Corrosion estimation and analysis apparatus and corrosion estimation and analysis method

Abstract

To provide a corrosion estimation and analysis device capable of easily estimating and analyzing corrosion of a metal structure at low cost.SOLUTION: A corrosion estimation analysis device 1 estimates and analyzes corrosion of a pipe 5 (metal structure) through which fresh water 6 (liquid) flows. The corrosion estimation and analysis device 1 includes a measurement probe 10 in which a first metal portion 20 and a second metal portion 21 formed of the same metal as the pipe 5 are connected in series, the first metal portion 20 is exposed to the fresh water 6, and the second metal portion 21 is shielded from the fresh water 6, a power supply unit 11 that applies a current to the metal portions 2021 and, a voltage measurement unit 12 that measures the voltage of each of the metal portions 2021 and, and a corrosion potential measurement unit 14 that measures the corrosion potential of the first metal portion 20 with respect to a reference electrode 13 that provides a reference potential.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a corrosion estimation and analysis device and a corrosion estimation and analysis method for estimating and analyzing corrosion of a metal structure. [Background technology]

[0002] A test method (test device) for investigating the corrosiveness of metal materials to industrial water is known (Non-Patent Document 1). In this test method (test device), a test specimen fixed inside a metal structure such as a pipe is exposed to industrial water, and the test specimen is recovered after a certain period of time, and the corrosion rate or erosion rate (corrosion rate) is calculated from the change in mass of the recovered test specimen. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] JIS K0100-1990 Industrial water corrosivity test method Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned techniques have the problem that, in order to calculate the corrosion rate, etc., test pieces must be recovered from inside the metal structure, which requires a lot of time and effort, as well as a lot of expense. Furthermore, for example, when analyzing the corrosion state of a metal structure from multiple corrosion rates, etc., multiple test pieces must be prepared and the recovery work must be performed multiple times, which makes the above-mentioned problems more pronounced. Furthermore, the above-mentioned techniques do not allow for immediate acquisition of information regarding the corrosion of the metal structure.

[0005] In consideration of the above circumstances, the present invention provides a corrosion estimation and analysis device and a corrosion estimation and analysis method that can estimate and analyze corrosion of a metal structure simply and at low cost. [Means for solving the problem]

[0006] The present invention is a corrosion estimation and analysis device that estimates and analyzes corrosion of a metal structure through which a liquid flows or is stored, and includes a measurement probe that connects a first metal part and a second metal part in series, each of which is made of the same or similar metal as the metal structure, exposing the first metal part to the liquid and shielding the second metal part from the liquid, a power supply unit that applies current to the first metal part and the second metal part, a voltage measurement unit that measures the voltage for each of the first metal part and the second metal part, a reference electrode that is electrically connected to the first metal part and provides a reference potential, a corrosion potential measurement unit that measures the corrosion potential of the first metal part relative to the reference electrode, and a recording unit that records the elapsed time since the first metal part began to be exposed to the liquid and periodically records the voltage value measured by the voltage measurement unit and the corrosion potential measured by the corrosion potential measurement unit.

[0007] In this case, the measurement probe is preferably electrically connected to the metal structure and has the same potential as the metal structure.

[0008] The present invention provides a corrosion estimation and analysis method for estimating and analyzing corrosion of a metal structure through which a liquid flows or is stored, the method comprising the steps of: connecting a first metal part and a second metal part formed of the same or similar metal as the metal structure in series; exposing the first metal part to the liquid; shielding the second metal part from the liquid; applying a current to the first metal part and the second metal part; measuring a voltage for each of the first metal part and the second metal part; estimating the thickness of the first metal part based on the measured voltage values; and estimating the amount of thickness reduction of the first metal part based on the estimated thickness of the first metal part; a corrosion rate calculation step; calculating the corrosion rate of the first metal part, which is the change over time in the amount of thickness reduction of the first metal part; and a corrosion reaction analysis step; electrically connecting a reference electrode that provides a reference potential to the first metal part; and analyzing the corrosion reaction of the first metal part from the relationship between the corrosion rate and the corrosion potential of the first metal part with respect to the reference electrode. [Effects of the Invention]

