Cathodic corrosion protection with current limiter

Abstract

To provide a method for cathodically protecting and / or passivating a metal section in an ionically conductive material such as steel reinforcement in concrete or mortar.SOLUTION: A method comprises the steps of: providing an anode for communication of an ion current to the metal section in the ionically conductive material; generating a voltage difference between the anode and the metal section so as to cause a current to flow through the ionically conductive material between the anode and the metal section so as to provide cathodic protection of the metal section; and providing electrical components which limit the current to a maximum value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for cathodic protection and / or passivation of a metal part in an ion-conductive material using a battery or a battery of batteries to supply voltage, and / or to an anode assembly, and more particularly to a configuration for restricting the supply of current by an electrode assembly.

Background Art

[0002] External power supply systems using batteries are known. Such external power supply systems can use other types of power sources including a common rectifier that rectifies an alternating voltage to a direct current voltage required for an impressed current between an anode and steel from a suitable power source. It is also known to provide a solar panel used in this type of system.

[0003] In any case, such external power supply systems require normal maintenance and inspection of the power source state to ensure that the power source does not cause unexpected unacceptable corrosion or overprotection of the steel within the structure to be protected. While such maintenance is carried out and thus the safety of the power source is ensured, this is a relatively costly process.

[0004] Alternatively, a direct current electrical system that does not require a power source can be used because a voltage between the steel and the anode is provided by selecting a suitable material for the anode that is sufficiently electrochemically negative to ensure that a current that provides cathodic protection is generated. These systems have been very successful and are widely used.

[0005] Ordinary galvanic anodes, such as those used in reinforced concrete, have two main limitations. The first limitation relates to the mass of zinc per anode, which limits the service life of the anode depending on the required current output. The second limitation is the actual current output of the anode, which may or may not be sufficient to stop the corrosion of steel. The current output is limited by the driving voltage and is either essentially stable or varies over time due to exposure conditions, the age of the anode, and the generation of corrosion products.

[0006] U.S. Patent No. 8,961,746 (Sergi), issued February 24, 2015, U.S. Patent No. 8,968,549 (Sergi), issued March 3, 2015, and U.S. Patent No. 7,264,708 (Whitmore), issued September 4, 2007, are also cited, all of which are assigned to the assignee hereof, and the disclosures of which are hereby incorporated by reference herein or may be referred to for more related information. SUMMARY OF THE INVENTION

[0007] According to one aspect of the invention, there is provided an anode assembly for use in an ion-conductive material to protect and / or passivate metal reinforcing bars, the anode assembly comprising: an anode body for at least partially mounting within the ion-conductive material, wherein: the anode body includes an anode for transmitting an ionic current to the metal reinforcing bar through the ion-conductive material; the anode body is configured and arranged such that a voltage difference is generated between the anode and the metal reinforcing bar when the anode is ionically connected to the ion-conductive material, thereby causing a current to flow through the ion-conductive material between the anode and the metal reinforcing bar to provide cathodic protection of the metal reinforcing bar; and a mounting assembly for fixing and installing the anode body to the metal reinforcing bar such that the anode body is at least partially supported by the reinforcing bar within the ion-conductive material so that current can flow from the anode to the metal reinforcing bar, wherein: an elongated rod member extending forward from the anode body to the front end of the elongated rod member for engagement with a first adjacent surface of the metal reinforcing bar; A hook member for engaging a second opposing surface of the metal reinforcing bar and a mounting assembly including the same; and A connecting portion for pulling the front end of the rod member and the hook member together to hold the metal reinforcing bar therebetween is provided.

[0008] According to another aspect of the present invention, there is provided an anode assembly for use in an ion-conductive material to corrode and / or passivate a metal reinforcing bar, the anode assembly comprising: An anode body for at least partially mounting within an ion-conductive material, wherein the anode body includes an anode for transmitting an ionic current to the metal reinforcing bar through the ion-conductive material; the anode body is configured and arranged such that a voltage difference is generated between the anode and the metal reinforcing bar when the anode is ionically connected to the ion-conductive material, thereby causing a current to flow through the ion-conductive material between the anode and the metal reinforcing bar to provide cathodic protection of the metal reinforcing bar; and A mounting assembly for fixing and installing the anode body to the metal reinforcing bar so as to be supported by ionic contact with the ion-conductive material such that an ionic current can flow from the anode to the metal reinforcing bar, the mounting assembly comprising: A first abutting member extending forward from the anode body to the front end of the first abutting member for engagement with the first adjacent surface of the metal reinforcing bar; A second abutting member for engaging a second opposing surface of the metal reinforcing bar; The first abutting member has at least a part thereof with a male thread, and the second abutting member has a connecting portion with a female thread for engaging the male thread to pull the second abutting member toward the anode body to hold the metal reinforcing bar therebetween.

[0009] According to another aspect of the present invention, there is provided an anode assembly for use in an ion-conductive material to corrode and / or passivate a metal reinforcing bar, the anode assembly comprising: An anode body for at least partially mounting within an ion-conductive material, wherein An anode for transmitting an ionic current to the metal reinforcing bar in the ion-conductive material An electrical energy storage component having first and second electrodes for transmitting a current generated by releasing electrical energy; The first electrode is an anode body having an electrical connection to the anode; and A mounting assembly for fixing and installing the anode body to the metal reinforcing bar so as to be supported by the metal reinforcing bar in ionic contact with an ion-conductive material so that an ionic current can flow from the storage component through the anode to the metal reinforcing bar; Connected to the second electrode for electrical connection of the second electrode to the metal reinforcing bar; A first abutting member connected to the anode body for engaging one surface of the metal reinforcing bar; A second abutting member for engaging a second opposite surface of the metal reinforcing bar; and A mounting assembly including a connecting portion for pulling the first and second abutting members together to hold the metal reinforcing bar therebetween.

[0010] This configuration particularly relates to attaching an anode body to a conventional steel reinforcing bar attached to a fixing material such as concrete or another cementitious material such as mortar. However, the configuration may be used in other positions in some cases.

