JP2019168383A - Electrode structure - Google Patents

Abstract

To provide an electrode structure which has structure capable of highly accurately measuring an electric potential of an anode while flowing anti-corrosion current from the anode even in such a situation that the anode is buried under the ground.SOLUTION: The electrode structure comprises a nonconductive container 2, an internal electrolyte 7, a reference electrode 8 disposed in a state of electrically contacting the internal electrolyte 7, metals 9a and 9b for a corrosion prevention electrode electrically connected to the reference electrode 8 and disposed on the outer surface of the container 2, and potential measurement means 16. The metals 9a and 9b for a corrosion prevention electrode can be electrically brought into contact with an external electrolyte G. The container 2 includes an open hole 5 electrically insulated from the metals 9a and 9b for a corrosion prevention electrode is formed in the vicinity of the metals 9a and 9b for a corrosion prevention electrode so as to communicate the inside and the outside of the container 2. A partition wall 6 made of porous material is installed in the open hole 5 and thereby the internal electrolyte 7 and the external electrolyte G can be electrically connected through the partition wall 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode structure used for cathodic protection.

  Steel pipes (steel buried pipes) used by being buried in the ground are generally subjected to cathodic protection in combination with the surface coating. For example, in the case of cathodic protection by the external power supply method, an electrode embedded in the ground (for example, an electrode obtained by firing an Ir-based metal oxide on the surface of a Ti base (MMOTi electrode)) is used as an anode, and the anticorrosion target from the anode. An anti-corrosion state is achieved by flowing an electric current toward the steel buried pipe and maintaining the potential of the steel buried pipe at a reference value or lower.

  Here, in the anti-corrosion by the external power source method, oxygen is usually generated by electrolysis of water on the surface of the anode and a current flows. However, if the anode deteriorates due to long-term use, it is necessary to set the anode potential to a higher value in order to allow a sufficient anticorrosion current to flow. For example, when the seawater exists in the ground, chlorides are required. In an environment where there are many ions, there is a concern that toxic chlorine gas, not oxygen, is generated on the anode surface, which adversely affects the ecosystem.

  In order to solve such a problem, for example, Patent Document 1 proposes an anticorrosion electrode that can keep the chlorine generation rate low. The electrode for anticorrosion described in Patent Document 1 is prepared by electrodeposition of a composite oxide composed of a combination of manganese dioxide and tungstic acid on the ground of a composite oxide composed of a noble metal oxide and a valve metal oxide. According to the anticorrosion electrode, the chlorine generation rate can be kept low by using this electrode as an anode in seawater.

  In addition, when the anode deteriorates and shows a potential that generates chlorine gas, it is necessary to take measures such as replacing the anode, in order to grasp that the anode has reached such a potential. A method for measuring the potential of an anode installed in seawater is conventionally known.

Japanese Patent No. 3497707

  However, the anticorrosion electrode described in Patent Document 1 loses the effect of suppressing the generation of chlorine gas by losing the electrodeposited composite oxide when it is used for many years, and keeps the chlorine generation rate low. I can't do that.

  As for the method of measuring the potential of the anode installed in the seawater, since the electrical resistance of seawater is relatively low, the potential of the anode can be measured with a certain degree of accuracy, but the anode is buried in the ground. In such a situation, since the electrical resistance of the soil is high, when the potential of the anode is measured in a state where an anticorrosion current flows from the anode, the IR error (the product of the current and resistance value becomes the error as the measured potential). The included phenomenon) may be 1 V or more, and it is difficult to measure accurately.

  The present invention has been made in view of the above circumstances, and even in a situation where the anode is buried in the ground, the potential of the anode can be measured with high accuracy while the anticorrosion current is flowing from the anode. An object is to provide an electrode structure having a structure.

The characteristic structure of the electrode structure according to the present invention for achieving the above object is an electrode structure used for cathodic protection,
A non-conductive container;
An internal electrolyte housed in the container;
In the container, a reference electrode disposed in electrical contact with the internal electrolyte,
While being electrically connected to the reference electrode, an external power source is electrically connected, and the metal for the anticorrosion electrode disposed on the outer surface of the container,
A potential measuring means for measuring the potential of the metal for the anticorrosion electrode with respect to the potential of the reference electrode;
The metal for the anticorrosion electrode can be in electrical contact with an external electrolyte outside the container,
In the container, at least one through hole electrically insulated from the metal for the anticorrosion electrode is formed in the vicinity of the metal for the anticorrosion electrode so as to communicate with the inside and the outside of the container,
The through hole is filled with the internal electrolyte, and a partition wall made of a porous body is installed,
The internal electrolyte and the external electrolyte can be electrically connected through the partition wall.

