A method for manufacturing an electrode for measuring pitting corrosion potential, an electrode for measuring pitting corrosion potential, and a method for measuring pitting corrosion potential.

Abstract

Provided are a method for producing an electrode for measuring pitting corrosion potential, which allows for the easy production of an electrode for measuring pitting corrosion potential having a uniform measurement area, the electrode for measuring pitting corrosion potential, and a method for measuring pitting corrosion potential using the electrode for measuring pitting corrosion potential. [Solution] This pitting potential measuring electrode 80 and its manufacturing method involve sandwiching a test metal plate 30 between two thermally laminated films 34, one of which has an opening 36 of a predetermined size formed therein, and then pouching the resulting material to enclose the test metal plate 30 within an insulating pouch coating 34a. This makes it easy to manufacture a pitting potential measuring electrode 80 in which a predetermined area is exposed as the measurement surface 31a and the remaining area is insulated and waterproofed by the pouch coating 34a. In particular, by forming the opening 36 using a punching die, a pitting potential measuring electrode 80 with a measurement surface 31a of the same area can be manufactured extremely easily and in a short time.

Description

[Technical Field]

[0001] The present invention involves applying a potential to a test metal plate in a test solution to cause pitting corrosion. The present invention relates to pitting potential measurement, which evaluates the corrosion resistance of a test metal by measuring the pitting potential, and more particularly to a method for producing a pitting potential measurement electrode used in this pitting potential measurement, the pitting potential measurement electrode, and a pitting potential measurement method using this pitting potential measurement electrode. [Background technology]

[0002] Stainless steel, a general term for steels containing approximately 11% or more chromium, is recognized as a highly corrosion-resistant metal. This high corrosion resistance is due to the formation of a highly protective film called a passive film on the surface of stainless steel. This passive film is an oxide (hydroxide) containing iron and chromium, and is extremely thin, measuring 1–3 nm, formed by the oxidation of chromium by atmospheric oxygen. Even if the passive film is damaged by a scratch or other cause, temporarily exposing the underlying metal, it quickly repairs itself upon contact with air or water, maintaining its corrosion resistance. However, corrosion can occur in stainless steel pipes, for example, depending on the operating environment and the quality of the water flowing through the pipe. Such corrosion in stainless steel pipes occurs when the passive film does not recover even after it is damaged, resulting in an anodic reaction that dissolves the iron. Furthermore, when the water pH is neutral, a cathodic reaction occurs simultaneously in areas where the passive film is intact, forming a corrosion cell, leading to localized corrosion known as localized corrosion.

[0003] In addition to physical damage such as scratches, the passive film is also said to be chemically damaged by halogen elements in water. Halogen elements are known to inhibit the formation of the passive film, and chloride ions (Cl), which are present in large quantities in the environment, are particularly effective. -) is often a problem. It is also known that the risk of localized corrosion mentioned above occurs when the natural immersion potential becomes more noble (higher) than the critical potential for localized corrosion. There are various forms of localized corrosion, but one of these is a phenomenon called pitting corrosion, in which small holes form locally and corrode deeply, eventually penetrating the metal part and causing water leaks in pipes, etc. When assessing the risk of pitting corrosion in stainless steel materials, it is important to know the value of the pitting potential, which corresponds to the critical potential for localized corrosion mentioned above.

[0004] The method for measuring this pitting potential involves first preparing a measurement electrode using a plate of the test metal. Next, this measurement electrode is immersed in a test solution, and the potential of this measurement electrode is swept (raised) toward the noble side at a preset rate. When the current density flowing through this measurement electrode exceeds a predetermined potential, this potential is taken as the pitting potential of the test metal. Patent Document 1 below discloses an invention relating to a pitting potential measuring device capable of measurements under special conditions.