[0011] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of the present specification, the hook member includes two balance hooks spaced longitudinally along the reinforcing bar and connected together for general engagement with the reinforcing bar. This acts to engage the reinforcing bar at three positions of the longitudinally spaced reinforcing bar with a first abutting portion or rod on one intermediate surface and two hook portions on either side of the opposite surface. That is, the hook member preferably includes two surface portions each arranged to engage the metal reinforcing bar on each side at positions directly opposite to the first surface.

[0012] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of this specification, the anode body is attached to an elongated rod or a first abutting member, such that the rotation of the anode body drives the rotation of the front end of the elongated rod member relative to the first face of the reinforcing bar. In this configuration, preferably, the front end of the elongated rod member includes one or more protrusions for biting into the metal reinforcing bar. This can be provided by one or more protrusions on the outer circular end of the end of the rod, or on the face itself.

[0013] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of this specification, the elongated rod member is at least partially threaded along its length so as to act as a screw to drive the female threaded portion of the second abutting member in the direction of the anode body.

[0014] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of this specification, the hook member includes a female threaded portion for engaging the elongated rod member so as to pull it together towards the front end of the rod member or the first abutment and the hook member or the second abutment to hold the metal reinforcing bar therebetween.

[0015] Preferably, the female threaded portion is fixed to the hook member such that rotation of the rod member moves the hook member towards the anode body. However, other configurations are possible where the female portion includes a nut that rotates about a screw relative to the second abutment so as to drive the second abutment towards the anode body.

[0016] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of this specification, the hook member or the second abutment engages the elongated rod member at a position spaced from the anode body to prevent contact between the anode body and the metal reinforcing bar. This is particularly important when the anode is powered by a battery or a power source forming part of the anode body to prevent a short circuit in the power supply to the metal reinforcing bar.

[0017] In accordance with one important feature of the present invention that can be used in conjunction with any of the configurations of this specification, the elongated rod member is firmly connected to the anode body in order to be fixed and held at a predetermined distance and orientation with respect to the metal reinforcement. In this way, the anode body can be placed on the reinforcement before pouring concrete or other materials. Therefore, the anode body is held in place with respect to the metal reinforcement and other adjacent metal reinforcements in order to better arrange a series of anodes with respect to the metal reinforcement. Alternatively, the hook member may be firmly connected to the anode body, and the threaded elongated member may be used to hold the anode body at a predetermined distance and orientation with respect to the metal reinforcement.

[0018] The configuration disclosed in this specification can be used with an anode body that includes an anode of a material that is not as expensive as the metal reinforcement and can be sacrificed.

[0019] Alternatively, in other embodiments, the voltage difference is generated by an electrical energy storage component having two poles for transmitting the current generated by the release of electrical energy, by electrically connecting one pole to the metal reinforcement, and by electrically connecting the other pole to the anode on the anode body.

[0020] According to one aspect of the present invention, a method for preventing corrosion and / or passivating a metal part in an ion-conductive material is provided, the method comprising: providing an anode for transmitting current to the metal part in the ion-conductive material; generating a voltage difference between the anode and the metal part so as to cause a current to flow through the ion-conductive material between the anode and the metal part to provide cathodic protection for the metal part; and providing an electrical component for limiting the current to a maximum value.

[0021] The above configuration provides a mechanical clamp for the anode body on the reinforcement. This configuration can provide the following advantages:

[0022] The contact acts so as to bite into the reinforcing bar; the contact makes sufficient connection even in cases where the surface of the reinforcing bar is not clean, such as being corroded or contaminated with concrete residues.

[0023] The clamp is adaptable to different reinforcing bar sizes / diameters and sizes / diameters caused by corrosion.

[0024] The clamp creates a firm attachment.

[0025] The clamp supports the anode body at a position spaced from the connection point.

[0026] Since the anode is held at a position not too close to the reinforcing bar with the anode, the mounting device promotes a more uniform current distribution, and thus most of the current flows more uniformly due to a reduction in differences in resistance.

[0027] The clamp does not rotate easily around the steel reinforcing bar like a wire wrap connection.

[0028] The clamp connection does not loosen as a result of any rotation of the anode body relative to the reinforcing bar.

[0029] The anode body does not rotate / lower its position due to gravity.

[0030] The mechanical clamp enables the installer to place the anode on selected reinforcing bars within the concrete / mortar part to be cast.

[0031] The connector has a standard threaded rod as a first abutment to enable the manufacture of the anode.

[0032] In a configuration using a power source, the connection acts to firmly connect one pole of the power source to the reinforcing bar and ensure that the other pole is spaced apart and does not contact the steel, because this would cause a short circuit, drain the battery, and not provide corrosion protection to the steel.

[0033] Different connectors can be provided for different size ranges.

[0034] Teeth or a knife / sharp edge can be provided within the opening of a cavity defined by a hook member for biting into the reinforcing bar.

[0035] The concave end and additional teeth on the end of the threaded rod can act to cut into the reinforcing bar.

[0036] These features ensure a safe, firm, physical and electrical connection.

[0037] According to another aspect of the present invention, there is provided a method for preventing corrosion and / or passivating a metal part in an ion-conductive material, the method comprising: providing an anode for transmitting a current to the metal part in the ion-conductive material; generating a voltage difference between the anode and the metal part so as to pass a current through the ion-conductive material between the anode and the metal part to provide cathodic protection of the metal part; and providing an electrical component for limiting the current to a maximum value.

[0038] According to another aspect of the present invention, there is provided an anode assembly for use in preventing corrosion and / or passivating a metal part in an ion-conductive material, the anode assembly comprising: an anode for transmitting an ionic current to the metal part in the ion-conductive material; an electrical energy storage component having first and second poles for transmitting a current generated by discharging electrical energy; a connector for electrically connecting the first pole to the metal part; including, the second pole being connected to the anode; the anode being arranged to be attached in ionic contact with the ion-conductive material such that an ionic current can flow from the storage component through the anode to the metal part; and the anode assembly includes an electrical component for limiting the current to a maximum value.

[0039] Preferably, in this configuration exposed to the maximum available voltage from the storage component, the current can be varied by the electrical component from a maximum value to a lower value according to the conductivity of the ion conductive material such that the component acts as a limiter rather than a regulator. Thus, the power draw by the limiter can be kept very low. The current is not maintained at a value higher than the natural value caused by the voltage of the electrical component and the intrinsic resistance of the system.

