Current density measuring device and corrosion measurement method

Abstract

This invention provides a current density measuring device and a corrosion measurement method that can reduce the effort required of the user when measuring the corrosion of an object under inspection in water. [Solution] This current density measuring device 100 includes an underwater electric field sensor 1 which includes a pair of electrode parts 10 and a potential difference measuring unit 17 which measures the potential difference V between the pair of electrode parts 10 in a non-contact manner with respect to an object to be inspected 80 placed in water; a conductivity meter 2 which measures the conductivity σ in water; and a control unit 3 which uses the potential difference V measured by the underwater electric field sensor 1 and the conductivity σ measured by the conductivity meter 2 to acquire the current density J of the currents 70 and 71 flowing from the object to be inspected 80 into the water.

Description

Technical Field

[0001] The present invention relates to a current density measuring device and a corrosion measuring method.

Background Art

[0002] Conventionally, a corrosion measurement method for an object to be inspected in water is known (see, for example, Patent Document 1).

[0003] Patent Document 1 mentioned above discloses a current measuring device comprising: a metal to be measured arranged in seawater within a test tank; a counter electrode arranged in the seawater within the test tank; an AC power source connected to the metal to be measured and the counter electrode; and a DC ammeter. The DC ammeter is provided in series between the metal to be measured and the counter electrode. In this method for measuring corrosion of a metal to be measured in seawater, the current measuring device is used to measure a DC current value in a circuit, and the corrosion amount of the metal to be measured is measured based on the measured DC current value.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] The corrosion measurement method described in Patent Document 1 requires measuring the DC current value by electrically connecting the metal to be measured, which is placed in seawater in a test tank, to a counter electrode. However, in reality, marine organisms and other organisms are attached to the metal to be measured in the sea (underwater). Therefore, surface preparation work is required to electrically connect the metal to be measured (object under inspection) to the counter electrode, and this preparation work is a burden on the user. Surface preparation refers to removing marine organisms attached to the metal to be measured by crushing or peeling them off. Therefore, it is desirable to reduce the effort required of the user when measuring the corrosion of objects underwater.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a current density measuring device and a corrosion measuring method that can reduce the effort required of the user when measuring the corrosion of an object under inspection in water. [Means for solving the problem]

[0007] A current density measuring device comprising: an underwater electric field sensor including a pair of electrode sections and a potential difference measuring section that non-contactively measures the potential difference between the pair of electrode sections with respect to an object under inspection placed in water; a conductivity meter for measuring the conductivity of water; and a control unit that uses the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter to obtain the current density of the current flowing from the object under inspection into the water. Furthermore, a corrosion measurement method comprising the steps of: acquiring current density non-contact with an object to be inspected placed in water using the potential difference between a pair of electrode parts; and determining corrosion of the object to be inspected or detecting corrosion of the object to be inspected using the acquired current density. Here, current density refers to the amount of electric charge (electricity) flowing per unit area per unit time. [Effects of the Invention]

[0008] The above-described current density measuring device uses the potential difference measured non-contact with the object under inspection by an underwater electric field sensor and the conductivity of the water measured by a conductivity meter to obtain the current density of the current flowing from the object under inspection into the water, without contact with the object under inspection. Therefore, since the current density of the current flowing near the object under inspection in water can be obtained without directly connecting to the object under inspection, surface preparation work for direct electrical connection to the object under inspection is unnecessary. Thus, it is possible to provide a current density measuring device that can reduce the effort required of the user when measuring corrosion of objects under inspection in water. Furthermore, the above corrosion measurement method allows for the detection of corrosion in an object under inspection using the current density obtained non-contact with the object. Therefore, in corrosion measurement of an object under inspection in water, the current density of the current flowing near the object under inspection can be obtained without directly connecting to the object under inspection, eliminating the need for surface preparation work to directly connect to the object under inspection. Thus, a corrosion measurement method can be provided that reduces the effort required of the user when measuring corrosion of an object under inspection in water. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the overall configuration of the current density measuring device. [Figure 2] This shows a cross-sectional view of a pair of electrode sections, and a schematic diagram of the pair of electrode sections and the pair of conductivity measuring electrodes viewed from one side. [Figure 3] This is a schematic diagram illustrating the acquisition of current density. [Figure 4] This is a schematic diagram illustrating the first example of a corrosion determination method for determining corrosion in an object under inspection. [Figure 5] This is a schematic diagram illustrating a second example of a corrosion detection method for detecting corrosion in an object under inspection. [Figure 6] This figure shows an example of the current density waveform acquired continuously in the second example. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments embodying the present invention will be described based on the drawings.

[0011] (Overall configuration of the current density measuring device) The overall configuration of the current density measuring device 100 according to this embodiment will be described with reference to Figures 1 and 2.

[0012] As shown in Figure 1, the current density measuring device 100 comprises an underwater electric field sensor 1, a conductivity meter 2, and a control unit 3.

[0013] The underwater electric field sensor 1 is used to measure the underwater electric field (UEP). The underwater electric field (potential difference V) is a minute potential difference in the sea 90 (underwater). The underwater electric field sensor 1 includes a pair of electrode sections 10 and a potential difference measuring section 17. The pair of electrode sections 10 includes a first measuring electrode 12 and a second measuring electrode 15. The underwater electric field sensor 1 is configured to measure the potential difference V between the pair of electrode sections 10 without contacting the object under inspection 80 in the sea 90. Specifically, the underwater electric field sensor 1 is configured to measure the potential difference V between the first measuring electrode 12 of the first electrode section 11 and the second measuring electrode 15 of the second electrode section 14 without contacting the object under inspection 80 in the sea 90. Note that the first housing 13 of the first electrode section 11 and the second housing 16 of the second electrode section 14 may be measured by contacting marine organisms attached to the object under inspection 80 in the sea 90.

[0014] In this embodiment, a current density measuring device 100 for measuring current density J in "seawater" and a corrosion measurement method for an object to be inspected 80 in "seawater" are described, but the method is not limited to "seawater" and is not particularly limited to "water." "Water" means, for example, seawater, lake water, river water, etc. Also, "water" means, for example, water stored in artificial structures such as swimming pools, tanks, and aquariums. Furthermore, "water" in the context of "water" means, for example, seawater, freshwater, brackish water, etc., and does not include pure water.