[0005] Furthermore, when the test metal is stainless steel, the conditions for measuring pitting potential are specified in the Japanese Industrial Standard JIS G 0577, which lists "crevice corrosion prevention electrodes" and "coated electrodes using insulating materials such as resin" as usable measurement electrodes. However, "crevice corrosion prevention electrodes" have a complex structure, and there is a considerable cost burden for producing the measurement electrodes. In addition, there is the problem that they are difficult to handle, as it is necessary to "adjust the amount of distilled water or ion-exchanged water seeping out of the "crevice corrosion prevention electrodes" to 2-6 mL / h" during pitting potential measurement. In this regard, "coated electrodes using insulating materials such as resin" require a pitting potential measurement when the exposed part of the test metal plate is 1 cm 2 It is specified that the electrode should be covered or embedded with an insulating material such as epoxy resin, vinyl chloride resin, or silicone resin so that the electrode does not need to be filled with water during measurement, and it has a simpler structure and is easier to handle than a "crevice corrosion prevention electrode." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 07-092131 Summary of the Invention [Problem to be solved by the invention]

[0007] However, although the structure of the "applied electrode using insulating material such as resin" is simple, the measurement area (exposed area) is 1cm 2 It is not easy to manually apply the insulating resin to the test metal plate so that the required thickness is achieved, and the degree of completion varies depending on the skill of the worker. In particular, if there is variation in the area of ​​the measurement part, this becomes a major factor in reducing the reliability of the measurement results.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a method for manufacturing an electrode for measuring pitting potential, which allows for easy manufacture of an electrode for measuring pitting potential having a uniform area of ​​the measurement portion, the electrode for measuring pitting potential, and a method for measuring pitting potential using the electrode for measuring pitting potential. [Means for solving the problem]

[0009] The present invention provides (1) a procedure for connecting a lead wire 32 to a test metal plate 30; forming an opening 36 in one of the insulating thermal laminate films 34; a step of sandwiching the test metal plate 30 between a thermal lamination film 34 having the opening 36 formed therein and a thermal lamination film 34 having no opening 36 formed therein while positioning the opening 36 on the measurement surface 31 of the test metal plate 30; The above problem is solved by providing a method for manufacturing an electrode 80 for measuring pitting corrosion potential, which includes the steps of: pouching the test metal plate 30 by thermocompressing a thermally laminated film 34 while sandwiching the test metal plate 30; enclosing the test metal plate 30 in a pouch cover 34a formed by the thermally laminated film 34; and bringing the opening 36 into close contact with the measurement surface 31. (2) The above problems are solved by providing a method for producing the electrode 80 for measuring pitting corrosion potential according to (1) above, characterized in that the opening 36 in the thermally laminated film 34 is formed by punching. (3) A circular die with a diameter of 11.5 mm is used to punch out a 1 cm2 piece. 2 The above problem is solved by providing a method for producing the electrode 80 for measuring pitting corrosion potential described in (2) above, which is characterized by forming the opening 36 in the thermally laminated film 34. (4) a conductor 32 connected to the test metal plate 30; an insulating pouch cover 34a enclosing the test metal plate 30; The pouch cover 34a is formed with the Test metal plate 30 an opening 36 that partially exposes the measurement surface 31; The above problem is solved by providing an electrode for measuring pitting corrosion potential (80) having a waterproof coating (38) applied to the gap between the pouch coating (34a) and the conductive wire (32). (5) The area of ​​the opening 36 of the pouch covering 34a is 1 cm 2 The above problem is solved by providing the electrode 80 for measuring pitting corrosion potential according to (4) above, which is characterized by: (6) A procedure for producing a pitting potential measuring electrode 80 by the method for producing a pitting potential measuring electrode 80 according to any one of (1) to (3) above; a step of immersing the pitting potential measuring electrode 80 and the counter electrode 22 in a test solution maintained at a predetermined liquid temperature, and immersing the reference electrode 20 in the predetermined solution; a step of sweeping the potential of the pitting potential measuring electrode 80 at a preset speed and measuring the current density flowing through the pitting potential measuring electrode 80; The above problem is solved by providing a pitting potential measuring method including a step of obtaining a pitting potential based on the potential when the current density exceeds a predetermined value. [Effects of the Invention]

