Method for estimating corrosion of metal materials immersed in environmental water, test structure used for estimating corrosion of metal materials immersed in environmental water, and system for estimating corrosion of metal materials

Abstract

This invention provides a method for accurately estimating the corrosion of metal materials subjected to various environmental changes in aquatic environments. [Solution] A method for estimating corrosion of a metal material immersed in environmental water. This method includes a potential difference calculation step of immersing a test piece of the metal material and a test piece of a reference material resistant to environmental water in environmental water, measuring the potential of each test piece, and calculating the potential difference between the reference material test piece and the metal material test piece, and a corrosion estimation step of estimating that corrosion of the metal material has occurred if the potential difference is 0.5V or more.

Description

Technical Field

[0001] The present invention relates to a method for estimating the corrosion of a metal material immersed in environmental water, a test structure used for estimating the corrosion of a metal material immersed in environmental water, and a corrosion estimation system for a metal material.

Background Art

[0002] Structures installed by being immersed in environmental water such as dams, lakes, rivers, and seas are often composed of metal materials. For example, river infrastructure facilities such as sluice gates and dam water intake facilities use structures composed of metal materials. The corrosion situation of metal materials in environmental water varies depending on various factors such as the distance from the river mouth. Therefore, in order to ensure the corrosion resistance of structures installed by being immersed in environmental water, it is important to select an appropriate metal material in consideration of various factors in the environmental water. Therefore, conducting an exposure test of a metal material in the actual environmental water used is effective for grasping an appropriate metal material because it can accurately evaluate the corrosion (or corrosion resistance) of the metal material in the environmental water.

[0003] However, the corrosion situation often varies depending on the type of environmental water, season, and time zone. For example, the salt concentration of a river changes greatly depending on the seasonal change in flow rate and the ebb and flow of the day, and the progress and stop of the corrosion of the metal material are repeated, so it is very difficult to estimate the corrosion of the metal material. In addition, since microorganisms and the like exist in environmental water, the formation of a biofilm on the surface of the metal material may affect the corrosion state of the metal material.

[0004] Therefore, in Patent Document 1, a test piece of stainless steel is directly immersed in the water at a site such as a dam, lake, river, or sea, the natural potential of the test piece is measured at predetermined time intervals or continuously, and the natural potential is compared with the corrosion crevice repassivation potential of the test piece measured using the water. A corrosion prediction method for determining that corrosion by microorganisms occurs when the natural potential is higher than the corrosion crevice repassivation potential is described.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-39473 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the method described in Patent Document 1 uses either a sample of the water and a corresponding published data on the chloride concentration of the water as the repassivation potential of the corrosion gap, which is compared with the natural potential measured in the water at the site, such as in a dam. Therefore, the influence of the biofilm formed on the surface of the test specimen (metal material) in the water at the site, such as in a dam, on the change in the natural potential of the test specimen is not taken into consideration. Furthermore, the change in the natural potential of the test specimen due to biofilm is also affected by environmental changes such as the accumulation of mud on the surface of the test specimen. Since the natural potential changes due to various environmental changes such as the formation of biofilm, the method described in Patent Document 1 makes it difficult to determine whether the increase in the natural potential is due to environmental changes or corrosion of the test specimen (metal material), and thus it is not possible to accurately grasp the corrosion status of the test specimen.

[0007] This invention was made to solve the above-mentioned problems and aims to provide a method for accurately estimating the corrosion of metal materials subjected to various environmental changes in environmental water, a test structure used therefor, and a corrosion estimation system. [Means for solving the problem]

[0008] The inventors of this invention conducted intensive research to solve the above problems and, as a result, discovered that by immersing a metal material test piece and a reference material test piece in ambient water, measuring the potential, and calculating the potential difference between these test pieces, it is possible to accurately estimate whether or not corrosion of the metal material has occurred. This led to the completion of the present invention.

[0009] In other words, the present invention is a method for estimating the corrosion of a metal material immersed in environmental water, A potential difference calculation step is performed by immersing the test specimens of the metal material and the test specimens of the reference material resistant to the environmental water in the environmental water, measuring the potential of each test specimen, and calculating the potential difference between the test specimen of the reference material and the test specimen of the metal material. The method includes a corrosion estimation step in which it is estimated that corrosion of the metal material has occurred when the potential difference becomes 0.5V or more.