  According to the above characteristic configuration, the internal electrolyte in electrical contact with the reference electrode and the external electrolyte outside the container can be electrically connected through the partition provided in the through hole, and the through hole is for the anticorrosive electrode. Since it is formed in the vicinity of the metal, the amount of the external electrolyte interposed between the reference electrode and the metal for the anticorrosion electrode can be reduced as much as possible, and the IR error that depends on the resistance of the external electrolyte is reduced. Since it can be made small, the potential of the metal for anticorrosion electrodes can be measured with high accuracy. That is, in the situation where the electrode structure is buried in the ground and the external electrolyte is a highly resistant soil, the corrosion protection is performed when the steel buried pipe is subjected to electrocorrosion protection using the metal for the corrosion protection electrode of the electrode structure as an anode. Since the resistance based on the external electrolyte is small even when the anticorrosion current is applied from the electrode metal, the IR error can be reduced and the potential of the anode can be measured with high accuracy.

  In order to reduce the IR error that depends on the resistance of the external electrolyte, it is preferable to reduce the external electrolyte interposed between the through hole and the metal for the anticorrosion electrode as much as possible.

  That is, a further characteristic configuration of the electrode structure according to the present invention is that the through hole is formed through the container and the anticorrosion electrode metal in a state of being electrically insulated from the anticorrosion electrode metal. There is in point.

  According to the above characteristic configuration, since the through hole and the metal for the anticorrosion electrode are in a very close state, the amount of the external electrolyte interposed between them can be extremely reduced, and the IR error can be extremely reduced. Therefore, the potential of the anticorrosion electrode metal can be measured with higher accuracy.

Moreover, the further characteristic configuration of the electrode structure according to the present invention is such that the anticorrosion electrode metal and the reference electrode are electrically connected by a conducting wire,
The conducting wire is in a point that it penetrates the container and is connected to the metal for the anticorrosion electrode and is connected to the reference electrode through the container.

  According to the above characteristic configuration, since the conductive wire for electrically connecting the anticorrosion electrode metal and the reference electrode is housed in the container, the electrode structure itself can be made compact, and the conductive wire is used in the container. As compared with the case where the electrode structure is exposed to the outside, breakage or the like of the conductive wire is less likely to occur when the electrode structure is embedded in the ground.

The electrode structure according to the present invention is further characterized in that the anticorrosion electrode metal is divided into a first anticorrosion electrode metal and a second anticorrosion electrode metal that are electrically insulated from each other. ,
The first and second anticorrosion electrode metals are electrically connected to the reference electrode, respectively, the external power source is electrically connected, and can be in electrical contact with the external electrolyte,
The first and second anticorrosion electrode metals are electrically connected to AC impedance measuring means for measuring AC impedance using either one of the two anticorrosion electrode metals as a test electrode and the other as a counter electrode. There is in point.

  By the way, when the electrode structure is used for many years for the electric corrosion protection of steel buried pipes, the resistance value increases due to deterioration of the metal for the corrosion protection electrode, or when the corrosion protection current is extremely large, the IR The error can be so large that it cannot be ignored.

  However, according to the above characteristic configuration, the resistance of each metal for the anticorrosion electrode is measured by an AC impedance measuring instrument connected with one of the first and second anticorrosion electrode metals as the test electrode and the other as the counter electrode. The IR error can be calculated from the resistance and the current flowing from each anticorrosion electrode metal. Therefore, it is possible to measure an accurate potential obtained by correcting the calculated IR error.

It is sectional drawing which shows the structure of the electrode structure which concerns on 1st Embodiment. It is a schematic block diagram of the cathodic protection system using the electrode structure which concerns on 1st Embodiment.

[First Embodiment]
Hereinafter, the electrode structure 1 according to the first embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of the electrode structure 1, and FIG. 2 is a schematic configuration diagram of an cathodic protection system 100 using the electrode structure 1.

