Corrosion sensor

Abstract

A corrosion sensor according the present disclosure is provided with: a working electrode formed from metal; an insulating layer which is provided with a space exposing an exposed part that is a portion of a surface of the working electrode, and which is arranged on the surface of the working electrode; a counter electrode which has a nobler potential than the working electrode, and which is arranged on at least a portion of the surface of the insulating layer located around the exposed part; and a structure which is arranged at a position facing the exposed part, and which holds a liquid on the exposed part so that a corrosion current flows between the working electrode and the counter electrode.

Description

Corrosion Sensors

[0001] The present disclosure relates to corrosion sensors.

[0002] 2. Description of the Related Art Corrosion sensors are used to detect corrosion of refrigerant piping in refrigeration cycle devices such as air conditioners.

[0003] For example, Patent Document 1 discloses a refrigeration cycle device having a refrigerant pipe, an ACM sensor that detects a corrosion current, and a processing unit that determines corrosion of the refrigerant pipe.

[0004] Japanese Patent Application Laid-Open No. 2022-36621

[0005] The refrigeration cycle device described in Patent Document 1 still has room for improvement in terms of improving the accuracy of the corrosion current detection by the corrosion sensor.

[0006] The present disclosure provides a corrosion sensor with improved accuracy in detecting corrosion current.

[0007] A corrosion sensor according to one aspect of the present disclosure includes: a working electrode formed of metal; an insulating layer disposed on the surface of the working electrode and having a space for exposing an exposed portion, which is a portion of the surface of the working electrode; a counter electrode having a potential more noble than the working electrode and disposed on at least a portion of the surface of the insulating layer located around the exposed portion; and a structure disposed opposite the exposed portion and holding a liquid in the exposed portion so that a current flows between the working electrode and the counter electrode.

[0008] According to the present disclosure, it is possible to provide a corrosion sensor with improved detection accuracy of corrosion current.

[0009] 2 is a diagram showing a state in which a liquid is attached to an exposed portion of the corrosion sensor without a structure; FIG. 3B is a graph showing the relationship between the corrosion current detected by the corrosion sensor 1 of FIG. 1 and time; FIG. 3C is a graph showing the relationship between the corrosion current detected by the corrosion sensor without a structure and time;

[0010] (Background to the Disclosure) Refrigeration cycle devices such as air conditioners use refrigerant piping made of copper pipes. Detecting corrosion of copper pipes has been studied to prevent refrigerant leakage. For example, Patent Document 1 discloses detecting corrosion current in refrigerant piping using an ACM sensor.

[0011] The ACM sensor detects the corrosion current flowing between the substrate and the cathode electrode through a water film formed on the surface of the sensor, and determines corrosion based on changes in the corrosion current detected by the ACM sensor.

[0012] In the ACM sensor, the state of the water film or water droplets formed on the surface of the sensor causes the corrosion current to be disturbed, so there is a demand for improving the detection accuracy of the corrosion current.

[0013] Therefore, the present inventors have studied corrosion sensors that can improve the accuracy of detecting corrosion currents, and have arrived at the following invention.

[0014] (First embodiment) [Overall configuration] Fig. 1 is a plan view schematically showing a corrosion sensor 1 according to a first embodiment of the present disclosure. Fig. 2 is a cross-sectional view taken along line A-A of the corrosion sensor 1 in Fig. 1. Note that the ammeter 50 shown in Fig. 2 is omitted from Fig. 1.

[0015] The corrosion sensor 1 is a sensor for detecting a corrosion current. As shown in Figures 1 and 2, the corrosion sensor 1 includes a working electrode 10, an insulating layer 20, a counter electrode 30, and a structure 40.

[0016] A portion of the surface of the working electrode 10 is provided with an exposed portion 11 that is exposed to the outside. Liquid, such as condensed water generated inside a refrigeration cycle device, adheres to the exposed portion 11. When liquid adheres to the exposed portion 11, corrosion progresses in the exposed portion 11. As the corrosion progresses, a corrosion current flows between the working electrode 10 and the counter electrode 30 via the liquid adhered to the exposed portion 11. In this embodiment, the corrosion current is measured using an ammeter 50 shown in FIG. 2. By monitoring changes in the corrosion current, the progress of corrosion of the working electrode 10 can be grasped. Note that the ammeter 50 is not an essential component of the corrosion sensor 1. In this embodiment, localized corrosion due to stress corrosion cracking can be detected by measuring the corrosion current.

[0017] The working electrode 10 is made of a metal for which corrosion is to be detected. The working electrode 10 is made of, for example, copper, a phosphorus copper alloy, aluminum, an aluminum manganese alloy, or an aluminum zinc alloy. In this embodiment, an example in which the working electrode 10 is made of copper will be described.