[0040] Thus, the electrical component acts to extend the life of a battery, or other power supply system, or a flowing current anode system that has a limited capacity and does not function after the limited capacity has been consumed.

[0041] Preferably, the electrical component includes a transistor, where the current through the transistor is limited to a maximum value. The transistor can be a conventional transistor or FET. In this configuration, preferably, the electrical component uses, as a reference voltage for the transistor, the voltage difference between the first and second poles, or the voltage difference between the anode and the metal part. Of course, this draws very little current, and as a result, the electrical component is configured to consume power of 1 μA or less. Thus, the circuit is very simple and can consist solely of transistors and resistors. Other low-power limiters are available, but typically, a high-power regulator is not suitable because it draws more current than is saved by the limitation of the current between the anode and the rebar. Additionally, in other configurations, a second sacrificial anode is provided and the electrical component uses the voltage difference between the two anodes and the resistor to generate a reference current for the electrical component.

[0042] Typically, the current can be limited within plus / minus 20%, 10%, 5%, 2% of the maximum value according to the stability of the voltage source, the gain of the transistor, and the resistance of the resistor.

[0043] Preferably, the electrical component forms part of a combined unit including an anode and a connector for connection to the reinforcing bars, for example forming a configuration of the type as described above.

[0044] Preferably, the above current limiter is associated with a single anode and operates only with respect to a single anode and is not part of a larger system that limits or regulates current to a plurality of anodes.

[0045] In one particularly preferred method, while the anode is installed and connected to the metal part, the ion-conductive material is removed, and the current limitation by the electrical component prevents the generation of gas during the curing of the ion-conductive material. The generation of gas during setting is a serious problem in that it forms bubbles in the concrete.

[0046] The configuration described herein can be used in a system in which a voltage difference is generated by electrically connecting one pole to the metal part and another pole to the anode by means of an electrical energy storage component having two poles for transmitting the current generated by the release of electrical energy. However, the same current limiting system and the same mechanical connection can be used with sacrificial anodes or impressed current anodes, and can also be used in a composite system in which both an impressed current anode driven by a power source and individual sacrificial anodes are present.

[0047] In this configuration, preferably, both the anode and the storage component are at least partially contained in or embedded in an ion-conductive material, typically concrete. In this configuration, preferably, the storage component is connected as a single unit to an impressed current anode or non-sacrificial anode and / or a sacrificial anode.

[0048] In this configuration, preferably, the storage component is contained within a closed or sealed canister that defines an anode on its outer surface. In this case, the anode can be made of stainless steel.

[0049] In this configuration, in some cases, in order to provide long-life replacement, electrical energy can be introduced by recharging the storage component or by replacing the storage component.

[0050] The storage component may be a battery or a battery of batteries, or it may be a capacitor.

[0051] Therefore, the above configuration provides a configuration that acts to limit the current between the anode and the reinforcing bar. This configuration can provide one or more of the following features:

[0052] It acts to regulate the current from the battery or the current anode.

[0053] It uses, as a reference voltage, the voltage difference across the energy storage device, or between the energy storage device and the steel, or between the current anode and the steel.

[0054] It provides a simple limiting system typically formed by only two components including a conventional transistor or FET and a resistor that determines the adjustment voltage of the transistor.

[0055] The circuit consumes very little power and can be less than 1 μA.

[0056] These have a limited capacity (limited stored energy) and do not function after the limited capacity is consumed, so they are ideal for battery or current anode systems.

[0057] The current can be limited over a wide range of circuit resistances from short circuit to resistance, where the available voltage is sufficient to provide the set current value.

[0058] The current can be adjusted within +20%, 10%, 5%, 2% depending on the stability of the voltage source (battery / anode).

[0059] The current limiter can be part of a composite unit including a battery or capacitor, or part of the anode and the connector.

[0060] The current limiter enables the installation of a battery / high-output anode in fresh concrete / mortar and connection to steel without the harmful effects of high current density discharge through a low-resistance fresh material. The cans are used to prevent gas generation (oxygen and hydrogen) during curing that produces gas bubbles, excretes, reduces bonding to steel, and leaves holes / capillaries in the concrete / mortar. Hole / cavity formation allows water and salts to penetrate and enables a direct path to the steel for CO2 to carbonize the concrete. All of these result in premature corrosion of the steel.

[0061] As described above, when the anode does not sacrifice itself to the metal part, typically the material is electropositive with respect to the metal part. However, some parts of the anode may sacrifice themselves, or the anode may be completely sacrificed.

[0062] The configuration herein can be used when the anode takes the form of a plurality of related anodes all connected to a battery or a battery of batteries.

[0063] An accumulation component as defined above may be a battery, a battery of batteries, or a battery of battery packs, or it may be a capacitor, a supercapacitor, or an ultracapacitor, which provides a system for charge accumulation different from that of a conventional electrolytic cell or battery. A supercapacitor is a high-capacity electrochemical capacitor with a much higher capacitance value than other capacitors. These capacitors typically have a lower voltage limit than standard or conventional capacitors. They can typically store 10 to 100 times more energy per unit volume or unit mass than standard capacitors, accept and deliver much more charge than batteries, and allow for many more charge-discharge cycles than rechargeable batteries. Supercapacitors do not use the conventional solid dielectrics of standard capacitors. Supercapacitors instead use electrostatic double-layer capacitance, or electrochemical pseudo-capacitance, or a combination of both. An electric double-layer capacitor uses carbon electrodes or derivatives with a much higher electric double-layer capacitance than electrochemical pseudo-capacitance to achieve charge separation in the Helmholtz double layer at the interface between the surface of the conductive electrode and the electrolyte. The charge separation is on the order of a few angstroms (0.3 - 0.8 nm), much smaller than the separation in conventional capacitors.

[0064] A supercapacitor is a significant advancement over ordinary capacitors in that it can store a high charge once fully charged. With a capacitance of 2.7V 200F, it can hold a charge exceeding approximately 500C (A×seconds). Since a typical cathodic protection system requires about 170 - 400C / m² of steel per day, such a capacitor, when fully charged, can provide sufficient charge to protect more than 1m² of steel in a day. This corresponds to a current density of 2 - 5mA / m². For example, to double this value, the capacitance needs to be doubled to approximately 400F. If the capacitor is charged daily, theoretically, a system utilizing supercapacitors of this size spaced apart to provide current to more than 1m² of steel can be an effective cathodic protection system. Daily recharging can be easily provided by solar panels, but other means, such as generating a moderately regular burst of current, may be used as a charging component for the supercapacitor. Examples of such means may be piezoelectric materials that can be incorporated into roads, parking lots, bridges, runways, etc., enabling the generation of current by the load and / or movement of structures or vehicles passing over them.

