Measurement method

Abstract

In this measurement method, before a solid electrolyte 10 containing chloride ions is cured, a reference electrode 11 is embedded in the solid electrolyte 10, and electrochemical measurement is performed using the reference electrode 11. The reference electrode 11 is formed from a metal material containing chloride ions.

Description

Measurement method

[0001] The present disclosure relates to a measurement method.

[0002] Corrosion of reinforcing steel bars inside structures made of solid electrolytes such as concrete progresses as chloride ions penetrate into the concrete. This is because the alkalinity of the concrete creates a passive state on the surface of the reinforcing steel bars, but as the chloride ion concentration increases, this passive state is destroyed.

[0003] It is known that, not only concrete but also metal materials that spontaneously form a stable protective film on their surface, when halogen ions such as chloride ions are present, the protective film is locally destroyed, causing pitting corrosion (see Non-Patent Document 1).

[0004] Non-Patent Document 2 discloses that a CSE (Copper Sulfate Electrode) or an SSE (Silver Silver Chloride Electrode) is a reference electrode that is often used to determine corrosion of reinforcing steel in concrete. Non-Patent Document 2 also discloses reference values ​​for corrosion determination.

[0005] Hiroo Nagano, "5. Pitting and Crevice Corrosion", Journal of Materials Science, Vol. 27, No. 294, pp. 309-314, 1978. Toshiya Nishimura, "IV. Electrochemical Measurements in Various Environments - Concrete -", Journal of Materials Science and Environment, Vol. 67, No. 9, pp. 356-361, 2018.

[0006] However, Non-Patent Document 3 discloses that in measurements using electrodes such as CSE or SSE, a sponge or the like containing an electrolytic solution is sandwiched between the concrete surface and the electrodes, and the electrodes are pressed against the concrete surface. This is because the concrete surface needs to be kept wet to ensure electrical continuity between the rebar and the reference electrode.

[0007] Concrete structures are sometimes used in environments where there is concern about corrosion of internal reinforcing bars due to chloride ions such as sea salt particles. When the chloride ion concentration in concrete becomes high, the natural potential may take on unstable values ​​depending on the type of metal material selected for the reference electrode.

[0008] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a technique capable of electrochemically measuring materials in a solid electrolyte that contain chloride ions.

[0009] In a measurement method according to one aspect of the present disclosure, a reference electrode is embedded in a solid electrolyte containing chloride ions before the solid electrolyte hardens, and electrochemical measurement is performed using the reference electrode, the reference electrode being made of a metal material containing chloride ions.

[0010] According to the present disclosure, it is possible to provide a technique that enables electrochemical measurement of materials in a solid electrolyte that contain chloride ions.

[0011] FIG. 1 is a diagram illustrating a measurement device according to the present disclosure. FIG. 2 is a diagram illustrating a measurement device for measuring the natural potential of a reference electrode according to the present disclosure relative to a base electrode for each sodium chloride concentration. FIG. 3 is a calibration curve showing the natural potential of a reference electrode relative to a base electrode for each sodium chloride concentration. FIG. 4 is a diagram illustrating the natural potential of a reference electrode embedded in mortar for an SSE. FIG. 5 is a diagram illustrating the natural potential of iron for a general SSE and the natural potential relative to a reference electrode according to the present disclosure. FIG. 6 illustrates the difference between the natural potential of iron for a general SSE and the natural potential relative to a reference electrode according to the present disclosure. FIG. 7 is a flowchart illustrating a measurement method according to the present disclosure.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0013] (Measurement Method) In the measurement method according to the present disclosure, as shown in FIG. 1 , a reference electrode 11 is embedded in a solid electrolyte 10 containing chloride ions before the solid electrolyte 10 hardens, and electrochemical measurement is performed using the reference electrode 11. The reference electrode 11 is formed of a metal material containing chloride ions. A portion of the reference electrode 11, such as the lower end, abuts against the solid electrolyte 10, and the rest of the reference electrode 11 is covered with a predetermined member. The predetermined member is an epoxy resin or the like. In the present disclosure, the solid electrolyte 10 is mortar, concrete, or the like.

[0014] Before being embedded in the solid electrolyte 10, the reference electrode 11 is immersed in an aqueous solution 21 having a predetermined sodium chloride concentration, as shown in FIG. 2, and the natural potential of the reference electrode 11 before embedding relative to the base electrode 20 for each sodium chloride concentration is measured to obtain a calibration curve.

[0015] After the calibration curve is obtained, as shown in FIG. 1 , electrochemical measurement is performed using a base electrode 20 and a reference electrode 11 embedded in a solid electrolyte 10. The electrochemical measurement is, for example, measurement of the natural potential. The base electrode 20 is made of the same material as the base electrode used when the calibration curve was obtained, and serves as a reference electrode for the reference electrode 11.