[0015] As shown in Fig. 2(a) and Fig. 2(b), the pair of electrode portions 10 includes a first electrode portion 11 and a second electrode portion 14. The pair of electrode portions 10 is used in the sea 90 (see Fig. 4) in a state of being in contact with seawater. The pair of electrode portions 10 is used in a non-contact manner with the object to be inspected 80 in the vicinity of the object to be inspected 80 (see Fig. 4) in the sea 90. The pair of electrode portions 10 may be disposed and used on a self-propelled device such as an underwater robot, an underwater drone or an autonomous unmanned underwater vehicle, or may be held and used by a diver.

[0016] The first electrode portion 11 includes a first measurement electrode 12 and a first housing 13. The first measurement electrode 12 is configured to measure the potential of the sea 90. As an example, the first measurement electrode 12 is constituted by a silver-silver chloride electrode containing silver (Ag) and silver chloride (AgCl). The first measurement electrode 12 is connected to a first cable 133. The first measurement electrode 12 is connected to a potential difference measurement unit 17 (see Fig. 1) via the first cable 133.

[0017] The first measurement electrode 12 is disposed inside the first housing 13. The first measurement electrode 12 has a cylindrical shape and is disposed so as to extend in the longitudinal direction of the first housing 13. The first measurement electrode 12 is disposed in the sea 90 so as to be aligned with the second measurement electrode 15 at a predetermined interval. The first measurement electrode 12 and the second measurement electrode 15 are provided so as to maintain a constant interval.

[0018] The first housing 13 is configured to cover the first measuring electrode 12. The first housing 13 is made of an insulating material such as resin. The first housing 13 has a cylindrical shape, for example. Specifically, the first housing 13 has a rectangular cylindrical shape. A first opening 131 that communicates with the outside is formed on a first end face 130 on one side of the first housing 13. The first opening 131 is configured to allow seawater from the outside to flow into the first housing 13. When the current density measuring device 100 is used, the first measuring electrode 12 is immersed in seawater that flows into the first housing 13 through the first opening 131. A first cable 133 is inserted through a third end face 132 on the opposite side of the first housing 13.

[0019] The second electrode section 14 includes a second measuring electrode 15 and a second housing 16. The second measuring electrode 15 is located inside the second housing 16. The second measuring electrode 15 is connected to the potential difference measuring section 17 (see Figure 1) via a second cable 163. The second housing 16 also has a rectangular cylindrical shape, for example. A second opening 161 communicating with the outside is formed on a second end face 160 on one side of the second housing 16. The second cable 163 is inserted through a fourth end face 162 on the opposite side of the second housing 16. The other configurations of the second electrode section 14 are the same as those of the first electrode section 11, so a detailed explanation is omitted.

[0020] The second electrode portion 14 is positioned adjacent to the first electrode portion 11. Specifically, the pair of electrode portions 10 are integrally provided with the side surface of the first housing 13 of the first electrode portion 11 on the side facing the second electrode portion 14 and the side surface of the second housing 16 of the second electrode portion 14 on the side facing the first electrode portion 11 in contact. The pair of electrode portions 10 are integrally formed with the first opening 131 of the first electrode portion 11 and the second opening 161 of the second electrode portion 14 separated by a predetermined distance.

[0021] The pair of electrode portions 10 are integrally formed such that the first opening 131 and the second opening 161 maintain a predetermined distance from each other. The first opening 131 is located on the side of the second electrode portion 14 that is closer to the center 134 of the first end face 130, and the second opening 161 is located on the side of the first electrode portion 11 that is closer to the center 164 of the second end face 160. The distance L (distance between the centers of the openings) between the first opening 131 and the second opening 161 is not particularly limited and may be a few millimeters, a few centimeters, or 10 centimeters or more.

[0022] As shown in Figure 1, the potential difference measuring unit 17 is configured to measure the potential difference V (underwater electric field) between the first measuring electrode 12 of the first electrode unit 11 and the second measuring electrode 15 of the second electrode unit 14 without contacting the object under inspection 80 (see Figure 4) placed in water. In other words, the potential difference measuring unit 17 is configured to measure the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 in a non-contact state with respect to the object under inspection 80.

[0023] The potentiometer 17 is housed inside the main housing 4. The main housing 4 can be placed on land, at sea, underwater 90, inside a ship, or in self-propelled equipment such as an underwater robot, underwater drone, or autonomous submersible. When the main housing 4 is placed at sea or underwater 90 and comes into contact with seawater, the inside of the main housing 4 is sealed to prevent water from entering. The potentiometer 17 may also be housed inside a housing other than the main housing 4.

[0024] The potential difference measuring unit 17 includes an amplifier 18 and an AD converter (ADC) 19. The amplifier 18 is configured to generate a signal that amplifies the potential difference V between the first measuring electrode 12 and the second measuring electrode 15. One of the pair of input terminals of the amplifier 18 is connected to the first measuring electrode 12 via a first cable 133. The other of the pair of input terminals of the amplifier 18 is connected to the second measuring electrode 15 via a second cable 163.

[0025] The AD converter 19 is configured to convert the signal amplified by the amplifier 18 into a digital signal and output the converted digital signal to the control unit 3. As a result, the potential difference measuring unit 17 outputs the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 to the control unit 3. The AD converter 19 is connected to the amplifier 18 and the control unit 3.

[0026] The conductivity meter 2 is configured to measure the conductivity σ (electrical conductivity) of seawater 90. The conductivity meter 2 includes a pair of conductivity measuring electrodes 20, a constant current source 21, a voltmeter 22, an AD converter (ADC) 23, and a microcontroller 24. In other words, the conductivity meter 2 is an electrode-type conductivity meter. The conductivity meter 2 may also be an electromagnetic induction type conductivity meter. The constant current source 21, voltmeter 22, AD converter 23, and microcontroller 24 are housed inside the main housing 4. The constant current source 21, voltmeter 22, AD converter 23, and microcontroller 24 may also be located inside a housing other than the main housing 4.