[0010] Furthermore, the present invention relates to a test structure used to estimate the corrosion of a metal material immersed in environmental water, A first test specimen installation section on which the metal material test specimen is installed, A second test specimen installation section is provided, where a test specimen of the reference material resistant to the aforementioned environmental water is installed. A reference electrode installation section where a reference electrode is installed and The test structure is equipped with such a feature, and the test piece of the metal material and the test piece of the reference material are insulated from each other.

[0011] Furthermore, the present invention relates to the above-mentioned test structure, A potential measuring device for measuring the potential of each test specimen of the aforementioned test structure, Wiring connecting each test specimen of the test structure to the potential measuring device, A calculation device that calculates the potential difference based on the potential of each test piece measured by the aforementioned potential measuring device. The system comprises a calculation device which estimates that corrosion of the metal material has occurred when the potential difference becomes 0.5V or higher, and is a metal material corrosion estimation system. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for accurately estimating the corrosion of metal materials subjected to various environmental changes in environmental water, a test structure used therefor, and a corrosion estimation system. [Brief explanation of the drawing]

[0013] [Figure 1] It is a schematic diagram of the side surface of a typical test structure according to an embodiment of the present invention. [Figure 2] It is a schematic diagram of a cross-section of a typical assembly having each test piece and having an insulating structure. [Figure 3] It is a graph showing the change in potential of SUS304 (metal material) and SUS312L (reference material) from mid-December 2018 to mid-December 2019. [Figure 4] It is a graph showing the change in potential of SUS316L (metal material) and SUS312L (reference material) from mid-December 2018 to mid-December 2019. [Figure 5] It is a graph showing the change in potential of SUS304 (metal material) and SUS312L (reference material) from mid-December 2020 to mid-December 2021. [Figure 6] It is a graph showing the change in potential of SUS316L (metal material) and SUS312L (reference material) from mid-December 2020 to mid-December 2021.

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be specifically described. The present invention is not limited to the following embodiments, and it should be understood that those obtained by appropriately making changes, improvements, etc. to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention also fall within the scope of the present invention.

[0015] (1. Method for estimating corrosion of metal material immersed in environmental water) The method for estimating the corrosion of a metal material immersed in environmental water according to an embodiment of the present invention (hereinafter abbreviated as "corrosion estimation method") includes a potential difference calculation step and a corrosion estimation step. Here, in this specification, "environmental water" means water in public water areas such as rivers, lakes, and seas, and water in natural environments such as groundwater.

[0016] <Potential difference calculation step> The potential difference calculation step is a step of immersing a test piece of a metal material and a test piece of a reference material having resistance to environmental water in environmental water, then measuring the potential of each test piece, and calculating the potential difference between the test piece of the reference material and the test piece of the metal material. Here, the "potential" of each test piece in this specification means the natural potential of each test piece with respect to the reference electrode. The reference electrode is immersed in environmental water together with each test piece. The reference electrode is not particularly limited, and known ones can be used. Examples of the reference electrode include a standard hydrogen electrode (SHE), a silver / silver chloride electrode (SSE), a saturated calomel electrode (SCE), and the like.

[0017] Generally, when a test piece of a metal material is immersed in environmental water, the potential of the test piece of the metal material increases due to the formation of a biofilm in the initial stage, but decreases when corrosion starts. Also, when mud or the like accumulates on the surface of the test piece, the activity of aerobic microorganisms in the biofilm is inhibited, so the potential decreases. In order to distinguish the influence of such environmental changes from the influence of corrosion, a test piece of a reference material is immersed in the same environmental water together with the test piece of the metal material. By immersing the test pieces of both in the same environmental water, the test piece of the reference material is also affected by the formation of a biofilm and environmental changes in the same manner as the test piece of the metal material. In the potential difference calculation step of calculating the difference between the potential of the test piece of the metal material and the potential of the test piece of the reference material with the potential of the test piece of the reference material immersed in the same environmental water as a reference, the influence due to the common environmental changes on both test pieces can be removed. That is, even if the potential of the test piece of the metal material changes, if the potential of the test piece of the reference material also changes in the same way, it can be determined that it is the influence of environmental changes. Note that the potential fluctuation due to environmental changes is the same regardless of the type of metal material of the test piece.

