Test equipment

Abstract

To reduce the resistance of liquid ammonia.SOLUTION: A testing device 110 includes: a container 120 for storing a mixture solution M of liquid ammonia, carbamic acid ions, and inorganic ammonium salt; a cooling unit 130 for cooling the mixture solution M in the container 120; an electrode unit 140 having a test piece 142 and a counter electrode 144, the electrode unit being immersed in the mixture solution M in the container 120; and an application unit 160 for applying a current on the electrode unit 140.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a test apparatus.

Background Art

[0002] Metal materials such as steel are used for tanks storing liquid ammonia and equipment required for transporting liquid ammonia. In order to grasp the aging deterioration of such metal materials, stress corrosion cracking tests are being conducted.

[0003] As a stress corrosion cracking test of steel in liquid ammonia, a technique has been proposed in which gaseous ammonia is pressurized at room temperature to generate liquid ammonia, and a steel material and a counter electrode are immersed in the liquid ammonia to electrochemically anodically polarize the steel material (for example, Patent Document 1). For example, when conducting a test at 20 ° C, ammonia is liquefied by pressurizing it to 0.857 MPa or more. In the technique of Patent Document 1, ammonium carbamate is added to liquid ammonia to accelerate stress corrosion cracking.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional technology that conducts tests at room temperature as described in Patent Document 1, in order to liquefy gaseous ammonia, it is necessary to pressurize it to 0.8 MPa or more. Then, there are problems such as the cost of pumps required for pressurization, pressure-resistant containers for storing liquid ammonia, etc. increasing, or the procedures for satisfying regulations such as the High-Pressure Gas Safety Act becoming complicated.

[0006] Therefore, it is conceivable to cool gaseous and liquid ammonia to below room temperature and perform stress corrosion cracking tests at a pressure of less than 0.8 MPa. However, when liquid ammonia is cooled to below room temperature, ammonium carbamate dissociates less readily compared to when it is at room temperature. This leads to a problem in that the liquid resistance of the liquid ammonia increases compared to when it is at room temperature, and the degree to which stress corrosion cracking is accelerated by the application of current decreases.

[0007] In view of these challenges, this disclosure aims to provide a test apparatus capable of reducing the liquid resistance of liquid ammonia. [Means for solving the problem]

[0008] To solve the above problems, a test apparatus according to one aspect of the present disclosure comprises a container for storing a mixture of liquid ammonia, carbamate ions, and an inorganic ammonium salt; a cooling unit for cooling the mixture in the container; an electrode unit having at least a test piece and a counter electrode, and immersed in the mixture in the container; and an application unit for applying an electric current to the electrode unit.

[0009] Furthermore, the cooling unit may cool the mixture to -10°C or below.

[0010] Furthermore, the application unit may apply a voltage to the electrode unit that is below the upper limit voltage corresponding to the material of the counter electrode.

[0011] Furthermore, the container may be equipped with a unit that acquires the liquid resistance of the mixed liquid inside. [Effects of the Invention]

[0012] According to this disclosure, it is possible to reduce the liquid resistance of liquid ammonia. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram illustrating the test system according to this embodiment. [Figure 2]Figure 2 is a diagram illustrating the test apparatus according to this embodiment. [Figure 3] Figure 3 is a flowchart showing the processing flow of the test method according to this embodiment. [Figure 4] Figure 4 shows a polarization curve. [Figure 5] Figure 5 shows the measurement results of the liquid resistance. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for the purpose of facilitating understanding and do not limit this disclosure unless otherwise specified. In this specification and in the drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations. Elements not directly related to this disclosure are omitted from the illustrations.

