Cathode corrosion protection using current limiter

Abstract

SOLUTION: In a method for cathodically protecting and / or passivating a metal section in an ionically conductive material such as steel reinforcement in concrete or mortar, an applied current or sacrificial anode communicates ionic current to the metal section and a storage component of electrical energy which can be a cell, battery or capacitor is provided as a component of the anode. A current limiter is provided which prevents excess current from draining from the supply. This can be a semi-conductive device such as a transistor or diode, and is connected in the path from the anode to the metal section to limit the cathodic protection current to a value of the order of 1 mA. When a diode or similar device is used, the current can be limited to the reverse leakage current of the diode.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for cathodic corrosion protection and / or passivation of metal parts in ion-conductive materials, and particularly to a configuration for restricting the supply of current by an anode assembly.

Background Art

[0002] Applied current systems using batteries are known. In such applied current systems, other types of power sources may be used, such as a general-purpose rectifier that rectifies an AC voltage from a suitable power source to obtain the DC voltage required for the applied current between the anode and the steel. In this type of system, it is also known to provide a solar panel for use.

[0003] In any case, in such an applied current system, it is necessary to regularly perform maintenance and check the power supply status so that unexpected and unacceptable corrosion or over-corrosion does not occur on the steel to be protected in the structure due to a power supply failure. Although such maintenance can be performed, it is a relatively costly process.

[0004] Alternatively, a galvanic system may be used. The galvanic system provides a voltage between the steel and the anode by selecting an appropriate material for the anode that has sufficient electro-negativity so that it can reliably generate current to achieve corrosion protection and thus does not require any power source.

[0005] When used in steel reinforced concrete, ordinary galvanic anodes have two important drawbacks. The first is related to the mass of zinc per anode, which limits the service life of the anode according to the required current output. The second is the actual current output of the anode, which may be sufficient or insufficient to stop the corrosion of the steel. The current output is limited by the driving voltage, which is an essentially fixed characteristic and varies depending on the exposure conditions, the age of the anode, and the resistance of the circuit affected by the accumulation of corrosion products over time.

[0006] Furthermore, U.S. Patent No. 8,961,746 (Sergi) issued on 24 February 2015, U.S. Patent No. 8,968,549 (Sergi) issued on 3 March 2015, and U.S. Patent No. 7,264,708 (Whitmore) issued on 4 September 2007 are cited, and the disclosures of those documents are incorporated herein by reference or may be referenced for more relevant information. [Overview of the project]

[0007] According to a first aspect of the present invention, a method is provided for cathode protection and / or passivation of a steel member in an ion-conducting concrete or mortar material, the method being A step of providing an anode structure that transmits electric current to a steel member in an ion-conducting concrete or mortar material, A process to generate a potential difference between the anode structure and the steel member so that an electric current flows between the anode and the steel member via an ion-conducting concrete or mortar material, in order to achieve cathode corrosion protection of the steel member, A step of providing at least one conductive circuit between the anode structure and the steel member, The process includes a step of providing a field-effect transistor (FET) in a conductive circuit, wherein the field-effect transistor (FET) acts as a current regulating element that limits the current between the steel member and the anode structure to a maximum value.

[0008] Current regulating elements are often called constant current diodes and typically use field-effect transistors, but other configurations may be used.

[0009] A resistor is provided in parallel with the constant current diode according to the important performance characteristics that allow it to be used independently as described herein.

[0010] According to another aspect of the present invention, a method is provided for cathodic protection and / or passivation of steel elements in an ion-conducting concrete or mortar material, the method being A step of providing multiple anode structures that transmit electric current to steel elements within an ion-conducting concrete or mortar material, at intervals within the concrete or mortar material, The process of installing a DC power supply, A step of connecting a DC power supply in parallel to each anode structure so that a current flows between each anode structure and the steel element via an ion-conductive concrete or mortar material, thereby generating a potential difference between each anode structure and the steel member, in order to achieve cathode corrosion protection of the steel element, The method includes the step of providing a conductive circuit between each anode structure and a DC power supply, wherein the conductive circuit acts to limit the current passing through each anode structure to a maximum value.

[0011] In a preferred embodiment, each conductive circuit includes a field-effect transistor (FET) which acts as a current regulator that limits the current between the steel element and the anode structure to a maximum value.

[0012] A resistor is provided in parallel with the current regulating element according to the important performance characteristics that allow it to be used independently as described herein.

[0013] In a configuration where multiple individual anodes are provided within a body of ion-conducting concrete or mortar material and connected in parallel to a DC power supply, numerous known problems may arise, as follows: (a) The current from each anode is distributed non-uniformly depending on the installation environment around each anode. (b) It is difficult to design the required current level for each individual anode, and the current output must be designed for the anode region, resulting in an uneven distribution of current to the steel to be protected within each region. (c) Individual anodes are subjected to high voltages, thereby creating regions with high anode current densities, resulting in acid formation at the anode / mortar interface and / or anode destruction. (d) If individual anodes are accidentally positioned adjacent to or in contact with the steel, a short circuit occurs, and as a result, most of the active current in the anode region is discharged to this one contact point. (e) To avoid short circuits, strict quality control is required during installation to ensure that the anode is positioned as far away from the steel as possible, resulting in a costly process.

[0014] The present invention provides a variety of features. (a) The current regulating element operates as a "constant current" control for one or more anodes. (b) The current regulating element is a diode or a PN junction element, and the regulated current is the leakage current through the element. (c) The current regulating element is a constant current diode (CRD). (d) The CRD includes a FET that controls the current. (e) A resistor in parallel with the CRD controls the current output using different voltages. (f) The CRD can be selected for a specified maximum operating current density (e.g., 110 mA per square meter of anode surface, as recommended by ISO 12696-2016), and can be increased to up to 220 mA per square meter of anode surface in the short term by adding a resistor in parallel and changing the voltage as needed. (g) The controlled current limits the effect of a short circuit if the anode is accidentally positioned adjacent to or in contact with the steel. (h) The controlled current reduces the generation of acid at the point anode. (i) Because the current is controlled, if a point anode in a region or a series of point anodes fails or is damaged, the rest of the system is not affected, and each of the other anodes still generates the same amount of current as before.

[0015] The anode current control systems disclosed herein can be used with individual anodes, multiple separate anodes, or mesh anodes or ribbon anodes.

[0016] For example, a 1 mA CRD may be used in parallel with a resistor and can increase the current when a voltage is applied. Using this configuration, a current can be applied to temporarily limit it to 220 mA per square meter of the anode surface or other desired currents as permitted by ISO 12696-2016.

