JP4886577B2 - Corrosion rate measuring sensor, apparatus, and corrosion rate measuring method - Google Patents

Description

  The present invention relates to a technique for evaluating a corrosion deterioration environment of a structure, and more specifically, a corrosion rate measuring circuit, sensor, apparatus, and measuring method for measuring the corrosion rate of a structure in a non-contact manner. It is about.

  Maintenance of many structures built during the high growth period is now a major social issue. Therefore, corrosion rate evaluation technology that properly grasps the corrosion deterioration of steel, which is one of the deterioration factors of structures, has become an important issue to be developed. Therefore, techniques for predicting the corrosion rate and the amount of corrosion of steel materials in various environments have been considered so far. For example, Non-Patent Document 1 discloses a method for measuring the corrosion rate of steel using the AC impedance method. This method uses a general-purpose device configuration, a function generator, a frequency analyzer and a voltage application device, a minute AC voltage waveform created using a so-called potentiostat, about 5 to 20 mV, and the electrochemical impedance of the target steel It is a technique to measure. This method is for analyzing a complicated corrosion reaction, and can measure the corrosion rate of a steel material. Here, the measurement frequency generally ranges from 10 kHz to 0.001 Hz, and the apparatus power supply uses 100V. However, each unit weighs several tens of kilometers in order to measure the corrosion rate of steel materials that make up structures in the field, especially in the field. Installation is impossible. In addition, in order to achieve highly stable measurement that ensures accuracy by avoiding disturbance, wiring considering noise and wiring with low contact resistance are important. A stand that surpasses the weather and a storm cover are also required.

  In Non-Patent Document 2, as a method for measuring the corrosion rate of a steel material, electrochemical impedance measurement of the target steel material using a minute AC voltage waveform using only two frequencies specified as a simplified method of the AC impedance method. The law is disclosed. This method is characterized in that by specifying the frequency, the scan time is reduced and the measurement time is greatly reduced. In addition, the circuit of the function generator and frequency analyzer can be simplified, and the size of the device can be reduced to about 20 to 30 cm square and the weight can be somewhat reduced to about 20 kg. However, in order to measure the corrosion rate of the steel material constituting the structure at the site, it is difficult to install this apparatus in a high place or a narrow place. In addition, noise-conscious wiring is important for measurement that avoids disturbance and ensures accuracy, and it is necessary to connect with solder, shield the wiring cord, and of course, stand up to surpass wind and rain, and cover for storms. .

  Non-Patent Document 3 discloses an apparatus that digitizes a measurement circuit as much as possible as an AC impedance measurement system (SIMP-301E), generates a minute AC voltage waveform using a CPU, and digitally analyzes a response value. ing. The weight is 5kg, and the power supply can be used with 100V or battery. However, it is still difficult to install this apparatus in a high place or a narrow place for the purpose of measuring the corrosion rate of the steel material constituting the structure in the field. In addition, wiring with low noise and wiring with low contact resistance is important for highly stable measurement that avoids disturbances and ensures accuracy. Wiring with solder, wiring cord shielding measures, naturally surpassing wind and rain You will also need a stand and a storm cover.

Patent Document 1 discloses a patent in which a sensor electrode is inserted into a part of a steel structure to form a pair of electrodes and measure the corrosion rate of the steel structure. The present invention basically relates to a sensor arrangement at the time of measuring the corrosion rate by an electrochemical method in the field, and is not related to a measuring device. Therefore, it is inevitable that measurement is performed with high accuracy while avoiding installation and disturbance in a high place or a narrow place.
JP 2002-71616 A Rust prevention management, pp351-357, 11, 1986 Metal Physics Seminar, pp100-105, Vol.4, No.2, 1979 http://www.syrinx.co.jp/

  In the present invention, in view of the above-mentioned problems of the prior art, it is possible to easily measure even in high places and narrow places, and to measure the corrosion rate of a structure accurately and stably without contact, corrosion rate measurement It is an object to provide a circuit, a sensor, a device, and a measurement method.

  The present invention has the following features.

( 1 ) For corrosion rate measurement, comprising a pair of electrodes to be measured, an electrochemical resistance measurement circuit, a communication circuit, and a corrosion rate measurement circuit having a transmission / reception antenna that transmits and receives electromagnetic waves between external activators In the sensor, the electrochemical resistance measurement circuit measures the electrical resistance by applying a voltage or a current through a lead wire between the pair of measurement target electrodes, or the measurement in addition to the measurement of the electrical resistance. In addition to the measurement of the polarization resistance from the electrical resistance, or the measurement of the electrical resistance and the calculation of the polarization resistance, the impedance measurement circuit for calculating the corrosion rate from the calculated polarization resistance, the impedance measurement circuit It has a dual frequency application circuit capable of applying at least two kinds of voltages or two kinds of frequencies of the current frequency, the two-frequency indicia The circuit is configured such that one of the applied voltages of at least two frequencies or one of the applied currents of the at least two frequencies is the same as the frequency of the driving electromagnetic wave sent from the activator. Or a DC voltage generated from the driving electromagnetic wave sent from the activator, or one of the applied currents of at least two frequencies is a DC current generated from the driving electromagnetic wave sent from the activator. the corrosion rate measurement sensor, wherein you are.