[0015] Figure 1 is a diagram illustrating the test system 100 according to this embodiment. Figure 2 is a diagram illustrating the test apparatus 110 according to this embodiment. As shown in Figure 1, the test system 100 includes the test apparatus 110, an ammonia supply pipe 210, a first nitrogen supply pipe 220, a wash water tank 222, a second nitrogen supply pipe 230, a third nitrogen supply pipe 232, a first exhaust pipe 240, waste liquid tanks 242 and 244, a second exhaust pipe 246, a connecting pipe 250, an air supply pipe 252, a third exhaust pipe 254, a vacuum pump 260, a suction bottle 262, a pressure sensor 270, a scrubber 272, and a fume hood 274. Note that in Figure 1, a part of the test apparatus 110 is omitted for ease of understanding.

[0016] The test apparatus 110 performs, for example, a stress corrosion cracking (SCC) test. The stress corrosion cracking test is a test for determining whether the test piece 142 cracks, the time until cracking occurs, the stress at which cracking occurs when applied to the test piece 142, and the like. As shown in FIG. 2, the test apparatus 110 includes a container 120, a cooling unit 130, an electrode unit 140, and a control device 150.

[0017] The container 120 is a pressure-resistant container. The container 120 includes a main body 122 and a lid portion 124. The container 120 stores the mixed liquid M. The mixed liquid M contains liquid ammonia, carbamate ions (NH2CO2 - ), and an inorganic ammonium salt. Carbamate ions are generated in the mixed liquid M by supplying a carbamate ion precursor to the liquid ammonia. The carbamate ion precursor is, for example, one or more of ammonium carbamate (NH4CO2NH2), carbon dioxide (CO2), urea (CO(NH2)2), ammonium carbonate ((NH4)r2CO3), and ammonium bicarbonate (NH4HCO3). In the present embodiment, ammonium carbamate is exemplified as the carbamate ion precursor. The inorganic ammonium salt is, for example, one or more of ammonium nitrate (NH4NO3), ammonium chloride (NH4Cl), and ammonium sulfate ((NH4)2SO4).

[0018] In the present embodiment, the inorganic ammonium salt is mixed so that the liquid resistance of the mixed liquid M calculated by the calculation unit 164 described later is equal to or less than a predetermined value. The liquid resistance is indicated by the resistance value per unit length. The predetermined value is determined based on the distance between the test piece 142 and the counter electrode 144 and the current density flowing between the test piece 142 and the counter electrode 144. When the distance between the test piece 142 and the counter electrode 144 is determined, the voltage drop between the test piece 142 and the counter electrode 144 is proportional to the liquid resistance. Therefore, the liquid resistance at which the voltage drop can be ignored is set as the predetermined value.

[0019] The cooling unit 130 cools the mixed liquid M in the container 120. The cooling unit 130 includes, for example, a heat exchanger 132 and a chiller 134. The heat exchanger 132 is provided on the outer wall of the container 120. The chiller 134 circulates a refrigerant through the heat exchanger 132.

[0020] The cooling unit 130 cools the mixed liquid M to -10°C or lower and -34°C or higher. In this embodiment, the cooling unit 130 cools the mixed liquid M to, for example, -20°C.

[0021] The electrode unit 140 is immersed in the mixed liquid M in the container 120. In this embodiment, the electrode unit 140 includes a test piece 142, a counter electrode 144, and a reference electrode 146. The test piece 142 is made of a metal material used for a tank storing liquid ammonia or equipment required for transporting liquid ammonia. The test piece 142 is, for example, a steel material. The test piece 142 functions as a working electrode. In this embodiment, stress is applied to the test piece 142 by a jig (not shown).

[0022] The counter electrode 144 and the reference electrode 146 are made of a material that is inert in liquid ammonia. The materials constituting the counter electrode 144 and the reference electrode 146 are, for example, platinum (Pt), austenitic stainless steel, aluminum, or carbon. The austenitic stainless steel is, for example, SUS304 or SUS316.

[0023] The control device 150 includes a control unit 152 and a memory 154.