[0018] As shown in Figures 1 and 2, the working electrode 10 is formed, for example, in a plate shape. In this embodiment, the working electrode 10 is formed in a rectangular plate shape, but the shape of the working electrode 10 may be any shape. The surface of the working electrode 10 is covered with an insulating layer 20 except for the exposed portion 11. In this embodiment, the exposed portion 11 is formed in a circular shape in a plan view. The exposed portion 11 can be formed in a circular shape with a diameter of 0.5 mm or more and 5 mm or less, for example.

[0019] The insulating layer 20 is disposed on the surface of the working electrode 10. The insulating layer 20 has a space 21 that exposes an exposed portion 11, which is a portion of the surface of the working electrode 10. That is, a circular hole is provided in the insulating layer 20, and a portion of the surface of the working electrode 10 is exposed as the exposed portion 11. Because the insulating layer 20 has a circular hole, the insulating layer 20 is disposed so as to surround the periphery of the exposed portion 11. By providing the insulating layer 20 so as to surround the exposed portion 11, it becomes easier to retain liquid in the exposed portion 11, and the corrosion current can be detected more efficiently.

[0020] The insulating layer 20 is formed of an insulating material, such as a resin containing epoxy resin. The insulating layer 20 is formed to a thickness of, for example, 10 μm or more and 500 μm or less. Forming the insulating layer 20 to a thickness of 10 μm or more can suppress short-circuiting between the working electrode 10 and the counter electrode 30. Furthermore, forming the insulating layer to a thickness of 500 μm or less allows dissolved oxygen in the liquid to be supplied to the exposed portion 11, which is a portion of the surface of the working electrode 10. Therefore, the corrosion current detected by the corrosion sensor 1 can be treated as a current representative of corrosion of the surface of a metal made of the same material as the working electrode 10.

[0021] The counter electrode 30 is formed on at least a portion of the surface of the insulating layer 20 located around the exposed portion 11. More specifically, it is formed on the surface of the insulating layer 20, on at least a portion of the periphery of the space 21 of the insulating layer 20. The counter electrode 30 is laminated on the insulating layer 20 so that the counter electrode 30 and the working electrode 10 are insulated from each other when no liquid is attached to the exposed portion 11. In other words, the counter electrode 30 and the working electrode 10 are arranged with the insulating layer 20 sandwiched between them in the lamination direction. The counter electrode 30 is arranged to face the working electrode 10 with the insulating layer 20 sandwiched between them in the lamination direction. The counter electrode 30 is also arranged so as not to be in direct contact with the working electrode 10. The distance between the counter electrode 30 and the working electrode 10 in the lamination direction is determined by the thickness of the insulating layer 20. In this embodiment, the insulating layer 20 is laminated on the surface of the working electrode 10, and the counter electrode 30 is laminated on the insulating layer 20. The counter electrode 30 is formed of a conductive material having a more noble potential than the working electrode 10, such as silver or conductive carbon.

[0022] The structure 40 is for holding a liquid in the exposed portion 11 so that a corrosion current flows between the working electrode 10 and the counter electrode 30. The structure 40 is disposed in a position facing the exposed portion 11, as shown in FIG.

[0023] Fig. 3A is a diagram showing a state in which a liquid is attached to the exposed portion 11 of the corrosion sensor 1 of Fig. 2. Fig. 3B is a diagram showing a state in which a liquid is attached to the exposed portion 111 of the corrosion sensor 101 without the structure 40. The corrosion sensor 101 of Fig. 3B is an example of a corrosion sensor for comparison with the corrosion sensor 1 of Fig. 3A and is different from the corrosion sensor 1 according to the present embodiment. The corrosion sensor 101 has a working electrode 110, an insulating layer 120, a counter electrode 130, and an ammeter 150. The corrosion sensor 101 has the same configuration as the corrosion sensor 1 except that it does not have the structure 40.

[0024] When the structure 40 is disposed, a meniscus is formed on the liquid surface 61 of the liquid adhering to the exposed portion 11 due to surface tension, as shown in FIG. 3A . In other words, the liquid surface 61 of the liquid adhering to the exposed portion 11 has a concave shape due to surface tension. As a result, the liquid adheres to the surface 31 of the counter electrode 30 in the form of a film. On the other hand, when the structure 40 is not disposed, the liquid surface 161 of the liquid has a dome-like shape as shown in FIG. 3B , and the liquid film formed on the surface 131 of the counter electrode 130 is thicker than in the case of FIG. 3A .