[0018] The shapes of the test pieces of the metal material and the reference material are not particularly limited, and various shapes can be used. Also, the test piece of the metal material may include a welded part or the like. Since structures are often fabricated by welding metal materials, by using a test piece of a metal material including a welded part, the corrosion resistance of the welded part can also be evaluated.

[0019] The potential of each test specimen can be measured continuously or at regular intervals using a commercially available potential measuring device (e.g., an electrometer or other electrometer). Furthermore, these potentials can be recorded continuously or at regular intervals. For example, each potential can be recorded using a commercially available data logger.

[0020] The metallic material is not particularly limited as long as it is a material intended for use in environmental water, and may be either ferrous or non-ferrous metals. Examples of ferrous materials include stainless steel, ordinary steel, and special steel. Examples of non-ferrous metals include materials containing metals such as aluminum, titanium, magnesium, nickel, and copper. Among these various materials, stainless steel, ordinary steel, special steel, or aluminum are preferred as the metallic material, and stainless steel is particularly preferred as its use in environmental water is expected to expand.

[0021] The reference material is not particularly limited as long as it has resistance to environmental water. Examples of reference materials include stainless steel materials (e.g., SUS312L) and nickel-based alloys with a PI value of 50 or higher, which is an index of pitting corrosion resistance represented by the formula Cr+4.1Mo+27N (where the element symbol represents the content [mass%]), and nickel-based alloys.

[0022] <Corrosion Estimation Process> The corrosion estimation process is a step in which corrosion of the metal material is estimated to have occurred if the potential difference obtained in the potential difference calculation process is 0.5V or higher. The potential difference threshold at which corrosion is estimated to have occurred is an experimentally derived value. By setting this potential difference threshold to 0.5V, it is possible to clearly distinguish between the effects of environmental changes and the effects of corrosion. In other words, if the potential difference is less than 0.5V, it can be determined that the effect is due to environmental changes, and if the potential difference is 0.5V or greater, it can be determined that the effect is due to corrosion.

[0023] Furthermore, the corrosion estimation method according to the embodiment of the present invention may further include, if necessary, a removal step, a corrosion weight calculation step, a corrosion time calculation step, and a corrosion rate calculation step. By further including such steps, the corrosion rate of a metal material in environmental water can be calculated.

[0024] <Removal process> The removal process involves immersing a metal material test specimen in environmental water for a predetermined period, followed by washing and rust removal treatment of the metal material test specimen to remove dirt and corrosion products. While there are no particular limitations on the immersion period for metal material test specimens, if it is too short, it becomes difficult to accurately calculate the corrosion rate. For this reason, the immersion period for metal material test specimens is preferably 4 months or more, more preferably 6 months or more, and even more preferably 8 months or more.

[0025] The washing of metal specimens is performed to remove contaminants such as biofilms. Therefore, the washing conditions are not particularly limited as long as they can remove the contaminants, and can be carried out in accordance with known washing methods. Rust removal treatment of metal materials is performed to remove corrosion products. Therefore, the conditions for rust removal treatment are not particularly limited as long as it is possible to remove corrosion products while suppressing the dissolution of the metal material test piece, and can be carried out in accordance with known rust removal methods.

[0026] <Corrosion Loss Calculation Process> The corrosion weight loss calculation process involves measuring the mass of the test specimen after the removal process and calculating the difference (corrosion weight loss) between this mass and the mass of the metal material test specimen before immersion in environmental water. This process allows for the identification of the amount of corrosion that occurred during immersion of the metal material.

[0027] <Corrosion Time Calculation Process> The corrosion time calculation process involves determining the time (corrosion time) during immersion in environmental water when the potential difference reaches 0.5V or higher. This process allows for the identification of the corrosion time that occurs during immersion of the metal material.

[0028] <Corrosion rate calculation process> The corrosion rate calculation process involves calculating the corrosion rate by dividing the corrosion loss by the corrosion time. This process allows for the calculation of the corrosion rate of a metal material when immersed in environmental water.

[0029] The corrosion estimation method according to the embodiment of the present invention, having the above-described features, can accurately estimate the corrosion of metal materials subjected to various environmental changes in environmental water, and is therefore suitable for estimating the corrosion of metal materials constituting structures installed by being immersed in environmental water such as dams, lakes, rivers, and seas.