[0065] That is, piezoelectric materials may be used for electricity generation to directly power an external power supply system or to charge / recharge a battery or capacitor / supercapacitor.

[0066] In some embodiments, the anode is a sacrificial anode formed from a material less noble than the metal part to be protected. However, in other cases, the anode is not as noble as the metal part to be protected and is thus the same as or more noble than metal, typically steel; and is thus partially or completely inert during the process. If the anode is formed from an anode of a sufficiently inert material, it will not corrode significantly while electrons are flowing.

[0067] A high current output is required from a storage component such as a battery. As described above, one pole is connected to the metal part to be protected against corrosion. Electrons flow from the storage component to the metal part so that the corrosion of the metal part is reduced. The other pole is connected to the anode, or, if appropriate, the casing of the storage component itself can be used as the anode. In the case of a zinc alkaline battery, the polarization of the battery is such that the battery case acts as an anode when made of a suitable material and can distribute the required current through an ion-conductive material such as mortar or concrete. Most other batteries, such as lithium batteries, typically have only a small pole with an appropriate polarization that may not be large enough to transmit the required current to the ion-conductive material. A separate anode may be provided for connection to the appropriate pole. The anode may wrap or cover the entire storage component such as a battery or capacitor. The anode can be made of any inert conductive material such as MMO-coated titanium, or other precious metals, or sub-metals, conductive coatings, conductive ceramic materials, etc., and can be embedded in an inert material such as sand to which an alkaline mortar or alkaline solution can be added. Stainless steel can also become a suitable current carrier when embedded in a mortar or compacted sand to which an alkaline such as a saturated solution of lithium hydroxide has been added. The anode may also include a sacrificial material such as zinc that is less expensive than the metal part to be protected against corrosion.

[0068] Preferably, in some embodiments, the storage component is initially charged or continuously recharged during in-situ, i.e., while in contact with the ion-conductive material. The configuration may or preferably includes an automatic switching system to perform a periodic charging process. For example, the storage component can be charged by a solar cell or by an external power source such as a second battery or power supply. Also, in some cases, a system may be provided that operates to continuously, automatically, and repeatedly or periodically perform recharging.

[0069] In other cases, the storage component is continuously recharged by a rechargeable power source that is an integral unit comprising an anode and the storage component. However, the system may also operate as a periodic maintenance program in which the power source is periodically activated if needed to effect recharge of the anode assembly or set of anode assemblies in the structure.

[0070] Preferably, the storage component is continuously recharged by directly applying a voltage across both terminals or between a first connection to a terminal of the storage component and a second connection to a metal part.

[0071] In one configuration, the anode comprises a sacrificial anode material, or an anode that is sacrificial with respect to the metal part is associated with or in electrical contact with the body of the sacrificial anode material that causes a boost in current until the sacrificial anode material is consumed, after which current discharge is through that anode.

[0072] In one configuration, the storage component is connected and charged to the metal part during an initial charging step or during a subsequent recharge after installation by connection to one terminal and a second connection to the metal part. This connection method serves to direct excess current to the metal part during a charging or recharge step that passivates the metal part, or serves to maintain passivation of the metal part or reduce corrosion by reducing future current requirements.

[0073] Typically, a single unit comprising the storage component and anode(s) is at least partially embedded in an ionically conductive material. However, an attachment surface or other manner of application where the anode is in ionic contact with the material may be used.

[0074] In one particularly preferred configuration, the storage component includes a battery having an outer casing, where the outer casing is formed entirely or partially from the anode material, and thus the anode is formed by the outer casing of the same material or as a coating or layer on the outer surface of the outer casing. In this case, the outer casing or at least the outer layer can be formed from a material more precious than steel. In this configuration, the anode directly forms the outer casing of the battery, where the outer casing contains and houses the battery, the electrolyte, the anode material, and the cathode material of the other components of the battery. That is, in this embodiment, the anode is defined by a layer or coating on the outer surface of the storage component itself, or is actually the outer surface of the storage component and is not a separate additional element from the storage component. When the storage component is a battery, the outer casing of the battery can directly support the material of the anode, or the outer casing of the battery can even be the anode. The anode material can cover the entire surface or be a partial coating that exposes other areas.

[0075] In another case, the outer casing and the anode are formed independently, and the anode forms a separate body that conforms to the shape of the outer casing of the battery. Typically, such a battery is cylindrical, but other shapes can also be used. This configuration is particularly applicable when the battery is replaceable rather than rechargeable to take in additional energy after the original battery has been sufficiently depleted to be no longer effective.

[0076] In another case, the anode is a separate body that is electrically connected to one terminal of the storage component.

[0077] The above features can preferably be used for the corrosion protection of steel reinforcement members or structural members in concrete materials or mortar materials where it is well-known that corrosion can cause the collapse of concrete due to the expansion force of corrosion products and the decrease in the strength of steel. However, use in other situations can also occur.

[0078] As used herein, the term impressed current anode is intended to distinguish from sacrificial anodes, which are made of materials that are less noble than the metal parts and corrode preferentially over the metal parts to be protected, typically zinc. An impressed current anode is an anode that is used in conjunction with an external power source and need not be less noble than the metal parts. Typically, such impressed current anodes can be made of titanium, platinum, niobium, carbon, and other noble metals and oxides that do not corrode easily, or can be made of less noble substances such as iron or zinc.

[0079] With respect to use between the sacrificial or galvanic phases of operation of the above method, the ion-conductive filler preferably contains at least one activator to ensure continuous corrosion of the sacrificial anode. However, the activator can also be placed elsewhere in the system. Suitable fillers can be in solid, gel, or liquid form.