[0009] According to the present invention, corrosion of a metal structure can be estimated and analyzed simply and at low cost. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a corrosion estimation analysis device according to an embodiment of the present invention. [Figure 2] 1 is a flowchart illustrating a corrosion estimation analysis method according to an embodiment of the present invention. [Figure 3] FIG. 1 is an explanatory diagram illustrating a technique for analyzing a metal corrosion reaction from the relationship between corrosion rate and corrosion potential in a corrosion estimation analysis method according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram illustrating test conditions for a corrosion estimation analysis device according to an embodiment of the present invention. [Figure 5] 4 is a graph showing the relationship between the amount of reduction in thickness of the first metal part and the elapsed time, obtained using the corrosion estimation analysis device according to one embodiment of the present invention. [Figure 6] 1 is a graph showing the relationship between the amount of thickness reduction of the first metal part and the amount of thickness reduction of a comparative test piece, obtained using the corrosion estimation analysis device according to one embodiment of the present invention. [Figure 7] 4 is a graph showing the relationship between the corrosion rate and corrosion potential of the first metal part obtained using the corrosion estimation analysis device according to one embodiment of the present invention. [Figure 8] 8 is a graph illustrating the corrosion reaction of the first metal part immersed in the test solution (1) among the graphs shown in FIG. 7. [Figure 9] 8 is a graph illustrating the corrosion reaction of the first metal part immersed in the test solution (7) among the graphs shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that in each drawing, the shape and size of each component are not accurate and are shown schematically for the purpose of explanation.

[0012] [Corrosion estimation analysis device] A corrosion estimation analysis device 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the corrosion estimation analysis device 1.

[0013] The corrosion estimation analysis device 1 is provided for estimating and analyzing corrosion of building equipment piping 5 through which fresh water 6, such as tap water, flows. Specifically, the corrosion estimation analysis device 1 is used in a corrosion estimation analysis method that estimates the corrosion state and progression (average corrosion rate (V)) of a metal equivalent to the building equipment piping 5 (steel pipe) and analyzes the corrosion reaction occurring in the metal. The average corrosion rate (V) is used to evaluate the lifespan of the building equipment piping 5. By analyzing the corrosion reaction in the metal, it becomes possible to select a material for the building equipment piping 5 or change the flow rate of the fresh water 6 to improve the lifespan of the building equipment piping 5. Note that in this specification, the "building equipment piping 5" will be simply referred to as "piping 5," and the "average corrosion rate (V)" will be simply referred to as "corrosion rate (V)." Furthermore, in this specification, the fresh water 6 flowing inside the piping 5 is an example of a "liquid" as defined in the claims, and the piping 5 through which the fresh water 6 flows is an example of a "metal structure" as defined in the claims.

[0014] The corrosion estimation analysis device 1 includes a measurement probe 10 , a power supply unit 11 , a voltage measurement unit 12 , a reference electrode 13 , a corrosion potential measurement unit 14 , and a recording unit 15 .

[0015] <Measurement probe> The measurement probe 10 has two first metal parts 20, a second metal part 21, and an insulating base part 22. Since the two first metal parts 20 have the same structure, this specification will mainly describe one first metal part 20. In addition, in descriptions common to the "first metal part 20" and the "second metal part 21," they will simply be referred to as "metal parts 20, 21."

[0016] (1st metal part, 2nd metal part) The metal parts 20, 21 are formed from a metal (for example, carbon steel (SPCC (Steel Plate Cold Commercial)) that is the same as or similar to that of the piping 5 (metal structure). The first metal part 20 and the second metal part 21 are formed to have the same size and shape. The first metal part 20 and the second metal part 21 are connected in series so that the same current can be applied to each. The two first metal parts 20 are connected in series via electric wires, with the second metal part 21 sandwiched between them.

[0017] (insulating base part) The insulating base portion 22 is made of, for example, an electrically insulating synthetic resin and is formed in a substantially cylindrical shape capable of containing the metal portions 20, 21. The two first metal portions 20 and the second metal portion 21 are enclosed in the insulating base portion 22. Specifically, the first metal portion 20 is held by the insulating base portion 22 with at least a portion exposed on the surface of the insulating base portion 22. The second metal portion 21 is sealed inside the insulating base portion 22 and is held by the insulating base portion 22 so as not to be exposed. Note that the insulating base portion 22 is not limited to being made of synthetic resin, and may be made of an insulator such as ceramic or glass.

