherein the chambers are elongate and arranged side by side in a row.

11. The method according to claim 1 wherein the receptacle is formed of a flexible material shaped to form the chambers and bendable to release the flexible material from the cast covering material.

12. The method according to claim 1 wherein the anode bodies and the covering material after casting are transported in the receptacle to a location for use.

13. A method for forming sacrificial anodes for installation in an ionically conductive medium at an installation site which medium contains metal requiring cathodic protection comprising: locating in a casting receptacle at least one anode body comprising a sacrificial material and at least one connecting component for use in making an electrical connection between the anode body and the metal; the casting receptacle comprising walls defining at least one chamber; inserting said at least one anode body into a respective one of said at least one chamber of said casting receptacle; supporting said at least one anode body in said respective one of said at least one chamber of said casting receptacle so as to define a casting space between at least one of said walls and a surface of said at least one anode body; casting into the casting space in the receptacle a covering material such that the covering material is in contact with at least said surface of said at least one anode body and such that the covering material is confined and shaped by said at least one wall of the casting receptacle; and, after casting, transporting for use at a remote location said at least one anode body and the covering material while said at least one anode body and the covering material remain contained in the casting receptacle; wherein the casting receptacle is formed of a flexible material shaped to form said at least one chamber and bendable to release the flexible material from the cast covering material.

14. The method according to claim 13 wherein said at least one connecting component extends outwardly from the anode body and wherein said at least one anode body is supported and located in the receptacle during said casting by engagement of said at least one connecting component with at least one wall of said walls.

15. The method according to claim 14 wherein said at least one wall has at least one opening for receiving said at least one connecting component.

16. The method according to claim 14 wherein said at least one connecting component comprises a threaded rod.

17. The method according to claim 14 wherein said at least one connecting component comprises a pair of connecting components with each connecting component extending outwardly from a respective end of the anode body and said at least one wall of the receptacle comprises two end walls each engaging a respective one of said pair of connecting components of the anode body to support the anode body within the receptacle.

18. The method according to claim 17 wherein each of said two end walls has a slot for the connecting component.

19. The method according to claim 17 wherein each of said two end walls engages an end of said at least one anode body and reduces the covering material from engaging the connecting component as the covering material is cast.

20. A method for forming sacrificial anodes for installation in an ionically conductive medium at an installation site which medium contains metal requiring cathodic protection comprising: locating in a receptacle at least one anode body comprising a sacrificial material and at least one connecting component for use in making an electrical connection between the anode body and the metal; the receptacle comprising walls defining at least one chamber; inserting said at least one anode body into a respective one of said at least one chamber; supporting said at least one anode body in said respective one of said at least one chamber so as to define a space between at least one of said walls and a surface of said at least one anode body; casting into the space in the receptacle a covering material such that the covering material is in contact with at least said surface of said at least one anode body; wherein said at least one connecting component extends outwardly from the anode body; wherein said at least one anode body is supported and located in the receptacle during said casting by engagement of said at least one connecting component with at least one wall of said walls; and wherein the casting receptacle is formed of a flexible material shaped to form said at least one chamber and bendable to release the flexible material from the cast covering material.

21. The method according to claim 20 wherein said at least one wall has at least one opening for receiving said at least one connecting component.

22. The method according to claim 20 wherein said at least one connecting component comprises a pair of connecting components with each connecting component extending outwardly from a respective end of the anode body and said at least one wall of the receptacle comprises two end walls each engaging a respective one of said pair of connecting components of the anode body to support the anode body within the receptacle.

23. The method according to claim 22 wherein each of said two end walls has a slot for the connecting component.

24. The method according to claim 22 wherein each of said two end walls engages an end of said at least one anode body and reduces the covering material from engaging the connecting component as the covering material is cast.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:

(2) FIG. 1 is a cross-sectional view showing schematically a method according to the present invention for cathodic protection of steel members in concrete or mortar using an anode member having a sacrificial anode body attached by wires to the reinforcing steel members.

