Wetting evaluation terminal

Abstract

A wetting evaluation terminal 10 includes: a dry-wet part 111 showing a dryness / wetness response in accordance with an environment; a moisture retaining part 112 for retaining moisture; and an electrode 12 embedded in the moisture retaining part 112. The solution resistance is measured by applying an AC signal between the electrode 12 and a metal member 100 in a state where the dry-wet part 111 is impregnated with moisture and the dry-wet part 111 and the metal member 100 are made to contact each other.

Description

Wetness evaluation terminal

[0001] The present disclosure relates to a wettability evaluation terminal.

[0002] When metals come into contact with water, they dissolve as ions, causing corrosion reactions. Metal dissolution is an oxidation reaction from the metal's perspective, and a corresponding reduction reaction is also required. Hydrogen predominates in reduction reactions in acidic solutions, while oxygen predominates in neutral to alkaline aqueous solutions.

[0003] For metals to corrode, the metal surface must be wet. Therefore, the time of wetness is one of the indicators for evaluating a corrosive environment, and the classification method is organized in ISO 9223 (Non-Patent Documents 1 and 2).

[0004] The ISO defines the wetness time of a corroding surface as the time when the temperature is above 0°C and the relative humidity is above 80%. However, it has been pointed out that the wetness time defined by ISO may differ from the actual wetness time of a steel surface due to the influence of airborne salt in an actual environment (Non-Patent Document 3). The Atmospheric Corrosion Monitor (ACM) sensor has been developed as a method for measuring actual environments and is standardized in the Japanese Industrial Standards (JIS) (Non-Patent Documents 3 and 4).

[0005] The ACM sensor measures the current that flows when a water film forms on the interdigitated electrodes of a galvanic pair made of dissimilar metals, creating a corrosive environment. The wetness duration can be determined by setting an arbitrary threshold for the sensor output, i.e., the magnitude of the current value, to distinguish between three levels: rainfall, condensation, and dryness (Non-Patent Document 5).

[0006] ISO 9223, <https: / / www.iso.org / standard / 53499.html> Akira Tahara, "Evaluation of atmospheric corrosivity using steel materials," Journal of the Japan Color Materials Association, Japan Color Materials Association, 2011, Vol. 84, No. 6, pp. 205-211 Tadashi Shinohara, Shinichi Motoda, Wataru Oshikawa, "Evaluation of environmental corrosivity using ACM sensors," Zairyo-to-Kankyo, 2005, Vol. 54, No. 8, pp. 375-382 JIS Z 2384, <https: / / kikakurui.com / z2 / Z2384-2019-01.html> Wataru Oshikawa, "IV. Electrochemical measurements in various environments - ACM sensors -," Zairyo-to-Kankyo, 2018, Vol. 67, No. 7, pp. 273-279 Noriko Watanabe, "State of Water in Gels," Journal of the Japanese Society for Food Science and Technology, 1997, Vol. 44, No. 11, pp. 816-823

[0007] Conventional technologies require sensors to be installed in the environment, and the purpose is to evaluate the environment. However, it is difficult to quickly measure the wetness of the object itself, rather than the environment, on-site.

[0008] The present disclosure has been made in view of the above, and aims to evaluate the wetting time of a metal surface.

[0009] A wetness evaluation terminal according to one embodiment of the present disclosure is a wetness evaluation terminal that is brought into contact with a metal component to be evaluated and used to evaluate the wetness time of the metal component, and has a wet / dry section that flexibly responds to wet / dry conditions depending on the environment, a moisture retention section that retains moisture, and an electrode embedded in the moisture retention section. Moisture is impregnated into the wet / dry section, and an AC signal is applied between the electrode and the metal component while the wet / dry section is in contact with the metal component to measure the solution resistance.

[0010] According to the present disclosure, the wetting time of a metal surface can be evaluated.