[0016] In the present disclosure, the salinity concentration of the solid electrolyte 10 is estimated from the natural potential of the reference electrode 11 embedded in the solid electrolyte 10 and the natural potential of the reference electrode 11 before embedding relative to the base electrode for each sodium chloride concentration. This makes it possible to measure the natural potential of materials such as iron within the solid electrolyte 10 using the reference electrode 11 embedded in the solid electrolyte 10.

[0017] In the present disclosure, before embedding the reference electrode 11 in the solid electrolyte 10, the natural potential relative to the base electrode 20 is measured for each sodium chloride concentration to obtain a calibration curve, and the base electrode 20 is used to measure the natural potential of the reference electrode 11 embedded in the solid electrolyte 10 and estimate the salt concentration of the solid electrolyte 10. Furthermore, by using the base electrode 20 to measure the natural potential of the reference electrode 11 embedded in the solid electrolyte 10, the natural potential of the material in the solid electrolyte 10 measured using the reference electrode 11 can be evaluated.

[0018] The measurement method according to the present disclosure can electrochemically measure materials in a solid electrolyte containing chloride ions. In particular, the measurement method according to the present disclosure enables electrochemical measurement of a solid electrolyte 10 containing chloride ions by not only the polarization resistance method but also the natural potential method.

[0019] (Reference Electrode) In the present disclosure, the reference electrode 11 is made of silver chloride. The reference electrode 11 is formed of a metal material containing chloride ions as an electrode reaction. Here, the electrode reaction is MX + e－ = M + X － In the present disclosure, M is Ag and X is Cl. The metal material forming the reference electrode 11 is formed by an electrode reaction between a metal and chloride ions.

[0020] A silver chloride electrode is prepared by, for example, maintaining a constant potential on a silver wire in an HCl solution. The natural potential E(Ag / AgCl) of the silver chloride electrode in a chloride solution is theoretically given by the value of Equation (1).

[0021] E(Ag / AgCl) = E 0 (Ag / AgCl)-(RT / F)ln a Cl- E 0 (Ag / AgCl): Standard electrode potential R: Gas constant T: Temperature F: Faraday constant a Cl- :Cl - Activity of ... Equation (1) (Measurement of the Natural Potential of the Reference Electrode) The natural potential of a metal material that contains chloride ions as an electrode reaction varies from the theoretical value due to individual differences in the prepared electrode or differences in the measurement system. Therefore, a calibration curve is obtained in advance for the reference electrode 11 before it is embedded in the solid electrolyte 10.

[0022] As shown in Fig. 2, the natural potential of the fabricated silver chloride electrode reference electrode 11 is measured in aqueous solutions 21 with varying sodium chloride concentrations, using the base electrode 20 as the reference electrode. In this disclosure, the base electrode 20 is described as being saturated silver / silver chloride (SSE), but is not limited to this. The base electrode 20 may be any reference electrode that is used when evaluating corrosion of materials such as iron in the solid electrolyte 10.

[0023] The calibration curve thus obtained is shown in Figure 3. The calibration curve shows the natural potential of the reference electrode 11 relative to the base electrode 20 for each concentration of sodium chloride. Note that in the present disclosure, sodium chloride is an example of chloride ions, and is not limited to sodium chloride.

[0024] (Estimation of Salt Concentration in Solid Electrolyte) In the concrete of an actual structure to be measured, the chloride ion concentration fluctuates over a time scale of several months to several years. The chloride ion concentration does not change over the time range in which the material in the solid electrolyte 10 is electrochemically measured. Therefore, the chloride ion concentration when the material in the solid electrolyte 10 is electrochemically measured is considered to be estimated from the chloride ion concentration estimated from a calibration curve previously obtained using the base electrode 20.

[0025] 4 shows the measurement results of the natural potential of the reference electrode 11 embedded in mortar as a test specimen using an SSE as the base electrode 20. The final natural potential value was read, and the chloride ion concentration in the mortar was estimated to be 0.01 M from the calibration curve in FIG.

[0026] (Measurement of the spontaneous potential of the material in the solid electrolyte) In the present disclosure, since the salt ion concentration around the reference electrode 11 is estimated in advance, the material in the solid electrolyte 10 can be electrochemically measured using the reference electrode 11.

[0027] Furthermore, the natural potential measured using the reference electrode 11 can be converted to the natural potential relative to a general reference electrode. Here, the general reference electrode is a CSE or SSE, etc., which is generally used to determine corrosion of reinforcing steel in concrete, and corrosion determination criteria values ​​are provided. However, in order to determine corrosion using a general reference electrode, it is necessary to sandwich and press a sponge or the like containing an electrolytic solution onto the concrete surface, as shown in Non-Patent Document 2.

[0028] The present disclosure proposes a method for measuring concrete regardless of whether the surface of the concrete is wet or dry by embedding a reference electrode 11 in the concrete to be measured, as shown in FIG.