(3) FIG. 2 is a top plan view of the anode member of FIG. 1 prior to attachment.

(4) FIG. 3 is a top plan view of a method for casting the anode assembly of the present invention.

(5) FIG. 4 is a cross-sectional view along the lines 4-4 of FIG. 3.

(6) FIG. 4A is a cross-sectional view similar to that of FIG. 4 showing an alternative arrangement in which the receptacle includes a liner portion of a porous material to be inserted with the anode into the concrete during installation and a mold portion.

(7) FIG. 5 is a top plan view of a package containing the anode assembly of the present invention.

(8) FIG. 6 is a cross-sectional view along the lines 6-6 of FIG. 5.

(9) FIG. 7 is a top plan view similar to FIG. 5 of a further embodiment of package containing the anode assembly of the present invention.

(10) FIG. 8 is a cross-sectional view of a further embodiment of package containing the anode assembly of the present invention.

(11) In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION

(12) In FIG. 1 is shown a first embodiment according to the present invention of an improved cathodic protection device. The anode structure used is of a similar construction to that shown in the above application WO94/29496 and in U.S. Pat. Nos. 6,193,857 and 6,165,346, the disclosures of which are incorporated herein by reference or may be referenced for further detail.

(13) Thus, the cathodic protection device is arranged for use in a concrete structure generally indicated at 10 having reinforcing bars 11, 11A embedded within the concrete 13 and spaced from an upper surface 14 of the concrete.

(14) Embedded within the concrete at a position adjacent to the reinforcing bar 11 is a cathodic protection device generally indicated at 15 which includes an anode body 16.

(15) At opposed end positions on the peripheral surface 17 is attached a pair of connecting wires 19 and 20 which are flexible but sufficiently stiff to be self-supporting. Any suitable electrically conductive material such as copper, titanium or steel can be used.

(16) Around the anode body is provided a layer of a mortar material 21. In practice, the mortar material is moulded around the anode core to provide a thickness of a mortar material around the full periphery apart from the ends with the thickness being of the order of 1 cm. The wires 19 and 20 pass through the anode core and then the mortar is cast in place. The mortar forms an electrolyte which is in intimate communication with the concrete layer so that a current can flow from the anode to the steel reinforcement 11.

(17) The mortar material is preferably a solid so that it can contain and hold the anode without danger of being displaced during the process. However, gels and pastes can also be used. The mortar material preferably is relatively porous so that it can accommodate expansion of the zinc oxide during consumption of the anode. However, voids which might fill with water should be avoided.

(18) The use of the protection device is substantially as described in the above application WO94/29496 in that it is buried in the concrete layer either at formation of the concrete in the original casting process or more preferably in a restoration process subsequent to the original casting. Thus sufficient of the original concrete is excavated to allow the reinforcing bar 11 to be exposed. The wires 19 and 20 are then wrapped around the reinforcing bar and the protective device placed into position in the exposed opening. The device is then covered by a recast portion of concrete and remains in place buried within the concrete.

(19) This system is therefore only applicable to a sacrificial anode system where the anode is buried within the concrete.

(20) The cathodic protection device therefore operates in the conventional manner in that electrolytic potential difference between the anode and the steel reinforcing member causes a current to flow therebetween sufficient to prevent or at least reduce corrosion of the steel reinforcing bar.

(21) The anode and preferably the covering 21 preferably includes at least one activator such as a high pH and/or a humectant material at the sacrificial anode for ensuring continued corrosion of the anode. Suitable materials are disclosed in the above cited documents.

(22) The level of the pH and the presence of the humectant enhances the maintenance of the current so that the current can be maintained for an extended period of time in a range 5 to 20 years.

(23) The method thus includes locating the sacrificial anode 16 which is of a material which is less noble than the steel members 11 in contact with the ionically conductive concrete or mortar material and providing an electrically conductive connection 19, 20 between the sacrificial anode and the steel section to form a circuit with communication of ions between the sacrificial anode and the steel section through the ionically conductive concrete or mortar material so that the sacrificial anode acts to provide cathodic protection of the steel section.