[0011] Fig. 1 is a diagram showing an example of the configuration of a wetness evaluation terminal. Fig. 2 is a diagram showing an example of the configuration of a wetness evaluation terminal. Fig. 3 is a schematic diagram showing an example of a measurement result by electrochemical impedance spectroscopy, illustrated as a Nyquist plot. Fig. 4 is a graph showing an example of a change in impedance over time. Fig. 5 is a graph showing an example of the relationship between time and the logarithmic value of impedance.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0013] An example of the configuration of a wetness evaluation terminal 10 of this embodiment will be described with reference to Figures 1 and 2. The wetness evaluation terminal 10 shown in the figure includes a contact portion 11, an electrode 12, and a lead wire 13.

[0014] The contact portion 11 has a dry / wet portion 111 and a moisture retention portion 112, and retains moisture by surface tension, electrostatic force, or intermolecular force, etc., thereby providing electrical conductivity between the electrode 12 and the metal member 100 and exhibiting a dry / wet response according to the environment.

[0015] The wet / dry section 111 must retain water as a liquid and exhibit wet / dry response according to the environment. The wet / dry section 111 may be made of a porous material that retains moisture through capillary action, such as string or sponge. For example, the wet / dry section 111 may be made of any material, such as cotton, linen, silk, polypropylene (PP), polyvinyl alcohol, nylon, paper, or rubber. An insulating material is used for the wet / dry section 111 to prevent a battery reaction from occurring between the wet / dry section 111 and the metal member 100.

[0016] The moisture retention portion 112 needs to retain moisture more strongly than the wet / dry portion 111 in order to maintain the electrochemical reaction field near the electrode 12. The moisture retention portion 112 may be made of a polymer material having hydrophilic groups and capable of incorporating many water molecules into its molecule. The moisture retention portion 112 may have a denser structure, thinner fibers, smaller pore size, or higher pore density than the wet / dry portion 111. The moisture retention portion 112 may be made of a water-absorbent polymer or gel that retains moisture in the form of non-freezing water, bound water, structural water, bound water, hydrated water, glassy water, free water, or bulk water. The moisture retention portion 112 may be made of commercially available water-absorbent materials, such as sodium polyacrylate and aspartic acid.

[0017] As shown in FIG. 1, the contact portion 11 may have a contact surface with the same shape as the surface of the metal component 100, or may have the same shape as the expected contact object of the metal component 100 in service. For example, if a rope is attached to the metal component 100, the contact portion 11 may have the same shape as the rope, as shown in FIG. 2. FIG. 2 illustrates a cross section of the rope-shaped contact portion 11. The wet / dry portion 111 may be made of the same material as the rope. To address wetting and corrosion caused by tying strings used to secure communication equipment, the contact portion 11 may be made of polyvinyl alcohol with a diameter of 4 mm. If the target metal product already has a water-absorbent material, such as a string attached to it, it can be used as a contact portion to attach an electrode and treat it as a wetness evaluation terminal.

[0018] The electrodes 12 are embedded in the moisture retaining portion 112. Platinum, gold, carbon, iron, nickel, or a semiconductor material can be used for the electrodes 12. The electrodes 12 are connected to the electrochemical measurement device 50 by lead wires 13.

[0019] By constructing the contact portion 11 from a water-absorbent material, moisture remains near the contact surface between the contact portion 11 and the metal member 100 during the drying process, maintaining electrical conductivity, making it possible to perform electrochemical measurements of the metal member 100.

[0020] During the drying process, a significant increase in resistance occurs when moisture disappears from the vicinity of the contact portion between the contact portion 11 and the metal member 100 and from within the dry / wet portion 111. Therefore, the point at which a resistance value equal to or greater than a specified threshold is obtained is regarded as dry, and the wet time is evaluated. In addition to the resistance and impedance, the wet time may also be evaluated with reference to related current values ​​and potentials.

[0021] 1 and 2, during measurement, the contact part 11 is impregnated with water and brought into contact with the metal member 100. The electrode 12 serves as a counter electrode, and the metal member 100 serves as a working electrode, and these are connected to the electrochemical measurement device 50. In the case of the three-electrode method, a reference electrode is brought into contact with the water retention part 112. A common electrode such as silver or silver chloride is used as the reference electrode.