[0025] In this embodiment, by disposing the structure 40, the liquid film formed on the surface 31 of the counter electrode 30 can be made thinner, allowing more oxygen from the atmosphere to be supplied to the surface 31 of the counter electrode 30. Furthermore, because the exposed portion 11 of the working electrode 10 is located farthest from the interface between the liquid and air (liquid surface 61), oxygen is less likely to reach the exposed portion 11 than the surface 31 of the counter electrode 30. Therefore, most of the cathodic reaction (oxygen reduction reaction) occurs on the surface of the counter electrode 30. Therefore, a current corresponding to the anodic reaction at the exposed portion 11 of the working electrode 10 can be efficiently passed to the ammeter 50. Therefore, by disposing the structure 40, the corrosion sensor 1 can detect the corrosion current with greater accuracy.

[0026] Furthermore, by disposing the structure 40, it is possible to retain the liquid adhering to the exposed portion 11, and to easily maintain a state in which corrosion occurs in the exposed portion 11. The surface tension acting between the structure 40 and the liquid makes it difficult for the liquid to drop off from the exposed portion 11.

[0027] The structure 40 is formed of an insulating material, such as a resin containing an epoxy resin. In this embodiment, the structure 40 is formed in an elongated shape having a tip 41, and the tip 41 is arranged toward the exposed portion 11. The structure 40 is formed in, for example, a conical, pyramidal, cylindrical, or prismatic shape. As shown in FIG. 1 , the structure 40 is formed in, for example, a shape having a diameter smaller than the diameter of the exposed portion 11 so as not to block the exposed portion 11 in a plan view. In order to retain the liquid in the exposed portion 11, it is preferable that the structure 40 and the exposed portion 11 are not in contact with each other.

[0028] In the present embodiment, in a direction perpendicular to the exposed portion 11 on the surface of the working electrode 10, the tip 41 of the structure 40 is disposed at a height of approximately 2 mm from the surface of the exposed portion 11. At this time, when the liquid adhering to the surface of the exposed portion 11 becomes sufficiently large, the liquid is held by the tip 41 of the structure 40. When the tip 41 of the structure 40 is disposed at a position higher than the surface of the exposed portion 11 and lower than the surface 31 of the counter electrode 30, a liquid film is more easily formed on the surface 31 of the counter electrode 30.

[0029] In a plan view, structure 40 is preferably disposed near the center of exposed portion 11. By disposing structure 40 near the center of exposed portion 11, a liquid film can be formed evenly on surface 31 of counter electrode 30. As a result, the detection accuracy of the corrosion current can be improved.

[0030] It is preferable that a hydrophilic coating is applied to the surface of the structure 40. Examples of the hydrophilic coating include a resin coating, a glass coating, and a ceramic coating. If the surface of the structure 40 is hydrophilic, the ability to retain water droplets adhering to the exposed portion 11 can be improved.

[0031] In this embodiment, in order to maintain the structure 40 in the predetermined position described above, the structure 40 has a pair of arms 42 extending in a direction intersecting the direction in which the structure 40 extends. As shown in Fig. 2, the pair of arms 42 are supported by a support 43 formed on the surface of the counter electrode 30, and the tip 41 of the structure 40 can be maintained in a predetermined position. The support 43 can be formed of an insulating material.

[0032] The corrosion sensor 1 is disposed near a refrigerant pipe inside a refrigeration cycle device such as an air conditioner. The refrigerant flowing through the refrigeration cycle device can cause the surface temperature of the refrigerant pipe to become lower than the outside air temperature, resulting in condensation. The corrosion sensor 1 retains a liquid, such as condensed water, on the exposed portion 11, and detects a corrosion current flowing between the working electrode 10 and the counter electrode 30 via the adhered liquid. When the corrosion sensor 1 is used to detect corrosion in the refrigerant pipe of a refrigeration cycle device, the state of corrosion in the refrigerant pipe can be detected by forming the working electrode 10 from the same material as the material from which the refrigerant pipe is formed.

[0033] As corrosion of the exposed portion 11 of the working electrode 10 progresses, hydroxide ions are generated on the surface 31 of the counter electrode 30. By forming the counter electrode 30 from a material having a more noble potential than the working electrode 10, corrosion progresses more preferentially in the exposed portion 11 of the working electrode 10.

[0034] Next, a description will be given of the corrosion current detected by the corrosion sensor 1. Fig. 4A is a graph showing the relationship between time and the corrosion current detected by the corrosion sensor 1 of Fig. 1. Fig. 4B is a graph showing the relationship between time and the corrosion current detected by the corrosion sensor 101 not having the structure of Fig. 3B.