( 2 ) The corrosion rate measuring sensor according to (1) , wherein a plurality of the measurement target electrodes exist, and a voltage or a current is loaded through a lead wire between a pair of measurement target electrodes selected from the plurality of measurement target electrodes. .

( 3 ) Corrosion as described in (1) or (2) above, wherein at least one of the pair of measurement target electrodes is a structure itself of a corrosion rate measurement target object. Sensor for speed measurement.

( 4 ) The electromagnetic wave transmitted from the corrosion rate measuring sensor and the corrosion rate measuring sensor according to any one of the above (1) to (3) and the corrosion rate measuring sensor. An apparatus for measuring a corrosion rate, comprising: an activator capable of receiving the measurement data of the electrical resistance, the calculation data of the polarization resistance, or the calculation data of the corrosion rate converted into the above.

( 5 ) A corrosion rate measurement method using the apparatus for measuring corrosion rate according to ( 4 ) above, wherein the pair of measurement target electrodes are immersed in a medium in a corrosive environment, and the pair of measurement target electrodes are interposed between the pair of measurement target electrodes. Apply two different frequency voltages applied in the electrochemical resistance measurement circuit and pass two different currents, or apply two frequency currents applied in the electrochemical resistance measurement circuit To generate two different types of voltages, measure the electrical resistance between the electrodes to be measured corresponding to the two types of voltage values and current values, and use the measured electrical resistances in the electrochemical resistance measurement circuit. The corrosion rate is calculated by calculating the polarization resistance or calculating the polarization resistance between the electrodes after transmitting the electrical resistance measurement data to the activator.

( 6 ) The method for measuring a corrosion rate according to ( 5 ) above, wherein the medium of the corrosive environment is fresh water, seawater, cement, mortar, concrete, or air.

( 7 ) One of the two types of voltages or currents of the two frequencies is a high frequency voltage or current of 10 Hz or more, and the other is a low frequency voltage or DC voltage of 0.25 Hz or less, or the other is 0.25 Hz. The method for measuring a corrosion rate according to ( 5 ) or ( 6 ) above, wherein the corrosion rate is the following low frequency current or direct current.

  By using the corrosion rate measuring circuit, sensor, apparatus, and measuring method of the present invention, the corrosion rate of the steel material in the corrosion-degrading environment of the structure can be measured in a non-contact manner, which can be used for management of repair and maintenance. . Further, by using the present invention, it is possible to easily and non-contactly measure the corrosion rate even in an outdoor environment or a special environment without a power supply facility. In addition, since the corrosion rate measurement sensor of the present invention does not perform battery replacement or power supply arrangement, it can perform measurement without special management for a long time, and facilitates maintenance and management of the structure. Is.

  FIG. 1 shows the configuration of the corrosion rate measuring apparatus according to the first embodiment of the present invention. The corrosion rate measuring device M includes a corrosion rate measuring sensor 5 and an external activator 6. The corrosion rate measuring sensor 5 includes a corrosion rate measuring circuit 5 ′ and a pair of measurement target electrodes 1 outside the corrosion rate measuring circuit 5 ′.

  Further, the corrosion rate measuring circuit 5 ′ includes an electrochemical resistance measuring circuit 2, a transmission / reception antenna 4 that transmits and receives electromagnetic waves between the communication circuit 3 and an external activator 6. The activator 6 includes a transmission / reception antenna 7 and a transmission / reception circuit 8.

  The electrochemical resistance measurement circuit 2 has lead wires 13 connected to a pair of measurement target electrodes 1 located outside. The electrochemical resistance measurement circuit 2 includes an impedance measurement circuit 10, and the impedance measurement circuit 10 applies a voltage or a current between the pair of measurement target electrodes 1 through the lead wire 13. Electrical resistance can be measured. Furthermore, the impedance measuring circuit 10 can calculate a polarization resistance having an inversely proportional relationship with the corrosion rate, using the measured measurement data of electrical resistance. Furthermore, the impedance measuring circuit 10 can calculate the corrosion rate from the calculated polarization resistance. The electrochemical resistance measurement circuit 2 includes a two-frequency application circuit 9 that can apply at least two types of frequency voltages or two types of frequency currents to the impedance measurement circuit 10.

  The communication circuit 3 transmits the induced current converted by the transmission / reception antenna 4 to the electrochemical resistance measurement circuit 2 and calculates the measurement data of the electrical resistance and the polarization resistance from the electrochemical resistance measurement circuit 2. Means for receiving data or calculating data of the corrosion rate and transmitting the data to the transmitting / receiving antenna 4;

  The transmission / reception antenna 4 can convert a driving electromagnetic wave sent from the external activator 6 into an induced current, and also measures electrical resistance measurement data and polarization resistance sent from the impedance measurement circuit via the communication circuit. It has an induction coil capable of converting the signal current of the data or the calculation data of the corrosion rate into an electromagnetic wave.