[0080] Gels can include carboxymethyl cellulose, starch and their derivatives, fumed silica or polymeric gel electrolytes such as bentonite, propylene carbonate, and / or acrylic acid in an aqueous potassium hydroxide solution or polyvinyl chloride / acetate-KOH composite material with added alumina. The alkali hydroxides in these gels act as suitable activators.

[0081] Suitable activators include alkali hydroxides, wetting agents, catalytic materials, and other materials that are corrosive to the sacrificial anode metal. The activators can be used alone or in combination.

[0082] With respect to use between the sacrificial or galvanic phases of operation of the above method, the ion-conductive filler preferably has a sufficiently high pH to cause corrosion of the sacrificial anode and avoid the formation of a passive film on the sacrificial anode. Alternatively, the filler can have a lower pH and / or contain other activators for causing corrosion of the sacrificial anode and avoiding the formation of a passive film on the sacrificial anode.

[0083] The anodes and methods of this specification are preferably designed for use when the metal part is steel and the ion-conductive material is concrete or mortar.

[0084] An anode device comprising an impressed current component and a sacrificial component is typically embedded in concrete or other solid material so as to be completely encapsulated by the concrete or filling, but this is not essential, and the anode may be merely partially embedded or may be in physical or ionic contact with the concrete, either directly or indirectly.

[0085] An anode device comprising an impressed current component and a sacrificial component may be surrounded by a sealing material or an ion-conductive filling which may be a porous material or a porous mortar material. Suitable sealing materials may be inorganic or organic and may be any ion-conductive cementitious polymer, non-cementitious material, or geopolymers, or a mortar containing modified Portland cement. The sealing material may be solid, gel, or liquid and may be deformable.

[0086] The power source may include a solar panel for driving an impressed current anode and a rechargeable galvanic anode to provide long-term corrosion protection when solar power generation is intermittent.

[0087] The structures and methods proposed herein are designed assuming in particular the case where the metal part is steel and the ion-conductive material is concrete or mortar. However, the same configuration may be used in other corrosion protection systems such as pipes or other structures in the ground and in many other systems where such anodes can be used.

[0088] Preferably, the assembly includes a reinforcing layer as disclosed in U.S. Patent No. 7,226,532, issued to Whitmore on June 5, 2007, the disclosure of which is incorporated by reference or referred to for further details not disclosed herein to inhibit and resist forces such as expansion, contraction, and distortion forces that can be caused by corrosion of the anode, deposition of sacrificial anode ions, and other physical / environmental forces such as freezing, thawing, wetting, drying, and thermal expansion / thermal contraction.

[0089] The invention defined and described herein can also be provided as an assembly, as opposed to a method for cathodic protection and / or passivation of the metal portion of an ion-conductive material. Accordingly, the following definitions of the invention presented herein are included herein. Each of these independent definitions can be used in conjunction with one or all of the dependent features as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Here, embodiments of the invention are described with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Figure 5

[0091] In the figures, references to similar features indicate corresponding parts in different figures.

DETAILED DESCRIPTION OF THE INVENTION

[0092] In the example shown in FIG. 1, a battery that may be rechargeable is provided, as shown in co-pending application Ser. No. 15 / 341532, filed Nov. 2, 2016, the disclosure of which may be referenced or incorporated herein by reference, or it may be a simple non-rechargeable battery. The battery may form part of the anode structure or the anode and the battery may be physically separated. As shown in FIG. 1, the anode body (10) is defined by typical alkaline manganese dioxide-zinc, and the rechargeable battery includes the following main units: a steel can (12) defining a cylindrical internal space, a manganese dioxide cathode (14) formed by a plurality of hollow cylindrical pellets (16) pressed into the can, a lead anode (18) made of an anode gel and disposed inside the hollow of the cathode (14), and a cylindrical separator (20) separated from the cathode (14). The ionic conductivity (electrolyte) between the anode and the cathode is provided by the presence of potassium hydroxide, KOH, electrolyte added to the battery in a predetermined amount. Other types of rechargeable batteries include similar main components (can, cathode, anode, separator, and electrolyte), but the composition of the components may be different. However, some types of batteries may have different structures such as lead-acid batteries or lithium batteries.

[0093] The bottom of the can (12) is closed and has a central circular pipette (22) that serves as the positive terminal. The upper end of the can (12) is sealed airtight by a battery closure assembly that includes a negative cap (24) formed of a thin metal sheet, a current collector (26) attached to the negative cap (24) and penetrating into the anode gel to provide electrical contact with the anode, and a plastic top (28) that electrically insulates the negative cap (24) from the can (12) and separates the gas layers formed across the cathode and anode structures, respectively.

[0094] The material of the separator (20) consists of two different materials, namely: a first material (30) made of a fibrous sheet material wettable by the electrolyte, and a second material (32) that does not allow small particles to pass through but retains ion permeability. A material advantageous for the first layer is a sheet material of absorbent non-woven polyamide fibers that serves as a reservoir for the electrolyte. The macroporous structure of the absorption layer cannot prevent internal short circuits by zinc dendrites or deposits during the discharge / charge cycle.

[0095] The short circuit is prevented by the second material (32), which may be a layer (s) of a microporous or non-porous material that can be thinly stretched or coated onto the fibrous sheet material. One suitable material is one or more cellophane membranes thinly stretched onto a non-woven polyamide sheet. Another suitable material is one or more coatings of regenerated cellulose or viscose that are coated onto and partially penetrate into the non-woven polyamide sheet, resulting in a composite material.

[0096] Other types of rechargeable batteries may be used. In this configuration, the type described above is used in a method for cathodic protection and / or passivation of metal parts such as steel reinforcing bars (40) of ion-conductive materials such as concrete (41). Thus, the battery includes a first terminal (42) and a second terminal (43) defined by an outer casing (12). The first terminal (42) is connected to a pin or claw (26) that engages the anode material (18). The terminal (42) extends from the terminal (42) for a final connection to the steel reinforcing bar (40) shown in FIG. 1 through a mounting assembly generally indicated at (50) where the anode body is mechanically and electrically attached to the steel reinforcing bar (40), and is connected to a connecting wire (42A).

[0097] In FIG. 1, the anode (44) is applied as a coating on the casing (12) of the battery. In this embodiment, the anode (44) is an inert material and is thus more noble than steel. Examples of such materials are well known. Thus, during the cathodic protection process, the anode material (44) does not corrode or corrodes significantly less.