[0018] The measurement probe 10 is supported by, for example, a mounting cap 10A, and is attached in a liquid-tight manner to (the wall of) the pipe 5 via the mounting cap 10A. A male thread is formed on the outer peripheral surface of the mounting cap 10A, and a female threaded hole 5A into which the male thread of the mounting cap 10A engages is formed in the wall of the pipe 5. When the mounting cap 10A is screwed into the female threaded hole 5A and the measurement probe 10 is attached to the pipe 5, the first metal part 20 is exposed to (comes into contact with) the fresh water 6 in the pipe 5, and therefore corrodes over time. On the other hand, the second metal part 21 is shielded (isolated) from the fresh water 6, and therefore does not corrode.

[0019] <Power supply section> The power supply unit 11 is, for example, a DC stabilized power supply. The power supply unit 11 is connected via a power cable 23 to both ends of a circuit in which two first metal parts 20, in other words, metal parts 20 and 21, are connected in series. A power connection switching unit 24 that switches between connection and disconnection of the circuit is provided on the power cable 23 that connects one of the first metal parts 20 and the power supply unit 11. When the power connection switching unit 24 is turned on (see FIG. 1 ), one of the first metal parts 20 and the power supply unit 11 are connected. In this state, the power supply unit 11 applies current of the same value to the first metal part 20 and the second metal part 21. When the power connection switching unit 24 is turned off (not shown), one of the first metal parts 20 and the power supply unit 11 are disconnected.

[0020] The pipe 5 (metal structure) and the measurement probe 10 are connected via a reference cable 25. Specifically, one end of the reference cable 25 is connected to the pipe 5, and the other end of the reference cable 25 is connected to a power cable 23 that connects one of the first metal parts 20 and the power supply part 11. A reference connection switching part 26 that switches between connection and disconnection is provided on the reference cable 25. When the power connection switching part 24 is turned on (not shown), the power cable 23 and the pipe 5 are connected. In this state, the measurement probe 10 (metal parts 20, 21) is electrically connected to the pipe 5 and is at the same potential as the pipe 5. In FIG. 1, the reference connection switching part 26 is turned off, and the pipe 5 and the measurement probe 10 are disconnected.

[0021] <Voltage measurement section> The voltage measurement unit 12 includes a voltmeter such as a digital multimeter. The two first metal parts 20 and the second metal part 21 are individually connected to the voltage measurement unit 12 via voltage measurement cables 27. The voltage measurement unit 12 measures the voltages (voltage values ​​(V1, V2)) of the first metal part 20 and the second metal part 21. The voltage measurement unit 12 also includes a transmission unit (not shown) that transmits data (voltage values ​​(V1, V2)) using a wired or wireless communication standard such as a local area network (LAN) or Bluetooth (registered trademark). The voltage measurement unit 12 performs analog-to-digital conversion (A / D) on the measured data and transmits the data to the recording unit 15 using the function of the transmission unit.

[0022] <Reference electrode> The reference electrode 13 is, for example, a silver / silver chloride electrode, and is an electrode that provides an (electrochemical) reference potential. Similar to the measurement probe 10, the reference electrode 13 is attached in a liquid-tight manner to the female threaded hole 5B of the piping 5 via a mounting cap 13A. When the reference electrode 13 is attached to the piping 5 by screwing the mounting cap 13A into the female threaded hole 5B, the reference electrode 13 is exposed to the fresh water 6 in the piping 5 and is electrically connected to the first metal part 20 via the fresh water 6.

[0023] <Corrosion potential measurement unit> The corrosion potential measuring unit 14 includes a voltmeter such as a digital multimeter. The corrosion potential measuring unit 14 is connected to the reference electrode 13 and one of the first metal parts 20 via a potential measuring cable 28. Specifically, one end of the potential measuring cable 28 is connected to the reference electrode 13, and the other end of the potential measuring cable 28 is connected to a voltage measuring cable 27 that connects one of the first metal parts 20 and the voltage measuring unit 12. A potential connection switching unit 29 that switches between connection and disconnection is provided in the potential measuring cable 28. When the potential connection switching unit 29 is in an ON state (not shown), the reference electrode 13 and one of the first metal parts 20 are connected. In this state, the corrosion potential measuring unit 14 measures the corrosion potential (E) of the first metal part 20 relative to the reference electrode 13. Note that in FIG. 1 , the potential connection switching unit 29 is in an OFF state, and the reference electrode 13 and one of the first metal parts 20 are disconnected.