  As shown in FIG. 1, the electrode structure 1 according to the first embodiment includes a non-conductive container 2, an internal electrolyte 7 accommodated in the container 2, and an electrical connection to the internal electrolyte 7 in the container 2. The reference electrode 8 disposed in contact with the reference electrode 8 and the first and second electrodes electrically connected to the reference electrode 8 and electrically connected to the external power source 20 and disposed on the outer surface of the container 2. Corrosion-proof electrode metals 9 a and 9 b and a measurement unit 15 disposed in the container 2 are provided.

  The container 2 is a cylindrical member that is closed at the top and bottom, and has a small diameter portion 3 in a part in the axial direction, and is made of a resin having non-conductivity. In the following description, the upper side in the axial direction across the narrow diameter portion 3 in the container 2, the verification electrode installation portion 2 a in which the verification electrode is installed in the internal space, the lower side in the axial direction across the narrow diameter portion 3, the outer peripheral surface The first and second anticorrosion electrode metals 9a and 9b are referred to as anticorrosion electrode installation portions 2b. The verification electrode installation part 2 a and the anticorrosion electrode installation part 2 b communicate with each other through the small diameter part 3.

  On the outer peripheral surface of the anticorrosion electrode installation portion 2b, two groove portions 4a and 4b formed along the circumferential direction with an interval in the axial direction of the container 2 are formed. In addition, the verification electrode installation portion 2a is provided with an open / close door or the like for accessing the internal space, although not particularly illustrated.

  The verification electrode 8 is disposed in the verification electrode installation portion 2 a of the container 2 in a state where it is in electrical contact with the internal electrolyte 7, that is, in a state where at least a part is immersed in the internal electrolyte 7.

  The first and second anti-corrosion electrode metals 9a and 9b are disposed in two grooves 4a and 4b formed on the outer peripheral surface of the anti-corrosion electrode installation portion 2b, respectively. Insulated cylindrical metal body. The first and second anticorrosive electrode metals 9a and 9b can be electrically connected to an external electrolyte (soil) G outside the electrode structure 1 when the electrode structure 1 is embedded in the ground. It has become. The first and second anticorrosive electrode metals 9a and 9b are obtained by firing an Ir-based metal oxide on the surface of a Ti base material, for example.

  The first and second anti-corrosion electrode metals 9a and 9b are connected to the respective back surfaces through the container 2, and pass through the anti-corrosion electrode installation portion 2b and the small-diameter portion 3 to inside the reference electrode installation portion 2a. The lead wires (covered conductive wires) 10a and 10b taken out on the electrolyte 7 are connected to the measuring unit 15, respectively. The verification electrode 8 is also connected to the measurement unit 15 by the lead wire 11. Thus, the first and second anticorrosion electrode metals 9 a and 9 b and the verification electrode 8 are electrically connected to the measurement unit 15. Thus, since the lead wires 10a, 10b, and 11 for electrically connecting the first and second anticorrosive electrode metals 9a and 9b and the reference electrode 8 pass through the container 2, the electrode structure 1 Compared with the case where the lead wires 10a, 10b, 11 are exposed to the outside of the container 2, the lead wires 10a, 10b are embedded when the electrode structure 1 is embedded in the ground. , 11 are less likely to break. Each lead wire 10a, 10b is branched in the middle and connected to the external power source 20.

  The anti-corrosion electrode installation portion 2b has a plurality of through holes 5 that communicate the internal space with the outside so as to penetrate the container 2 and the first and second anti-corrosion electrode metals 9a and 9b. The plurality of through holes 5 are each provided with a partition wall 6 made of a porous material. Further, a part of the non-conductive container 2 is interposed between each through-hole 5 and the first and second anti-corrosion electrode metals 9a, 9b, and each through-hole 5 and each of the first and second anti-corrosion electrodes 9a, 9b are interposed. The metal for an anticorrosion electrode 9a, 9b is electrically insulated.