[0027] The pair of conductivity measuring electrodes 20 are used in the sea 90 in contact with seawater. The pair of conductivity measuring electrodes 20 are located inside the third housing 25. The third housing 25 has an opening (not shown) through which seawater flows into the third housing 25. As shown in Figure 2(b), the third housing 25 is integrally provided with the first housing 13 of the first electrode section 11 and the second housing 16 of the second electrode section 14. That is, the pair of conductivity measuring electrodes 20 are located in the vicinity of the first electrode section 11 and the second electrode section 14. The pair of conductivity measuring electrodes 20 are used in the sea 90 in contact with seawater, in the vicinity of the first electrode section 11 and the second electrode section 14. The pair of conductivity measuring electrodes 20 may be used together with the pair of electrode sections 10 in self-propelled equipment such as an underwater robot, underwater drone, or autonomous submersible, or they may be used together with the pair of electrode sections 10 by being grasped by a diver. Each of the pair of conductivity measuring electrodes 20 is connected to a voltmeter 22 via a cable.

[0028] As shown in Figure 1, the constant current source 21 is a power supply configured to maintain an output current approximately constant regardless of the load size (resistance between the pair of conductivity measuring electrodes 20). The pair of output terminals of the constant current source 21 are connected to the pair of conductivity measuring electrodes 20, respectively. The voltmeter 22 is connected between the pair of output terminals of the constant current source 21. The AD converter 23 is connected to the voltmeter 22 and the microcontroller 24.

[0029] The microcontroller 24 is connected to the constant current source 21, the AD converter 23, and the control unit 3. The microcontroller 24 includes a processor such as a CPU (Central Processing Unit) for performing calculations and memory for temporary storage during calculations.

[0030] When the constant current source 21 outputs a preset current, a current is generated through the seawater between the pair of conductivity measuring electrodes 20. The voltmeter 22 measures the potential difference between the pair of conductivity measuring electrodes 20 when the constant current source 21 outputs current. The AD converter 23 converts the output signal from the voltmeter 22 into a digital signal and outputs the converted digital signal to the microcontroller 24. The microcontroller 24 calculates the conductivity σ of the seawater between the pair of conductivity measuring electrodes 20 based on the output current value of the constant current source 21 and the potential difference obtained from the voltmeter 22. The microcontroller 24 outputs the calculated conductivity σ of the seawater between the pair of conductivity measuring electrodes 20 to the control unit 3.

[0031] The control unit 3 is configured to acquire the current density J of the current (70, 71) flowing from the object under inspection 80 into the water, using the potential difference V measured by the underwater electric field sensor 1 and the conductivity σ measured by the conductivity meter 2. The control unit 3 includes a processor such as a CPU (Central Processing Unit) that performs calculations and a memory for temporary storage during calculations.

[0032] The control unit 3 is provided in the control device 30. The control device 30 is configured, for example, as a PC (personal computer). The control device 30 includes the control unit 3, a storage unit 31, and an input / output unit 32. The control device 30 is connected to the display device 33 and the input device 34.

[0033] The storage unit 31 includes a volatile memory device and a non-volatile memory device. The input / output unit 32 consists of various interfaces for inputting and outputting signals to and from the control device 30. The input / output unit 32 is connected to the display device 33 and the input device 34. The display device 33 is, for example, a liquid crystal display device. The input device 34 includes a keyboard and a mouse. The control unit 3 obtains the potential difference V measured by the underwater electric field sensor 1 and the conductivity σ measured by the conductivity meter 2 via the input / output unit 32.

[0034] The control device 30 is located on land, at sea, or inside a ship. The control unit 3 does not necessarily have to be located in the control device 30. The control unit 3 may be housed inside the main housing 4, or it may be located inside a housing other than the main housing 4.

[0035] (Current density acquisition by the control unit) Referring to Figure 3, the acquisition of current density J by the control unit 3 will be explained. Note that in Figure 3, for the sake of explanation, the pair of electrode sections 10 of the underwater electric field sensor 1 and the conductivity meter 2 are shown in parallel, but this differs from the actual arrangement of the underwater electric field sensor 1 and conductivity meter 2.

[0036] The control unit 3 acquires the potential difference V [μV] between the first measuring electrode 12 and the second measuring electrode 15 output from the underwater electric field sensor 1. Furthermore, since the pair of electrode sections 10 are integrally formed so that the first opening 131 and the second opening 161 maintain a predetermined distance from each other, the distance L [m] (distance between the centers of the openings) between the first opening 131 and the second opening 161 is constant. The control unit 3 acquires the distance L between the openings, which is stored in the storage unit 31 beforehand, from the storage unit 31.

[0037] Furthermore, the control unit 3 acquires the conductivity σ [S / m] of seawater between the pair of conductivity measuring electrodes 20 output from the conductivity meter 2. Since the pair of conductivity measuring electrodes 20 are located near the pair of electrode units 10, the acquired conductivity σ can be estimated to be equivalent to the conductivity of seawater at the location where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured.

[0038] Then, based on the following equation (1), the control unit 3 calculates the current density J [μA / m³] at the position where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured. 2 [As described in ]. J[μA / m 2 ]=V[μV] / L[m]×σ[S / m] ···(1) Here, J is the current density at the position where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured, V is the potential difference between the first measuring electrode 12 and the second measuring electrode 15, L is the distance between the openings between the first opening 131 and the second opening 161, and σ is the conductivity σ of seawater between the pair of conductivity measuring electrodes 20.

[0039] The control unit 3 stores the calculated current density J in the storage unit 31. The control unit 3 may also store in the storage unit 31 the calculated current density J in association with the position of the object under inspection 80 corresponding to the position where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 was measured. Furthermore, the control unit 3 may use the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 when the underwater electric field sensor 1 outputs, and the conductivity σ of the seawater between the pair of conductivity measuring electrodes 20 when the conductivity meter 2 outputs, to calculate the real-time current density J when the potential difference V is output from the underwater electric field sensor 1 and when the conductivity σ is output from the conductivity meter 2, and may also display the calculated current density J in real time on the display device 33.

[0040] (Method for determining corrosion of an object under inspection using a current density measuring device) Next, with reference to Figure 4, a first example of a corrosion measurement method for an object under inspection 80 using a current density measuring device 100 will be described. The first example of a corrosion measurement method for an object under inspection 80 is a corrosion determination method that determines the corrosion of the object under inspection 80 using the current density J obtained by the current density measuring device 100. As an example, the object under inspection 80 is a sacrificial anode 81 in the sea 90. The sacrificial anode 81 is installed in an underwater structure 82 made of steel or the like, electrically connected to it.