[0035] As shown in FIG. 4A , the corrosion current detected by the corrosion sensor 1 according to this embodiment includes a background current, which is a current value that changes gradually from approximately 0.1 μA to 0.5 μA. A spike current is a current that occurs when localized corrosion occurs in the working electrode 10. The copper forming the working electrode 10 oxidizes due to localized corrosion, releasing many electrons in a short period of time. This causes a sudden increase in the current flowing between the working electrode 10 and the counter electrode 30, resulting in a spike current. Therefore, the occurrence of a spike current indicates the occurrence of localized corrosion. In the example shown in FIG. 4A , the arrows indicate the occurrence of spike currents. In the example shown in FIG. 4A , spike currents occur periodically after time T1, indicating that corrosion of the working electrode 10 progresses after time T1. In the corrosion sensor 1 according to this embodiment, the structure 40 can reduce changes in the state of the liquid adhering to the exposed portion 11, such as the size of the liquid. Reducing changes in the state of the liquid adhering to the exposed portion 11 stabilizes the background current, thereby enabling more accurate detection of spike currents.

[0036] Furthermore, the background current can be reduced by reducing the area of ​​the exposed portion 11 in a planar view. Reducing the background current can prevent the spike current from being buried in the background current. For this reason, it is preferable to reduce the area of ​​the exposed portion 11 in a planar view as much as possible, as long as it can retain liquid. As described above, the area of ​​the exposed portion 11 can be reduced by forming the exposed portion 11 into a circle with a diameter of 0.5 mm or more and 5 mm or less in a planar view.

[0037] 4B shows the corrosion current detected by the corrosion sensor 101 without the structure 40. Without the structure 40, it is difficult to maintain the state of the liquid adhering to the exposed portion 111. Due to changes in the state of the liquid, such as its size, a background current with a larger amplitude is generated, as shown in FIG. 4B, compared to the case of FIG. 4A. For this reason, it is more difficult for the corrosion sensor 101 without the structure 40 to accurately detect spike currents compared to the corrosion sensor 1.

[0038] In the corrosion sensor 1 of the present embodiment, by arranging a structure at a position facing the exposed portion 11, the liquid can be stably held in the exposed portion 11. This improves the detection accuracy of the corrosion current flowing between the working electrode 10 and the counter electrode 30 via the liquid.

[0039] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0040] The corrosion sensor 1 includes a working electrode 10, an insulating layer 20, a counter electrode 30, and a structure 40. The working electrode 10 is formed of metal. The insulating layer 20 is provided with a space 21 that exposes an exposed portion 11, which is a portion of the surface of the working electrode 10, and is disposed on the surface of the working electrode 10. The counter electrode 30 has a potential more noble than the working electrode 10. The counter electrode 30 is disposed on at least a portion of the surface of the insulating layer located around the exposed portion 11. The structure 40 is disposed opposite the exposed portion 11 and holds a liquid in the exposed portion 11 so that a current flows between the working electrode 10 and the counter electrode 30.

[0041] This configuration makes it possible to provide a corrosion sensor with improved corrosion current detection accuracy. By arranging the structure 40 in a position facing the exposed portion 11, a liquid film, such as condensed water, can be formed on the exposed portion 11. By arranging the structure 40, it becomes easier to retain the liquid adhering to the exposed portion 11, thereby suppressing disruptions in the corrosion current due to changes in the state of the liquid and improving the corrosion current detection accuracy. The structure 40 adjusts the thickness of the liquid film, allowing the liquid to absorb more oxygen from the atmosphere and deliver more oxygen to the surface 31 of the counter electrode 30. This allows corrosion to occur in the exposed portion 11, making it possible to detect the corrosion current.

[0042] When viewed from a direction perpendicular to the exposed portion 11 on the surface of the working electrode 10, the exposed portion 11 is formed in a circular shape with a diameter of 5 mm or less.

[0043] With this configuration, the background current can be further reduced, thereby further improving the accuracy of detecting the corrosion current.

[0044] The working electrode 10 is made of copper, a phosphorus copper alloy, aluminum, an aluminum manganese alloy, or an aluminum zinc alloy.

[0045] With this configuration, it is possible to provide a corrosion sensor that can detect corrosion currents of various metals.

[0046] The working electrode 10 is formed in a plate shape.

[0047] With this configuration, a corrosion sensor with a simpler configuration can be provided.

[0048] The insulating layer 20 is made of resin.

[0049] With this configuration, the working electrode 10 and the counter electrode 30 can be reliably insulated from each other when no liquid is attached to the exposed portion 11 .

[0050] The insulating layer 20 is formed to a thickness of 10 μm or more and 500 μm or less.

[0051] With this configuration, oxygen can be supplied to the liquid film formed on the surface 31 of the counter electrode 30 while maintaining insulation between the working electrode 10 and the counter electrode 30 when no liquid is held in the exposed portion 11, thereby enabling more efficient detection of corrosion current. Furthermore, because the thickness of the diffusion layer of dissolved oxygen in still water is 500 μm, by setting the thickness below the thickness of the diffusion layer, a small amount of oxygen can be delivered to the surface 31, and changes in corrosion morphology due to the formation of a galvanic couple with the counter electrode 30 can be mitigated.