[0098] In this configuration, the application of the anode (44) on the outer surface of the casing (12) provides a structure as a common single unit where the anode is directly connected to the battery and forms an integral element with the battery. The anode (44) may include one or more layers and may include a layer of mixed metal oxide (MMO), catalyst, or sub-oxide.

[0099] In this embodiment, since the anode (44) is formed from an inert material that does not corrode during the corrosion protection process, the anodes and batteries included herein can be directly incorporated into, or embedded in, concrete or other ionically conductive materials, such as a porous mortar matrix, without the need for an intervening sealing material. Since there are no corrosion products, there is no need to absorb such products or the expansion forces created thereby. The process is not dependent on the continuous corrosion of a sacrificial anode, so no activator is necessary on the surface of the anode. Since the chemical reaction on the surface of the insoluble anode during operation produces an acid (or consumes an alkali), it is beneficial to embed the anode in an alkaline material such as concrete or highly alkaline mortar that prevents the material near the anode from becoming acidic. If desired, additional alkali may be added to the concrete or other material with which the anode is in contact.

[0100] The apparatus shown herein generally includes an anode body, indicated generally at (10), which is coupled to the reinforcing bar (40) by a mounting assembly, indicated generally at (50). Additionally, the anode body generally includes a current limiting system, indicated generally at (51), which restricts the flow of current from the anode body to the reinforcing bar (40).

[0101] As described above, the anode body can typically be defined by a power source in the form of a battery having an anode (44) on the outer surface of the battery and other terminals of the battery provided at the ends of the battery for connection to the reinforcing bar (40).

[0102] In other embodiments described below, when the anode body includes a sacrificial material that is not as expensive as steel reinforcing bars, such as zinc, the battery can is optional, where the voltage between the anode and the reinforcing bar includes the voltage of direct current electricity between the two metal components.

[0103] In yet other embodiments, the anode body can include a combination of both an impressed current anode and a sacrificial anode. In this way, when the anode is ionically connected to the concrete, a voltage difference is generated between the anode (44) and the reinforcing bar (40), whereby the anode is configured and arranged to pass a current through the concrete between the anode and the reinforcing bar (40) to provide corrosion protection and / or passivation of the reinforcing bars of the concrete.

[0104] In the embodiments shown in FIGS. 1, 3, and 4, the mounting assembly (50) includes a first abutment (52) in the form of a threaded rod (53) attached at one end to the anode body (10). The opposite end (54) of the threaded rod forms a front face for engaging one side of the reinforcing bar (40). As shown in FIGS. 2 and 4, the end face (54) of the threaded rod (53) includes a peripheral annular end (55) and intervening protrusions (56) arranged to bite into the face of the reinforcing bar (40) upon compressive contact.

[0105] The mounting assembly (50) further includes a second abutment (57) for generally engaging the opposing face of the reinforcing bar (40) at the face (59). Generally, the second abutment forms a hook member that contacts the opposing or rear face of the reinforcing bar (40) at at least two positions (59) and (60) on either side of a diameter (61) extending through the reinforcing bar (40) from the face (54). In this way, the reinforcing bar (40) contacts three tips (54), (59), and (60) spaced at regular intervals about the axis (62) of the reinforcing bar system to provide a stable engagement.

[0106] The hook member defined by surfaces (59) and (60) forms part of a C-shaped structure (63) with a bottom cross member (64) and an upper cross member (65) that support the surfaces at (59) and (60). These cross members are interconnected by extending legs (66) that extend parallel to the threaded rod (53). The cross member (64) includes a flange (67) perpendicular to the threaded rod (53) having a threaded hole (68) through the flange. The flange acts as a nut on the threaded rod, and thus rotation on the threaded rod drives the nut towards the anode body, pulling surfaces (59) and (60) towards surface (54) and clamping the reinforcing bar (40) therebetween.

[0107] Surfaces (59) and (60) can also be formed with teeth or other protrusions (59A), or sharp edges (59B), that bite into the surface of the reinforcing bar and cooperate with the teeth (55) and (56) of surface (54). In this way, a strong physical connection is provided between the first and second abutments and the reinforcing bar (40), and further, a strong electrical connection is provided between the rod (53) and the reinforcing bar (40). These teeth or sharp edges on some or all of the contact surfaces can bite into any contaminants such as corrosion or concrete residues on the surface of the reinforcing bar to ensure effective engagement and electrical contact with the metal of the reinforcing bar. That is, each of the first and second abutment members includes a component for cutting into the surface of the reinforcing bar, thus avoiding the need to clean the surface of the reinforcing bar.

[0108] According to another independent feature of the present invention, a sensor can be provided to measure the effectiveness of the connection to ensure the necessary engagement with the metal of the reinforcing bar by the protrusions and blades. This can be done, for example, by measuring the resistance across the connection by bridging a point on the connection with the reinforcing bar such that the resistance of the connection reliably meets the required low level of resistance. This output is provided to an indicator to output an indication to the installer, for example visually or audibly, regarding whether the connection properly meets the set criteria.

[0109] The hook member can include a single object on one side of the rod (53). However, as best shown in FIG. 4, the hook member is typically formed by two separate hook portions (68) and (69) connected by a rear plate (70). In this way, the rod (53) is included between the portions of (68) and (69) and in the rear plate (70). Each of the hook portions of (68) and (69) includes surfaces (59) and (60) that engage the rear surface of the reinforcing bar (40). Thus, the force pulling the second abutting member toward the anode body pulls on both hook portions and on both surfaces (59) and (60), providing four engagement points that cooperate with a single point of engagement from the surface (54) of the rod (53).

[0110] In this embodiment, the female threaded portion is provided by a threaded hole passing through the flange (67). Thus, the threading action of pulling out the second abutting member toward the anode body is provided by rotating the rod (53). This can be most effectively done by manually grasping the anode body and using it as a handle to rotate the rod (53). Of course, this requires a strong connection between the bottom end of the rod (53) and the anode body. In the configuration shown in FIG. 2, this connection is provided by a base plate (71) attached on the bottom end of the rod (53), which engages firmly on the upper end of the anode body. In a configuration using a solid anode (74) of sacrificial material, the rod (53) can be cast inside the anode body to provide the required structure and electrical connection. In FIG. 3, the solid anode object (74) includes a conventional covering of mortar material (75) to hold corrosion products and support the conventional active materials described above in this specification.