[0010] The pitting potential measuring electrode 80 and its manufacturing method according to the present invention involve sandwiching a test metal plate 30 between two thermally laminated films 34, one of which has an opening 36 of a predetermined size formed therein, and then thermocompression bonding the two together to form a pouch, thereby sealing the test metal plate 30 within an insulating pouch coating 34a. This allows for easy and inexpensive manufacture of a pitting potential measuring electrode 80 that corresponds to a "coated electrode using an insulating material such as resin." In particular, by forming the opening 36 using a punching die, pitting potential measuring electrodes 80 with the same area of ​​measurement surface 31a can be manufactured more easily and in a shorter time than conventional methods. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a flowchart of a method for producing an electrode for measuring pitting corrosion potential according to the present invention. [Figure 2] 1A to 1C are diagrams illustrating a method for producing an electrode for measuring pitting corrosion potential according to the present invention. [Figure 3] FIG. 1 is a schematic diagram showing a pitting corrosion potential measuring device. [Figure 4] 1 is a graph showing the verification results of the electrode for measuring pitting corrosion potential according to the present invention. [Figure 5] 1 is a graph showing the verification results of the electrode for measuring pitting corrosion potential according to the present invention. [Figure 6] 1 is an anodic polarization curve showing the verification results of the electrode for measuring pitting corrosion potential according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A method for producing a pitting potential measuring electrode 80 according to the present invention, the pitting potential measuring electrode 80, and a method for measuring pitting potential using the pitting potential measuring electrode 80 will be described with reference to the drawings. Fig. 1 is a flowchart of the method for producing the pitting potential measuring electrode 80. Fig. 2 is a diagram illustrating the method for producing the pitting potential measuring electrode 80.

[0013] In the method for producing a pitting potential measurement electrode 80 according to the present invention, first, a test metal plate 30 of the metal to be measured is obtained. There are no particular limitations on the thickness of this test metal plate 30, as long as it is thick enough to be pouched using a typical thermal lamination film 34, and it is preferably approximately 0.1 mm to 0.6 mm. There are also no particular limitations on the length and width dimensions, but it is preferably approximately 20 mm x 30 mm to 50 mm x 50 mm (test metal plate obtaining step S102).

[0014] Next, as shown in FIG. 2(a), a conductor 32 is connected to one side of the test metal plate 30 by soldering, spot welding, or the like (conductor connection step S104). As specified in JIS G 0577, the connection is preferably performed as far away as possible from the back surface to avoid the heat generated during connection from affecting the measurement surface 31. In this configuration, the conductor 32 is not positioned on the measurement surface 31, maintaining its smoothness. This also ensures that the opening 36, described below, is tightly attached to the measurement surface 31. The conductor 32 used here is not particularly limited; well-known conductive copper wire or stainless steel wire can be used. This establishes electrical continuity between the test metal plate 30 and the conductor 32. Because a thicker conductor 32 increases the gap S between the thermally laminated film 34, a diameter of approximately 0.5 mm to 2 mm is preferred.

[0015] Next, an insulating thermal lamination film 34 is prepared. This thermal lamination film 34 can be, for example, a well-known film basically composed of a base layer and a thermoplastic resin layer, with a layer thickness of, for example, 100 μm to 150 μm. The base layer is made of highly insulating materials such as PET (polyethylene terephthalate) or PP (polypropylene), and the thermoplastic resin layer is made of EVA (ethylene vinyl acetate copolymer). Here, a plate-shaped object (here, a test metal plate 30) is sandwiched between two thermal lamination films 34 larger than the object, with the thermoplastic resin layers facing inward (toward the object). This state is thermocompression-bonded to melt and harden the thermoplastic resin layers, sealing the object within the front and back thermal lamination films 34. This pouch coating 34a is essentially waterproof. Note that a typical pouch-use thermal lamination film 34 consists of two sheets joined at one edge, with the thermoplastic resin layers facing inward. 2(b), an opening 36 is formed on one side of the thermal lamination film 34 (opening forming step S106). The opening 36 is preferably formed by punching using a die to reduce variations in the opening area. In particular, when the test metal plate 30 is made of stainless steel, the area of ​​the measurement surface 31a exposed from the opening 36 is set to 1 cm. 2 Here, a typical thermal lamination film 34 hardly undergoes any dimensional change before and after the pouch. 2 To obtain a circular measurement surface 31a, the diameter of the opening 36 formed in the thermally laminated film 34 is preferably approximately φ11.5 mm. In this case, it is particularly preferable to form the opening 36 using a circular punching die having an inner diameter of approximately φ11.5 mm. When using a thermally laminated film 34 whose dimensions change before and after pouching, it is necessary to form the opening 36 in the thermally laminated film 34 with a size that takes into account the dimensional change of the thermally laminated film 34.