[0030] (2. Test structures used to estimate the corrosion of metal materials immersed in environmental water) A test structure (hereinafter referred to as "test structure") used to estimate the corrosion of a metal material immersed in environmental water according to an embodiment of the present invention comprises a first test piece installation section where a metal material test piece is installed, a second test piece installation section where a reference material test piece resistant to environmental water is installed, and a reference electrode installation section where a reference electrode is installed, with insulation between the metal material test piece and the reference material test piece. By having a test structure with such a configuration, it is easier to make the environment for each test piece the same when immersed in environmental water. For this reason, this test structure can be suitably used in the above-described corrosion estimation method.

[0031] Here, Figure 1 shows a schematic side view of a typical test structure according to an embodiment of the present invention. The test structure shown in Figure 1 comprises a first test specimen mounting section 15 on which a metallic test specimen 10 is placed, a second test specimen mounting section 25 on which a reference material test specimen 20 is placed, and reference electrode mounting sections 35a and 35b on which reference electrodes 30a and 30b are placed. Although Figure 1 shows an example where there is one first test specimen mounting section 15 and one second test specimen mounting section 25, there may be multiple first test specimen mounting sections 15 and second test specimen mounting sections 25.

[0032] The first test specimen mounting section 15, the second test specimen mounting section 25, and the reference electrode mounting sections 35a and 35b can be fixed by a support material 40. By fixing them to the support material 40, it is possible to prevent the first test specimen mounting section 15, the second test specimen mounting section 25, and the reference electrode mounting sections 35a and 35b from coming into contact and being damaged. In Figure 1, an example is shown where the support material 40 is frame-shaped, but it may be in various shapes such as a plate shape as long as it can fix the first test specimen mounting section 15, the second test specimen mounting section 25, and the reference electrode mounting sections 35a and 35b.

[0033] It is preferable that the reference electrodes 30a and 30b are placed within a region of 1 m from each test piece 10 and 20. By placing the reference electrodes 30a and 30b in such a region, the complexity of the wiring 50 can be suppressed. Each test specimen 10, 20 and reference electrodes 30a, 30b are connected to a potential measuring device 60 via wiring 50, and the potential of each test specimen 10, 20 can be measured by the potential measuring device 60.

[0034] The method of installation in the first test specimen installation section 15 and the second test specimen installation section 25 is not particularly limited, as long as insulation can be maintained between the test specimen 10 and the test specimen 20. For example, insulation can be maintained between the test specimen 10 and the test specimen 20 by placing an insulating material between each test specimen 10, 20 and the support material 40. Alternatively, each test specimen 10, 20 may be arranged as an assembly having an insulating structure.

[0035] Here, Figure 2 shows a schematic cross-sectional view of a typical assembly having an insulating structure and equipped with test pieces 10 and 20. The assembly shown in Figure 2 is an effective assembly for evaluating crevice corrosion. It provides a gap by sandwiching each test piece 10, 20 between two titanium plates 100 with a gap-forming material 110 in between. This assembly is assembled using titanium bolts 120, titanium nuts 130, and titanium washers 140. Therefore, holes are formed in each test piece 10, 20 and the titanium plate 100 so that the titanium bolts 120 can be inserted. In addition, to ensure the insulation of each test piece 10, 20, fluororesin tubes 150 (for example, Teflon® tubes) are provided between each test piece 10, 20 and the titanium bolts 120, and between the support material 40 and the titanium bolts 120. By installing such an assembly in the first test piece installation section 15 and the second test piece installation section 25, crevice corrosion occurring in the test piece 10 can be evaluated.

[0036] (3. Corrosion estimation system for metallic materials) A corrosion estimation system for metal materials according to an embodiment of the present invention (hereinafter abbreviated as "corrosion estimation system") comprises the above-described test structure, a potential measuring device 60 for measuring the potential of each test piece 10, 20 of the test structure, wiring 50 connecting each test piece 10, 20 of the test structure to the potential measuring device 60, and a calculation device that calculates the potential difference based on the potential of each test piece 10, 20 measured by the potential measuring device 60. Furthermore, the calculation device estimates that corrosion of the metal material has occurred when the potential difference becomes 0.5V or more. With a corrosion estimation system having such a configuration, corrosion estimation of metal materials can be easily realized.