[0111] In another configuration (not shown), the female threaded portion engaged with the rod (53) can be formed by a separate nut that can rotate itself relative to the second abutting member (67) on the flange. In the present embodiment, instead of rotating the rod, the nut can be rotated to drive the flange (67) towards the anode body. Other configurations of the screw connection can also drive the second abutting member towards the anode body. In other examples, the hook is part of the anode body, and the screw is rotated to press the reinforcing bar against the hook.

[0112] Turning now to FIG. 2, the connection between the terminal (42) of the battery and the rod (53) electrically connected to the above-mentioned reinforcing bar (40) is shown in more detail.

[0113] The terminal (42) is connected to a wire (42A), and the wire (42A) is connected to a transistor (78).

[0114] The output wiring (79) of the transistor (78) is connected to a base plate (71) connected to the rod (53). The transistor (78) can be a conventional transistor, in which case the base of the transistor (78) has a control current provided by a wire (80) connected through a resistor (81) connected via a wire (82) to the positive terminal of the battery connected to the anode (44).

[0115] The transistor (78) can also be a FET, in which case the wire (80) controls the gate of the FET via a resistor (81).

[0116] Since the transistor (78) is connected to the steel reinforcement (40) and the wire (82) is connected to the anode (44), the control current to the transistor (78) is determined by the voltage across the battery and the resistance of the resistor (81). Since this voltage is typically relatively constant until the battery reaches the end of its life, this constant control current controls the amount of current flowing from the battery, through the transistor, to the steel reinforcement (40). As is well known, the resistor (81) can be selected to provide current based on the control of the transistor that sets the maximum value of the current flow through the transistor. This maximum value is maintained regardless of the conductivity between the anode (44) and the steel reinforcement (40) through the concrete. If the conductivity through the concrete is very high, such as during initial installation, the current is maintained at the maximum value. As the conductivity through the concrete drops to a lower level, the current is maintained at a desirable level until the maximum voltage of the battery is reached. As the conductivity drops to an even lower level, the current through the transistor further decreases according to the conductivity and is not maintained by the operation of the transistor. Thus, the combined circuit provided by the resistor and the transistor does not act as a regulator but instead acts only as a current limiter.

[0117] Figures 2A and 2B show the application of a current limiting device used with a galvanic anode.

[0118] Figure 2A shows a galvanic anode (86) connected to a transistor (78). An individual battery (87) is connected to the resistor (81) and to the transistor (78) to provide a control current to the transistor to control the maximum current flowing into the steel reinforcement (40).

[0119] Figure 2B shows a galvanic anode (88) connected to a transistor (78). In this case, the control current to the transistor is provided by a second galvanic anode (89) and the resistor (81). As in the above example, the control current controls the maximum current flowing into the steel reinforcement (40).

[0120] Figure 2C shows a current limiting circuit for use with a system in which both an applied current anode (10) having a battery supply and a galvanic anode (90) are used, and the voltage across resistor (81) is used to control FET (78). The outputs from anode (10) and anode (90) are added downstream of the FET, or the current from anode (10) generated by the battery is limited using the current limiting circuit. Thus, the current from the applied current anode is used to "top up" the current from the galvanic anode to maintain a current suitable for providing the necessary corrosion protection. As is known, the current from anode (90) can vary in response to the changing state of the concrete so that it is only used when top-up from the battery is required. Since the current obtained from the battery is limited, the system can be designed to match the life of the battery to the life of anode (90).

[0121] When the electrical circuit includes a normally-closed FET, the FET can prevent current flow from the galvanic anode (86) to the reinforcing steel (40) after the above-mentioned separate battery or separate galvanic anode has stopped functioning.

[0122] This limitation of the current to the maximum value set during manufacture by the selection of resistor (81) can ensure that the current remains at a relatively low level during the life of the system, and thus can dramatically increase the life of the battery compared to typical values in the absence of a current limiter, which can be, for example, a more appropriate life of from about 1 year to a maximum of 10 years. Thus, the current is maintained at a value such that there is no excessive current above this desirable value which would be suitable for cathodic corrosion protection but could damage the concrete or empty the battery prematurely and not provide corrosion protection within the desired time frame.

[0123] This configuration is particularly valuable with respect to configurations that use a non-sacrificial impressed current anode and a battery as a power source for generating the required voltage. In such configurations, the current generated between the anode (44) and the reinforcing bar (40) can, in some cases, significantly exceed the desired value. Additionally, the mechanical attachment of the anode body to the reinforcing bar provides an effective electrical connection. Further, the strong physical connection between the anode body and the reinforcing bar ensures that the anode body can be placed in a desired orientation with respect to gravity, for example, that the anode body is on one side of the reinforcing bar or on top of the reinforcing bar as required.

[0124] To connect the terminal (42) to the rod (53), an insulating or protective collar (83) surrounding the transistor (78) and the resistor (81) is provided. The bottom end of the collar is attached to the top end of the battery, and the top end of the collar receives the base plate (71) at an appropriate receptacle portion. The collar (83) is attached to the battery (44) by surrounding it with an insulating layer (84) of a suitable plastic material. Inside the collar (83), a conventional potting material (85) is provided, which surrounds the electrical components and wires to maintain the connection and prevent damage from moisture penetration. The structure is thus strong enough to ensure that the base plate (71) is securely attached to the battery in a manner that allows the battery to be manually grasped and rotated as an operating handle to rotate the rod (53).

[0125] As shown in FIG. 5, generally, the anode body indicated by (90) is installed within the patch repair (91) of the concrete material (92). The anode body includes a mounting assembly (50) as described above, including a rod (53) and a hook portion (57). In this embodiment, the anode body (90) is made from a battery (93) and a sacrificial material portion (94). The battery (93) has an outer surface (95) that acts as an impressed current anode. The battery has a terminal (96), and the terminal (96) is attached by a wire (97) that includes a diode (98) that sends voltage from the terminal (96) to the rod (53). During initial operation, thus the system operates mainly as an external power source mode, where the battery generates most of the current flowing between the anode of (95) and the reinforcing bar (40). However, when the battery runs out, the cathodic protection is taken over by the sacrificial anode (94) that is directly connected to the rod (53). In this configuration, the diode (98) can act to reverse the sacrificial process and prevent the backflow of current through the battery (93) that would otherwise corrode the steel more aggressively. The battery (93) and the anode (94) are appropriately connected by a structural mounting element (99) that is only schematically shown, and the structural mounting element (99) is physically attached to the anode (94) sufficiently to prevent the battery from detaching from the anode during installation.