[0017] In a configuration using four steel bars provided in a parallel array and four ribbon strip anodes provided at the four corners of the array, a 0.1 mA CRD connected to each ribbon was attached between the DC power supply and the anode. The fourth ribbon had a 50 kΩ resistor in parallel with the CRD. A maximum of 10 V was applied between the anode and the steel.

[0018] For anodes 1 to 3, even when the voltage increased from 1 V to 10 V, the current was controlled to a nominal 0.1 mA (anode 1 was 0.1 mA to 0.13 mA, anode 2 was exactly 0.07, and anode 3 was 0.11 mA to 0.12 mA). For anode 4, since the current could pass through the resistor, it increased proportionally with the increase in voltage and exceeded that range, reaching a maximum of 0.26 mA at 10 V (an increase of about three times from 0.09 mA at 1 V). Regardless of which bar was used, if any of the anodes short-circuited, the anode was found to continue carrying the same amount of current.

[0019] In a configuration using only the CRD without adding a resistor, there are the following advantages. (a) The current from each anode is accurately adjusted to the required current over a wide range of applied voltages. (b) For any short circuit from an anode to the steel, the current carried from the short-circuited anode does not increase and does not affect the current carried from any other anode within the same area / series. (c) Since each anode carries the same controlled level of current, the current is better distributed in the steel. (d) If any anode fails, it has no harmful effect on the remaining anodes within the same area.

[0020] By using a further built-in resistor in parallel with the current regulating element, an adjustable and optimal current distribution can be ensured by adjusting the applied voltage.

[0021] If the CRD is not attached to a series of dot anodes in a region, each individual anode carries a variable current to the surrounding steel according to the conductivity of the local concrete, and as a result, the current is distributed unevenly. This is often addressed by selecting a smaller region according to the local concrete environment. By introducing the CRD, the current output of each anode can be controlled to a preset desired level, so that the steel can reliably receive a more evenly distributed current, and the influence of the conductivity of the local concrete is minimized. As a result, especially by selecting an appropriate CRD, an anode in a low-conductivity part is selected to carry a higher current locally, so the size of the region can be increased.

[0022] In one configuration, the resistance of the CRD circuit is used to generate a control current or a control voltage from the potential difference between the anode and the steel member.

[0023] In one configuration, the anode structure and the CRD form a component of a general-purpose body, and this general-purpose body is at least partially buried or attached as one unit to a concrete material or a mortar material.

[0024] In one configuration, the potential difference between the anode structure and the steel member is used to generate a reference voltage or a reference current of the CRD.

[0025] In one configuration, the general-purpose body is buried in the concrete material or the mortar material while the concrete material or the mortar material is not yet coagulated, and the concrete material or the mortar material coagulates together with the general-purpose body therein. During the coagulation of the concrete material or the mortar material, a current limiting element that limits the current to a maximum value restricts the formation of air bubbles in the steel member and / or the anode in the concrete material or the mortar material.

[0026] In one configuration, the anode structure includes a sacrificial anode. In this configuration, a CRD can be provided as a general-purpose structure along with the anode, as described above. In this case, the CRD is attached to a connecting wire extending from the anode body to connect to the steel. Thus, the anode has the connecting wire portion embedded within its body, the connecting wire portion is attached to one terminal of the CRD, and the other terminal of the CRD is attached to another wire portion extending from the CRD to one end to connect to the corrosion-resistant steel. The CRD is embedded in the mortar material surrounding the anode body using a connecting wire extending outward from the mortar layer. Other connection configurations, including a threaded rod portion and two wire connectors, can also be used.

[0027] In one configuration, the anode structure includes a sacrificial anode and an applied current anode, and a potential difference is generated between the sacrificial anode and the steel member so that a first current flows between the first sacrificial anode and the steel member via an ion-conducting concrete or mortar material to achieve cathode corrosion protection of the steel member, and a second current is generated by an electrical energy storage element having two electrodes, which transmits a second current generated by releasing electrical energy by electrically connecting one electrode to the steel member and the other electrode to the second anode.

[0028] In this configuration, the storage element can be housed in a sleeve or canister that defines the anode on the outer surface. In this configuration, the applied current anode may include stainless steel.

[0029] Preferably, the transistor is a normally closed transistor, and if the control voltage or control current falls below a threshold, the transistor can continue to pass current between the anode and the steel member.

[0030] Preferably, the transistor is an FET with a source and a drain, and the current through the FET is controlled by the gate voltage.

[0031] In this configuration, the gate voltage may be generated by the resistance of the electrical circuit.

[0032] In this configuration, the gate voltage may be generated by a resistor across the transistor.

[0033] In this configuration, the gate voltage may be generated across a battery connected between the anode and the transistor.

[0034] In this configuration, the gate voltage may be generated by a sacrificial anode separate from the anode structure.

[0035] Another aspect of the present invention, which can be used independently of the above-described performance, relates to a method for cathode protection and / or passivation of a metallic portion in an ion-conducting material, the method being: A process of providing an anode that transmits electric current to the metal portion in an ion-conducting material, To achieve cathode corrosion protection of the metal part, a process is performed to generate a potential difference between the anode and the metal part so that an electric current flows between the anode and the metal part via an ion-conducting material, The process includes providing an electrical element that limits the current to a maximum value. A configuration is provided in which a semiconductor element is connected to a conductive path between the anode and the metal, and this semiconductor element is arranged to limit the current to a leakage current, thereby limiting the current to a maximum value defined by the leakage current.

[0036] It is known that semiconductor devices containing PN junctions should not conduct any current when reverse biased. However, as the barrier potential increases, holes on the N-type side are attracted to the negative terminal, and free electrons on the P-type side are attracted to the positive terminal. This generates a current of minority charge carriers, and therefore the amount of current is small. Within a typical temperature range, the reverse current is almost constant.

[0037] The reverse leakage current of a semiconductor device is the current emanating from the semiconductor device when it is reverse-biased. This condition is particularly applicable to most semiconductor couplings, especially diodes and thyristors. Generally, such leakage currents can be used in devices such as silicon diodes, Schottky diodes, Zener diodes, and constant-current diodes. The same configuration can be used in transistors such as FETs, IFETs, and MOSFETs. The same configuration can also be used in other devices such as analog switches, capacitors, or other PN elements.

[0038] In electronics, leakage is the gradual movement of electrical energy / electrons across an interface that is normally considered an insulator. The natural discharge of a charged capacitor. Current flows through a transistor in a "closed" state. One possible cause is that the polarity of the diode is reversed.