[0052] The counter electrode 30 is made of silver or conductive carbon.

[0053] With this configuration, the counter electrode 30 can be easily formed.

[0054] The structure 40 is made of resin.

[0055] With this configuration, it is possible to prevent short circuits between the structure 40 and the working electrode 10 or the counter electrode 30 .

[0056] The structure 40 is formed in an elongated shape having a tip 41. The tip 41 of the structure 40 is arranged facing the exposed portion 11.

[0057] With this configuration, the liquid adhering to the exposed portion 11 can be retained more efficiently.

[0058] In a direction perpendicular to the exposed portion 11 on the surface of the working electrode 10 , the tip 41 of the structure 40 facing the exposed portion 11 is positioned higher than the surface of the exposed portion 11 and lower than the surface of the counter electrode 30 .

[0059] With this configuration, a liquid film is formed on the surface 31 of the counter electrode 30 while retaining the liquid adhering to the exposed portion 11, thereby enabling more accurate detection of the corrosion current.

[0060] A support 43 for supporting the structure 40 is formed on the surface 31 of the counter electrode 30. The support 43 is made of an insulating material.

[0061] With this configuration, the structure 40 can be supported at a predetermined position.

[0062] Furthermore, an ammeter is provided to detect the current flowing between the working electrode 10 and the counter electrode 30 via the liquid.

[0063] With this configuration, the corrosion current flowing between the working electrode 10 and the counter electrode 30 can be measured.

[0064] In the above-described embodiment, the exposed portion 11 has a circular shape in a plan view, but the shape is not limited to this. The exposed portion 11 may have an elliptical or polygonal shape in a plan view.

[0065] In the above-described embodiment, the insulating layer 20 is disposed so as to surround the periphery of the exposed portion 11 in a plan view, but the present invention is not limited to this. The insulating layer 20 may be disposed on at least a portion of the periphery of the exposed portion 11.

[0066] In the above-described embodiment, the structure 40 is formed from a resin, but the present invention is not limited to this. The structure 40 may be formed from a conductive material. In this case, it is preferable that the structure 40 and the exposed portion 11 of the working electrode 10 are insulated from each other.

[0067] In the above-described embodiment, the surface of the structure 40 is coated with a hydrophilic coating, but the present invention is not limited to this. The surface of the structure 40 may be hydrophobic.

[0068] In the above-described embodiment, the working electrode 10 is formed from a metal for which corrosion detection is to be performed, but the present invention is not limited to this. For example, the working electrode 10 may be formed from a part of a refrigerant pipe of a refrigeration cycle device such as an air conditioner.

[0069] (Embodiment 2) Embodiment 2 will be described with reference to Figures 5 and 6. In Embodiment 2, components that are the same as or equivalent to those in Embodiment 1 will be denoted by the same reference numerals. In addition, in Embodiment 2, descriptions that overlap with those in Embodiment 1 will be omitted.

[0070] Fig. 5 is a plan view schematically illustrating a corrosion sensor 1A according to a second embodiment of the present disclosure. Fig. 6 is a cross-sectional view taken along line B-B of the corrosion sensor 1A in Fig. 5. Note that the ammeter 50 shown in Fig. 6 is omitted from Fig. 5. As shown in Figs. 5 and 6, the second embodiment differs from the first embodiment in that the structure 240 is formed in a film shape.

[0071] 5 and 6 , in the corrosion sensor 1A, a film-like structure 240 is disposed so as to cover the exposed portion 11 and the counter electrode 30. The structure 240 is formed of a film that is permeable to oxygen and water vapor, such as cellophane. Because the structure 240 is impermeable to liquid, it is possible for the structure 240 to retain the liquid while efficiently incorporating oxygen from the atmosphere into the liquid retained in the exposed portion 11. This allows more oxygen to be delivered to the exposed portion 11, enabling more accurate detection of the corrosion current.

[0072] The structure 240 is disposed such that a predetermined gap is formed between the structure 240 and the counter electrode 30 by a support 243 provided on the counter electrode 30. By forming a gap between the structure 240 and the counter electrode 30, a liquid can be held in the gap to form a liquid film. In this embodiment, as shown in FIG. 5 , a ring-shaped support 243 is provided on the outer edge of the counter electrode 30.

[0073] In this embodiment, the structure 240 is formed in a circular shape in a plan view. Furthermore, in this embodiment, the support 243 can be formed to a height such that the distance between the counter electrode 30 and the structure 240 is, for example, 10 μm or more and 100 μm or less. By adjusting the height of the support 243, the thickness of the liquid film formed on the surface of the counter electrode 30 can be adjusted. By making the liquid film formed on the surface of the counter electrode 30 thinner, the cathode reaction can be generated more efficiently.