(24) The first and second wires 19, 20 each extend from the sacrificial anode core 15 to a free end 19A, 20A remote from the anode. As shown in FIG. 2, the first and second wires are shaped to define a loop 19B, 20B at each of the first and second free ends by turning back the end. However, this is provided merely to assist in manual handling of the end and the ends can be simple terminations shown in FIG. 1.

(25) Typically, the first and second wires form portions of a common wire 19C extending through the anode material 16 which has a core cast onto the common wire. This method of manufacture is very simple and provides an excellent connection both structurally and electrically between the wire and the sacrificial anode material.

(26) Turning now to FIGS. 3, 4 and 5 there is shown a method for forming the anode described above and for transporting the anode assembly to the installation site shown in FIGS. 1 and 2.

(27) In FIGS. 3 and 4 is shown a receptacle 30 which is molded to form end walls 31 and 32 and a main body 33. The main body is molded to form a generally undulating shape with raised ribs 34 and valleys 35. The valleys form chambers 36 for molding the anodes described above. The ribs 34 form spacers for holding each anode spaced from the next. The receptacle can be molded from many different types of material including plastics and paper so that it has a thin flexible wall and is thus light weight and inexpensive. The material may be water impermeable or may be porous so as to retain the coating when cast but to allow penetration of liquid after installation in the concrete.

(28) Thus, the method forms a plurality of sacrificial anodes for installing in the ionically conductive medium or concrete 13 at an installation site 10.

(29) The receptacle or tray 30 forms both a casting tray and a transportation receptacle. The ribs 34 and end walls 31, 32 act as dividing members defining a plurality of chambers 36 in an array in the tray. These are elongated and side by side to form elongate rod-shaped anodes, but of course alternative shapes and spacings are possible. Each chamber 26 is arranged to act as a mold for and to contain a respective one of a plurality of the anodes side by side.

(30) Each anode as set out above comprises the anode core 16 forming a body of a sacrificial material and a connecting wire 19 which passes through the core and forms two exposed end portions 19 and 20.

(31) As shown in FIGS. 3 and 4 at the manufacturing location, the anode cores and wires are inserted into the respective chambers 36 and each anode has a cast covering material 21 for the anode cores with each anode core 16 having a coating of the covering material 21 at least partly surrounding the anode core 16 surrounding the outer surface but with the connecting wire 19 exposed at the ends.

(32) At the manufacturing location, therefore the material 21 in a supply 21A is poured onto the tray to enter the chambers 36 and surround the core 16. While the casting action occurs, the tray is set on a pad 38 with a raised peripheral rib 39 containing the tray to support the tray sufficiently to receive the casting material. When the cast material is set, the tray is transported containing the series of anodes in a row or other array to the installation site where the anodes are removed from the receptacle at the installation site and inserted individually into the concrete 13. The shape of the anodes with the coating thereon can vary so as to include elongate anodes or puck shaped anodes. When the anodes are elongate, they can extend horizontally as shown in FIGS. 4 to 7 or vertically as shown in FIG. 8 with the coating material cast around the anode body.

(33) As shown in FIGS. 4 and 6, it will be noted that the end walls 31 and 32 and the end ribs 34A are raised to a top edge 40 higher than the top edge 41 of the intervening ribs 34. When the cast material is filled in the tray up to the line 40, this forms a portion of the cast material so that the anodes are connected in the receptacle each to the next by a frangible bridge portion 42 of the cast covering material 21. That is a portion of the cast material bridges over the rib 34 from one chamber 36 to the next to hold the two side by side anodes connected.

(34) As the structure while remaining intact is transported in the tray from the manufacturing site to the installation site, the bridge portion 42 is broken at the installation site as the installer separates each anode in turn from the series of anodes supplied. This bridge portion 42 holds the anodes together as a structural body for transportation and assists in the casting process as the cast material holds the structure together during handling, packaging and transporting. However, the bridge portion 42 is sufficiently thin to allow it to be broken without damaging the layer 21 surrounding the core 16.