[0041] As shown in Figure 4, an underwater structure 82 is positioned on the seabed. The underwater structure 82 is formed of, for example, steel whose main component is iron (Fe). The sacrificial anode 81 is installed in contact with the underwater structure 82. The sacrificial anode 81 is formed of, for example, zinc (Zn).

[0042] Furthermore, the materials for the sacrificial anode 81 and the underwater structure 82 are not limited to the examples above; the material for the sacrificial anode 81 may have a higher ionization tendency than the material for the underwater structure 82. For example, the underwater structure 82 may be made of steel with iron (Fe) as its main component, while the sacrificial anode 81 may be made of aluminum (Al), which has a higher ionization tendency than iron (Fe). Also, the underwater structure 82 may be installed between the seabed and the sea surface, rather than being located on the seabed.

[0043] The sacrificial anode 81, formed from zinc (Zn), has a higher ionization tendency than the underwater structure 82, which is formed from steel whose main component is iron (Fe). In other words, the sacrificial anode 81, formed from zinc (Zn), is more easily ionized than the underwater structure 82, which is formed from steel. Therefore, the sacrificial anode 81 oxidizes (dissolves and corrodes) the underwater structure 82 while supplying a corrosion-preventive current 70. As a result, corrosion of the underwater structure 82 is suppressed.

[0044] However, as oxidation (dissolution, corrosion) of the sacrificial anode 81 progresses, the corrosion-preventive current 70 supplied from the sacrificial anode 81 decreases. Therefore, it becomes difficult to suppress the corrosion of the underwater structure 82. To address this, the corrosion (deterioration) of the sacrificial anode 81 is determined using the current density J obtained by the current density measuring device 100.

[0045] The determination of corrosion of the sacrificial anode 81 using the current density J acquired by the current density measuring device 100 comprises the steps of acquiring the current density J non-contact with the sacrificial anode 81 placed in the sea 90 using the potential difference V between a pair of electrode parts 10 of the underwater electric field sensor 1, and determining corrosion of the sacrificial anode 81 using the acquired current density J.

[0046] The process for obtaining the current density J includes measuring the potential difference V between a pair of electrode portions 10 in a non-contact manner with respect to the sacrificial anode 81, measuring the conductivity σ of the seawater 90, and obtaining the current density J of the current 70 (corrosion current) flowing from the sacrificial anode 81 to the seawater 90 using the measured potential difference V and the measured conductivity σ.

[0047] The process of measuring the potential difference V between a pair of electrode sections 10 in a non-contact manner with respect to the sacrificial anode 81 is performed by using the pair of electrode sections 10 of the underwater electric field sensor 1 to measure in a non-contact manner with respect to the sacrificial anode 81. Specifically, the pair of electrode sections 10 of the underwater electric field sensor 1 are placed on self-propelled underwater equipment such as an underwater robot, underwater drone, or autonomous submersible, or are held by a diver. The underwater equipment or diver moves in the vicinity of the sacrificial anode 81 and moves the pair of electrode sections 10 along the vicinity of the surface of the sacrificial anode 81. The potential difference measurement unit 17 measures the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 in a non-contact state with respect to the sacrificial anode 81. The potential difference measurement unit 17 outputs the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 to the control unit 3.

[0048] The process of measuring the conductivity σ of the seawater 90 is performed by calculating the conductivity σ of the seawater using a pair of conductivity measuring electrodes 20 of a conductivity meter 2, which is integrally provided with a pair of electrode sections 10 of the underwater electric field sensor 1. Specifically, the pair of conductivity measuring electrodes 20, like the pair of electrode sections 10 of the underwater electric field sensor 1, are either placed on a self-propelled underwater device or held by a diver. The underwater device or diver moves near the sacrificial anode 81 and moves the pair of conductivity measuring electrodes 20 along the surface of the sacrificial anode 81. The microcontroller 24 of the conductivity meter 2 calculates the conductivity σ of the seawater between the pair of conductivity measuring electrodes 20 based on the output current value of the constant current source 21 and the potential difference V obtained from the voltmeter 22. The microcontroller 24 outputs the calculated conductivity σ of the seawater between the pair of conductivity measuring electrodes 20 to the control unit 3.

[0049] The process of obtaining the current density J of the current 70 flowing from the sacrificial anode 81 to the seawater 90 is performed by the control unit 3 using the potential difference V measured by the underwater electric field sensor 1 and the conductivity σ measured by the conductivity meter 2. Based on the above equation (1), the control unit 3 obtains the current density J by calculating the current density J at the position where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured. The control unit 3 also stores the obtained current density J in the storage unit 31.

[0050] The current density J to be obtained may be only the current density J at one location where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured, or it may be multiple current densities J at multiple locations where the potential difference V between the first measuring electrode 12 and the second measuring electrode 15 is measured. In addition, in the estimation of the sum of currents 70 flowing from the sacrificial anode 81, which will be described later, it is preferable to obtain multiple current densities J at multiple locations, as estimating the sum of currents 70 using multiple current densities J is more likely to yield the true value of the currents 70 flowing from the sacrificial anode 81 than estimating the sum of currents 70 using only one current density J.

[0051] The step of determining corrosion of the sacrificial anode 81 using the acquired current density J includes the steps of estimating the sum of the currents 70 flowing from the sacrificial anode 81 by integrating the acquired current densities J, and determining corrosion of the sacrificial anode 81 using the estimated sum of currents 70. The step of determining corrosion of the sacrificial anode 81 using the acquired current density J may be performed approximately simultaneously with the step of acquiring the current density J, or it may be performed after the step of acquiring the current density J.

[0052] The process of estimating the total current 70 flowing from the sacrificial anode 81 is performed by the control unit 3 by integrating the acquired current density J. Specifically, the process of estimating the total current 70 flowing from the sacrificial anode 81 is performed by the control unit 3 by integrating the acquired current density J over the area of ​​the sacrificial anode 81. As described above, current density J is the amount of electricity (charge) flowing per unit area per unit time. By integrating the acquired current density J over the area of ​​the sacrificial anode 81, the total current 70 flowing from the sacrificial anode 81 can be estimated. Alternatively, the process of estimating the total current 70 flowing from the sacrificial anode 81 may also be performed by the control unit 3 by adding up multiple acquired current densities J.