[0039] Reverse leakage current, also known as "zero gate voltage-drain current" along with MOSFETs, increases with temperature. For example, the reverse leakage current of the Fairchild Semiconductor FDV303N is a maximum of 1 μA at room temperature and increases to 10 μA at 50 degrees Celsius at the junction. For any basic purpose, leakage current is negligible and can therefore usually be ignored.

[0040] However, to date, those involved in the field of cathodic protection have not understood that the reverse current or leakage current of diodes, PN junctions, or similar elements that perform the above-mentioned functions, would provide the necessary level of current for use in cathodic protection, at the required voltage, for the required duration.

[0041] The configurations described herein are preferably provided as general-purpose elements having an anode, so that both can be attached to, embedded in, or engaged with an ion-conducting material. However, this configuration may be separate from the material and the anode in contact with a semiconductor element located in a different location, such as outside the material, for performing services or other operations.

[0042] In the typical systems described herein, the reverse potential difference across semiconductor elements is typically in the range of 0.2 to 6 V. This range is acceptable for galvanic voltages using sacrificial anodes or low-voltage power supplies, and for cathode corrosion protection systems using applied current anodes. The inventors have found that this voltage level is appropriate and fits within the operating range of commercially available semiconductor elements.

[0043] Preferably, the current at one anode is in the range of 0.1 to 5 mA and may be about 100 μA or less. Typically, when using conventional systems that do not employ a current control configuration, the current can be more than 10 times higher, especially initially. The inventors have come to understand that the current may be too high initially and can be reduced by using the system herein, thereby allowing the cathode corrosion protection system to have a longer service life until the current falls below an acceptable level. The inventors of this specification have come to find that the leakage current of electronic elements such as commercially available semiconductors is suitable for this requirement.

[0044] In this way, a long-life system with high charge capacity can be designed using this simple and inexpensive configuration, which utilizes the leakage current of a diode or other similar element to control the current during the initial period, and sometimes for many years from the beginning, when the current would normally be high. This allows the anode to remain active and provide the desired current for a longer period.

[0045] Furthermore, this system allows the sacrificial anode to have a configurable current over many years. This characteristic was not previously possible with sacrificial anodes because the current of a sacrificial anode installed in an outdoor environment exposed to the elements increases or decreases significantly due to changes in temperature, humidity, and the durability of ion-conducting materials such as concrete. Preferably, in one configuration, the semiconductor element forms part of a coupling unit including an anode and a connector, which is inserted into or ion-contacted within an ion-conducting material. In this configuration, preferably, the semiconductor element is associated with only one anode and operates with respect to only one anode.

[0046] The current limiting system can be used when an anode is installed and connected to a metal component while the ion-conducting material is not yet condensed, and by limiting the current with a semiconductor element, it prevents gas generation while the ion-conducting material is curing.

[0047] In an applied current system, preferably, a potential difference is generated by an electrical energy storage element having two electrodes, which transmits the current generated by releasing electrical energy by electrically connecting one electrode to a metal part and the other electrode to the anode.

[0048] Preferably, the diode is of the type having two connecting wires, one wire directly or indirectly connected to the anode, and the other wire directly or indirectly connected to a mounting element for mounting to a metal part, or directly or indirectly connected to the metal part itself. The metal part is usually rebar. Typically, the diode and its connecting wires cannot withstand the large force required to mount the anode to the metal part, and a fixing element is attached to the anode to provide the mounting force. In some configurations, this may be a simple wire winding system well known in the art.

[0049] Preferably, the current limiter described above is associated with and operates for only one anode, and is not part of a larger system that limits or regulates the current of multiple anodes.

[0050] In a particularly preferred method, an anode is placed while the ion-conducting material is not yet set, connected to a metal component, and the current is limited by an electrical element to prevent gas generation while the ion-conducting material is hardening. Gas generation during setting is a major problem because it can lead to the formation of air bubbles in the concrete.

[0051] The configuration described herein can be used in a system in which a potential difference is generated by an electrical energy storage element having two electrodes, which transmits the current generated by the release of electrical energy by electrically connecting one electrode to a metal part and the other electrode to an anode. However, the current limiting system and the mechanical connection can be used with a sacrificial anode or a galvanic anode, and can also be used with a coupling system in which both an applied current anode driven by a power source and a separate sacrificial anode are present.

[0052] In this configuration, preferably, both the anode and the storage element are at least partially housed or embedded in an ion-conducting material, typically in concrete.

[0053] In this configuration, preferably, the storage element is connected as a single unit to the applied current anode or non-sacrificial anode and / or to the sacrificial anode.

[0054] In this configuration, preferably, the storage element is housed in a sealed or enclosed canister that defines an anode on its outer surface. In this case, the anode may be made of stainless steel.

[0055] In this configuration, in some cases, alternative electrical energy can be introduced by recharging the storage element or by replacing the storage element, in order to extend its lifespan.

[0056] The storage element may be a battery or a battery consisting of batteries, or it may be a capacitor.

[0057] Therefore, the above configuration realizes a configuration that acts to limit the current between the anode and the reinforcing bar. This configuration provides one or more of the following properties:

[0058] It acts to regulate the current from a battery, capacitor, or galvanic anode.

[0059] When the current is limited, the circuit can reduce the effective voltage, but it will not reduce the total effective voltage to prevent corrosion of the steel. This is ideal for battery or galvanic anode systems because their capacity is limited (the stored charge is limited) and they cease to function after the limited capacity is consumed.

[0060] The current can be limited across a wide range of circuit resistances, from short circuits to resistors, and the effective voltage is sufficient to produce the full, desired current value.

[0061] The current limiter forms part of a coupling unit that includes a battery, capacitor, or anode and connector.

[0062] A current limiter allows for the installation of a battery or high-power anode, which can be connected to the steel in the fresh concrete / mortar. This prevents the release of high current density through the low-resistance fresh material, which can generate gases (oxygen and hydrogen) during curing. These gases can form bubbles and gaps, reducing the bond with the steel and leaving voids / capillaries within the concrete / mortar. These voids / gaps become direct pathways to the steel, allowing water and salt to pass through and carbon dioxide to carbonate the concrete. All of these lead to premature corrosion of the steel.

[0063] Furthermore, current limiters extend the service life of high-voltage anodes such as batteries, as well as high-sacrificial anodes and high-current anodes in the surface region (for initial high-current output). Using current limiters conserves battery and / or anode capacity, thereby enabling improved performance and higher current output from the anode in the future. The desired current output, made possible by current limiters, can be achieved over a much longer period.