[0024] The control unit 152 is composed of a semiconductor integrated circuit (control board or PLC (programmable logic controller)) including a CPU (central processing unit). The control unit 152 reads out programs, parameters, etc. for operating the CPU from the ROM. The control unit 152 manages and controls the entire test device 110 in cooperation with a RAM as a work area and other electronic circuits.

[0025] Memory 154 consists of ROM, RAM, flash memory, HDD, etc. Memory 154 stores programs and various data used by the control unit 152.

[0026] In this embodiment, the control unit 152 also functions as an application unit 160, a measurement unit 162, and a calculation unit 164.

[0027] The application unit 160 monitors the voltage between the test piece 142 and the reference electrode 146, and applies a DC current between the test piece 142 and the counter electrode 144 so that this voltage reaches a predetermined value. In this embodiment, the application unit 160 applies a voltage between the test piece 142 and the reference electrode 146 that is less than or equal to the upper limit voltage depending on the material of the counter electrode 144. The upper limit voltage is determined by the progress of ammonia electrolysis. The upper limit voltage differs depending on the material of the counter electrode 144. For example, when the application unit 160 uses a platinum electrode as the counter electrode 144, it applies a voltage between the test piece 142 and the reference electrode 146 that is greater than 0.0V and less than or equal to 0.7V (upper limit voltage). Also, when the application unit 160 uses a SUS304 electrode as the counter electrode 144, it applies a voltage between the test piece 142 and the reference electrode 146 that is greater than 0.0V and less than or equal to 1.0V (upper limit voltage).

[0028] The measurement unit 162 (acquisition unit) measures the impedance of the electrode unit 140. The calculation unit 164 (acquisition unit) calculates the liquid resistance of the mixed liquid M based on the impedance.

[0029] Returning to Figure 1, the ammonia supply pipe 210 connects the ammonia supply source to the container 120. The ammonia supply source is, for example, an ammonia gas cylinder. The ammonia supply pipe 210 is equipped with an on-off valve V10, a pressure reducing mechanism 212, and an on-off valve V6.

[0030] The on-off valve V10 opens and closes the flow path formed in the ammonia supply pipe 210. The pressure reducing mechanism 212 is provided between the on-off valve V10 in the ammonia supply pipe 210 and the container 120. The pressure reducing mechanism 212 reduces the pressure of the ammonia supplied from the ammonia source and adjusts the flow rate of ammonia supplied to the container 120. The on-off valve V6 is provided between the pressure reducing mechanism 212 in the ammonia supply pipe 210 and the container 120. The on-off valve V6 opens and closes the flow path formed in the ammonia supply pipe 210.

[0031] The first nitrogen supply pipe 220 connects the nitrogen supply source to the wash water tank 222. The nitrogen supply source is, for example, a nitrogen gas cylinder. The wash water tank 222 stores wash water. The first nitrogen supply pipe 220 is equipped with an on-off valve V1, a pressure reducing mechanism 224, a gas flow meter 226, and an on-off valve V3.

[0032] The shut-off valve V1 opens and closes the flow path formed in the first nitrogen supply pipe 220. The pressure reducing mechanism 224 is installed between the shut-off valve V1 in the first nitrogen supply pipe 220 and the wash water tank 222. The pressure reducing mechanism 224 reduces the pressure of the nitrogen supplied from the nitrogen supply source and adjusts the flow rate of nitrogen supplied to the wash water tank 222.

[0033] The gas flow meter 226 is installed between the pressure reducing mechanism 224 and the wash water tank 222 in the first nitrogen supply pipe 220. The gas flow meter 226 adjusts the flow rate of nitrogen. The on-off valve V3 is installed between the gas flow meter 226 and the wash water tank 222 in the first nitrogen supply pipe 220. The on-off valve V3 opens and closes the flow path formed in the first nitrogen supply pipe 220.