[0053] The process for determining corrosion of the sacrificial anode 81 is, for example, performed by determining that the sacrificial anode 81 is corroded if the sum of the estimated currents 70 is below a predetermined threshold. As oxidation (dissolution, corrosion) progresses, the current 70 (corrosion prevention current) supplied to the sacrificial anode 81 decreases, thereby reducing its function as a sacrificial anode 81. Here, the current 70 (corrosion prevention current) supplied from the sacrificial anode 81 can be considered equivalent to the sum of the estimated currents 70 flowing from the sacrificial anode 81. Therefore, if the sum of the estimated currents 70 is below a predetermined threshold, the sacrificial anode 81 is determined to be corroded. Also, if the sum of the estimated currents 70 exceeds a predetermined threshold, the sacrificial anode 81 is determined not to be corroded. The predetermined threshold is not particularly limited and may be 90%, less than 90%, or greater than 90% of the sum of the estimated currents 70 at the time the sacrificial anode 81 is installed in the sea 90.

[0054] The determination of corrosion of the sacrificial anode 81 using the estimated sum of currents 70 may be performed by the control unit 3 or by the user. When the control unit 3 determines the corrosion of the sacrificial anode 81, for example, the control unit 3 is configured to estimate the sum of currents 70 flowing from the sacrificial anode 81 by integrating the current density J stored in the memory unit 31 with respect to the area of ​​the sacrificial anode 81, which is also stored in the memory unit 31. The control unit 3 is configured to determine that the sacrificial anode 81 is corroded if the estimated sum of currents 70 is less than or equal to a predetermined threshold, and to determine that the sacrificial anode 81 is not corroded if the estimated sum of currents 70 exceeds a predetermined threshold.

[0055] Furthermore, when the user determines whether the sacrificial anode 81 is corroded, the control unit 3 is configured to estimate the total current 70 flowing from the sacrificial anode 81 by, for example, integrating the current density J stored in the memory unit 31 over the area of ​​the sacrificial anode 81 previously stored in the memory unit 31, and to display the estimated total current 70 on the display device 33. The user determines that the sacrificial anode 81 is corroded if the total current 70 estimated by the control unit 3 and displayed on the display device 33 is less than or equal to a predetermined threshold, and determines that the sacrificial anode 81 is not corroded if the estimated total current 70 exceeds a predetermined threshold.

[0056] (Method for detecting corrosion in an object under inspection using a current density measuring device) Next, with reference to Figure 5, a second example of a corrosion measurement method for an object under inspection 80 using a current density measuring device 100 will be described. The second example of a corrosion measurement method for an object under inspection 80 is a corrosion detection method that detects corrosion of the object under inspection 80 using the current density J acquired by the current density measuring device 100. The object under inspection 80 is, as an example, an underwater structure 82. The underwater structure 82 is formed of, for example, uncorrosion-resistant steel material 83. Uncorrosion-resistant steel material 83 is steel material that has not been treated with corrosion protection.

[0057] As shown in Figure 5, an underwater structure 82 is positioned on the seabed. The underwater structure 82 is formed of, for example, an unprotected steel material 83 whose main component is iron (Fe). However, the material of the underwater structure 82 is not limited to the above example, and may be aluminum, for example. Furthermore, the underwater structure 82 may not be positioned on the seabed, but rather installed between the seabed and the sea surface.

[0058] The unprotected steel material 83 placed in the sea 90 will, over time, have depressions (thinned areas) on its surface due to corrosion and protrusions 86 where rust has accumulated near the depressions caused by corrosion. Specifically, the unprotected steel material 83 placed in the sea 90 will, over time, develop anodes 84 and cathodes 85 on its surface with different potential differences V. The anode 84 is a depression (thinned area) due to corrosion. The cathode 85 may be a portion near the anode 84.

[0059] As iron (Fe) oxidizes, the electric current 71 flows through the inside of the steel material from the anode portion 84 to the cathode portion 85, and the current 71 that flows through the anode portion 84 flows through the seawater and returns to the cathode portion 85. In other words, the electric current 71 flows between the anode portion 84 and the cathode portion 85 formed in the unprotected steel material 83 placed in the sea 90.

[0060] The corrosion reaction can be expressed by the following equation. Anode section 84: Fe → Fe 2+ +2e - Cathode region 85: 1 / 2O2 + H2O + 2e - →2OH -

[0061] The corrosion reaction of steel is the sum of the anodic and cathode reactions, resulting in the formation of ferrous hydroxide (Fe(OH)2). Fe + 1 / 2O2 + H2O → Fe 2+ +2OH - →Fe(OH)2 Because this ferrous hydroxide is unstable, it is further oxidized to ferric hydroxide and ferric oxide (red rust), which then deposits, causing the steel to thin and forming a rust layer.

[0062] In this case, if the corroded recessed areas (thinned areas) are covered by marine organisms, it is difficult to detect the corroded recessed areas through visual inspection by divers or by visually examining images taken by cameras mounted on self-propelled underwater equipment. Therefore, the corrosion of the unprotected steel material 83 is detected using the current density J obtained by the current density measuring device 100.

[0063] The detection of corrosion of unprotected steel material 83 using the current density J acquired by the current density measuring device 100 comprises the steps of acquiring the current density J non-contact with the unprotected steel material 83 placed in the sea 90 using the potential difference V between a pair of electrode parts 10 of the underwater electric field sensor 1, and detecting corrosion of the unprotected steel material 83 using the acquired current density J. The step of acquiring the current density J is the same as the step of acquiring the current density J in the corrosion determination method of the object under inspection 80 described above, so the explanation is omitted here.

[0064] The process of obtaining the current density J is performed by screening the surface of the unprotected steel material 83 using a current density measuring device 100. That is, the underwater equipment or diver continuously obtains the current density J near the surface of the unprotected steel material 83 by moving a pair of electrode sections 10 and a pair of conductivity measuring electrodes 20 along the vicinity of the surface of the unprotected steel material 83.