  The internal electrolyte 7 is, for example, a sodium sulfate aqueous solution or a soil impregnated with a sodium sulfate aqueous solution. The internal electrolyte 7 is in the middle of the anticorrosive electrode installation portion 2b and the reference electrode installation portion 2a so that the internal electrolyte 7 enters each through hole 5. A lid (not shown) for preventing the evaporation of moisture in the internal electrolyte 7 is provided on the internal electrolyte 7 in the verification electrode installation portion 2a. Thus, the internal electrolyte 7 can be electrically connected to the external electrolyte G through the through holes 5 and the partition walls 6 when the electrode structure 1 is embedded in the ground.

  The measurement unit 15 tests an electrometer (potential measuring means) 16 for measuring the potentials of the first and second anticorrosion electrode metals 9a and 9b with reference to the potential of the reference electrode 8, and the first anticorrosion electrode metal 9a. The electrode comprises an AC impedance measuring device (AC impedance measuring means) 17 for measuring AC impedance using the second anticorrosive electrode metal 9b as a counter electrode. The AC impedance measuring device 17 is connected by a terminal or the like, and can be removed as appropriate when the AC impedance measuring device 17 is not used, such as when it is not necessary to measure the AC impedance. It has become.

  As shown in FIG. 2, the electrode structure 1 includes a reference electrode installation portion 2 a in the same soil as a steel buried pipe 22 (an example of a structure serving as an anticorrosion object) embedded in the external electrolyte G. Are buried so that the anticorrosion electrode installation part 2b is located in the ground, and the external power source 20 and the steel buried tube 22 are electrically connected by lead wires, and the first and (2) An anticorrosion current can flow from the metal 9a, 9b for the anticorrosion electrode toward the steel buried tube 22. Thereby, the steel buried pipe 22 is protected from corrosion by the external power supply method.

  In the electrode structure 1 according to the present embodiment, the internal electrolyte 7 and the external electrolyte G in which the reference electrode 8 is in electrical contact are electrically connected through the partition wall 6 provided in the through hole 5, Since the through hole 5 is in a state of being very close to the first and second anticorrosion electrode metals 9a and 9b, the through hole 5 is interposed between the reference electrode 8 and the first and second anticorrosion electrode metals 9a and 9b. The amount of the external electrolyte G is extremely reduced. Therefore, even when the anticorrosive current is flowing from the first and second anticorrosive electrode metals 9a and 9b toward the steel buried tube 22, the resistance based on the external electrolyte G is extremely small, and therefore the IR error is small. The potential of the first and second anticorrosive electrode metals 9a and 9b, which are anodes, can be measured with high accuracy.

  Further, in the electrode structure 1 according to the present embodiment, the first and second anticorrosive electrode metals 9 a and 9 b are provided so as to be in electrical contact with the internal electrolyte 7 through the plurality of through holes 5. Therefore, the variation in potential in the first and second anticorrosion electrode metals 9a and 9b is suppressed.

  By the way, when the electrode structure 1 is used for many years, the resistance value may increase due to deterioration of the first and second anticorrosion electrode metals 9a and 9b, and the first and second anticorrosion electrode metals 9a and 9b When the anticorrosion current flowing from 9b toward the steel buried pipe 22 is extremely large, the IR error may be a magnitude that cannot be ignored.

  However, in the electrode structure 1 according to the present embodiment, an AC impedance measuring device 17 that measures AC impedance using the first anticorrosion electrode metal 9a as a test electrode and the second anticorrosion electrode metal 9b as a counter electrode is provided, By measuring the resistance of each of the anticorrosion electrode metals 9a and 9b by the AC impedance measuring instrument 17, and calculating the product of the current flowing out of each of the anticorrosion electrode metals 9a and 9b, the IR error can be obtained. it can. Therefore, the potential measured by the electrometer 16 is corrected based on the obtained IR error, and the accurate potentials of the first and second anticorrosive electrode metals 9a and 9b can be obtained. In addition, the electric current (namely, anticorrosion current) which flows out from each metal 9a, 9b for anticorrosion electrodes is measured by the ammeter 21.

  As described above, according to the electrode structure 1 according to the present embodiment, the amount of the external electrolyte G interposed between the reference electrode 8 and the first and second anticorrosive electrode metals 9a and 9b is reduced, Since the IR error that depends on the resistance of the external electrolyte G can be reduced, the potentials of the first and second anticorrosion electrode metals 9a and 9b can be accurately measured. That is, even when the anticorrosion current flows from the first and second anticorrosion electrode metals 9a and 9b toward the steel buried tube 22, the resistance based on the external electrolyte G is reduced, so that the current and resistance The IR error based on the product of the above becomes small, and the potentials of the first and second anticorrosion electrode metals 9a and 9b serving as anodes can be measured with high accuracy.