[0034] The second nitrogen supply pipe 230 connects the gas flow meter 226 and the on-off valve V3 in the first nitrogen supply pipe 220 to the pressure reducing mechanism 212 and the on-off valve V6 in the ammonia supply pipe 210. The second nitrogen supply pipe 230 is equipped with on-off valves V2 and V5. On-off valves V2 and V5 open and close the flow path formed in the second nitrogen supply pipe 230. On-off valve V2 is located on the first nitrogen supply pipe 220 side. On-off valve V5 is located on the ammonia supply pipe 210 side.

[0035] One end of the third nitrogen supply pipe 232 is connected between the on-off valve V2 and the on-off valve V5 in the second nitrogen supply pipe 230. The other end of the third nitrogen supply pipe 232 is immersed in the cleaning water stored in the cleaning water tank 222.

[0036] The first exhaust pipe 240 connects the on-off valve V6 in the ammonia supply pipe 210 and the container 120 to the waste liquid tank 242. The waste liquid tanks 242 and 244 store water. The first exhaust pipe 240 is equipped with a safety valve SV. The safety valve SV opens when the pressure in the container 120 exceeds a first predetermined pressure. The first predetermined pressure is, for example, 0.2 MPa.

[0037] The second exhaust pipe 246 connects the container 120 and the waste liquid tank 244. The second exhaust pipe 246 is equipped with on-off valves V9 and V13. The on-off valves V9 and V13 open and close the flow path formed in the second exhaust pipe 246. On-off valve V9 is located on the container 120 side. On-off valve V13 is located on the waste liquid tank 244 side.

[0038] The connecting pipe 250 connects the container 120 to the on-off valves V9 and V13 in the second exhaust pipe 246. The connecting pipe 250 is equipped with on-off valves V7 and V8. On-off valves V7 and V8 open and close the flow path formed in the connecting pipe 250. On-off valve V7 is located on the container 120 side. On-off valve V8 is located on the second exhaust pipe 246 side.

[0039] One end of the air supply pipe 252 is open to the atmosphere. The other end of the air supply pipe 252 is located between the on-off valve V9 and the on-off valve V13 in the second exhaust pipe 246. The air supply pipe 252 is equipped with on-off valves V11 and V12. The on-off valves V11 and V12 open and close the flow path formed in the air supply pipe 252. On-off valve V11 is located on the other end side. On-off valve V12 is located on the one end side.

[0040] The third exhaust pipe 254 connects the area between the on-off valves V11 and V12 in the air supply pipe 252 to the suction side of the vacuum pump 260. The suction bottle 262 is provided between the connection point of the third exhaust pipe 254 to the air supply pipe 252 and the suction side of the vacuum pump 260. The suction bottle 262 removes any liquid contained in the gas supplied through the third exhaust pipe 254. By providing the suction bottle 262, it is possible to prevent liquid from being drawn into the vacuum pump 260. This prevents failure of the vacuum pump 260.

[0041] A pressure sensor 270 measures the pressure inside the container 120. A scrubber 272 is connected to waste liquid tanks 242 and 244. The scrubber 272 purifies ammonia. A fume hood 274 houses the container 120. The fume hood 274 exhausts gas from its internal space.

[0042] [Test Method] Next, a test method using the test system 100 described above will be explained. Figure 3 is a flowchart showing the processing flow of the test method according to this embodiment. As shown in Figure 3, the test method includes an installation step S110, a vacuum step S120, an additive gas supply step S130, a cooling step S140, a liquefaction step S150, a test step S160, and a removal step S170. Note that in the initial state, the on / off valves V1 to V13 are closed. Each step will be explained below.

[0043] [Installation process S110] Ammonium carbamate and an inorganic ammonium salt are placed inside the main body 122 of the container 120. An electrode unit 140 is also placed inside the main body 122. Finally, the opening of the main body 122 is closed with the lid 124.

[0044] [Vacuum process S120] Vacuum process S120 is a process of evacuating the inside of container 120. In vacuum process S120, on-off valves V7, V8, V9, and V11 are opened. Then, the vacuum pump 260 is operated. When the pressure measured by the pressure sensor 270 reaches a second predetermined pressure, the operation of the vacuum pump 260 is stopped. The second predetermined pressure is, for example, -0.1 MPa.