[0065] The process of detecting corrosion of the unprotected steel material 83 using the acquired current density J is performed by detecting corrosion of the unprotected steel material 83 using the peak portion 60 (see Figure 6) of the waveform of the acquired current density J. That is, the process of detecting corrosion of the unprotected steel material 83 using the acquired current density J is performed by detecting that the unprotected steel material 83 is corroded if a peak portion 60 exists in the waveform of the continuously acquired current density J, based on the fact that a current 71 flows between the anode portion 84 and the cathode portion 85 formed on the unprotected steel material 83 placed in the sea 90. Note that the process of detecting corrosion of the unprotected steel material 83 using the acquired current density J may be performed approximately simultaneously with the process of acquiring the current density J, or it may be performed after the process of acquiring the current density J.

[0066] Here, the gap between the anode portion 84 and the cathode portion 85 formed in the uncorrosion-resistant steel material 83 is extremely small, and the current 71 flows through this minute gap. Therefore, it is preferable that the distance L (distance between the centers of the openings) between the first opening 131 and the second opening 161 shown in Figure 3 be small. By reducing the distance L between the first opening 131 and the second opening 161, the spatial resolution of the water potential (potential difference V) can be improved.

[0067] As shown in Figure 6, the detection of the peak portion 60 of the acquired current density J waveform is performed by extracting the peak portion 61 and the peak portion 62 of the valley from the generated current density J waveform. Here, if an anode portion 84 and a cathode portion 85 are formed in the unprotected steel material 83, the continuously acquired current density J waveform will have a peak portion 61 and a peak portion 62 of the valley. The peak portion 61 in the current density J waveform indicates the anode portion 84. That is, the peak portion 61 in the current density waveform indicates a recess (thinned portion) which is a corroded area. Also, the peak portion 62 in the current density J waveform indicates the cathode portion 85. Therefore, if the continuously acquired current density J waveform contains a peak portion 60, it means that the unprotected steel material 83 is corroded.

[0068] In the process of detecting corrosion of the unprotected steel material 83, the control unit 3 generates the waveform of the continuously acquired current density J. Furthermore, the extraction of the peak portion 60 in the generated waveform of current density J may be performed by the control unit 3 or by the user. When the control unit 3 detects corrosion of the unprotected steel material 83, for example, the control unit 3 is configured to generate the waveform of the continuously acquired current density J and to determine whether or not there is a peak portion 60 in the waveform of current density J. The control unit 3 is configured to detect corrosion of the unprotected steel material 83 if there is a peak portion 60 in the waveform of current density J, and not to detect corrosion of the unprotected steel material 83 if there is no peak portion 60 in the waveform of current density J.

[0069] Furthermore, when the user detects corrosion of the unprotected steel material 83, the control unit 3 is configured to generate a waveform of the continuously acquired current density J and to display the generated waveform of current density J on the display device 33. The user then determines, for example, whether or not there is a peak portion 60 in the generated waveform of current density J. If there is a peak portion 60 in the waveform of current density J, the user detects corrosion of the unprotected steel material 83; if there is no peak portion 60 in the waveform of current density J, the user does not detect corrosion of the unprotected steel material 83.

[0070] Furthermore, continuous acquisition of the current density J near the surface of the unprotected steel material 83 is performed by moving a pair of electrode sections 10 and a pair of conductivity measuring electrodes 20 along the vicinity of the surface of the unprotected steel material 83 using underwater equipment or a diver. Therefore, if the measurement time and measurement route of the pair of electrode sections 10 and the pair of conductivity measuring electrodes 20 to the unprotected steel material 83 are known, the horizontal axis of the current density J waveform can be said to indicate the measurement time by moving along the vicinity of the surface of the unprotected steel material 83, as well as the measurement position near the surface of the unprotected steel material 83. For this reason, the control unit 3 may be configured to detect the corrosion position of the unprotected steel material 83 based on the position of the peak portion 60 in the current density J waveform, or the user may detect the corrosion position of the unprotected steel material 83 based on the position of the peak portion 60 in the current density J waveform.

[0071] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims. For example, the control unit or user may be configured to use the acquired current density to determine corrosion of metals other than the sacrificial anode being inspected. The control unit or user may be configured to use the acquired current density to determine corrosion of metals coating an underwater structure. Furthermore, for example, the control unit or user may be configured to use the acquired current density to detect corrosion of metals other than unprotected steel as the object under inspection. For example, the control unit or user may be configured to use the acquired current density to detect corrosion of stainless steel in seawater. Furthermore, for example, a pair of electrode sections may be composed of multiple pairs of electrode sections. That is, it may include a first measuring electrode, a second measuring electrode, and a third measuring electrode, with the first measuring electrode being shared, and configured to measure the potential difference between the first measuring electrode and the second measuring electrode as a first pair of electrode sections, and to measure the potential difference between the first measuring electrode and the third measuring electrode as a second pair of electrode sections. In this case, the third measuring electrode may be positioned in a direction perpendicular to the direction in which the second measuring electrode is located relative to the first measuring electrode. Furthermore, for example, the pair of electrode sections do not necessarily have to be formed integrally. That is, the pair of electrode sections may not be integrally provided by the side of the first housing of the first electrode section facing the second electrode section and the side of the second housing of the second electrode section facing the first electrode section coming into contact with each other, but rather each of the pair of electrode sections may be provided separately. However, if the pair of electrode sections are formed integrally, a diver or the like can easily grasp the integrally formed pair of electrode sections with one hand, thereby improving convenience (usability). Also, for example, the pair of electrode sections may be configured such that the distance between the openings provided in each of the pair of electrode sections is variable. Furthermore, for example, the first opening may be located at the center of the first end face, or on the side opposite to the second electrode portion. Also, for example, the second opening may be located at the center of the second end face, or on the side opposite to the first electrode portion. Furthermore, for example, in determining the corrosion of a sacrificial anode, the corrosion of the sacrificial anode may be determined by estimating the total amount of current flowing from the sacrificial anode using the current density and other methods. Furthermore, for example, in detecting corrosion of unprotected steel materials, corrosion of the sacrificial anode may be detected using other methods that utilize current density, rather than using the peak portion of the current density waveform.