[0064] As mentioned above, if the anode is not sacrificed to the metal part, the material typically has a positive charge relative to the metal part. However, the anode may be partially or completely sacrificed.

[0065] The configurations described herein may be used when the anode takes the form of multiple associated anodes, all connected to a battery or a battery consisting of batteries.

[0066] As defined above, the storage element may be a battery, a battery consisting of batteries / multiple batteries, or a capacitor, supercapacitor, or ultracapacitor with a charge storage system different from conventional electrolyte batteries. A supercapacitor is a large-capacitance electrochemical capacitor with a much larger capacitance value than other capacitors. These capacitors typically have lower voltage limits than standard or conventional capacitors. Typically, they store 10 to 100 times more energy per unit volume or unit mass than standard capacitors, can transfer charge much faster than batteries, and withstand many more charge-discharge cycles than rechargeable batteries. Supercapacitors do not use conventional solid dielectrics as in standard capacitors. Instead, they use electrostatic double-layer capacitance, electrochemical pseudocapacitance, or a combination of both. Electrostatic double-layer capacitors use carbon electrodes or derivatives with much higher electrostatic double-layer capacitance than electrochemical pseudocapacitance to achieve charge isolation in the Helmholtz double layer at the interface between the conductive electrode surface and the electrolyte. The charge isolation is much smaller than in conventional capacitors, around a few angstroms (0.3 to 0.8 nm).

[0067] Supercapacitors are a significant improvement over conventional capacitors and, when fully charged, can store high levels of charge. A 2.7V, 200F supercapacitor can hold over 500C (A x s) of charge. A typical cathodic protection system requires approximately 170-400C per square meter of steel per day, and when such a capacitor is fully charged, it can provide enough charge to protect more than one square meter of steel per day. This represents a current density of 2-5mA per square meter. To double this value, for example, the capacitance would need to be doubled to approximately 400F. Logically, if the capacitor is to be charged on a daily basis, a system in which supercapacitors of this size are installed at regular intervals to supply current to more than one square meter of steel could be an effective cathodic protection system. Daily charging can be easily achieved, for example, by solar panels, but other means of generating relatively regular current bursts can also be used as the charging element for supercapacitors. One example of such a material may be a piezoelectric material incorporated into roads, parking garages, bridges, runways, etc., which can generate an electric current due to the load and / or movement of vehicles passing over or on the structure.

[0068] In other words, piezoelectric materials can be used to directly supply power to the applied current system, or to charge / recharge a battery or capacitor / supercapacitor.

[0069] In some embodiments, the anode is a sacrificial anode formed of a material that is not as noble as the metal portion being protected from corrosion. However, in other cases, the anode is as noble as or more noble than the metal portion being protected from corrosion, and thereafter the anode is identical to or more noble than the metal, typically steel, and is therefore partially or completely inert during processing. If the anode is formed of a sufficiently inert material, it will not corrode significantly while electrons flow through it.

[0070] High current output is required from storage elements such as batteries. As described above, one electrode is connected to the metal part to be protected from corrosion. Electrons flow from the storage element to the metal part, thereby reducing corrosion of the metal part. The other electrode is connected to the anode, or, if appropriate, the storage element's case itself can be used as the anode. In the case of zinc-alkaline batteries, the battery polarity is such that, if the battery case is made of a suitable material, the battery case acts as the anode, and the required current can be distributed through an ion-conducting material such as mortar or concrete. Most other batteries, such as lithium batteries, typically only have small electrodes with appropriate polarity, and these electrodes may not be large enough to carry the required current into the ion-conducting material. Another anode may be provided to connect to a suitable electrode. This anode may enclose or cover the entire storage element, such as a battery or capacitor. The anode may be made of any inert conductive material such as MMO-coated titanium, or other precious or metalloid metals, conductive coatings, or conductive ceramic materials, and may be embedded in alkaline mortar or in an inert material such as soil to which an alkaline solution may be added. Stainless steel can also be a suitable current carrier when embedded in mortar or in compacted soil to which an alkali has been added, such as a saturated solution of lithium hydroxide. The anode may also include sacrificial materials such as zinc, which are not as noble as the metal portion being protected from corrosion.

[0071] Typically, a single unit comprising a storage element and one or more anodes is at least partially embedded in an ion-conducting material. However, it can be applied to a surface or to other mounting configurations in which the anode is in ion contact with the material.

[0072] In a particularly preferred configuration, the storage element includes a battery having an outer casing, which is entirely or partially formed of an anode material, thereby forming the anode either by the outer casing of the same material or by the outer casing as a coating or layer on the outside of the casing. In this case, the outer casing or at least the outer layer may be formed of a material nobler than steel. In this configuration, the anode directly forms the outer casing of the battery, which houses and contains the cathode material, electrolyte, anode material, and other elements of the battery. That is, in this embodiment, the anode is defined by a layer or coating on the outer surface of the storage element itself, or is actually defined as the outer surface of the storage element, and is not defined as a further element separate from the storage element. If the storage element is a battery, the outer casing of the battery directly holds the anode material, or even the outer casing of the battery is the anode. The anode material may cover the entire surface or partially cover it, leaving other parts exposed.

[0073] In other configurations, the case and anode are formed independently, with the anode forming a separate body shaped to fit the battery casing. Typically, such batteries are cylindrical, but other shapes may be used. If the battery is not rechargeable but replaceable, this configuration can be particularly applied to introduce additional energy after the initial battery has been sufficiently depleted and is no longer effective.

[0074] In other configurations, the anode is another body electrically connected to one terminal of the storage element.

[0075] It is well known that corrosion can cause concrete failure due to the expansive force of corrosion products and the reduction in steel strength, and the above properties can preferably be used to protect steel reinforcing or structural members in concrete or mortar materials from corrosion. However, other applications may also occur.

[0076] As used herein, the term applied current anode is intended to distinguish it from a sacrificial anode, which is formed from a material less noble than the metal part, typically zinc, and therefore corrodes preferentially compared to the metal part being protected. An applied current anode is used with a power source and does not need to be less noble than the metal part. Typically, such an applied current anode may be formed from titanium, platinum, niobium, carbon, and other noble metals and oxides that do not corrode readily, or from iron or a less noble material such as zinc.

[0077] With regard to use during the sacrificial or galvanic stage in carrying out the above method, the ion-conducting filler material preferably contains at least one activator to ensure that the sacrificial anode continues to corrode. However, the activator may be located elsewhere in the system. The suitable filler material may be in the form of a solid, gel, or liquid.