[0045] [Additive gas supply process S130] The additive gas supply process S130 is the process of supplying an additive gas into the container 120. When the additive gas is air, the on-off valve V9 is closed and the on-off valve V12 is opened. Then, when the pressure measured by the pressure sensor 270 reaches the third predetermined pressure, the on-off valves V7, V8, V11, and V12 are closed. The third predetermined pressure is the pressure when a target amount of air is stored in the container 120. The target amount of air is set based on the target amount of oxygen to be dissolved in the liquid ammonia. Note that the more oxygen contained in the liquid ammonia, the more stress corrosion cracking will progress. Alternatively, oxygen may be supplied into the container 120 from an oxygen gas cylinder instead of air.

[0046] [Cooling process S140] The cooling process S140 is a process of cooling the inside of the container 120. In the cooling process S140, all on-off valves V1 to V13 are closed. Then, the cooling unit 130 is activated. The cooling unit 130 cools the inside of the container 120 to below -10°C or above -34°C.

[0047] [Liquefaction process S150] The liquefaction step S150 is a process in which ammonia is supplied into the container 120 and liquefied within the container 120. During the liquefaction step S150, the on-off valves V6 and V10 are opened. When the amount of liquid ammonia stored in the container 120 reaches a predetermined amount, the on-off valves V6 and V10 are closed. The predetermined amount is the amount of liquid ammonia that immerses the electrode unit 140 in. As a result of the liquefaction step S150, the mixed liquid M is stored in the container 120.

[0048] [Test process S160] In test step S160, all on-off valves V1 to V13 are closed. In test step S160, the control device 150 is connected to the electrode unit 140. The application unit 160 monitors the voltage between the test piece 142 and the reference electrode 146, and applies a DC current between the test piece 142 and the counter electrode 144 so that this voltage reaches a predetermined value. In this embodiment, the application unit 160 applies a voltage between the test piece 142 and the reference electrode 146 that is below the upper limit voltage corresponding to the material of the counter electrode 144. This performs a stress corrosion cracking test on the test piece 142. After test step S160 is completed, the removal step S170 is performed.

[0049] [Removal step S170] The removal step S170 is the process of removing the mixed liquid M from the container 120. In the removal step S170, the on-off valves V7, V8, and V13 are opened. The operation of the cooling unit 130 is also stopped. As a result, the mixed liquid M in the container 120 vaporizes and is supplied to the waste liquid tank 244.

[0050] Then, when the pressure inside container 120 drops to atmospheric pressure, valves V1, V2, V5, and V6 are opened. This replaces the inside of container 120 with nitrogen. Once the inside of container 120 has been replaced with nitrogen, valves V1, V2, V5, V6, V7, V8, and V13 are closed, and the test method is completed.

[0051] As described above, the test apparatus 110 of this embodiment is equipped with a cooling unit 130 for cooling the mixed liquid M. This makes it possible to lower the pressure inside the container 120 compared to when it is at room temperature. Therefore, it is possible to reduce the cost of the container 120 compared to when it is at room temperature.

[0052] Furthermore, in the test apparatus 110 of this embodiment, the mixed solution M into which the electrode unit 140 is immersed contains liquid ammonia, carbamate ions, and an inorganic ammonium salt. The inclusion of carbamate ions in the mixed solution M suppresses the formation of a passive film on the surface of the test specimen 142. This makes it possible to promote stress corrosion cracking on the test specimen 142.

[0053] Furthermore, because the mixture M contains an inorganic ammonium salt, the inorganic ammonium salt ionizes independently of ammonium carbamate. As a result, even when the mixture M is at a temperature lower than room temperature, the liquid resistance of the mixture M can be reduced to the same level as at room temperature, or even lower than at room temperature. Therefore, the test apparatus 110 can accelerate the stress corrosion cracking of the test piece 142 by applying an electric current to the same level as at room temperature, or even greater than at room temperature.