(35) As shown best in FIG. 4, during the casting process the anode cores are supported and located in the chambers by engagement of the end walls 31, 32 of the tray 30 with the wire 19. Thus, the walls 31 and 32 each have a slot 43 extending downwardly from the top edge 40 to a bottom end of the slot adjacent a center of the chamber 36. The wire 19 exiting from the core body 16 sits in the slot 43 of the wall 31, 32 of the receptacle 30 and holds the core 16 as shown at the right in FIG. 3 spaced away from other walls of the chamber 36 for the cast material 21 to properly surround at least some surface of the core as it is cast from the supply 21A. In this way, the two end wall portions 31 and 32 engaging the ends 16A and 16B of the core 16 act to support each wire 19 of the anode core 16 to support the anode core within its respective chamber 36 suspended across the two end wall portions 31, 32. In this way the core can be dropped into its chamber with the wires locating the core along the chamber.

(36) As shown in FIG. 3, the end walls 31 and 32 directly engage or butt against the end 16A, 16B of the anode core 16 so that as the material 21 is cast it cannot enter this area or is at least restricted from entering this area and thus prevents or restricts the covering material from reaching the wire 19. The chambers 36 are elongate and arranged side by side in a row to form finger shaped anodes with a center core and a surrounding ring of the cast covering material.

(37) As the receptacle is supported during the casting process on the support pad 38, it is formed of a flexible disposable plastics material which can be molded to form the chambers and is simply bendable to pull away from the cast material to release the flexible material from the cast covering material. The walls of the ribs 34 of the main body 33 as shown at 45 and 46 have tapered sides to allow the anodes to be pulled out. However, since the flexible material can be sufficiently flimsy the degree of taper may be reduced relative to those used in conventional rigid molds as the flexible material can be pulled away from the casting during the extraction of the anodes.

(38) As shown in FIGS. 5 and 6 the receptacle forms a tray and the trays are stacked one on top of the next in at least one column. The tray thus has a base and upstanding molded walls into which the casting material is placed. However other shapes and configurations of the receptacle can be used. The column or columns can then be contained in an external container 48 such as a cardboard box. A bottom wall of each tray onto which the material is cast acts for separating the anodes in the tray from the anodes of the next tray below to avoid frictional contact between the mortar layers which can damage the layers in transport. The amount of packaging material used is therefore reduced while providing a stable and effective transport system. The wires 19 and 20 are contained within an area 49 of the box 48 beyond the end walls 32, 32 where the wires can be bent, wrapped or folded to reduce the space required in that area. On arrival at the installation site, the individual anodes are pulled out of the chambers 36 with the respective wires being extracted from the storage areas 49.

(39) In FIG. 7 is shown a plan view of an alternative arrangement where the anode bodies 16 use a single threaded rod, or other similar mechanism, for fastening to the metal. In this embodiment, the rod 191 is located only at one end of the anode body 16. In this arrangement, therefore there is only a single chamber 491 at the end of the box 48 to receive the rods 191. The rods thus are mounted in the casting process by passing the rod through a hole 431 in the end wall 321. As this engagement is relatively tight and the other end of the body 16 tightly engages the wall 311, this mounting can operate to hold the bodies 16 in place. However, a rib 312 can be provided in the wall 311 facing the end of the body 16 to assist in ensuring the proper location of the body 16 within the chamber for receiving the casting material in the casting process.

(40) In FIG. 4A is shown an alternative arrangement in which the receptacle 30A is formed of or includes a porous material such as paper to be inserted with the anode into the concrete during installation. The paper receptacle 30A can be sufficiently stiff to form the mold and to form the transportation receptacle. However more typically, the paper receptacle 30A can be as shown in FIG. 4A where the receptacle including the main body 33, raised ribs 34 and valleys 35 is thinner so as to define in effect a liner which is located on and carried by the inside of a mold 38A including a base pad 38C and raised ribs 38B. the provision of the shaped mold allows the liner to be relatively thin and easily torn since the liner is not required to provide the strength to support the case material during casting.