[0037] The computing device is not particularly limited as long as it is capable of calculating potential differences. For example, the computing device may include a data input unit for inputting the potentials of each test piece 10, 20 measured by the potential measuring device 60, a CPU for calculating the potential difference between each test piece 10, 20 based on the input potentials, a storage device (ROM, RAM), a display device (display), and so on.

[0038] The corrosion estimation system according to the embodiment of the present invention, having the above-described features, can accurately estimate the corrosion of metal materials subjected to various environmental changes in environmental water, and is therefore suitable for estimating the corrosion of metal materials constituting structures installed by being immersed in environmental water such as dams, lakes, rivers, and seas. [Examples]

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0040] SUS304 and SUS316L with a thickness of 12 mm were prepared as metal materials, and SUS312L with a thickness of 12 mm was prepared as a reference material. The assembly shown in Figure 2 was then fabricated. Specifically, the metal materials and reference material were cut to 40 mm x 40 mm, and a hole was formed in the center so that a titanium bolt could be inserted to create a test specimen. Next, the surface of the test specimen was wet-polished with #400 grit, and then immersed in a 30% by mass nitric acid aqueous solution (room temperature) for 180 minutes to perform passivation treatment. Next, the part of the test specimen that comes into contact with the gap-forming material was wet-polished with #400 grit, and then the assembly shown in Figure 2 was fabricated. The titanium plate was 20 mm x 20 mm in size, and a hole was formed in the center so that a titanium bolt could be inserted, similar to the test specimen. The diameter of the titanium bolt was 8 mm.

[0041] Next, the assembled product obtained as described above was placed on a support material to create the test structure shown in Figure 1. In the test structure, a standard hydrogen electrode (SHE) was used as the reference electrode. Next, one end of a water-resistant cable (Fujikura Ltd., insulated cross-linked polyethylene sheathed cable) was connected to the test specimen and reference electrode, and the other end of the water-resistant cable was connected to a potential measuring device placed on the ground. To ensure waterproofing, the connection between the test specimen, reference electrode and the water-resistant cable was covered with F-Tape No. 1 (Furukawa Electric Industry Co., Ltd.) and SB Tape (3M Corporation). An electrometer (Shrinks Co., Ltd., SDAI-204) was used as the potential measuring device, and potential data was saved using a data logger (Graphtec Corporation, GL240).

[0042] The test structure was immersed in water 9.5 km from the mouth of the Edogawa River (Tokyo) and subjected to an exposure test for approximately one year. The exposure test was conducted twice: from mid-December 2018 to mid-December 2019 (hereinafter referred to as "Period A"), and from mid-December 2020 to mid-December 2021 (hereinafter referred to as "Period B"). Table 1 shows the time it takes for the potential difference to first exceed 0.5V after immersion of the test structure in water (corrosion onset time). Figures 3 to 6 show the results of measuring the potential of each test piece every hour during the exposure test period. Figure 3 is a graph showing the change in potential of SUS304 (metal material) and SUS312L (reference material) during period A. Figure 4 is a graph showing the change in potential of SUS316L (metal material) and SUS312L (reference material) during period A. Figure 5 is a graph showing the change in potential of SUS304 (metal material) and SUS312L (reference material) during period B. Figure 6 is a graph showing the change in potential of SUS316L (metal material) and SUS312L (reference material) during period B.

[0043] Next, the test structure was recovered and dismantled after the exposure test, and a metal specimen was collected. This specimen was then washed with water to remove the biofilm, and then immersed in a 30% by mass nitric acid aqueous solution (50°C) for 60 minutes to remove corrosion products. Next, the mass of this specimen was measured, and the difference between this mass and the mass of the metal specimen before the exposure test was calculated; this difference was defined as the corrosion loss. Furthermore, the time required for the potential difference to exceed 0.5V (corrosion time) was determined from the potential measurements taken during the exposure test. Next, the corrosion rate of the metal material during immersion in environmental water was calculated by dividing the corrosion loss obtained above by the corrosion time. These results are shown in Table 1.