[0054] Furthermore, inorganic ammonium salts ionize more readily at low temperatures than organic salts. Therefore, adding inorganic ammonium salts can reduce the liquid resistance of the mixture M more efficiently than adding organic salts.

[0055] Furthermore, as described above, the cooling unit 130 cools the mixed liquid M to -10°C or below. This allows the pressure inside the container 120 to be 0.2 MPa or less. Therefore, the test apparatus 110 can be exempted from the regulations of the High Pressure Gas Safety Act, and the procedures required to comply with the regulations of the High Pressure Gas Safety Act can be omitted.

[0056] Furthermore, as described above, the cooling unit 130 cools the mixed liquid M to -10°C or below and to -34°C or above. This allows the test apparatus 110 to perform stress corrosion cracking tests under conditions similar to those of a tank storing liquid ammonia. The temperature of a tank storing liquid ammonia at atmospheric pressure is -33.4°C.

[0057] Furthermore, as described above, the application unit 160 applies a voltage to the electrode unit that is below the upper limit voltage corresponding to the material of the counter electrode 144. This suppresses the electrolysis of ammonia. This makes it possible to suppress the generation of nitrogen gas. Therefore, the pressure rise in the container 120 due to nitrogen gas can be suppressed.

[0058] Furthermore, as described above, the test apparatus 110 includes a measuring unit 162 and a calculation unit 164. This allows the test apparatus 110 to obtain the liquid resistance of the mixed liquid M. Therefore, it becomes possible to determine the degree of acceleration of stress corrosion cracking on the test specimen 142.

[0059] [First Embodiment] The test conditions for Example A and Comparative Example A are shown in Table 1 below.

[0060] [Table 1]

[0061] As shown in Table 1, the only difference between Example A and Comparative Example A is the mixture used to immerse the test specimen 142. The mixture in Example A contains liquid ammonia, ammonium carbamate, ammonium nitrate, and 100 ppm of oxygen. On the other hand, the mixture in Comparative Example A contains liquid ammonia, ammonium nitrate, and 100 ppm of oxygen, but does not contain ammonium carbamate.

[0062] The temperature of the mixture was set to -20°C. HT80 (high-tensile steel) was used as test specimen 142. A platinum electrode was used as the reference electrode 146.

[0063] Then, the test specimen 142 was immersed in the mixed solution, and the holding potential between the test specimen 142 and the reference electrode 146 was set to +0.5V. The immersion time of the test specimen 142 in the mixed solution was set to one week.

[0064] As a result, stress corrosion cracking occurred in test specimen 142 in Example A. On the other hand, stress corrosion cracking did not occur in test specimen 142 in Comparative Example A.

[0065] Based on these results, it was confirmed that including carbamate ions in the mixture can accelerate stress corrosion cracking in test specimen 142.

[0066] [Second Example] Anode polarization was performed in a mixed solution using a platinum electrode or a SUS304 electrode as the counter electrode 144, an iron electrode as the working electrode, and a platinum electrode as the reference electrode 146. The mixed solution contained liquid ammonia, 5% by mass of ammonium carbamate, and 5% by mass of ammonium nitrate. The voltage (potential difference) between the working electrode and the reference electrode 146 was varied from 0.0V to 2.0V, and the current density flowing between the working electrode and the counter electrode 144 was measured.

[0067] Figure 4 shows a polarization curve. In Figure 4, the vertical axis represents current density [mA·cm²]. -2 The horizontal axis shows the potential difference [V]. In Figure 4, the solid line shows the polarization curve when a platinum electrode is used as the counter electrode 144. In Figure 4, the dashed line shows the polarization curve when a SUS304 electrode is used as the counter electrode 144.

[0068] As shown in Figure 4, whether a platinum electrode was used as the counter electrode 144 or a SUS304 electrode was used, increasing the potential difference increased the current density.