[0029] A method for converting the natural potential measured using the reference electrode 11 into a natural potential relative to a common reference electrode will be described.

[0030] 5 shows the natural potential of iron for a typical SSE and the natural potential for the reference electrode 11 according to the present disclosure. Although the natural potential of iron for a typical SSE and the natural potential for the reference electrode 11 according to the present disclosure have different values, the curves over time are shifted, and they can be converted into each other.

[0031] The difference between the natural potential of iron for a typical SSE and the natural potential of the reference electrode 11 according to the present disclosure will be described with reference to Fig. 6. The natural potential difference shown in Fig. 6 is 0.15 V. On the other hand, in Fig. 4, the natural potential of the reference electrode relative to the natural potential of the base electrode is 0.14 V, which roughly matches the natural potential difference shown in Fig. 6.

[0032] Therefore, the natural potential of the reference electrode 11 to be measured obtained in this disclosure can be converted to a value based on a general reference electrode by using the potential difference derived from the chloride ion concentration evaluated in advance. Specifically, the natural potential of iron with respect to the SSE in Figure 5 can be obtained by adding the value (0.15 V) obtained in Figure 4 to the natural potential of iron with respect to the reference electrode 11 in Figure 5.

[0033] As shown in Figure 6, when the SSE is used as the base electrode, the natural potential of the reference electrode 11 relative to the SSE does not change. Here, the reference electrode 11 is made of silver chloride. This shows that the reference electrode 11 can be used for measurements not only by the natural potential method but also by the polarization resistance method.

[0034] The natural potential of the reference electrode 11 embedded in the solid electrolyte 10 fluctuates less as the chloride ion concentration increases, resulting in a more stable reference electrode. Furthermore, when chloride ions penetrate the solid electrolyte 10 from the outside, the chloride ion concentration near the surface changes significantly. Therefore, by exposing only a portion of the reference electrode, such as the tip, inside the solid electrolyte 10 so that the natural potential of the reference electrode 11 can be measured, more stable electrochemical measurements can be achieved.

[0035] (Measurement Method) A measurement method according to the present disclosure will be described with reference to FIG.

[0036] In step S1, the present disclosure prepares a reference electrode 11 containing silver chloride ions, and also obtains a calibration curve for the prepared reference electrode 11.

[0037] In step S2, the present disclosure embeds the reference electrode 11 prepared in step S1 before the solid electrolyte 10 hardens.

[0038] Thereafter, when the measurement timing arrives in step S3, measurement is performed in step S4. In step S4, the base electrode 20 is used to measure the natural potential of the reference electrode 11 embedded in the solid electrolyte 10. In step S5, the salt concentration of the solid electrolyte 10 is estimated from the reference electrode 11 measured in step S5 and the calibration curve obtained in step S1.

[0039] Furthermore, in step S6, the natural potential of the material in the solid electrolyte 10 is measured using a reference electrode 11 embedded in the solid electrolyte 10. The measured natural potential may be converted into a natural potential using a general reference electrode, and corrosion of the material in the solid electrolyte 10 may be evaluated.

[0040] If there are multiple measurement timings, the processes of steps S3 to S6 may be repeated multiple times.

[0041] In the present disclosure, by embedding a reference electrode 11 formed of a metal material containing chloride ions in a solid electrolyte 10 before the solid electrolyte 10 containing chloride ions hardens, the material in the solid electrolyte 10 can be electrochemically measured without keeping the surface of the solid electrolyte 10 wet. Regarding the measurement of rebar corrosion in concrete structures containing chloride ions, electrochemical measurement by the half-cell potential method can be performed in addition to the polarization resistance method.

[0042] In this manner, the present disclosure allows for electrochemical measurement of materials in the solid electrolyte 10 that contain chloride ions.

[0043] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the present disclosure.

[0044] REFERENCE SIGNS LIST 1 Measuring device 10 Solid electrolyte 11 Reference electrode 20 Base electrode 21 Aqueous solution

Claims

1. A measurement method comprising: embedding a reference electrode in a solid electrolyte containing chloride ions before the solid electrolyte hardens; and performing electrochemical measurement using the reference electrode, the reference electrode being formed from a metal material containing chloride ions.

2. The measurement method according to claim 1, wherein a portion of the reference electrode abuts against the solid electrolyte.

3. The measurement method according to claim 1, wherein the reference electrode is immersed in an aqueous solution having a predetermined chloride ion concentration before being embedded in the solid electrolyte, and the natural potential of the reference electrode before embedding relative to the base electrode for each chloride ion concentration is measured.

4. The measurement method according to claim 3, wherein the base electrode is used to measure the natural potential of a reference electrode embedded in the solid electrolyte, and the salt concentration of the solid electrolyte is estimated from the natural potential of the reference electrode embedded in the solid electrolyte and the natural potential of the reference electrode before embedding relative to the base electrode for each chloride ion concentration.

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