[0016] Next, the test metal plate 30 is sandwiched between the thermally laminated film 34 on the measurement surface 31 side where the opening 36 is formed and the thermally laminated film 34 on the back side where no opening is formed. At this time, the opening 36 is positioned at a predetermined position on the measurement surface 31 of the test metal plate 30, usually at a position near the center of the test metal plate 30 and away from the conductive wire 32, as shown in Figure 2(c) (test metal plate positioning step S108).

[0017] Next, in this state, both thermal lamination films 34 are heated and pressurized to thermocompression bond them. This melts the thermoplastic resin layer of the thermal lamination film 34 and welds it to the test metal plate 30. The thermoplastic resin layers of the front and back thermal lamination films 34 are also welded together in the margins. These then harden as they cool, pouching the test metal plate 30. As a result, as shown in FIG. 2(d), the test metal plate 30 is sealed by the pouch cover 34a formed by the front and back thermal lamination films 34 and enclosed within the pouch cover 34a (thermocompression bonding step S120). At this time, the opening 36 is in close contact with the measurement surface 31 of the test metal plate 30, and the measurement surface 31a is exposed through the hardened opening 36. The periphery of the opening 36 is welded to the test metal plate 30, providing a waterproof function.

[0018] Next, as shown in FIG. 2(e), the excess portion of the pouch coating 34a is cut off. Note that in the thick portion of the conductor 32, the thermally laminated film 34 may not completely adhere to the conductor 32, resulting in a gap S between the pouch coating 34a and the conductor 32 after curing. In this case, this gap S is filled with a well-known waterproof coating 38, such as an epoxy resin, vinyl chloride resin, silicone resin, or other waterproof resin, or by applying waterproof tape (waterproofing step S122). This completes the pitting potential measurement electrode 80 according to the present invention, as shown in FIG. 2(f).

[0019] Next, the pitting potential measuring electrode 80 according to the present invention will be verified, and the pitting potential measuring method according to the present invention will be explained. Here, FIG. 3 is a schematic diagram showing the configuration of a pitting potential measuring device 100. [Example]

[0020] First, a shim plate made of stainless steel SUS304 (18Cr-8Ni) cold-rolled to a thickness of 0.1 mm was cut to a size of approximately 30 mm x 40 mm to prepare a test metal plate 30 (test metal plate obtaining step S102). Next, a 2 mm diameter copper wire was soldered to one short edge of the test metal plate 30 as a conductor 32 (conductor wire connecting step S104). Next, a pair of thermally laminated films 34 for a pouch using PET as a base layer was prepared, and an opening 36 was formed in one of the thermally laminated films 34 using a 11.5 mm diameter punch (opening forming step S106). Next, the test metal plate 30 was sandwiched between the above-mentioned pouch thermal lamination films 34, and with the opening 36 positioned on the measurement surface 31 of the test metal plate 30 (test metal plate placement step S108), it was pouched using a predetermined laminator (pouch thermocompression machine) (thermocompression bonding step S120). As a result, the test metal plate 30 was enclosed in a pouch coating 34a to which the front and back thermal lamination films 34 were welded. Next, excess portions of the pouch coating 34a were cut off. Next, if the conductor 32 was exposed, it was covered with a heat-shrinkable insulating tube or the like and thermally shrunk to provide insulation and waterproofing. Next, a waterproof resin was applied to the gap S at the connection portion between the conductor 32 and the pouch coating 34a, and cured to form a waterproof coating 38 (waterproofing step S122). This completed the pitting potential measurement electrode 80 according to the present invention.