[0069] Furthermore, it was found that when a platinum electrode was used as counter electrode 144, the current density increased sharply when the potential difference exceeded 0.7V. Also, when a SUS304 electrode was used as counter electrode 144, it was found that the current density increased sharply when the potential difference exceeded 1.0V.

[0070] From these results, it can be inferred that when a platinum electrode was used as the counter electrode 144, the reaction shown in equation (1) below proceeded when the potential difference was 0.7V or less, and when the potential difference exceeded 0.7V, the reaction shown in equation (2) below proceeded in addition to equation (1). Fe → Fe2+ + 2e - ...Formula (1) 8NH3 → N2+ 6NH4 + +6e - …Formula (2)

[0071] Similarly, when SUS304 is used as the counter electrode 144, it is presumed that the reaction shown in equation (1) proceeds when the potential difference is 1.0V or less, and when the potential difference exceeds 1.0V, the reaction shown in equation (2) proceeds in addition to the reaction in equation (1).

[0072] From the above results, it was confirmed that when a platinum electrode is used as the counter electrode 144, the application unit 160 can suppress the decomposition of ammonia and the generation of nitrogen gas by applying a voltage between the test piece 142 and the reference electrode 146 that is greater than 0.0V and less than or equal to 0.7V (upper limit voltage). Furthermore, it was confirmed that when a SUS304 electrode is used as the counter electrode 144, the application unit 160 can suppress the decomposition of ammonia and the generation of nitrogen gas by applying a voltage between the test piece 142 and the reference electrode 146 that is greater than 0.0V and less than or equal to 1.0V (upper limit voltage).

[0073] [Third embodiment] Solutions A through F were prepared. Then, 100 ppm of oxygen was dissolved in solutions A through F, the temperature was set to -20°C, and the liquid resistance was measured. The composition of solutions A through F, excluding liquid ammonia and oxygen, is shown in Table 2.

[0074] [Table 2]

[0075] Solution A is prepared by dissolving ammonium carbamate in liquid ammonia. Solution B is prepared by dissolving ammonium nitrate in solution A. Solution C is prepared by dissolving ammonium chloride in solution A.

[0076] Solution D is prepared by dissolving ammonium sulfate in liquid ammonia. Solution E is prepared by dissolving ammonium nitrate in liquid ammonia. Solution F is prepared by dissolving ammonium chloride in liquid ammonia.

[0077] Figure 5 shows the measurement results of the liquid resistance. In Figure 5, the vertical axis represents the liquid resistance RS [Ω·cm], and the horizontal axis represents the elapsed time [hr (hours)]. Also, in Figure 5, the white squares represent the measurement results for solution A, the black squares represent the measurement results for solution B, and the gray squares represent the measurement results for solution C. In Figure 5, the white circles represent the measurement results for solution D, the black circles represent the measurement results for solution E, and the gray circles represent the measurement results for solution F.

[0078] As shown in Figure 5, it was confirmed that the liquid resistance decreased over time in solutions A to F. This suggests that ammonium carbamate and inorganic ammonium salts dispersed in the liquid ammonia over time.

[0079] Furthermore, in solution A, the liquid resistance remained above 1.0E+03 [Ω·cm] even after 50 hours. On the other hand, in solution B, the liquid resistance fell below 1.0E+03 [Ω·cm] after 3 hours, and below 1.0E+02 [Ω·cm] after 23 and 28 hours. In solution C, although the liquid resistance was higher than in solution B, the liquid resistance fell below 1.0E+03 [Ω·cm] after 3 hours, and below 1.0E+02 [Ω·cm] after 23 and 28 hours.

[0080] From the above results, it was confirmed that adding ammonium chloride as an inorganic ammonium salt to liquid ammonia and carbamate ions reduced the liquid resistance of the mixture. Furthermore, it was confirmed that adding ammonium nitrate as an inorganic ammonium salt to liquid ammonia and carbamate ions further reduced the liquid resistance of the mixture.

