JP6096682B2 - Pitting potential monitoring reference electrode, pitting potential monitoring device - Google Patents

Description

  The present invention relates to a pitting potential monitoring reference electrode and a pitting potential monitoring apparatus using the same.

  If water leakage due to pitting corrosion occurs in piping of an air conditioning system or various plants, the operation of the entire system or plant may have to be stopped, and much time and labor are required for restoration. As an example of such a pipe, there is a heat transfer copper pipe through which cooling water of an absorption chiller / heater is supplied. It has been confirmed that pitting corrosion occurs in this heat transfer copper pipe due to the water quality conditions and operating conditions (pressure / flow conditions) of the flowing cooling water.

  In order to prevent water leakage due to pitting corrosion of piping, pitting corrosion potential in piping is monitored. The prior art described in Patent Document 1 below uses a pilot plant that simulates an actual cooling water system, and circulates cooling water that is open to the cooling tower pit via a cooling water feed pipe with a water feed pump. A test pipe (cooling water) is fed to the monitoring device by pulling a branch pipe from the water pipe. The monitoring device forms a monitoring channel that flows test water through the monitoring test pipe connected to the branch pipe and returns it to the cooling tower pit. The monitoring equipment is immersed in the test water and the test pipe that is electrically insulated from the surroundings. The pitting potential (corrosion potential) is monitored by measuring the potential difference with the reference electrode over time.

JP-A-11-51849

  In the piping such as the heat transfer copper pipe of the absorption chiller / heater described above, a closed circulation channel is formed, and the cooling water is continuously supplied at a predetermined pressure during operation. For such a pipe, the actual pitting corrosion generation environment cannot be accurately reproduced in a pilot plant such as the above-described prior art. In other words, as in the prior art, when the potential is measured with the test water released to the atmosphere after being once released to the atmosphere, the pressure and flow velocity are actually reduced by about 50%, which is one of the pitting corrosion factors. It is known that the degree of adhesion of the deposit in the pipe will be different from the actual state. Moreover, since the reference electrode is immersed in the test water that flows out of the test pipe and returns to the cooling tower pit, the potential difference between the test water flowing in the test pipe and the test pipe is not accurately measured.

  In addition, in the conventional technology, if the potential is continuously measured in a pressure / flow state of about 0.6 MPa, which is a use environment such as a heat transfer copper tube through which the cooling water of the absorption chiller / heater is passed, the reference electrode can be obtained in a few days. There was a problem that bubbles were generated inside the liquid junction and the liquid junction could not be taken, and the potential could not be continuously measured. For this reason, there was a problem that constant potential polarization measurement could not be performed under the same pressure and flow conditions as the operating environment, and the potential could not be continuously measured under the same pressure and flow conditions during normal operation. .

  This invention makes it an example of a subject to cope with such a problem. That is, it is an object of the present invention to enable pitting potential monitoring that reproduces the actual pitting corrosion generation environment, to enable potential measurement that is continued under a relatively high pressure and flow state, and the like.

In order to achieve such an object, a reference electrode for monitoring a pitting corrosion potential according to the present invention comprises the following configurations among several inventions described in the specification.
A reference electrode used to monitor the pitting corrosion potential of a pipe that forms a circulation channel of environmental water, comprising an electrode lead-out portion for drawing out a lead wire from one end of the metal electrode, and an electrolyte solution in which the metal electrode is immersed A salt bridge portion that is filled, and a liquid junction portion that has a liquid junction with the electrolyte solution and environmental water that flows in the pipe, and one end facing upward is disposed in the salt bridge portion in proximity to the liquid junction portion And the other end is provided with a bubble removing pipe drawn out to the outside of the salt bridge portion. In addition, environmental water here refers to the water which makes piping a pitting corrosion generating environment.

  The reference electrode for pitting corrosion potential monitor according to the present invention having such a feature can suck the bubbles to the outside through the bubble removing tube even when bubbles are generated near the liquid junction. It is possible to continuously measure the potential between the environmental water circulating through the pipe at a relatively high pressure / flow state and the pipe.

  Then, by using this pitting potential monitor reference electrode, a bypass closed flow path is formed in the pipe forming the environmental water circulation flow path, and a part of the bypass closed flow path is used as a test pipe. The same environmental water pressure / flow state as normal operation can be created in the pipe, and the potential between the environmental water and the pipe can be continuously measured. This makes it possible to perform pitting potential monitoring that reproduces the actual pitting corrosion generation environment.