  In the electrode structure 1 according to this embodiment, the first and second anticorrosive electrode metals 9 a and 9 b are provided so as to be in electrical contact with the internal electrolyte 7 through the plurality of through holes 5. Therefore, the potential variation in the first and second anticorrosive electrode metals 9a and 9b can be suppressed.

  Furthermore, since the resistance in each of the anticorrosion electrode metals 9a and 9b can be measured by the AC impedance measuring instrument 17, the product of the measured resistance and the current flowing out of each of the anticorrosion electrode metals 9a and 9b is calculated. By obtaining the IR error and correcting the potential measured by the electrometer 16 based on the obtained IR error, the accurate potentials of the first and second anticorrosion electrode metals 9a and 9b can be obtained.

[Another embodiment]
[1] In the above embodiment, the configuration of the electrode structure 1 has been described with a specific example, but the configuration can be changed as appropriate. For example, in the above embodiment, the plurality of through holes 5 penetrating the container 2 and each of the anticorrosion electrode metals 9a and 9b are formed. However, the number of the through holes 5 is not particularly limited and is one. There may be. Further, the position where the through hole 5 is formed is not particularly limited, and it is formed in a position not penetrating each of the anticorrosion electrode metals 9a, 9b as long as it is in the vicinity of each of the anticorrosion electrode metals 9a, 9b. Also good.

[2] In the above embodiment, the two electrically insulated anticorrosion electrode metals 9a and 9b are provided. However, the present invention is not limited to this, and there is only one anticorrosion electrode metal. Also good.

  The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in the other embodiment, as long as no contradiction occurs. The embodiment disclosed in this specification is an exemplification, and the embodiment of the present invention is not limited to this. The embodiment can be appropriately modified without departing from the object of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for an electrode structure having a structure capable of measuring the potential of the anode with high accuracy while the anticorrosion current flows from the anode even in a situation where the anode is buried in the ground. .

DESCRIPTION OF SYMBOLS 1 Electrode structure 2 Container 5 Through-hole 6 Partition 7 Internal electrolyte 8 Reference electrode 9a, 9b Metal for anticorrosion electrode 16 Electrometer G External electrolyte

Claims (4)

An electrode structure used for cathodic protection,
A non-conductive container;
An internal electrolyte housed in the container;
In the container, a reference electrode disposed in electrical contact with the internal electrolyte,
While being electrically connected to the reference electrode, an external power source is electrically connected, and the metal for the anticorrosion electrode disposed on the outer surface of the container,
A potential measuring means for measuring the potential of the metal for the anticorrosion electrode with respect to the potential of the reference electrode;
The metal for the anticorrosion electrode can be in electrical contact with an external electrolyte outside the container,
In the container, at least one through hole electrically insulated from the metal for the anticorrosion electrode is formed in the vicinity of the metal for the anticorrosion electrode so as to communicate with the inside and the outside of the container,
The through hole is filled with the internal electrolyte, and a partition wall made of a porous body is installed,
An electrode structure in which the internal electrolyte and the external electrolyte can be electrically connected through the partition wall.   2. The electrode structure according to claim 1, wherein the through hole is formed so as to penetrate the container and the anticorrosion electrode metal while being electrically insulated from the anticorrosion electrode metal. The metal for the anticorrosive electrode and the reference electrode are electrically connected by a conducting wire,
3. The electrode structure according to claim 1, wherein the conductive wire passes through the container and is connected to the anticorrosion electrode metal, and is connected to the reference electrode through the container. The metal for the anti-corrosion electrode is divided into a first anti-corrosion electrode metal and a second anti-corrosion electrode metal that are electrically insulated from each other,
The first and second anticorrosion electrode metals are electrically connected to the reference electrode, respectively, the external power source is electrically connected, and can be in electrical contact with the external electrolyte,
The first and second anticorrosion electrode metals are electrically connected to AC impedance measuring means for measuring AC impedance using either one of the two anticorrosion electrode metals as a test electrode and the other as a counter electrode. The electrode structure according to any one of claims 1 to 3.

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