[0022] An AC signal is applied using an electrochemical measurement device 50 while varying the frequency in the range of 1 MHz to 1 Hz, and the solution resistance between the electrode 12 and the metal member 100 is measured. Electrochemical impedance spectroscopy (EIS) can be applied to measure the solution resistance. While a measurement method using a bridge circuit, as in general conductivity measurement, can also be used, EIS has the advantage of being extensible, such as being able to measure the natural potential by using a reference electrode.

[0023] During the drying process of the surface of the metal member 100 and the contact portion 11, the solution resistance is measured at a predetermined timing, and the wetting time is evaluated based on the measurement results.

[0024] Figure 3 shows a schematic diagram of an example of measurement results when EIS was operated at frequencies ranging from 1 MHz to 10 mHz, illustrated as a Nyquist plot. In the Nyquist plot, two incomplete semicircles are obtained due to the corrosion reaction at the contact point with the contact portion 11. Of these, the semicircle on the left (high frequency side) is due to the corrosion reaction, and the semicircle on the right (low frequency side) is due to an accompanying reaction. In the Nyquist plot, the point on the high frequency side (toward the origin) where the semicircle on the high frequency side intersects with the real axis corresponds to the solution resistance. Therefore, it is sufficient to obtain the first half of the semicircle on the high frequency side between 1 MHz and approximately 1 Hz. Measuring only the high frequency side is sufficient to measure the solution resistance, shortening the measurement time compared to conventional EIS.

[0025] As shown in Figure 4, the solution resistance increases as the solution dries, so it can be determined that the solution is dry when the impedance of the solution resistance is equal to or greater than a specified threshold value A. The threshold value A can be set to a value that is clearly higher than that of a typical aqueous solution, for example, 100 Ω.

[0026] During the drying process, the contact area 11 has a higher moisture-retaining function than the surface of the metal component 100, and therefore dries more slowly. Therefore, under certain conditions, the drying rate, i.e., the rate of increase in resistance, is greatest at the metal surface, followed by the wet / dry area and the moisture-retaining area. The measured solution resistance is a mixture of these influences, and is thought to reflect the influence of the dominant factor. As shown in Figure 5, the logarithm of the impedance is plotted against time, and the gradient of the change is calculated. The metal surface may be considered dry when a certain rate of change or greater is observed. For example, the metal surface is considered dry when the rate of change in the logarithm of the impedance is one-tenth of that at the previous measurement point.

[0027] As described above, the wetness evaluation terminal 10 of this embodiment has the wet / dry portion 111 that exhibits a wet / dry response in response to the environment, the moisture retention portion 112 that retains moisture, and the electrode 12 embedded in the moisture retention portion 112. The wet / dry portion 111 is impregnated with moisture, and with the wet / dry portion 111 and the metal member 100 in contact with each other, an AC signal is applied between the electrode 12 and the metal member 100 to measure the solution resistance. By utilizing the wet / dry portion 111, which exhibits a flexible wet / dry response in response to the environment, as a conductor, the wetness time can be estimated by an electrochemical method.

[0028] REFERENCE SIGNS LIST 10 Evaluation terminal 11 Contact portion 111 Dry / wet portion 112 Moisture retention portion 12 Electrode 13 Lead wire 50 Electrochemical measurement device 100 Metal member

Claims

1. A wetness evaluation terminal that is brought into contact with a metal component to be evaluated and used to evaluate the wetting time of the metal component, the wetness evaluation terminal having a wet / dry section that responds to the environment, a moisture retention section that retains moisture, and an electrode embedded in the moisture retention section, wherein the wet / dry section is impregnated with moisture, and with the wet / dry section and the metal component in contact, an AC signal is applied between the electrode and the metal component to measure the solution resistance.

2. A wettability evaluation terminal according to claim 1, wherein the moisture-retaining portion is made of a polymer material that has a hydrophilic group and can capture water molecules within its polymer network.

3. A wetness evaluation terminal according to claim 1, wherein the wet / dry portion is a rope-shaped polyvinyl alcohol.

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