[0024] Furthermore, corrosion potential measuring unit 14 includes a transmitting unit (not shown) that transmits data (corrosion potential (E)) using the same communication standard as the transmitting unit of voltage measuring unit 12. Corrosion potential measuring unit 14 A / D converts the measured data (corrosion potential (E)) and transmits the data to recording unit 15 using the function of the transmitting unit.

[0025] <Recording Department> The recording unit 15 is, for example, a personal computer, a smartphone, a tablet, or a data logger. The recording unit 15 is connected to the voltage measurement unit 12 and the corrosion potential measurement unit 14 in a state where data communication is possible. The recording unit 15 includes a receiving unit (not shown) that receives data using the same communication standard as the transmitting unit of the voltage measurement unit 12, etc. The recording unit 15 receives data such as the voltage values ​​(V1, V2) transmitted from the voltage measurement unit 12 and the corrosion potential (E) transmitted from the corrosion potential measurement unit 14 using the function of the receiving unit. The recording unit 15 periodically (at regular intervals) records (saves) the received data (voltage values ​​and corrosion potential (E)). The recording unit 15 also records the elapsed time since the first metal part 20 began to be exposed to fresh water 6 using a clock function or the like that is provided as standard.

[0026] [Corrosion estimation analysis method] Next, a corrosion estimation analysis method using the corrosion estimation analysis device 1 will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing the corrosion estimation analysis method. Figure 3 is an explanatory diagram explaining a technique for analyzing the corrosion reaction of metals from the relationship between the corrosion rate (V) and the corrosion potential (E).

[0027] As shown in FIG. 2 , the corrosion estimation analysis method includes a corrosion estimation step S1, a corrosion rate calculation step S2, and a corrosion reaction analysis step S3. The corrosion estimation analysis method (corrosion estimation step S1, corrosion rate calculation step S2, and corrosion reaction analysis step S3) may be performed manually by a human operator who checks data (such as voltage values ​​(V1, V2), corrosion potential (E), and elapsed time) recorded in the recording unit 15, automatically by software (a program) stored in the recording unit 15, or semi-automatically by collaboration between the operator operating the recording unit 15 and the software. When the corrosion estimation analysis method is performed automatically or semi-automatically by software, information on the dimensions of the metal parts 20 and 21, such as their thicknesses, and the materials of the metal parts 20 and 21, is stored in the recording unit 15. In addition, in the initial state before the corrosion estimation analysis method is performed, the reference connection switching unit 26 is set to the ON state, and the power supply connection switching unit 24 and the potential connection switching unit 29 are set to the OFF state.

[0028] <Corrosion estimation process> The corrosion estimation step S1 is based on the basic principle that the electrical resistance value changes as the corrosion of the metal progresses, and accordingly, the voltage value also changes when a constant current is applied. The corrosion state of the surface of the first metal part 20, which is made of the same (similar) metal as the pipe 5, is assumed to match the corrosion state of the inner surface of the pipe 5. Prior to the execution of the corrosion estimation step S1, the power supply connection switching unit 24 is turned on, the reference connection switching unit 26 and the potential connection switching unit 29 are each turned off (see FIG. 1), and the power supply unit 11 is started up.

[0029] In the corrosion estimation step S1, the power supply unit 11 applies a current to the metal parts 20 and 21, and the voltage measurement unit 12 measures the voltage value (V1) of the first metal part 20 exposed to the fresh water 6 and the voltage value (V2) of the second metal part 21 shielded (isolated) from the fresh water 6 under the same conditions (environment). The recording unit 15 records the measured voltage values ​​(V1 and V2). The recording unit 15 (or an operator) estimates the thickness of the first metal part 20 based on the voltage values ​​(V1 and V2) recorded in the recording unit 15. Specifically, it is known that the thickness (δ(t)) of the first metal part 20 after a certain time (t) has elapsed can be calculated (estimated) by substituting the voltage values ​​(V1 and V2) of the metal parts 20 and 21 at each elapsed time and the initial thickness of the first metal part 20 (δ(t=0)) into the following equation 1:

[0030]

number

[0031] Furthermore, in the corrosion estimation step S1, the thickness reduction amount (D1) of the first metal part 20 is estimated (calculated) based on the estimated (calculated) thickness (δ(t)) of the first metal part 20. Specifically, the thickness reduction amount (D1) of the first metal part 20 is calculated as the difference between the thickness (δ(t)) after a certain time (t) has elapsed and the initial thickness (δ(t=0)). The thickness reduction amount (D1) of the first metal part 20 corresponds to the amount of corrosion of the first metal part 20 (piping 5).

[0032] <Corrosion rate calculation process> In the corrosion rate calculation step S2, the recording unit 15 (or an operator) calculates the corrosion rate (V) of the first metal part 20, which is the change over time in the amount of thickness reduction (D1) of the first metal part 20. The corrosion rate (V) of the first metal part 20 is the amount of thickness reduction (D1) of the first metal part 20 per elapsed time, and is calculated by dividing the amount of thickness reduction (D1) by the elapsed time (time (t)) at the time of calculation. Because the first metal part 20 is the same as (similar to) the metal constituting the pipe 5, the corrosion rate (V) of the first metal part 20 can be estimated to be the corrosion rate (V) of the pipe 5. The calculated corrosion rate (V) may be recorded in the recording unit 15. In addition, in the corrosion rate calculation step S2, the power supply connection switching unit 24 is maintained in an ON state, and the reference connection switching unit 26 and the potential connection switching unit 29 are each maintained in an OFF state (see FIG. 1).

[0033] As a result of the above, the amount of thickness reduction (D1) of the first metal part 20 and the corrosion rate (V) as a change over time can be determined, and based on these, it is possible to evaluate the corrosion state and progression of corrosion of the piping 5, and to evaluate the lifespan of the piping 5.

[0034] <Corrosion reaction analysis process> As shown in Figure 3, a method is known for analyzing the corrosion reaction (corrosion mode) of metals from the relationship between the corrosion rate (V) and the corrosion potential (E). This method analyzes the reactions that change on the metal surface based on the increase or decrease in the corrosion rate (V) and the increase or decrease in the corrosion potential (E). <1> ~ <4> The corrosion reaction analysis step S3 is based on the basic principle of analyzing the corrosion reaction of the first metal part 20 using the above-mentioned method. Prior to the execution of the corrosion reaction analysis step S3, the power supply unit 11 is stopped, the power supply connection switching unit 24 and the reference connection switching unit 26 are each turned OFF, and the potential connection switching unit 29 is turned ON.

[0035] In the corrosion reaction analysis step S3, the reference electrode 13 is electrically connected to the first metal part 20, the corrosion potential measurement unit 14 measures the corrosion potential (E) of the first metal part 20 relative to the reference electrode 13, and the recording unit 15 records the measured corrosion potential (E). After measuring the corrosion potential (E), the reference connection switching unit 26 is turned ON, and the power supply connection switching unit 24 and the potential connection switching unit 29 are each turned OFF (returned to their initial states).

[0036] Furthermore, in the corrosion reaction analysis step S3, the recording unit 15 (or an operator) analyzes the corrosion reaction of the first metal part 20 from the relationship between the corrosion potential (E) and corrosion rate (V) of the first metal part 20 recorded in the recording unit 15. That is, the reactions that change on the surface of the first metal part 20 are classified and the corrosion state is grasped. The corrosion reaction on the surface of the first metal part 20 coincides with the corrosion reaction on the inner surface of the pipe 5. The analysis results of the corrosion reaction may be recorded in the recording unit 15.

[0037] The recording unit 15 (or an operator) repeatedly executes the above-described corrosion estimation step S1, corrosion rate calculation step S2, and corrosion reaction analysis step S3 at regular intervals (regular periods).