[0126] As shown in FIG. 5, the anode body (90) stands outwardly towards one side of the reinforcing bar (40) within the patch. In this way, the anode body is supported at a position spaced from the reinforcing bar (40) defined by the length of the rod (53) and the mechanical connection of the clamp assembly. The mechanical connection of the clamp assembly ensures that the anode body remains in its horizontal extension direction during filling of the patch (91) with additional concrete. During the setting of the additional concrete, the above current limiting system prevents the generation of gas on the surfaces of the anode and the reinforcing bar that could enter the setting concrete and cause significant damage to the concrete.

[0127] Various modifications may be made to the invention as described hereinabove, and since clearly different embodiments thereof may be made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification be interpreted as illustrative only and not in a limiting sense.

Claims

1. A method for cathodic protection and / or passivation of steel reinforcing members of an ionically conductive concrete or mortar material, the method comprising: providing an anode for conducting electrical current to the steel reinforcing member of the ionically conductive concrete or mortar material; generating a voltage difference between the anode and the steel reinforcing member to cause an electric current to flow through the ionically conductive concrete or mortar material between the anode and the steel reinforcing member to provide cathodic protection of the steel reinforcing member; the anode is an impressed current anode; generating, wherein the voltage difference is generated by a discharge of electrical energy and by an electrical energy storage component having two poles for carrying a current generated by electrically connecting one pole to the steel reinforcing member and another pole to the anode; providing a current limiting component that limits the current to a maximum value and allows the current to vary from the maximum value to a lower value depending on the conductivity through the ionically conductive concrete or mortar material; The method wherein the anode and the storage component are both at least partially contained in the ionically conductive concrete or mortar material.

2. The method of claim 1, wherein the current limiting component has a limited capacity and does not function after the limited capacity is consumed, thereby acting to extend the life of the storage component.

3. A method as described in claim 1 or 2, wherein the current limiting component includes at least one conductor and a transistor, and the current passing through the transistor is limited to a maximum value.

4. The method of claim 3, wherein the current limiting component comprises the at least one conductor, the transistor and a resistor.

5. The method described in claim 3 or 4, wherein the transistor is a FET.

6. A method described in any one of claims 1-5, wherein the current limiting component is configured to consume less than 1 μA of power.

7. A method according to any one of claims 1-6, wherein the current is limited to within 20% of the maximum value depending on the stability of the voltage source.

8. A method according to any one of claims 1-7, wherein the current limiting component forms part of a composite unit including the anode and a connector.

9. A method according to any one of claims 1-8, wherein the current limiting component is associated with a single anode and operates only with respect to a single anode.

10. A method according to any one of claims 1-9, wherein the storage component is connected to the anode as a single unit.

11. A method according to any one of claims 1-10, wherein the storage component is contained within a closed or sealed canister defining the anode on an outer surface thereof.

12. A method according to any one of claims 1-11, wherein the replacement electrical energy is introduced by recharging the storage component.

13. A method according to any one of claims 1-12, wherein replacement electrical energy is introduced by replacing the storage component.

14. The method of claim 1, wherein the anode comprises stainless steel.

15. A method according to any one of claims 1 to 14, wherein a second anode of a material less noble than the steel reinforcing member metal part is provided, thereby generating a galvanic voltage difference between said second anode and the steel reinforcing member metal part, and passing a current between said anode and said steel reinforcing member metal part through said ionically conductive concrete or mortar material to provide cathodic protection of said steel reinforcing member metal part, and said current limiting component uses the voltage difference between one anode and said steel reinforcing member metal part and a resistor to generate a reference current for said current limiting component.

16. A method for cathodic protection and / or passivation of steel reinforcing metal parts of an ionically conductive concrete or mortar material, the method comprising: providing an anode for conducting electrical current to the steel reinforcing member metal portion of the ionically conductive concrete or mortar material; the anode is an impressed current anode; generating a voltage difference between the anode and the steel reinforcing member metal portion so as to cause an electric current to flow in the ionically conductive concrete or mortar material between the anode and the steel reinforcing member metal portion to provide cathodic protection of the steel reinforcing member metal portion; providing an electrical component that limits the current to a maximum value; A method wherein the storage component is contained within a closed or sealed canister defining said anode on an exterior surface.

17. The method of claim 16, wherein a second sacrificial anode is provided for transmitting current to the steel reinforcing member of the ionically conductive concrete or mortar material.

18. A method as described in claim 16 or 17, wherein the current limiting component acts to extend the life of the storage component, which has a limited capacity and is non-functional after the limited capacity is consumed.

19. A method according to any one of claims 16-18, wherein the current limiting component includes at least one conductor and a transistor, and the current passing through the transistor is limited to the maximum value.

20. The method of claim 19, wherein the current limiting component comprises the at least one conductor, the transistor, and a resistor.

21. The method described in claim 19 or 20, wherein the transistor is a FET.

22. A method as described in any one of claims 16-21, wherein the current limiting component is configured to consume less than 1 μA of power.

23. A method according to any one of claims 16-22, wherein the current is limited to within 20% of the maximum value depending on the stability of the voltage source.

24. A method according to any one of claims 16-23, wherein the current limiting component forms part of a composite unit including the anode and a connector.

25. A method according to any one of claims 16-24, wherein the current limiting component is associated with a single anode and operates only with respect to a single anode.

26. The method of claim 16, further comprising a storage component connected to the anode as a single unit.

27. The method of claim 26, wherein the replacement electrical energy is introduced by recharging the storage component.

28. A method according to any one of claims 16-26, wherein replacement electrical energy is introduced by replacing the storage component.

29. The method of any one of claims 16-28, wherein the anode comprises stainless steel.

Images