[0021] [Verification experiment 1] Next, a pitting potential measuring device 100 was prepared, and approximately 400 mL of an aqueous NaCl solution was poured as a test solution into a glass test container 10 having an effective liquid volume of 500 mL for the pitting potential measuring device 100. Measurements were performed while varying the chloride ion concentration of the test solution in the range of 0.0005 mol / L to 1.0 mol / L. Next, the test container 10 was immersed in a thermostatic water bath 14, and the liquid temperature of the test solution was maintained at 30°C ± 1°C.

[0022] Next, a counter electrode 22 made of a meshed platinum electrode, a saturated KCl silver-silver chloride electrode (RE-1CP manufactured by BAS Corporation) as the reference electrode 20, a vent pipe 12a, and an exhaust pipe 12b were installed on the lid 10a of the test vessel 10. Next, the measurement surface 31a (exposed through the opening 36) of the pitting potential measurement electrode 80 of Example 1 according to the present invention was dry-polished with #600 sandpaper. Next, the polished pitting potential measurement electrode 80 was set on the lid 10a as the working electrode. Next, the lid 10a was placed on the test vessel 10 and fixed in a sealed state. As a result, the measurement surface 31a of the pitting potential measurement electrode 80, the counter electrode 22, and the reference electrode 20 were immersed in the test solution in the test vessel 10. In this example, since the measurement time is relatively short, the reference electrode 20 and the pitting potential measurement electrode 80 are immersed in the same test vessel 10. However, if the measurement time is long, it is preferable to immerse the reference electrode 20 in a separate vessel to prevent adverse effects of the test solution on the reference electrode 20.

[0023] Next, the lead wire 32 of the pitting potential measuring electrode 80, the counter electrode 22, and the terminal electrode of the reference electrode 20 were each connected to the appropriate terminals of a potentiostat 24 (HZ-7000 series HAG1232m, manufactured by Hokuto Denko Corporation). Nitrogen gas was then supplied to the vent pipe 12a at a flow rate of approximately 100 mL / min, and the test solution was bubbled for 30 minutes. The supplied nitrogen gas was then exhausted from the exhaust pipe 12b along with the air in the tank, thereby degassing the test vessel 10 and the test solution. The vent pipe 12a and exhaust pipe 12b were then closed, and the test vessel 10 was sealed.

[0024] Next, the potentiostat 24 was started. This caused the potential sweep device 26 in the potentiostat 24 to sweep the potential of the pitting potential measuring electrode 80 from the natural potential to the noble side at a rate of 20 mV / min relative to the reference electrode 20. The potentiostat 24 also acquired the current density flowing through the pitting potential measuring electrode 80 at this time, and the recording unit 28 recorded the potential and current density at this time, and also recorded the current density of the pitting potential measuring electrode 80 when the current density was 1000 μA / cm 2 The measurement was terminated when the current density of the pitting potential measuring electrode 80 exceeded 100 μA / cm 2The potential at which this occurred was determined as the pitting potential of the sample. Note that measurements were continued until five pieces of pitting potential data were obtained for each condition. [Comparative Example 1]

[0025] A circular SUS304 steel plate with a thickness of 2 mm and a diameter of 24.5 mm and a BA surface finish was used as the test metal plate, which was set in an existing sample holder for pitting potential measurement (VM-1, manufactured by EC Frontier Co., Ltd.) to serve as an electrode for measuring pitting potential. Then, pitting potential was measured under the same measurement conditions as in Verification Experiment 1. Note that the measurement surface of the test metal plate was dry-polished with #600 sandpaper as in [Example 1], and then immediately set in the sample holder for measuring pitting potential and measurement was performed.

[0026] The results of these measurements are shown in Figure 4. Here, the horizontal axis of Figure 4 represents the chloride ion concentration (mol / L) of the test solution, and the vertical axis represents the pitting potential (V vs. Ag / AgCl). Figure 4 shows that the behavior of the pitting potential with respect to the chloride ion concentration in [Example 1] (pouch sample) and [Comparative Example 1] (existing holder sample) tended to be similar.