[0078] The gel may contain carboxymethylcellulose, starch and its derivatives, fine particle silica, or polymer gel electrolytes, such as potassium hydroxide solution or polyvinyl chloride / acetate-KOH composite material with added bentonite, propylene carbonate, and / or alumina. The alkali hydroxide in these gels acts as a suitable activator.

[0079] Suitable activators include alkali hydroxides, humectants, catalytic materials, and other materials that are corrosive to the sacrificial anode metal. Activators may be used alone or in combination.

[0080] With regard to use during the sacrificial or galvanic stage in carrying out the above method, the ion-conducting filler material preferably has a pH high enough to cause corrosion of the sacrificial anode and prevent the formation of a passivation film on the sacrificial anode. Alternatively, the filler may have a lower pH and / or may contain other activators to cause corrosion of the sacrificial anode and prevent the formation of a passivation film on the sacrificial anode.

[0081] The anodes and methods described herein are preferably designed for use when the metal part is steel and the ion-conducting material is concrete or mortar.

[0082] The anode apparatus, including the applied current element and the sacrificial element, is typically embedded in concrete or other solid material, thereby being completely encased in the concrete or filler material; however, this is not mandatory, and the anode may be partially embedded, in direct or indirectly in contact with the concrete, or in ionic contact.

[0083] The anode apparatus, including the applied current element and the sacrificial element, may be surrounded by an encapsulating material or ion-conducting filler material, which may be a porous material or a porous mortar material. Suitable encapsulating materials may be inorganic or organic, and may be any ion-conducting cement-based material, polymer material, or non-cement-based material, or mortar containing geopolymer or modified Portland cement. The encapsulating material may be solid, gel, or liquid, and may be deformable.

[0084] The power source may include a solar panel that drives an applied current anode and a rechargeable galvanic anode, thereby achieving long-term corrosion protection when photovoltaic power generation is intermittent.

[0085] The configurations and methods proposed herein are designed in particular for cases where the metal part is steel and the ion-conducting material is concrete or mortar. However, these configurations may also be used in a number of other systems in which such anodes can be used, such as in other corrosion protection systems for piping or other structures in soil.

[0086] Preferably, the assembly includes a reinforcing layer, such as that disclosed in U.S. Patent No. 7,226,532 issued to Whitmore on June 5, 2007, to suppress and resist forces such as expansion, contraction, and deformation forces that may arise from anode corrosion, sacrificial anode ion accumulation, and other physical / environmental influences such as freezing, thawing, moisture, drying, and heat. The disclosure in said document is incorporated herein by reference or may be referenced for further details not disclosed herein.

[0087] The inventions defined and described herein can also be provided as assemblies, in contrast to methods for cathode protection and / or passivation of metal portions in ion-conducting materials. Therefore, the following definitions of the inventions shown herein are incorporated herein. Each of these independent definitions can be used in conjunction with any or all of the auxiliary properties defined above. [Brief explanation of the drawing]

[0088] Herein, embodiments of the present invention will be described with reference to the attached drawings.

[0089] [Figure 1] Figure 1 is a cross-sectional view of an anode assembly using a sacrificial anode for use in a corrosion prevention method according to the present invention. [Figure 2] Figure 2 is a side view of the anode assembly shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of an anode assembly similar to the anode assembly in Figure 1, but using a conventional wire-wrapping attachment method for the metal part. [Figure 4] Figure 4 is an enlarged cross-sectional view of an anode assembly of a type that uses a battery to provide current through the applied current anode, and also uses the current limiting element and mounting configuration shown in Figures 1 and 2. [Figure 5] Figure 5 is an enlarged cross-sectional view of an anode assembly of a type that uses a battery to provide current through the applied current anode and a bipolar transistor to limit the current flowing from the battery to the steel. [Figure 6] Figures 6 to 9 show schematic diagrams of four embodiments of a current limiting system that uses a gate-controlled FET, also known as a constant current diode (CRD), to limit the current in a conductive circuit connecting the anode and a steel member. [Figure 7] Figures 6 to 9 show schematic diagrams of four embodiments of a current limiting system that uses a gate-controlled FET, also known as a constant current diode (CRD), to limit the current in a conductive circuit connecting the anode and a steel member. [Figure 8] Figures 6 to 9 show schematic diagrams of four embodiments of a current limiting system that uses a gate-controlled FET, also known as a constant current diode (CRD), to limit the current in a conductive circuit connecting the anode and a steel member. [Figure 9] Figures 6 to 9 show schematic diagrams of four embodiments of a current limiting system that uses a gate-controlled FET, also known as a constant current diode (CRD), to limit the current in a conductive circuit connecting the anode and a steel member. [Figure 10] Figure 10 shows a schematic diagram of a corrosion protection system using multiple anodes powered by a single power source, with each anode associated with a current control circuit having a CRD. [Figure 11] Figure 11 shows a schematic diagram of a corrosion protection system using multiple anodes powered by a single power source, each anode associated with a current control circuit, which includes a resistor in parallel with a CRD.

[0090] In drawings, the same reference numeral indicates a corresponding part, even if the drawing is different. [Modes for carrying out the invention]

[0091] In the examples shown in Figures 4 and 5, a battery is provided, which may be rechargeable, as shown in the earlier PCT application International Publication No. 2017 / 075699, filed on November 2, 2016, and published on May 11, 2017, or a simple non-rechargeable battery. The disclosure of said document is incorporated herein by reference or otherwise. The battery may form an anode structure or part of an anode, and the battery may be physically separate. The anode body (10) is defined by a typical rechargeable alkali-zinc-manganese dioxide battery and includes key units such as a steel can (12) defining a cylindrical internal space, a manganese dioxide cathode (14) formed by a plurality of cylindrical hollow pellets (16) pressed into the can, a zinc anode (18) made of anode gel and positioned inside the hollow of the cathode (14), and a cylindrical separator (20) separating the anode (18) and the cathode (14). The presence of a predetermined amount of potassium hydroxide, KOH, or electrolyte added to the battery provides ionic conductivity (electrolyte) between the anode and cathode. Other types of rechargeable batteries contain similar main components (can, cathode, anode, separator, and electrolyte), but the configuration of these components may differ. However, some types of batteries, such as lead-acid batteries or lithium batteries, may have different structures.