[0074] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0075] Structure 240 is a film that is permeable to oxygen and water vapor.

[0076] With this configuration, it is possible to efficiently generate a cathode reaction by supplying oxygen to the liquid on the surface of the counter electrode 30 while maintaining the liquid on the surface of the counter electrode 30 .

[0077] In the above-described embodiment, the structure 240 is an oxygen- and water vapor-permeable film, but the structure 240 is not limited to this. The structure 240 may be a mesh-like film.

[0078] (Embodiment 3) Embodiment 3 will be described with reference to Figures 7 and 8. In Embodiment 3, components that are the same as or equivalent to those in Embodiment 1 will be denoted by the same reference numerals. In Embodiment 3, descriptions that overlap with those in Embodiment 1 will be omitted.

[0079] FIG. 7 is a plan view schematically illustrating a corrosion sensor 1B according to a third embodiment of the present disclosure. FIG. 8 is a partial cross-sectional view taken along the line CC of the corrosion sensor 1B in FIG. 7. As shown in FIGS. 7 and 8 , the third embodiment differs from the first embodiment in that the working electrode 310 is formed in a tubular shape. The third embodiment also differs from the first embodiment in that the working electrode 310 has a bent portion 312 that is bent in a U-shape.

[0080] For example, refrigeration cycle devices such as air conditioners may use refrigerant piping having a bend as shown in Fig. 7. Bent piping having a bend is prone to stress corrosion cracking. The corrosion sensor 1B of this embodiment can more accurately detect corrosion in bent refrigerant piping used in air conditioners and the like.

[0081] In the corrosion sensor 1B, the working electrode 310 is formed as a metal tube. Furthermore, the working electrode 310 is provided with a bent U-shaped bent portion 312 formed by bending a portion of the metal tube. In this embodiment, an insulating layer 320 is formed to cover the outer surface of the bent portion 312. Furthermore, the exposed portion 311 of the working electrode 310 is formed in the bent portion 312. The bent portion 312 of the working electrode 310 is a location in the working electrode 310 where stress corrosion cracking is likely to occur due to the presence of residual stress. Therefore, by providing the exposed portion 311 in the bent portion 312, it is possible to detect the corrosion current at the bent portion 312 and monitor stress corrosion cracking.

[0082] In this embodiment, the structure 340 is formed in an elongated linear shape and is wound around the working electrode 310 in the circumferential direction so as to face the exposed portion 311. The linear shape includes, for example, a tape-like shape having a width, and in this embodiment, the structure 340 is formed in an elongated shape having a width of, for example, 1 mm or more and 3 mm or less. The structure 340 can be formed, for example, by a resin cable tie or the like. This configuration allows the structure 340 to be easily positioned. A support 343 is provided on the counter electrode 330, and the structure 340 is wound around the bent portion 312 so as to contact the support 343 but not the counter electrode 330.

[0083] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0084] The working electrode 310 is formed in a tubular shape, and the exposed portion 311 is provided on the outer surface of the working electrode 310 .

[0085] With this configuration, the corrosion sensor 1B can be configured using a working electrode having a shape similar to that of a refrigerant pipe of a refrigeration cycle device, for example, thereby further improving the accuracy of corrosion detection.

[0086] The working electrode 310 has a U-shaped bent portion 312. The exposed portion 311 is formed in the bent portion 312.

[0087] With this configuration, it is possible to detect the corrosion current in the portion where residual stress exists, and therefore it is possible to detect stress corrosion cracking.

[0088] (Fourth Embodiment) A fourth embodiment will be described with reference to Fig. 9. In the fourth embodiment, the same or equivalent components as those in the first embodiment will be denoted by the same reference numerals. In the fourth embodiment, descriptions that overlap with those in the first embodiment will be omitted.

[0089] Fig. 9 is a cross-sectional view that schematically shows a corrosion sensor 1C according to embodiment 4. As shown in Fig. 9, embodiment 4 differs from embodiment 1 in that a structure 440 also serves as a counter electrode.

[0090] In the present embodiment, the structure 440 is formed of a conductive material, such as silver or conductive carbon, that has a more noble potential than the working electrode 10. Therefore, in the present embodiment, the structure 440 also serves as a counter electrode. The structure 440 is disposed on an insulating layer 20 that is laminated on the working electrode 10. The working electrode 10 and the structure 440 form a galvanic couple, and the current flowing between the working electrode 10 and the structure 440 is measured with an ammeter 50, thereby enabling corrosion to be detected.