[0038] [Verification of corrosion estimation analysis device (method)] The applicant conducted a test (verification) to confirm the effectiveness of the corrosion estimation analysis device 1 (corrosion estimation analysis method) described above. Hereinafter, the test conditions and test results (verification) for the corrosion estimation analysis device 1 (corrosion estimation analysis method) will be described with reference to FIGS. 4 and 9. FIG. 4 is a schematic diagram illustrating the test conditions for the corrosion estimation analysis device 1. FIG. 5 is a graph showing the relationship between the thickness reduction (D1) of the first metal part 20 and the elapsed time. FIG. 6 is a graph showing the relationship between the thickness reduction (D1) of the first metal part 20 and the thickness reduction (D2) of the comparative test piece 16. FIG. 7 is a graph showing the relationship between the corrosion rate (V) of the first metal part 20 and the corrosion potential (E). FIG. 8 is a graph of FIG. 7 illustrating the corrosion reaction of the first metal part 20 immersed in the test solution (1). FIG. 9 is a graph of FIG. 7 illustrating the corrosion reaction of the first metal part 20 immersed in the test solution (7).

[0039] <Test conditions> As shown in Table 1, eight types of tap water with different water qualities (test solutions (1) to (8): 500 ml each) were prepared as an example of fresh water 6 (liquid).

[0040] [Table 1]

[0041] As shown in FIG. 4, each of the fresh waters 6 was placed in a beaker 30 (500 ml capacity) together with a stirrer 32, and the beaker 30 was placed on a stirrer 31. The measurement probe 10 of the corrosion estimation analysis device 1 described above and a comparative test piece 16 made of the same metal as the first metal part 20 (SPCC, 0.3 mm thick, known mass) were immersed in the fresh water 6 in the beaker 30. In this state, the first metal part 20 and the comparative test piece 16 were exposed to the fresh water 6, while the second metal part 21 was not exposed to the fresh water 6. The reference electrode 13 was immersed in a container 33 containing a saturated potassium chloride solution 34, and the saturated potassium chloride solution 34 in the container 33 was connected to the fresh water 6 in the beaker 30 via a salt bridge 35 made of saturated potassium chloride solidified with agar.

[0042] Although FIG. 4 shows one corrosion estimation analysis device 1 (test device), eight corrosion estimation analysis devices 1 (test devices) are prepared corresponding to eight freshwaters 6 (test solutions (1) to (8)), and the same test is performed on the eight freshwaters 6. Also, in FIG. 4, the power cable 23, power supply connection switching unit 24, reference cable 25, reference connection switching unit 26, voltage measurement cable 27, potential measurement cable 28, and potential connection switching unit 29 are not labeled and are omitted from the illustration as appropriate. Test solutions (1) to (7) are tap water collected at different locations, and test solution (8) is treated water that has been treated to prevent corrosion of the first metal part 20 and the comparative test piece 16.

[0043] The fresh water 6 (beaker 30) and the corrosion estimation analysis device 1 were placed in an environment at room temperature of 25°C, and the agitator 31 was operated with the rotation speed of the agitator 32 set to 300 rpm, causing the fresh water 6 in the beaker 30 to flow (stir) (start of test). The test period (the period from the start of the test to the end of the test) was 30 days, and the current applied to the measurement probe 10 (first metal part 20 and second metal part 21) was 3 A. The current applied to the measurement probe 10 can be freely set depending on the size, material, measurement environment, etc. of the first metal part 20 and second metal part 21, but is preferably 1 to 10 A, preferably 2 to 5 A, and more preferably 3 A.

[0044] <Verification 1> In Verification 1, the effect of the type of fresh water 6 on the corrosion of the first metal part 20 was examined. As shown in FIG. 5, it was possible to detect changes in the thickness of the first metal part 20 over time in all of the test solutions (1) to (8). Specifically, it was confirmed that the amount of thickness reduction (D1) (amount of corrosion) of the first metal part 20 increased over time in the measurement probe 10 immersed in the test solutions (1) to (7). Furthermore, the rate of increase in the amount of thickness reduction (D1) (corrosion rate (V)) showed different changes depending on the type of fresh water 6 (test solutions (1) to (7)). Note that there was no significant change in the thickness of the first metal part 20 in the test solution (8).

[0045] From the above, it was confirmed that it is possible to evaluate the effect of the type of fresh water 6 on the corrosion of the first metal part 20 (piping 5). In addition, the corrosion rate (V) can be calculated from the slope of the graph in Figure 5, and the corrosion rate (V) obtained by this method is considered to be more accurate than the corrosion rate (V) obtained by an electrochemical method such as the polarization resistance method.