[0092] The can (12) has a sealed bottom and a central circular pip that acts as the positive terminal. The upper end of the can (12) is hermetically sealed by a sealed battery assembly, which includes a negative electrode cap (24) formed of a thin metal plate, a nail (26) which is a current collector attached to the negative electrode cap (24) and penetrates deep into the anode gel to electrically contact the anode, and a plastic top (28) which electrically insulates the negative electrode cap (24) from the can (12) and separates the gaseous space formed beyond the cathode structure and the anode structure, respectively.

[0093] Other types of rechargeable batteries may be used. In this configuration, the above types are used in a method for cathode protection and / or passivation of metal parts such as steel reinforcing bars (40) in an ion-conductive material (41) such as concrete. 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 nail (26) that engages into the anode material (18). The terminal (42) is connected to a connecting wire (42A), which extends from the terminal (42) to a screw-in connector (53) and is ultimately connected to the steel reinforcing bar (40) via a mounting assembly generally represented as (50) as shown in Figure 4, the mounting assembly mechanically and electrically attaches the anode to the bar (40).

[0094] In Figure 4, the anode (44) is applied as a coating to the battery case (12). In this embodiment, the anode (44) is made of an inert material, which is nobler than steel. Examples of such materials are well known. Thus, the anode material (44) does not corrode, or corrodes significantly, during the cathode corrosion protection treatment.

[0095] In this configuration, the anode (44) is applied to the outer surface of the case (12) to realize a structure as a single general-purpose unit, and the anode is directly connected to the battery, forming an integrated element with the battery. The anode (44) may include one or more layers, which may include layers of mixed metal oxide (MMO), catalyst, or sub-oxide.

[0096] In this embodiment, since the anode (44) is formed of an inert material that will not corrode with the anticorrosion treatment, the anode and the cell contained therein may be directly incorporated into or embedded in concrete or other ion-conducting material, without requiring an intervening encapsulating material such as a porous mortar matrix. Since no corrosion products are present, there is no need to absorb such products or the expansion forces they generate. Since this treatment does not rely on the sacrificial anode continuing to corrode, no activator is required on the anode surface. Since chemical reactions occur on the surface of any inert anode during operation, producing acid (consuming alkali), it is beneficial to embed the anode in an alkaline material such as concrete or highly alkaline mortar to prevent the material near the anode from becoming acidic. If desired, additional alkali may be added to the concrete or other material in contact with the anode.

[0097] The apparatus described herein includes an anode body generally represented by (10), which is connected to the reinforcing bar (40) by a mounting assembly generally represented by (50). Furthermore, the anode body includes a current limiting system generally represented by (51), which limits the flow of current from the anode body to the reinforcing bar (40).

[0098] As previously described, the anode body can be defined by a power source, typically in the form of a battery, with an anode (44) on the outer surface of the battery and the other terminal of the battery, which is connected to a rod (40), at the end of the battery.

[0099] In other embodiments shown in Figures 1, 2, 3, 6-8, the battery may be omitted, in which case the anode body includes a sacrificial material that is not as noble as steel rebar, such as zinc, and the voltage between the anode and the rod includes a galvanic voltage between the two metallic elements.

[0100] In yet another embodiment, the anode body may include a combination of both an applied current anode and a sacrificial anode.

[0101] Thus, the anode is configured and positioned such that when the anode is ionically connected to the concrete, a potential difference is generated between the anode (44 and / or 74) and the reinforcing bar (40), thereby causing a current to flow between the anode and the reinforcing bar (40), which in turn provides cathode protection and / or passivation of the reinforcing bars in the concrete.

[0102] In the embodiments shown in Figures 1, 2, 4, and 5, the mounting assembly may be of the type shown in PCT application International Publication No. 2019 / 006540, filed on 15 May 2018 and published on 10 January 2019, the disclosure of which is incorporated herein by reference or otherwise.

[0103] The mounting portion (50) includes a first contact portion in the form of a threaded rod (53) with one end attached to the anode body (10), and a second contact portion that generally engages with the opposing surface of the rod (40). Generally, the second contact portion forms a hook member with two legs (68, 69), the legs contact the opposing or rear surface of the rod (40) to achieve a stable engagement.

[0104] In this embodiment, the female threaded portion is provided by a threaded hole passing through the flange (67). Therefore, by rotating the rod (53), a screw action is achieved that pulls the second contact member toward the anode. This can be done most effectively by manually gripping the anode and using it as a handle to rotate the rod (53).

[0105] Of course, this requires a strong connection between the lower end of the rod (53) and the anode. This connection is achieved by a substrate (71) attached to the lower end of the rod (53) and firmly engaged with the upper end of the anode. For the purpose of holding corrosion products and carrying the conventional activating material previously described herein, the solid anode (74) includes a conventional cover (75) of mortar material.

[0106] Referring to Figure 4, the connection between the battery terminals (42) and the rod (53) which is electrically connected to the rod material (40) as described above is shown in more detail.

[0107] Terminal (42) is connected to wire (42A), and wire (42A) is then connected to diode (51). The output wire (79) of diode (51) is connected to circuit board (71), and circuit board (71) is connected to rod (53).

[0108] The diode (51) may be a conventional diode connected in reverse polarity to prevent current from flowing between the anode and the rod (40). In this configuration, the reverse current or leakage current acts to limit the current flowing from the anode to the rod (40) to a value of approximately 0.1 to 1 mA. This maximum value is maintained regardless of the conductivity between the anode (44) and the rod (40) through the concrete. If the conductivity through the concrete is very high, for example, during the initial installation while the concrete is fresh, the current will be maintained at the maximum value. As the conductivity through the concrete decreases to a low level (the low Efficiency increases), the voltage through the concrete decreases and the circuit (V=IR) becomes 1 Max The current is maintained at the desired level until the battery voltage is reached. If the conductivity drops to an even lower level, the current through the diode or transistor will also decrease according to that conductivity, and the diode or transistor (51) will no longer be able to maintain the current. Therefore, the simple circuit provided by the diode (51) does not act as a regulator, but rather simply as a current limiter.

[0109] Figures 1 and 2 illustrate applications of current limiting elements used with galvanic anodes. In this configuration, a diode or transistor (51) is connected by wires (51A, 51B) between the anode (74) and the support plate (71), and the support plate (71) is connected to a rod (53).

[0110] By limiting the current to the maximum value set during manufacturing using the desired diode (51), the current is ensured to remain at a relatively low level throughout the life of the system, thereby dramatically increasing the current lifetime from a typical value without a current controller, for example, from about one year to a more appropriate lifetime of up to 10 years. The life of the galvanic anode can be extended, for example, from 5-10 years to over 50 years. In this way, the current is maintained at an optimal value for cathode corrosion protection, but soon an excessive current exceeding this desired value can occur, which can damage the concrete, prematurely deplete the battery, reduce and shorten the life of the galvanic anode, and thereby corrosion protection will not be achieved over the desired period.