[0081] Furthermore, in solution D, the liquid resistance was less than 1.0E+04 [Ω·cm] after 3 hours, but after 22 hours, the liquid resistance became less than 1.0E+03 [Ω·cm]. In solution E, the liquid resistance was less than 1.0E+02 [Ω·cm] after 3 hours, and after 21 hours, the liquid resistance became less than 1.0E+01 [Ω·cm]. In solution F, the liquid resistance was less than 1.0E+03 [Ω·cm] after 3 hours, and after 21 hours, the liquid resistance became less than 1.0E+02 [Ω·cm].

[0082] From these results, it was confirmed that adding ammonium sulfate, like ammonium nitrate and ammonium chloride, reduces the liquid resistance of liquid ammonia. Therefore, it is inferred that adding ammonium sulfate as an inorganic ammonium salt to liquid ammonia and carbamate ions can reduce the liquid resistance of the mixture to less than 1.0E+03 [Ω·cm].

[0083] We also attempted to measure the liquid resistance of liquid ammonia alone, but the resistance was too high to measure.

[0084] While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0085] For example, in the above embodiment, the electrode unit 140 was given as comprising a test piece 142, a counter electrode 144, and a reference electrode 146. However, the electrode unit 140 only needs to include at least the test piece 142 and the counter electrode 144. In this case, the control device 150 may measure the liquid resistance of the mixed liquid M.

[0086] Furthermore, in the above embodiment, an example was given in which the application unit 160 applies a voltage to the electrode unit 140 that is below the upper limit voltage. However, the application unit 160 may also apply a voltage to the electrode unit 140 that is above the upper limit voltage.

[0087] Furthermore, in the above embodiment, an example was given in which the test apparatus 110 includes a calculation unit 164. However, the calculation unit 164 is not an essential component. For example, the test apparatus 110 may or may not include an acquisition unit separate from the electrode unit 140 for acquiring the liquid resistance of the mixed liquid M.

[0088] Furthermore, in the above embodiment, the case in which the cooling unit 130 cools the mixed liquid M to -10°C or below was given as an example. However, there are no limitations on the cooling temperature of the cooling unit 130. The cooling unit 130 only needs to cool the mixed liquid M to below room temperature (for example, 25°C).

[0089] Alternatively, the surface area of ​​the test specimen 142 may be reduced to decrease the amount of current flowing between the test specimen 142 and the counter electrode 144. This makes it possible to suppress the generation of nitrogen gas.

[0090] Furthermore, a stirrer may be provided inside the container 120. This can accelerate the diffusion of carbamate ions and inorganic ammonium salts into the liquid ammonia.

[0091] Furthermore, in the above embodiment, the case in which the test apparatus 110 performs a stress corrosion cracking test was given as an example. However, the test apparatus 110 may also perform electrochemical tests other than stress corrosion cracking tests. [Explanation of Symbols]

[0092] M mixture 110 Test equipment 120 containers 130 Cooling section 140 electrode units 142 test specimens 144 Opposite 160 Application part 162 Measurement Department (Acquisition Department) 164. Calculation Department (Acquisition Department)

Claims

1. A container for storing a mixture of liquid ammonia, carbamate ions, and an inorganic ammonium salt, A cooling unit for cooling the mixed liquid in the container, An electrode unit having at least a test specimen and a counter electrode, and immersed in the mixed liquid in the container, The electrode unit is provided with an application unit for applying current, A test apparatus equipped with the following features.

2. The test apparatus according to claim 1, wherein the cooling unit cools the mixed liquid to -10°C or below.

3. The test apparatus according to claim 1 or 2, wherein the application unit applies a voltage to the electrode unit that is less than or equal to an upper limit voltage corresponding to the material of the counter electrode.

4. The test apparatus according to claim 1 or 2, further comprising an acquisition unit for acquiring the liquid resistance of the mixed liquid in the container.

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