[0091] [Effects] According to the above-described embodiment, it is possible to provide a corrosion sensor with improved accuracy in detecting a corrosion current.

[0092] In the example of FIG. 9, the corrosion sensor 1B does not include the counter electrode described in the first embodiment, but the corrosion sensor 1B may also include a counter electrode.

[0093] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0094] (Technology 1) A corrosion sensor comprising: a working electrode formed of metal; an insulating layer having a space exposing an exposed portion that is a portion of the surface of the working electrode and disposed on the surface of the working electrode; a counter electrode having a more noble potential than the working electrode and disposed on at least a portion of the surface of the insulating layer located around the exposed portion; and a structure disposed opposite the exposed portion and holding a liquid in the exposed portion so that a current flows between the working electrode and the counter electrode.

[0095] With this configuration, it is possible to provide a corrosion sensor with improved accuracy in detecting corrosion current.

[0096] (Technical Aspect 2) The corrosion sensor according to Technical Aspect 1, wherein the exposed portion on the surface of the working electrode is formed in a circular shape with a diameter of 5 mm or less when viewed from a direction perpendicular to the exposed portion.

[0097] With this configuration, the background current can be further reduced, thereby further improving the accuracy of detecting the corrosion current.

[0098] (Technology 3) The corrosion sensor according to Technology 1 or 2, wherein the working electrode is made of copper, a phosphorus copper alloy, aluminum, an aluminum manganese alloy, or an aluminum zinc alloy.

[0099] With this configuration, it is possible to provide a corrosion sensor that can detect corrosion currents of various metals.

[0100] (Technology 4) The corrosion sensor according to any one of Technologies 1 to 3, wherein the working electrode is formed in a tubular shape, and the exposed portion is provided on an outer surface of the working electrode.

[0101] With this configuration, the corrosion sensor can be configured using a working electrode having the same shape as the refrigerant pipe of a refrigeration cycle device, for example, and therefore the accuracy of corrosion detection can be further improved.

[0102] (Technology 5) The corrosion sensor according to Technology 4, wherein the working electrode has a bent portion bent in a U-shape, and the exposed portion is formed in the bent portion.

[0103] With this configuration, it is possible to detect partial corrosion currents where residual stress exists, and therefore it is possible to detect stress corrosion cracking.

[0104] (Technology 6) The corrosion sensor according to any one of Technologies 1 to 3, wherein the working electrode is formed in a plate shape.

[0105] With this configuration, a corrosion sensor with a simpler configuration can be provided.

[0106] (Technology 7) The corrosion sensor according to any one of Technologies 1 to 6, wherein the insulating layer is made of resin.

[0107] With this configuration, the working electrode and the counter electrode can be reliably insulated from each other when no liquid is attached to the exposed portion.

[0108] (Technology 8) The corrosion sensor according to any one of Technologies 1 to 7, wherein the insulating layer is formed to a thickness of 10 μm or more and 500 μm or less.

[0109] With this configuration, it is possible to suppress insulation between the working electrode and the counter electrode when no liquid is held in the exposed portion, while supplying oxygen to the liquid film formed on the surface of the working electrode, thereby enabling more efficient detection of corrosion current.

[0110] (Technology 9) The corrosion sensor according to any one of Technologies 1 to 8, wherein the counter electrode is made of silver or conductive carbon.

[0111] With this configuration, the counter electrode can be easily formed.

[0112] (Technology 10) The corrosion sensor according to any one of Technologies 1 to 9, wherein the structure is made of resin.

[0113] With this configuration, it is possible to suppress short circuits between the structure and the working electrode or the counter electrode.

[0114] (Technology 11) The corrosion sensor according to any one of technologies 1 to 10, wherein the structure is formed in an elongated shape having a tip, and the tip of the structure is arranged facing the exposed portion.

[0115] With this configuration, the liquid adhering to the exposed portion can be more efficiently retained.

[0116] (Technology 12) A corrosion sensor according to Technology 11, wherein a tip of the structure facing the exposed portion is positioned higher than the surface of the exposed portion and lower than the surface of the counter electrode in a direction perpendicular to the exposed portion on the surface of the working electrode.

[0117] With this configuration, a liquid film is formed on the surface of the counter electrode while retaining the liquid adhering to the exposed portion, thereby enabling more accurate detection of corrosion current.

[0118] (Technology 13) The corrosion sensor according to any one of technologies 1 to 10, wherein the structure is a film that is permeable to oxygen and water vapor.

[0119] With this configuration, it is possible to efficiently generate a cathode reaction by supplying oxygen to the liquid on the surface of the counter electrode while maintaining the liquid on the surface of the counter electrode.

[0120] (Technology 14) The corrosion sensor according to any one of Technologies 1 to 12, wherein the structure is formed in a linear or mesh shape.