(41) In this way, the molded anode structure as a body including the anodes and the bridge portions can be pulled out of the mold structure with the liner material attached for transportation to the installation site in stacks in an exterior box as described above.

(42) The liner thus provides sufficient structural integrity and cushioning for transportation of the anode assembly in the stack while reducing damage in transportation and storage. At the installation site the anode assembly is separated into individual pieces with each individual anode including a separate torn portion of the liner with each portion engaging a respective anode at the installation site. Thus if the material can be torn, the anodes can be broken away from the whole structure while the receptacle is torn into the separate pieces. The porous paper material can be easily torn into the separate pieces as the anodes are separated and also the paper pieces partly surrounding or engaging the anode can be inserted into the concrete with the anode without interfering with the communication of ions after the installation is complete. That is the selected material, typically porous paper is penetrated by the liquid of the concrete mixture during pouring so that the paper in effect becomes a part of the concrete structure.

(43) Alternatively the whole of the receptacle both for casting and for transportation may be provided in the form of the porous material and separated into the individual portions at the installation. The advantage of using the porous material as the receptacle at the site is that the material can be inserted into the medium with the anodes rather than discarded as waste material on site. In this way the transportation receptacle is conveniently introduced into the medium without requiring the installer to carry out the separation of these components and to manage the disposal of the receptacle.

(44) In FIG. 8 is shown a further embodiment where anodes 50 are cast in a receptacle 51. In this embodiment the elongate anodes are arranged standing vertically in an array which can include a number of rows and columns of pockets 52 into each of which a separate anode 50 is formed and transported. Each anode 50 includes a central anode body 53 of a sacrificial material such as zinc surrounding a connecting wire 54 forming a component for electrical connection of the body 53 to the metal to be protected. Both the pocket and the body are cylindrical with a circular outer periphery 55 and flat ends 56. Different shapes can also be used. The wire 54 emerges from each flat end. The flat bottom end of the body 53 sits on the flat bottom of the pocket with the wire 54A projecting through a hole 57 in the flat bottom. This cooperation between the flat bottom of the anode body on the flat bottom of the pocket and the protrusion of the wire through the hole acts to located the body upright centrally within the pocket. When all of the pockets contain the respective body, the covering material 58 is cast into place around each anode body up to a top surface of the pocket which is coincident with the top of the anode body. The cooperation between the flat bottoms prevents the penetration of the covering material when cast around the wire 54. The flat top surface of the anode body is not covered with the material 58. The pockets are connected each to the next by a bridging portion 59 between the pockets which forms a generally flat sheet with the pockets recessed therein.

(45) The structure including the receptacle and the anodes carried therein is transported to the installation site where the anodes are pulled out for individual use. In this embodiment there is no frangible portion connecting he anodes so that the structural shapes is maintained by the receptacle and by any supporting material such as a cardboard divider between each receptacle and the next when formed into a stack for transportation.

(46) The receptacle can be formed of a plastics material which is flexible to help release of the anodes when required. Such receptacle s might be re-used or recycled. As an alternative, the receptacle can be formed of paper or other fiber board which is sufficiently resistant to contain the covering material when cast in a wet form and can be sufficiently porous to be used in the concrete which the anode when installed without interfering with the passage of ions. When a fibrous material is used and is not intended to be installed with the anode, before casting each pocket is coated with a release coat for example of silicone to allow the anode to be pulled out of its pocket. As there is no frangible connection in this embodiment as shown, the anodes can be readily separated and where required the receptacle can be torn into cylinders each surrounding the respective anode.

(47) However channels can be formed in the top wall 59 to allow casting of connecting portions which will break when required. This of course assists in maintaining the structure as a stiff integral body for transportation to the installation site.