[0027] In addition, when the approximation formula for both was calculated, the pitting potential measuring electrode 80 (pouch sample) was y=-0.11ln(x)+0.27 Correlation function R 2 =0.91, The existing holder sample of [Comparative Example 1] is y=-0.12ln(x)+0.13 Correlation function R 2 =0.86, The correlation function is R 2 =0.9, both of which were high values. The slopes of both were approximately the same, at 0.11 and 0.12. These findings demonstrate that the pitting potential measurement electrode 80 according to the present invention can be used to replace existing sample holders for pitting potential measurement and can be used to measure pitting potential. The pitting potential values ​​of [Example 1] (pouch sample) were generally 10 mV to 100 mV higher than the pitting potential values ​​of [Comparative Example 1] (existing holder sample), but this difference is thought to be due to differences in the sample material and surface finish, etc. Comparative Example 2

[0028] An electrode for measuring pitting corrosion potential (existing holder sample) was prepared in the same manner as in [Comparative Example 1] except that the surface finish was in a 2B state.

[0029] [Verification experiment 2] Then, the pitting potential of the electrode 80 (pouch sample) for measuring pitting potential in [Example 1] and the existing holder sample in [Comparative Example 2] was measured under the same conditions as in Verification Experiment 1, with the chloride ion concentrations of the test solution set to 1 mol / L and 0.5 mol / L.

[0030] The results are shown in a graph in Figure 5. As can be seen from Figure 5, there is no significant difference between the pitting potential values ​​of Example 1 (pouch sample) and Comparative Example 2 (existing holder sample) at chloride ion concentrations of 1 mol / L and 0.5 mol / L, and nearly equivalent results were obtained. Therefore, it can be seen that the pitting potential measurement electrode 80 according to the present invention can be used in place of existing sample holders for pitting potential measurement and can be used to measure pitting potential. [Example]

[0031] The electrode 80 for measuring pitting potential was prepared in the same manner as in Example 1, except that the measurement surface 31a was wet-polished with #600 sandpaper and then passivated by immersing it in 30 wt % nitric acid at 50°C ± 1°C for 1 hour.

[0032] [Verification experiment 3] Then, the pitting potential measurement electrode 80 of [Example 1] and [Example 2] was performed under the same conditions as in Verification Experiment 1, except that the chloride ion concentration of the test solution was set to 1 mol / L.

[0033] Graphs of potential and current density (anodic polarization curves) for these samples are shown in Figures 6(a) and 6(b). Figure 6(a) shows the anodic polarization curve for Example 1 without passivation treatment, and Figure 6(b) shows the anodic polarization curve for Example 2 with passivation treatment. Figure 6(c) shows the anodic polarization curve for SUS304 according to Japanese Industrial Standard JIS G 0577, using a SCE (calomel electrode) as the reference electrode 20.

[0034] 6(a) and 6(b), the pitting potentials measured with the pitting potential measuring electrode 80 (pouch sample) according to the present invention without passivation treatment (Example 1) were 0.347 V, 0.351 V, 0.353 V, 0.351 V, and 0.338 V, respectively, with a maximum value of 0.353 V and an average value of 0.348 V. Furthermore, with passivation treatment (Example 2), the pitting potentials were 0.331 V, 0.346 V, 0.360 V, 0.349 V, and 0.358 V, respectively, with a maximum value of 0.360 V and an average value of 0.349 V. The conversion value of the reference electrode 20 from a saturated KCl silver-silver chloride electrode to an SCE (calomel electrode) is set to -0.0473 V in accordance with Japanese Industrial Standard JIS G 0577. Therefore, after conversion to a calomel electrode, the maximum value without passivation (Example 1) was 0.306 V and the average value was 0.301 V, and the maximum value with passivation (Example 2) was 0.313 V and the average value was 0.302 V. The maximum pitting potential of SUS304 listed in Japanese Industrial Standard JIS G 0577 was 0.321 V and the average was 0.290 V, which were nearly equivalent to the results obtained using the pitting potential measurement electrode 80 according to the present invention. This demonstrates that pitting potential can be measured satisfactorily using the pitting potential measurement electrode 80 (pouch sample) according to the present invention.

[0035] Thus, the measurement results of the pitting potential using the pitting potential measuring electrode 80 according to the present invention showed values ​​almost equivalent to those obtained using existing sample holders for pitting potential measurement. The values ​​also showed almost equivalent values ​​to the pitting potential specified in Japanese Industrial Standard JIS G 0577. Therefore, it can be seen that the pitting potential measuring electrode 80 according to the present invention can be satisfactorily used for measuring pitting potential.