[0046] <Verification 2> In verification 2, the correlation between the thickness reduction amount (D1) of the first metal part 20 obtained using the measurement probe 10 and the thickness reduction amount (D2) of the comparative test piece 16 was verified. The thickness reduction amount (D2) of the comparative test piece 16 (average thickness reduction amount) was calculated from the weight reduction amount of the comparative test piece 16. As shown in Figure 6, the coefficient of determination R^2 value calculated from the two variables, the thickness reduction amount (D1) of the first metal part 20 and the thickness reduction amount (D2) of the comparative test piece 16, was 0.9876.

[0047] From the above, it was confirmed that there is an extremely strong correlation between the thickness reduction amount (D1) of the first metal part 20 and the thickness reduction amount (D2) of the comparative test piece 16.

[0048] <Verification 3> In Verification 3, the corrosion reaction (corrosion mode) of the first metal part 20 was analyzed. Figure 7 was obtained by plotting the corrosion rate (V) and corrosion potential (E) of the first metal part 20 in test solutions (1) to (3), (6), and (7) out of eight types of freshwater 6 (test solutions (1) to (8)). For example, when analyzing the corrosion of the first metal part 20 in test solution (1), as shown in Figure 8, it can be inferred that the anodic reaction was promoted on the surface of the first metal part 20, followed by the promotion of a cathodic reaction due to the peeling of corrosion products from the surface of the first metal part 20. Furthermore, when analyzing the corrosion of the first metal part 20 in test solution (7), as shown in Figure 9, it can be inferred that the anodic reaction was promoted on the surface of the first metal part 20, followed by the formation of a coating on the cathodic reaction site, which inhibited the cathodic reaction, and then the anodic reaction was promoted again.

[0049] From the above, it was confirmed that the corrosion reaction occurring on the surface of the first metal part 20 can be analyzed with high accuracy. Furthermore, from the analysis results of the corrosion reaction of the first metal part 20, it is possible to infer not only the corrosion (change) of the first metal part 20 but also changes in the environment (fresh water 6) to which the first metal part 20 is exposed. For example, if the cathodic reaction is accelerated, it is possible to infer that the cause is an increase in the flow rate of the fresh water 6 flowing through the pipe 5 or an increase in the concentration of dissolved oxygen in the fresh water 6.

[0050] According to the corrosion estimation analysis device 1 (corrosion estimation analysis method) of the present embodiment described above, the thickness (δ(t)) of the first metal part 20 can be estimated from the voltage values ​​(V1, V2) obtained using the measuring probe 10. This allows the amount of corrosion to be estimated as the thickness reduction (D1) of the first metal part 20, and the corrosion rate (V) can be calculated from the thickness reduction (D1) of the first metal part 20 over time. As a result, the corrosion state and progression of the corrosion of the pipe 5 can be estimated in real time without retrieving the measuring probe 10 placed inside the pipe 5. Furthermore, the corrosion reaction occurring in the first metal part 20 can be analyzed from the relationship between the corrosion potential (E) and the corrosion rate (V) obtained using the measuring probe 10 and the reference electrode 13, etc. As described above, corrosion of the pipe 5 (metal structure) can be estimated and analyzed quickly, easily, and at low cost, without the time and effort required for retrieving the measuring probe 10.

[0051] Furthermore, according to the corrosion estimation analysis device 1 of this embodiment, the measuring probe 10 and the pipe 5 are at the same potential, so it is possible to accurately estimate the corrosion state and progress of corrosion of the pipe 5. Furthermore, for example, if cathodic protection is applied to the pipe 5 (metal structure), the effectiveness of the cathodic protection can be determined by electrically connecting the measuring probe 10 and the pipe 5.