It is explanatory drawing which showed the reference electrode for pitting corrosion potential monitors which concerns on one Embodiment of this invention. It is explanatory drawing explaining the pitting corrosion monitoring apparatus and pitting corrosion monitoring method using the reference electrode for pitting corrosion monitoring shown in FIG. 1 ((a) is monitoring at the time of pitting corrosion potential measurement by constant potential polarization. (B) shows corrosion potential monitoring during normal operation.)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a pitting potential monitor reference electrode according to an embodiment of the present invention. The reference electrode 1 includes an electrode lead part 2, a salt bridge part 3, and a liquid junction part 4. The electrode lead portion 2 includes a metal electrode 20 and a lead wire 21 drawn from one end of the metal electrode 20. The salt bridge portion 3 includes a metal electrode housing portion 30, an insertion portion 31, and a connecting portion 32, and the electrolyte solution 5 is filled in these. The liquid junction 4 is provided at the distal end of the insertion portion 31 and has a function of liquid junction between the electrolyte solution 5 and environmental water flowing in a pipe (not shown).

  For example, a silver-silver chloride (Ag / AgCl) electrode can be used as the metal electrode 20, and a potassium chloride (KCl) saturated solution or the like can be used as the electrolyte solution 5 in which the metal electrode 20 is immersed.

  The liquid junction part 4 can be comprised with a porous body, for example. The thickness of the porous body is preferably increased within a range where appropriate potential measurement is possible. For example, when the thickness of the porous body is set to 60 mm or more, bubbles are less likely to be generated inside the salt bridge portion 3 even in environmental water having a pressure / flow state of about 0.6 MPa. As the porous body, a porous ceramic capable of ion exchange (for example, Vycor glass having a circular diameter of 6 mm (manufactured by Corning)) or the like can be used.

  The reference electrode 1 includes a bubble removing tube 6. One end of the bubble removing tube 6 is disposed in the salt bridge portion 3 in the vicinity of the liquid junction portion 4, and the other end is drawn out of the salt bridge portion 3. By providing such a bubble removal tube 6, bubbles generated near the liquid junction 4 in the salt bridge 3 can be sucked into the bubble removal tube 6 and released to the outside of the salt bridge 3. . In order to suck the bubbles, a needle of a suction tool such as a syringe is inserted into the end of the bubble removing tube 6 pulled out to generate a negative pressure in the bubble removing tube 6.

  In a preferred embodiment of the reference electrode 1, as shown in the figure, the salt bridge portion 3 is formed in a U shape, the liquid junction portion 4 is provided on one end side of the salt bridge portion 3, and the electrode lead-out portion 2 is provided on the other end side. Provided. By adopting such a configuration, when bubbles are generated in the salt bridge portion 3, the bubbles are gathered immediately below the liquid junction portion 4, and one end of the bubble is removed close to the liquid junction portion 4. The tube 6 can easily suck out bubbles.

  FIG. 2 is an explanatory diagram for explaining a pitting potential monitoring device and a pitting potential monitoring method using the above-described pitting corrosion potential monitoring reference electrode. FIG. 2 (a) shows a monitoring device and a monitoring method at the time of pitting corrosion potential measurement by constant potential polarization, and FIG. 2 (b) shows an apparatus and a method for monitoring the corrosion potential during normal operation. . Here, an example is shown in which the pitting corrosion potential of a pipe such as a heat transfer copper pipe in a suction-type chiller / heater plant that forms a closed circulation channel of environmental water (cooling water) is monitored.

  In FIG. 2A, (A) is an inflow port for environmental water (cooling water), (B) is an outflow port for environmental water (cooling water), and is a pipe to be monitored such as a heat transfer copper pipe. A bypass closed flow path is formed in which environmental water that branches off from the inlet (A) and returns from the outlet (B) to the monitored pipe passes through the test pipe Pe. The test pipe Pe is a pipe having the same quality and the same diameter as the monitored pipe. By forming the bypass closed flow path described above and forming a part of it as the test pipe Pe, the environmental water flowing through the monitored pipe can be flowed into the test pipe Pe in the same pressure and flow state as during normal operation.

  The pitting corrosion potential monitoring device 10 provided with such a test pipe Pe performs pitting corrosion potential measurement by constant potential polarization. The reference electrode 1 described above, the counter electrode 11 disposed inside the test pipe Pe, A potential measurement unit 12 and a potentiostat 14 including a constant voltage power supply 13 are provided. Here, the reference electrode 1 has the liquid junction 4 inserted in the test pipe Pe. The potential measuring unit 12 measures the potential between the lead wire 21 of the electrode lead-out unit 2 in the reference electrode 1 and the lead wire 15 connected to two points of the test pipe Pe. The constant voltage power supply 13 applies a constant voltage via the lead wires 16 and 17 between the counter electrode 11 drawn out from the inside of the test pipe Pe and the lead wire 15 connected to the test pipe Pe.