[0121] This configuration makes it easier to retain liquid on the exposed portion while increasing the efficiency of supplying oxygen to the liquid adhering to the exposed portion, thereby improving the accuracy of detecting corrosion current.

[0122] (Technology 15) The corrosion sensor according to any one of Technologies 1 to 14, wherein a support for supporting the structure is formed on a surface of the counter electrode, and the support is made of an insulating material.

[0123] Such a configuration allows the structure to be supported in place.

[0124] (Technology 16) The corrosion sensor according to any one of Technologies 1 to 15, further comprising an ammeter that detects a current flowing between the working electrode and the counter electrode via the liquid.

[0125] With this configuration, the corrosion current flowing between the working electrode and the counter electrode can be measured.

[0126] (Technology 17) A corrosion sensor comprising: a working electrode formed of a metal; an insulating layer disposed on the surface of the working electrode, with a space provided to expose an exposed portion that is a part of the surface of the working electrode; and a structure having a more noble potential than the working electrode and disposed in a position facing the exposed portion, wherein the structure holds a liquid in the exposed portion so that a corrosion current flows between the working electrode and the structure.

[0127] With this configuration, it is possible to provide a corrosion sensor with improved accuracy in detecting corrosion current.

[0128] The present disclosure is useful in detecting corrosion currents in metals.

[0129] REFERENCE SIGNS LIST 1, 1A, 1B Corrosion sensor 10, 310 Working electrode 11, 311 Exposed portion 20, 320 Insulating layer 21 Space 30, 330 Counter electrode 31 Surface 40, 240, 340 Structure 41 Tip 42 Arm 43, 243, 343 Support 50 Ammeter

Claims

1. A corrosion sensor comprising: a working electrode made of metal; an insulating layer disposed on the surface of the working electrode and having a space for exposing an exposed portion, which is a portion of the surface of the working electrode; a counter electrode having a more noble potential than the working electrode and disposed on at least a portion of the surface of the insulating layer located around the exposed portion; and a structure disposed opposite the exposed portion and holding a liquid in the exposed portion so that a corrosion current flows between the working electrode and the counter electrode.

2. The corrosion sensor according to claim 1, wherein when viewed from a direction perpendicular to the exposed portion on the surface of the working electrode, the exposed portion is formed in a circular shape with a diameter of 5 mm or less.

3. The corrosion sensor according to claim 1 or 2, wherein the working electrode is made of copper, a phosphorus copper alloy, aluminum, an aluminum manganese alloy, or an aluminum zinc alloy.

4. The corrosion sensor according to any one of claims 1 to 3, wherein the working electrode is formed in a tubular shape, and the exposed portion is provided on an outer surface of the working electrode.

5. The corrosion sensor according to claim 4, wherein the working electrode has a bent portion bent in a U-shape, and the exposed portion is formed in the bent portion.

6. The corrosion sensor according to any one of claims 1 to 3, wherein the working electrode is formed in a plate shape.

7. The corrosion sensor according to any one of claims 1 to 6, wherein the insulating layer is made of resin.

8. The corrosion sensor according to any one of claims 1 to 7, wherein the insulating layer is formed to a thickness of 10 µm or more and 500 µm or less.

9. The corrosion sensor according to any one of claims 1 to 8, wherein the counter electrode is made of silver or conductive carbon.

10. The corrosion sensor according to any one of claims 1 to 9, wherein the structure is made of resin.

11. The corrosion sensor according to any one of claims 1 to 10, wherein the structure is formed in an elongated shape having a tip, and the tip of the structure is positioned toward the exposed portion.

12. The corrosion sensor according to claim 11, wherein, in a direction perpendicular to the exposed portion on the surface of the working electrode, the tip of the structure facing the exposed portion is positioned higher than the surface of the exposed portion and lower than the surface of the counter electrode.

13. The corrosion sensor of claim 1, wherein the structure is a film that is permeable to oxygen and water vapor.

14. The corrosion sensor according to any one of claims 1 to 10, wherein the structure is formed in a linear or mesh shape.

15. The corrosion sensor according to any one of claims 1 to 14, wherein a support for supporting the structure is formed on a surface of the counter electrode, and the support is made of an insulating material.

16. The corrosion sensor according to any one of claims 1 to 15, further comprising an ammeter that detects a corrosion current that flows between the working electrode and the counter electrode via the liquid.

17. A corrosion sensor comprising: a working electrode formed of metal; an insulating layer disposed on the surface of the working electrode and having a space for exposing an exposed portion that is a portion of the surface of the working electrode; and a structure having a more noble potential than the working electrode and disposed in a position facing the exposed portion, wherein the structure holds a liquid in the exposed portion so that a corrosion current flows between the working electrode and the structure.

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