[0111] This configuration is valuable compared to configurations that use a non-sacrificial current anode and battery as the power source to generate the required voltage. In such a configuration, the current generated between the anode (44) and the rod (40) can, under certain circumstances, significantly exceed the desired value.

[0112] An insulating collar or protective collar (83) is provided around the diode (51) to connect the terminal (42) and the rod (53). The lower end of the collar is attached to the upper end of the battery, and the upper end of the collar houses the circuit board (71) in the appropriate receptacle portion. The collar (83) is attached to the battery (44) by an insulating layer (84) made of appropriate plastic material. Inside the collar (83) is a conventional potting material (85) which surrounds the diode (51) and wires to maintain the connection and prevent damage from moisture penetration. Thus, the structure is sufficiently strong to ensure that the circuit board (71) is securely attached to the battery and that the battery can be manually gripped and rotated using it as an operating handle to rotate the rod (53).

[0113] In this method for cathode protection and / or passivation of a metal portion in an ion-conducting material, a sacrificial anode (74) is provided to transmit an ionic current to the metal portion (40) in the ion-conducting material (91), as shown in Figures 1 and 2. The anode acts to generate a potential between the anode and the metal portion (40) so that an ionic current flows between the anode (74) and the metal portion (40) through the ion-conducting material (91), as in conventional methods for protecting the metal portion from corrosion.

[0114] By connecting a semiconductor diode element (51) in the conductive path between the anode and the metal part, the current flowing between the anode and the metal part is limited to a desired low value. The semiconductor element (51) may be of a type that allows current to pass in a first direction and limits current in a second direction to leakage current, and is connected so that the current between the anode and the metal part passes in the second direction, thereby limiting the current to a maximum value defined by the leakage current.

[0115] The semiconductor element diode (51) forms part of a coupling unit, which includes an anode that is inserted into or mounted in an ion-conductive concrete or mortar material, and a mounting configuration or electrical connector.

[0116] If a coating (75) is provided on the anode of a porous absorbent material, the diode (51) may be located either within the coating or within the potting material to achieve adequate corrosion protection.

[0117] The wire or electrical connection (51A) must be electrically connected to the anode. Preferably, the wire or electrical connection may be dipped into the anode as shown in (51C), or connected to a connector and the connector dipped into the anode. A less durable connection, such as a mechanical connection or soldering, may be made directly outside the anode. The wire or connector (51B) must be electrically connected to the rod (40). This wire or connector may be soldered or otherwise connected to a support plate (71) which is connected to a mounting mechanism. The diode is typically provided with a wire, but since this wire is not suitable for direct connection to the rod (40), the diode typically needs to be mounted to a mounting part (71) which can structurally support the mounting mechanism.

[0118] Many types of mounting methods can be used, including the hook-rod system described above and conventional flexible wire configurations. The conventional flexible wire configuration is used by wrapping it around a rod (40) as shown in Figure 3, where two wires (71A, 71B) are connected to the mounting part (71) or directly to at least one wire or other electrical connector and connected to the rod (40). The sacrificial anode (74) is structurally attached to the mounting plate (71) by an insulating member (78), forming a general-purpose unit. This general-purpose unit is easy to handle and can be inserted into material.

[0119] Therefore, in the shown embodiment, the anode (74) includes an electrically conductive connector that electrically connects the anode to the metal part (40), and the diode (51) is located at the electrical connection between the anode and the connector.

[0120] Referring here to the configurations shown in Figures 5 to 9, there is a method for cathode protection and / or passivation of a steel member (101) embedded in or in contact with an ion-conductive concrete or mortar material (99). Using the structures shown in Figures 1 to 4, an anode structure (100) is provided to transmit an electric current to the steel member (101) in the ion-conductive material (99).

[0121] By using the sacrificial anodes shown in Figures 6-8, or the applied current anode shown in Figure 9, a potential difference is generated between the anode structure (100 or 104) and the steel member (101) so that a current flows between the anode (100, 104) and the steel member via an ion-conducting material (99) to achieve cathode corrosion protection of the steel member. The anode (104) in Figure 9 is powered by a power source (105), such as a simple battery, connected between the anode and the steel (101).

[0122] According to the invention described herein, an electrical element (106) is provided for limiting the current to a maximum value, and the electrical element (106) includes at least one electrical conductor (107) connected to an anode structure. As schematically shown in these figures and as shown in more detail in Figures 1 to 4, the electrical element, including the electrical conductor and the anode structure, forms an element of a general-purpose body, which is mounted or embedded in a concrete or mortar material as a single unit.

[0123] Referring to Figure 5, the connection between the battery terminals (42) and the rod (53) which is electrically connected to the rod material (40) as described above is shown in more detail.

[0124] Terminal (42) is connected to wire (42A), which in turn is connected to transistor (78). The output wire (79) of transistor (78) is connected to a circuit board (71) which is connected to rod (53).

[0125] The transistor (78) in this embodiment is either a conventional transistor or a bipolar transistor. In the case of a bipolar transistor, the substrate of the transistor (78) has a control current, which is provided by a wire (80) connected via a resistor (81) connected via a wire (82) to the positive terminal of a battery connected to the anode (44).

[0126] When the transistor (78) is connected to the steel rod (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 the voltage is typically relatively constant, at least until the end of the battery's life, this constant control current controls the amount of current flowing from the battery to the rod (40) through the transistor. As is well known, a resistor (81) can be selected to provide a control base current to the transistor, and the transistor sets the current flowing through it to a maximum value. This maximum value is maintained regardless of the conductivity between the anode (44) and the rod (40) through the concrete. When the conductivity through the concrete is very high, for example, during the initial period of installation, the current is maintained at the maximum value. As the conductivity through the concrete decreases to a lower level, the current is maintained at the desired level until the maximum voltage of the battery is reached. If the conductivity decreases to an even lower level, the current through the transistor also decreases according to that conductivity, and the transistor no longer maintains the current. Therefore, a simple circuit consisting of resistors and transistors does not act as a regulator, but rather simply as a current limiter.

[0127] As shown in Figures 6 to 9, the current limiting circuit between the anode (100) and the steel member (101) uses a field-effect transistor (102) in a conductive circuit (107) that acts to limit the current between the steel member and the anode structure to a maximum value. The current through the transistor is limited by a control voltage applied to the gate of the transistor. The transistor is typically a field-effect transistor of a suitable form such that the control terminal acts as the gate. A configuration is provided in the conductive circuit to generate the control voltage from the potential difference between the anode and the steel member. In Figures 6 to 8, this potential difference is galvanic. In Figure 8, it is generated according to the power supply (105).