[0044] [Table 1]

[0045] As shown in Figures 3-6, the potential of each metal material (SUS304 and SUS316L) and the reference material (SUS312L) increased in the initial stages of the exposure test due to the formation of biofilm. Furthermore, while the reference material tended to maintain its high potential, a decrease in potential was observed for each metal material as time progressed. In particular, in Example 1 (Figure 3), a rapid decrease in the potential of the metal material (SUS304) began approximately one month after the start of exposure, and a long corrosion time was confirmed. In Example 2 (Figure 4), the potential of the metal material (SUS316L) decreased rapidly approximately four months after the start of exposure, but the corrosion time was shorter than in Example 1. In Examples 3 and 4, although not clearly evident from the graphs shown in Figures 5 and 6, the corrosion time of SUS316L was shorter than that of SUS304, similar to Examples 1 and 2. In Figures 5 and 6, there are areas where the potential of the reference material drops sharply. This is presumed to be because the activity of the biofilm was temporarily inhibited by the accumulation of mud and other materials on the biofilm surface of the test specimen. Also, in Figures 3 and 4, data from mid-January to February is missing, which is due to the battery running out. Furthermore, as shown in Table 1, the corrosion rates of Examples 1 to 4 were similar, confirming a correlation between corrosion time and corrosion loss.

[0046] As can be seen from the above results, the present invention provides a method for accurately estimating the corrosion of metal materials subjected to various environmental changes in environmental water, as well as a test structure and corrosion estimation system used therefor. [Explanation of Symbols]

[0047] 10,20 test specimens 15. Installation section of the first test specimen 25. Second test specimen installation section 30a,30b Reference electrode 35a,35b Reference electrode installation part 40 Support material 50 Wiring 60 Potential measuring device 100 Titanium Plates 110 Gap-forming material 120 Titanium Bolts 130 Titanium Nuts 140 Titanium Washers 150 Fluoropolymer tubes

Claims

1. A method for estimating the corrosion of metal materials immersed in environmental water, A potential difference calculation step is performed by immersing the test specimens of the metal material and the test specimens of the reference material resistant to the environmental water in the environmental water, measuring the potential of each test specimen, and calculating the potential difference between the test specimen of the reference material and the test specimen of the metal material. A corrosion estimation step in which, when the potential difference becomes 0.5V or more, it is estimated that corrosion has occurred in the metal material. A method that includes this.

2. A removal step involves immersing a test piece of the metal material in the environmental water for a predetermined period, followed by washing and rust removal treatment of the test piece to remove dirt and corrosion products. A corrosion loss calculation step involves measuring the mass of the test piece after the removal step and calculating the difference (corrosion loss) between that mass and the mass of the metal material test piece before immersion in the environmental water, A corrosion time calculation step for determining the time (corrosion time) during immersion in the aforementioned environmental water in which the potential difference is 0.5V or more, A corrosion rate calculation step, which involves calculating the corrosion rate by dividing the corrosion loss by the corrosion time, The method according to claim 1, further comprising:

3. The method according to claim 1 or 2, wherein the metal material is stainless steel, ordinary steel, special steel, or aluminum.

4. The method according to claim 1 or 2, wherein the reference material is a stainless steel material or Ni-based alloy with a PI value of 50 or more, represented by Cr + 4.1Mo + 27N (wherein the formula, the element symbol is the content [mass%]).

5. A test structure used to estimate the corrosion of metal materials immersed in environmental water, A first test specimen installation section on which the metal material test specimen is installed, A second test specimen installation section is provided, where a test specimen of the reference material resistant to the aforementioned environmental water is installed. A reference electrode installation section where a reference electrode is installed and A test structure comprising the above, wherein the test piece of the metal material and the test piece of the reference material are insulated from each other.

6. The test structure according to claim 5, wherein the reference electrode is located within 1 m of the test piece of the metal material and the test piece of the reference material.

7. The test structure according to claim 5 or 6, further comprising a support member for fixing the first test specimen mounting section, the second test specimen mounting section, and the reference electrode mounting section.

8. A test structure according to claim 5 or 6, A potential measuring device for measuring the potential of each test specimen of the aforementioned test structure, Wiring connecting each test specimen of the test structure to the potential measuring device, A calculation device that calculates the potential difference based on the potential of each test piece measured by the aforementioned potential measuring device. A metal material corrosion estimation system comprising the calculation device which estimates that corrosion has occurred in the metal material when the potential difference becomes 0.5V or more.

Images