[0072] [Aspect] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0073] (Item 1) An underwater electric field sensor including a pair of electrode sections and a potential difference measuring section that measures the potential difference between the pair of electrode sections in a non-contact manner with respect to an object to be inspected placed in water, A conductivity meter for measuring the conductivity of the water, A current density measuring device comprising a control unit that acquires the current density of the current flowing from the object under inspection into the water using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter. By using the potential difference measured non-contact with the object under inspection by an underwater electric field sensor and the conductivity of the water measured by a conductivity meter, the current density of the current flowing from the object under inspection into the water can be obtained non-contact with the object under inspection. Therefore, since the current density of the current flowing near the object under inspection can be obtained in the water without directly connecting to the object under inspection, surface preparation work for direct electrical connection to the object under inspection is unnecessary. Thus, a current density measuring device can be provided that reduces the effort required of the user when measuring corrosion of objects under inspection in water. (Item 2) The current density measuring device according to item 1, wherein the pair of electrode portions are formed such that the openings provided in each of the pair of electrode portions are separated by a predetermined distance. In this case, since the distance between the openings provided in each of the pair of electrode sections is a predetermined value, the current density of the current flowing from the object under inspection into the water can be easily obtained using this predetermined distance between the openings. (Item 3) The current density measuring device according to item 1 or 2, wherein the control unit is configured to determine or detect corrosion of the object under inspection using the acquired current density. In this case, the corrosion of the object to be inspected can be determined or detected using the current density obtained without direct contact with the object to be inspected. Therefore, the effort required of the user, such as scraping, in determining or detecting corrosion of the object to be inspected can be effectively reduced. (Item 4) The aforementioned potential difference is measured non-contact with respect to the sacrificial anode, which is the object under inspection, by the underwater electric field sensor, which measures the potential difference between the pair of electrode portions. The control unit, Control to obtain the current density of the current flowing from the sacrificial anode into the water using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter, A current density measuring device according to any one of items 1 to 3, which performs control to determine corrosion of the sacrificial anode using the acquired current density. In this case, by obtaining the current density of the current flowing from the sacrificial anode, which is the object under inspection, into the water, the corrosion of the sacrificial anode, which is oxidized (dissolved) while supplying a corrosion-preventive current to the underwater structure, can be appropriately determined using the obtained current density. Furthermore, since the corrosion of the sacrificial anode is determined by the control unit using the obtained current density, the corrosion of the sacrificial anode can be easily determined. (Item 5) The current density measuring device according to item 4, wherein the control unit is configured to estimate the total current flowing from the sacrificial anode by integrating the acquired current densities, and to determine corrosion of the sacrificial anode using the estimated total current. In this case, by integrating multiple acquired current densities, the total current flowing from the sacrificial anode can be estimated. Furthermore, by using this estimated total current, the corrosion of the sacrificial anode, which oxidizes (dissolves) while supplying a corrosion-preventive current to the underwater structure, can be accurately determined. (Item 6) The aforementioned potential difference is measured non-contact with the unprotected steel material being inspected by the underwater electric field sensor, which measures the potential difference between the pair of electrode portions. The control unit, Control to obtain the current density of the current flowing from the uncorrosion-resistant steel material into the water, using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter, A current density measuring device according to any one of items 1 to 3, which performs control to detect corrosion of the unprotected steel material using the acquired current density. In this case, by obtaining the current density of the current flowing through the water from the untreated, corrosion-resistant steel material being inspected, the obtained current density can be used to appropriately detect the untreated, corrosion-resistant steel material that has been oxidized. Furthermore, since the control unit uses the obtained current density to detect the corrosion of the untreated steel material, corrosion of the untreated steel material can be easily detected. (Item 7) The current density measuring device according to item 6, wherein the control unit is configured to detect corrosion of the unprotected steel material using the peak portion of the acquired current density waveform. In this case, the peak portion of the acquired current density waveform can be used to easily detect unprotected steel materials that have been corroded by oxidation. (Item 8) The pair of electrode sections includes a first electrode section comprising a first measuring electrode for measuring the potential in the water and a cylindrical first housing covering the first measuring electrode, having a first opening on its first end face that communicates with the outside; and a second electrode section adjacent to the first electrode section comprising a second measuring electrode for measuring the potential in the water and a cylindrical second housing covering the second measuring electrode, having a second opening on its second end face that communicates with the outside. The current density measuring device according to item 2, wherein the first opening is provided on the side of the second electrode portion that is closer to the center of the first end face, and the second opening is provided on the side of the first electrode portion that is closer to the center of the second end face. In this case, compared to the case where the first opening is located at the center of the first end face and the second opening is located at the center of the second end face, the distance between the first and second openings can be reduced, thereby improving the spatial resolution of the underwater potential (potential difference). Therefore, for example, accuracy can be improved in determining corrosion of an object under inspection using current density or in detecting corrosion of an object under inspection. (Item 9) A step of acquiring current density in a non-contact manner for an object to be inspected placed in water using the potential difference between a pair of electrode parts, A corrosion measurement method comprising the steps of determining corrosion of the object under inspection or detecting corrosion of the object under inspection using the acquired current density. Corrosion of an object can be detected using the current density acquired non-contact with the object under inspection. Therefore, in measuring corrosion of an object under inspection in water, the current density of the current flowing near the object under inspection can be acquired without directly connecting to the object under inspection, eliminating the need for surface preparation work to directly connect to the object under inspection. Thus, a corrosion measurement method can be provided that reduces the effort required of the user when measuring corrosion of an object under inspection in water. (Item 10) The step of obtaining the current density is: The steps include measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the object to be inspected, The steps include measuring the conductivity of the water, A corrosion measurement method according to item 9, comprising the step of obtaining the current density of the current flowing from the object under inspection into the water using the measured potential difference and the measured conductivity. In this case, the current density of the current flowing from the object under inspection into the water can be appropriately obtained non-contact with the object under inspection by using the potential difference measured non-contact with the object under inspection and the measured conductivity of the water. Therefore, the current density can be obtained accurately non-contact with the object under inspection. (Item 11) The step of measuring the potential difference involves measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the sacrificial anode, which is the object under inspection. The corrosion measurement method according to item 10, wherein the step of determining or detecting corrosion of the object under inspection is to determine the corrosion of the sacrificial anode using the acquired current density. In this case, by obtaining the current density of the current flowing from the sacrificial anode, which is the object under inspection, into the water, the corrosion of the sacrificial anode, which is oxidized (dissolved) while supplying a corrosion-preventive current to the underwater structure, can be appropriately determined using the obtained current density. (Item 12) The corrosion measurement method described in item 11, wherein the step of determining the corrosion of the sacrificial anode is to estimate the total current flowing from the sacrificial anode by integrating the acquired current densities, and to determine the corrosion of the sacrificial anode using the estimated total current. In this case, by integrating multiple acquired current densities, the total current flowing from the sacrificial anode can be estimated. Furthermore, by using this estimated total current, the corrosion of the sacrificial anode, which oxidizes (dissolves) while supplying a corrosion-preventive current to the underwater structure, can be accurately determined. (Item 13) The step of measuring the potential difference involves measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the unprotected steel material being inspected. The corrosion measurement method according to item 10, wherein the step of determining or detecting corrosion of the object under inspection is to detect corrosion of the unprotected steel material using the acquired current density. In this case, by obtaining the current density of the electric current flowing through water from the untreated, corrosion-resistant steel material being inspected, the obtained current density can be used to appropriately detect the untreated, corrosion-resistant steel material that has been corroded by oxidation. (Item 14) The corrosion measurement method described in item 13, wherein the step of detecting corrosion of the unprotected steel material involves detecting corrosion of the unprotected steel material using the peak portion of the acquired current density waveform. In this case, the peak portion of the acquired current density waveform can be used to easily detect unprotected steel materials that have been corroded by oxidation. [Explanation of Symbols]