[0128] The anode structure and transistor form the components of a general-purpose body as shown in Figures 1 to 4, which is at least partially embedded as a single unit in a concrete or mortar material. The transistor uses the potential difference between the anode structure and the steel member, and possibly a resistor, to generate the transistor's reference voltage or reference current.

[0129] In Figure 6, resistor R1 is positioned between the source S and the anode (100). This creates a voltage drop between the gate and source, and the gate voltage acts to control the current flow through the transistor, limiting the current to the desired value. This can be achieved by selecting an appropriate transistor with current and control functions, along with the value of the resistor, to provide a substantially constant current as described above.

[0130] In Figure 7, the gate voltage is set by the voltage generated by a small sacrificial anode (110) located within the concrete. This anode is separate from anode (100) and is not provided to directly or significantly aid in corrosion protection, but rather to provide a reference voltage for the gate. The voltage is galvanically generated against the steel (101) and remains constant over a long period of time so that the current through the transistor is set to the required limit.

[0131] In this configuration, the anode (110) may typically be located within the conventional mortar cover surrounding the anode (100).

[0132] In Figure 8, the control wiring for gate G is connected at the location between the drain and the steel. At this location, the voltage drop across the transistor provides the appropriate gate voltage to set the current flow to the required limiting level.

[0133] In each of these configurations, the circuit operates to generate the required gate voltage and maintain the gate voltage above or below a threshold, thereby controlling the current passing through the transistor between the source S and drain D to the required limit as described herein.

[0134] In these configurations in Figures 7 and 8, there are no further resistors in the wiring from the anode to the steel, but if present, they would act to reduce the current flow when the system reaches a point in years and circumstances where the transistor no longer acts to limit the current. At that stage, the system provides the maximum effective current due to the limiting voltage drop between the anode and the steel.

[0135] In the configuration used in Figure 9, a battery (105) is used to generate a voltage between the applied current anode (104) and the steel (101). Note that the battery is located in the wiring from the anode to the transistor, and the gate voltage is set by the voltage drop across the battery.

[0136] Alternatively, although not shown in the diagram, the gate voltage may be supplied by a battery located within the circuit. This configuration has the advantage of making it easier to determine and maintain the voltage, but of course, it increases cost and complexity.

[0137] Typically, transistor (102) is a normally closed transistor, and when the control voltage or control current falls below a threshold, the transistor returns to its initial closed position, allowing current to continue to pass between the anode and the steel member.

[0138] The transistor is typically a closed-state MOSFET transistor, where the voltage between the gate and source is less than 0.7V.

[0139] Referring now to Figures 10 and 11, these include a field-effect transistor (FET) (102) in the conductive circuit (106), which acts as a current regulator or constant current diode to limit the current between the steel member and the anode structure to a maximum value. The configuration used in Figure 10 is identical to that shown in Figure 6, and when a resistor R1 is connected between the source and drain, it operates like a constant current diode, with resistor R1 operating to limit the current passing through the constant current diode to a maximum value as defined above, in a known manner.

[0140] Figure 10 shows a schematic diagram of a corrosion protection system using multiple anodes A1, A2, A3, etc., powered by a single DC power supply (110), which is connected to a bus line (111), and the bus line (111) is individually connected to each anode by another drop (116). Each anode is associated with a current control circuit that defines a constant current diode (106). The anodes cooperate with steel elements (112) in concrete (113), and the steel elements are connected together to the positive side of the power supply by lead wires (114).

[0141] In Figure 10, the current in each drop (116) is controlled solely by the FET (102).

[0142] In Figure 11, each diode (106) is associated with its respective resistor (115) which is connected in parallel with the diode (106).

[0143] This anode configuration provides the advantages and operating conditions described above when using individual current control circuits.

[0144] The inventions described herein can be modified in various ways, and many clearly and significantly different embodiments can be made within the scope and spirit of the claims without departing from the scope and spirit. Therefore, it should be understood that all matters contained in the appended specification are to be construed as illustrative and not to be limiting.

Claims

1. A method for cathode protection and / or passivation of steel members in ion-conducting concrete or mortar materials, A step of providing an anode structure that transmits electric current to the steel member in the ion-conducting concrete material or mortar material, A step of generating a potential difference between the anode structure and the steel member so that an ionic current flows between the anode structure and the steel member via the ion-conducting concrete material or mortar material in order to achieve cathode corrosion protection of the steel member, A step of providing a conductive circuit between the anode structure and the steel member, The step of providing a current regulating element in the conductive circuit, wherein the current regulating element limits the maximum current flowing between the steel member and the anode structure through the current regulating element of the conductive circuit, A resistor is provided in parallel with the current regulating element within the conductive circuit. A method characterized in that, by using the resistor in parallel with the current regulating element, the current can be increased when the voltage applied to the conductive circuit increases.

2. The method according to claim 1, wherein each conductive circuit includes a field-effect transistor (FET) that acts as the current regulating element.

3. The method according to claim 2, wherein, in order to make the FET act as the current regulating element, the maximum current flowing through the FET is limited by a control current or control voltage applied to the gate of the FET.

4. The method according to any one of claims 1 to 3, characterized in that the anode structure and the conductive circuit acting to limit the current form a component of a general-purpose body, and the general-purpose body is at least partially embedded or attached as a single unit in the ion-conductive concrete or mortar material.

5. A step of providing multiple anode structures at intervals within the ion-conducting concrete or mortar material, which transmit electric current to steel elements within the ion-conducting concrete or mortar material, The process of installing a DC power supply, The steps include: connecting the DC power supply in parallel to each anode structure so that a current flows between each anode structure and the steel element via the ion-conducting concrete or mortar material, thereby generating a potential difference between each anode structure and the steel element, in order to achieve cathode corrosion protection of the steel element; The method according to any one of claims 1 to 4, comprising the step of providing a conductive circuit between each anode structure and the DC power supply, each acting to limit the maximum current flowing through each anode structure.

6. The method according to claim 5, characterized in that each conductive circuit includes a field-effect transistor (FET), and the FET acts as a current regulating element that limits the maximum current flowing through it.

7. The method according to claim 6, characterized in that, in order to make the FET act as the current regulating element, the maximum current flowing through the FET is limited by a control current or control voltage applied to the gate of the FET.

Images