  Such a pitting corrosion potential monitoring device 10 has a counter electrode 11 in a rod shape and is passed in the axial direction of the test pipe Pe, and is provided with a waterproof / pressure-resistant part Pe1 at the test pipe Pe penetration part of the counter electrode 11, and the reference electrode 1 described above. Is used to enable constant potential polarization of the test pipe Pe in a pressure / flow state. The pitting corrosion potential monitoring device 10 applies a constant potential from the constant voltage power supply 13 between the test pipe Pe and the environmental water to generate pitting corrosion on the test pipe Pe, and the potential between the test pipe Pe and the environmental water at that time The (pitting corrosion potential) is measured by the potential measuring unit 12.

  According to such a pitting corrosion potential monitoring device 10 or a pitting corrosion potential monitoring method using the same, even if bubbles are generated in the reference electrode 1, potential measurement is performed by sucking the bubbles outside through the bubble removal tube 6. Since it can be continued, it is possible to measure the pitting corrosion potential even in a situation where environmental water is flowing through the test pipe Pe in a relatively high pressure / flow state. And by forming the bypass closed flow path described above and making a part of it the test pipe Pe, the same pressure and flow state as the environmental water flowing through the monitored pipe can be reproduced in the test pipe Pe. The pitting potential monitoring that reproduces the actual pitting corrosion generation environment becomes possible.

  Fig. 2 (b) shows the pitting corrosion potential (corrosion potential) during normal operation by providing the environmental water (cooling water) inlet (A) and outlet (B) in a part of the monitored pipe P. doing. Here, the liquid junction part 4 of the reference electrode 1 is inserted into the monitoring target pipe P, and the potential between the lead wire 21 of the electrode lead-out part 2 and the lead wire 15 connected to two points of the monitoring target pipe P is measured. A potential measuring unit 12 is provided. It is possible to monitor the corrosion state of the monitoring target pipe P in the normal operation state by measuring the potential in a time series by the potential measuring unit 12 during the operation period and comparing the measurement result with the pitting corrosion potential. become.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention. In addition, the above-described embodiments can be combined by utilizing each other's technology as long as there is no particular contradiction or problem in the purpose and configuration.

1: reference electrode, 2: electrode lead-out part, 20: metal electrode, 21: lead wire,
3: salt bridge part, 30: metal electrode accommodation part, 31: insertion part, 32 connection part,
4: Liquid junction part, 5: Electrolyte solution, 6: Bubble removal pipe,
10: Pitting potential monitoring device,
11: Counter electrode, 12: Potential measurement unit, 13: Constant voltage power supply,
14: Potentiostat, 15, 16, 17: Lead wire,
Pe: Test piping, P: Monitored piping

Claims (5)

A reference electrode used to monitor the pitting corrosion potential of a pipe forming a circulation path of environmental water,
An electrode lead-out portion that pulls out the lead wire from one end of the metal electrode;
A salt bridge filled with an electrolyte solution into which the metal electrode is immersed;
A liquid junction part that has a liquid junction with the electrolyte solution and the environmental water flowing in the pipe,
A pitting corrosion potential monitoring reference electrode, comprising: a bubble removal pipe having one end facing upward in the salt bridge portion and in close proximity to the liquid junction portion, and the other end drawn out to the outside of the salt bridge portion.   The pitting corrosion potential monitoring reference electrode according to claim 1, wherein the liquid junction portion is formed of a porous body, and the thickness of the porous body is set to 60 mm or more.   The pitting corrosion according to claim 1 or 2, wherein the salt bridge portion is formed in a U-shape, the liquid junction portion is provided on one end side of the salt bridge portion, and the electrode lead-out portion is provided on the other end side. Reference electrode for potential monitor. Using the reference electrode for pitting corrosion potential monitoring according to any one of claims 1 to 3,
A bypass closed flow path is formed with respect to the pipe and a part of the bypass closed flow path is used as a test pipe.
Insert the liquid junction into the test pipe,
A potential measuring unit for measuring a potential between a lead wire of the electrode lead portion and a lead wire connected to the test pipe; a counter electrode drawn out from the inside of the test pipe; and a lead connected to the test pipe A pitting corrosion potential monitoring device, comprising: a constant voltage power source that applies a constant voltage to a wire. Using the reference electrode for pitting corrosion potential monitoring according to any one of claims 1 to 3,
Inserting the liquid junction into the pipe,
A pitting corrosion potential monitoring device comprising a potential measuring unit that measures a potential between a lead wire of the electrode lead portion and a lead wire connected to the pipe.

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