[0052] Although the corrosion estimation analysis device 1 according to this embodiment is illustrated with the measurement probe 10 attached to a pipe 5 made of steel, the present invention is not limited thereto. The measurement probe 10 may be attached to, for example, an iron pipe or lead pipe, or to a pipe 5 made of cast iron, copper, zinc, aluminum, or an alloy containing these metals, or a metal (alloy) whose base material is surface-treated, such as painted. The measurement probe 10 may also be attached to a tank (another example of a metal structure) that contains (retains) a liquid such as fresh water 6. That is, the measurement probe 10 may be attached to a metal structure that circulates or retains a liquid. Furthermore, the metal parts 20 and 21 of the measurement probe 10 may be made of the same or similar metal as the pipe 5, tank, or other metal structure. For example, in the case of carbon steel, the metal parts 20 and 21 may be made of carbon steel with slightly different carbon contents, so that they can be considered almost identical. The liquid inside the metal structure is not limited to fresh water 6, but may also be salt water, alcohol, or the like.

[0053] Furthermore, in the corrosion estimation analysis device 1 according to this embodiment, two first metal parts 20 are provided on the measurement probe 10, but this is not limited to this, and one first metal part 20 may be provided, or three or more first metal parts 20 may be provided (neither is shown).

[0054] Furthermore, although the corrosion estimation analysis device 1 according to this embodiment includes the recording unit 15 for recording various data including voltage values ​​(V1, V2), thickness reduction (D1), corrosion rate (V), and corrosion potential (E), the present invention is not limited to this. For example, a second recording unit for recording corrosion potential (E) may be connected to the corrosion potential measurement unit 14 (not shown), in addition to the recording unit 15 for recording voltage values ​​(V1, V2), etc. Alternatively, for example, the recording unit 15 may be omitted (not shown). In this case, an operator may periodically visually check the voltage measurement unit 12 and the corrosion potential measurement unit 14 and manually perform the corrosion estimation analysis method (corrosion estimation step S1, corrosion rate calculation step S2, and corrosion reaction analysis step S3).

[0055] The above-described embodiment illustrates one aspect of the corrosion estimation analysis device and corrosion estimation analysis method according to the present invention, and the technical scope of the present invention is not limited to the above-described embodiment. The present invention may be modified, substituted, or altered in various ways without departing from the spirit of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept. [Explanation of symbols]

[0056] 1. Corrosion estimation analysis device 5 Building equipment piping (metal structures) 6 Fresh water (liquid) 10 Measuring probe 11 Power supply section 12 Voltage measurement section 13 Reference electrode 14 Corrosion potential measurement section 15 Recording section 20 1st metal part 21 2nd metal part S1 Corrosion estimation process S2 Corrosion rate calculation process S3 Corrosion reaction analysis process

Claims

1. A corrosion estimation and analysis device for estimating and analyzing corrosion of a metal structure through which a liquid flows or is stored, comprising: a measurement probe in which a first metal part and a second metal part, each made of the same or similar metal as the metal structure, are connected in series, the first metal part being exposed to the liquid and the second metal part being shielded from the liquid; a power supply unit that applies a current to the first metal portion and the second metal portion; a voltage measurement unit that measures a voltage for each of the first metal portion and the second metal portion; a reference electrode electrically connected to the first metal portion and providing a reference potential; a corrosion potential measuring unit for measuring a corrosion potential of the first metal part with respect to the reference electrode; a recording unit that records the elapsed time since the first metal part began to be exposed to the liquid, and that periodically records the voltage value measured by the voltage measuring unit and the corrosion potential measured by the corrosion potential measuring unit.

2. 2. The corrosion estimation and analysis device according to claim 1, wherein the measurement probe is electrically connected to the metal structure and has the same potential as the metal structure.

3. A corrosion estimation and analysis method for estimating and analyzing corrosion of a metal structure through which a liquid flows or is stored, comprising: a corrosion estimation process of connecting a first metal portion and a second metal portion formed of the same or similar metal as the metal structure in series, exposing the first metal portion to the liquid and shielding the second metal portion from the liquid, applying current to the first metal portion and the second metal portion, measuring voltages for the first metal portion and the second metal portion, estimating the thickness of the first metal portion based on the measured voltage values, and estimating the amount of thickness reduction of the first metal portion based on the estimated thickness of the first metal portion; a corrosion rate calculation step of calculating a corrosion rate of the first metal portion, which is a change over time in the amount of reduction in thickness of the first metal portion; a corrosion reaction analysis step of electrically connecting a reference electrode that provides a reference potential to the first metal part, and analyzing the corrosion reaction of the first metal part from the relationship between the corrosion potential of the first metal part relative to the reference electrode and the corrosion rate.

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