[0074] 1. Underwater electric field sensor 2. Conductivity meter 3. Control Unit 10 Pair of electrode sections 11 First electrode part 12 1st measurement electrode 13. First cabinet 14 Second electrode part 15 Second measurement electrode 16. Second cabinet 17 Potential difference measurement section 60 Peak section 70, 71 Current flowing from the object under inspection into the water 80. Object under inspection 81 Sacrificial Anode 83 Uncorrosion-resistant steel 100 Current density measuring device 130 First end surface 131 First opening (opening) 134 Center of the first end face 160 2nd end face 161 Second opening (opening) 164 Center of the second end face V potential difference σ conductivity J current density

Claims

1. An underwater electric field sensor including a pair of electrode sections and a potential difference measuring section that measures the potential difference between the pair of electrode sections in a non-contact manner with respect to an object to be inspected placed in water, A conductivity meter for measuring the conductivity of the water, A current density measuring device comprising a control unit that acquires the current density of the current flowing from the object under inspection into the water using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter.

2. The current density measuring device according to claim 1, wherein the pair of electrode portions are formed such that the openings provided in each of the pair of electrode portions are separated by a predetermined distance.

3. The current density measuring device according to claim 1, wherein the control unit is configured to determine corrosion of the object under inspection or to detect corrosion of the object under inspection using the acquired current density.

4. The aforementioned potential difference is measured non-contact with respect to the sacrificial anode, which is the object under inspection, by the underwater electric field sensor, which measures the potential difference between the pair of electrode portions. The control unit, Control to obtain the current density of the current flowing from the sacrificial anode into the water using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter, The current density measuring device according to claim 1, further comprising the control of determining corrosion of the sacrificial anode using the acquired current density.

5. The current density measuring device according to claim 4, wherein the control unit is configured to estimate the total current flowing from the sacrificial anode by integrating the acquired current densities, and to determine corrosion of the sacrificial anode using the estimated total current.

6. The aforementioned potential difference is measured non-contact with the unprotected steel material being inspected by the underwater electric field sensor, which measures the potential difference between the pair of electrode portions. The control unit, Control to obtain the current density of the current flowing from the uncorrosion-resistant steel material into the water, using the potential difference measured by the underwater electric field sensor and the conductivity measured by the conductivity meter, The current density measuring device according to claim 1, further comprising the function of using the acquired current density to control the detection of corrosion of the unprotected steel material.

7. The current density measuring device according to claim 6, wherein the control unit is configured to detect corrosion of the unprotected steel material using the peak portion of the acquired current density waveform.

8. The pair of electrode sections includes a first electrode section comprising a first measuring electrode for measuring the potential in the water and a cylindrical first housing covering the first measuring electrode, having a first opening on its first end face that communicates with the outside; and a second electrode section disposed adjacent to the first electrode section comprising a second measuring electrode for measuring the potential in the water and a cylindrical second housing covering the second measuring electrode, having a second opening on its second end face that communicates with the outside. The current density measuring device according to claim 2, wherein the first opening is provided on the side of the second electrode portion that is closer to the center of the first end face, and the second opening is provided on the side of the first electrode portion that is closer to the center of the second end face.

9. A step of acquiring current density in a non-contact manner for an object to be inspected placed in water using the potential difference between a pair of electrode parts, A corrosion measurement method comprising the steps of determining corrosion of the object under inspection or detecting corrosion of the object under inspection using the acquired current density.

10. The step of obtaining the current density is: The steps include measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the object to be inspected, The steps include measuring the conductivity of the water, A corrosion measurement method according to claim 9, comprising the step of obtaining the current density of the current flowing from the object under inspection into the water using the measured potential difference and the measured conductivity.

11. The step of measuring the potential difference involves measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the sacrificial anode, which is the object under inspection. The corrosion measurement method according to claim 10, wherein the step of determining or detecting corrosion of the object under inspection is to determine the corrosion of the sacrificial anode using the acquired current density.

12. The corrosion measurement method according to claim 11, wherein the step of determining the corrosion of the sacrificial anode is to estimate the total amount of current flowing from the sacrificial anode by integrating the acquired current densities, and to determine the corrosion of the sacrificial anode using the estimated total amount of current.

13. The step of measuring the potential difference involves measuring the potential difference between the pair of electrode portions in a non-contact manner with respect to the unprotected steel material being inspected. The corrosion measurement method according to claim 10, wherein the step of determining or detecting corrosion of the object to be inspected is to detect corrosion of the unprotected steel material using the acquired current density.

14. The corrosion measurement method according to claim 13, wherein the step of detecting corrosion of the unprotected steel material involves detecting corrosion of the unprotected steel material using the peak portion of the acquired current density waveform.

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