[0036] In addition, the pitting potential measurement electrode 80 and its manufacturing method according to the present invention involve sandwiching a test metal plate 30 between two thermally laminated films 34, one of which has an opening 36 of a predetermined size, and then thermocompressing the resulting film to form a pouch, thereby enclosing the test metal plate 30 within an insulating pouch coating 34a. This allows for easy manufacturing of a pitting potential measurement electrode 80, which corresponds to the "coated electrode using an insulating material such as resin" described in Japanese Industrial Standard JIS G 0577, in which a portion of the test metal plate 30 is exposed through the opening 36 as a measurement surface 31a of a predetermined area, while the remaining portion is insulated and waterproofed by the pouch coating 34a. In particular, by forming the opening 36 using a punching die, a pitting potential measurement electrode 80 with a uniform measurement surface 31a can be manufactured much more easily and in a shorter time than conventional methods, regardless of the skill level of the worker. Furthermore, the pitting potential measurement method according to the present invention uses the above-described pitting potential measurement electrode 80, significantly reducing the effort and time required for manufacturing the measurement electrode and facilitating measurement.

[0037] Furthermore, the pitting corrosion potential measuring electrode 80 and the method for manufacturing the same according to the present invention can use a commercially available thermal laminating film 34 for pouches and a commercially available laminator, so that the introduction cost and component cost can be kept extremely low.

[0038] The content, procedures, order, etc. of the method for producing the electrode for measuring pitting potential shown in this example are merely an example, and therefore, necessary procedures may be added as appropriate, and the present invention can be implemented with modifications within the scope of the present invention. Furthermore, the configuration, shape, material, dimensions, etc. of each part of the electrode for measuring pitting potential 80 shown in this example are merely an example, and therefore the present invention is not particularly limited to this example, and the present invention can be implemented with modifications within the scope of the present invention. [Explanation of symbols]

[0039] 20 Reference electrode 22 Opposite 30 Test metal plate 31, 31a Measuring surface 32 Conductor 34 Thermal Laminating Film 34a Pouch covering 36 Aperture 38 Waterproof coating 80 Pitting potential measurement electrode

Claims

1. connecting a lead to the test metal plate; forming an opening in one of the insulating thermal laminate films; a step of sandwiching the test metal plate between a thermal lamination film having the opening formed therein and a thermal lamination film having no opening formed therein while the opening is positioned on the measurement surface of the test metal plate; a step of sandwiching the test metal plate and thermocompressing a thermally laminated film to pouch the test metal plate, enclosing the test metal plate in the pouch coating formed by the thermally laminated film, and bringing the opening into close contact with the measurement surface.

2. 2. The method for producing an electrode for measuring pitting corrosion potential according to claim 1, wherein the opening is formed in the thermally laminated film by punching.

3. The area is 1 cm by punching with a φ11.5 mm circular punching die. ２ 3. The method for producing an electrode for measuring pitting corrosion potential according to claim 2, wherein the opening is formed in the thermally laminated film.

4. a conductor connected to a test metal plate; an insulating pouch covering enclosing the test metal plate; an opening formed in the pouch cover to partially expose the measurement surface of the test metal plate; A pitting corrosion potential measuring electrode having a waterproof coating applied to the gap between the pouch coating and the conductive wire.

5. The area of ​​the pouch cover opening is 1 cm ２ 5. The electrode for measuring pitting corrosion potential according to claim 4, wherein

6. a step of preparing an electrode for measuring pitting corrosion potential by the method for preparing an electrode for measuring pitting corrosion potential according to any one of claims 1 to 3; a step of immersing the pitting potential measuring electrode and a counter electrode in a test solution maintained at a predetermined liquid temperature, and immersing a reference electrode in the predetermined solution; a step of sweeping the potential of the pitting potential measuring electrode at a preset speed and measuring the current density flowing through the pitting potential measuring electrode; and acquiring a pitting potential based on the potential when the current density exceeds a predetermined value.

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