  Here, as shown in FIG. 2, the corrosion rate measurement sensor 5 may include a memory that stores an identification code unique to the measurement target electrode 1 in the communication circuit 3. The communication circuit 3 may have a function of transmitting the identification code stored in a memory in addition to the electrical resistance value.

  In the case shown in FIG. 1, an example is shown in which the transmitting / receiving antenna 4 is used as an antenna that serves as both a receiving antenna for capturing driving power of the sensor 5 for corrosion rate measurement and an antenna for transmitting data obtained by measurement. However, it is also possible to separately provide a data transmission antenna and a driving power reception antenna. The transmission / reception antenna 4 may be an antenna that can receive not only the driving power electromagnetic wave sent from the activator 6 but also data such as an identification number.

  The activator 6 used in the present invention has a function capable of inducing an electromotive force by transmitting an electromagnetic wave to the corrosion rate measuring sensor 5 and reading the data transmitted from the corrosion rate measuring sensor 5. There is no particular limitation. For example, as a commercial product, the RX2100 manufactured by Yoshikawa R-F System for 125kHz band can be used, and the RX-TP-RW-01 manufactured by Yoshikawa R-F System, etc. can be applied in the 13.56MHz band.

  In addition, the corrosion rate measuring sensor 5 in the present invention is separated into the measurement object electrode 1, the electrochemical resistance measurement circuit 2, the communication circuit 3, and the transmission / reception antenna 4. There is no problem even if it is connected.

  FIG. 2 shows details of the electrochemical resistance measurement circuit 2, the communication circuit 3, and the external activator 6. The communication circuit 3 has an internal memory 27 made up of, for example, d1, d2, d3, d4. Similarly, the transmission / reception circuit 8 in the external activator 6 has an internal memory 27 composed of, for example, d5, d6, d7, and d8.

  In measuring the corrosion rate of the metal surface of the pair of measurement target electrodes 1, first, the corrosion rate measuring sensor 5 first transmits the driving electromagnetic wave transmitted from the transmitting / receiving antenna 7 in the external activator 6 by the transmitting / receiving antenna 4. After receiving this and converting it into an induced current, it is transmitted to the communication circuit 3, and the communication circuit 3 sends the induced current to the electrochemical resistance measurement circuit 2. The two-frequency applying circuit 9 prepares a voltage having at least two frequencies, and first, for example, the high-frequency resistance of the measurement target electrode 1 is measured by the impedance measuring circuit 10 using a high-frequency power source. Then, the value is written in, for example, d1 in the internal memory 27. This value is called liquid resistance. Next, the low frequency resistance of the electrode 1 to be measured is measured by the impedance measurement circuit 10 using a low frequency power source.

  Then, the value is written in, for example, d2 in the internal memory 27. Thereafter, a resistance obtained by subtracting the value of d1 from the value of the internal memory d2, that is, a polarization resistance value is calculated, and the value is written in, for example, d3. Further, for example, the identification number of the measurement target electrode 1 is stored in d4, and the values d1, d2, d3, and d4 of the internal memory are stored in the activator 6 by electromagnetic waves using the transmission / reception antenna 4 of the communication circuit 3. The data is transferred to the transmission / reception antenna 7, and the respective resistance values and identification numbers are stored in d 5, d 6, d 7, d 8 in the internal memory 28 in the transmission / reception circuit 8. Here, the two-frequency application circuit has been described as an example. However, it is not always necessary to use two frequencies, and more information can be obtained by using two or more frequencies, so that selection may be made as necessary.

  In the above description, the polarization resistance is stored in the internal memory d3. However, when this data is transferred, the impedance measurement circuit 10 or the communication circuit 3 may use the coefficient K (to be described later) to convert it into a corrosion rate and transfer it. .

  In the above description, the two-frequency application circuit 9 prepares a voltage having at least two frequencies. However, this is a case where the circuit is configured by a voltage control method, and the voltage control method is not necessarily required. In the current control method, the two-frequency applying circuit 9 may prepare a current having at least two frequencies.

  Next, a second embodiment of the present invention will be described. In the second embodiment of the present invention, the corrosion rate measuring apparatus M receives the driving electromagnetic wave from the transmission / reception antenna 7 in the external activator 6 by the transmission / reception antenna 4, and receives this via the communication circuit 3 in the electrochemical manner. A voltage having two frequencies or a current having two frequencies is sent to the resistance measurement circuit 2 by the two-frequency application circuit 9. At the time of this preparation, a voltage or current having two frequencies can be arbitrarily created by using two oscillation circuits, but by making one of the two frequencies the same as the frequency of the driving electromagnetic wave from the activator, One frequency oscillation circuit can be omitted and the circuit can be simplified. Simplifying the circuit is important in terms of preventing failure and miniaturizing the circuit. For example, matching the high frequency side is reasonable and effective.

  Also, as a third embodiment of the present invention, one of the two frequencies is generated as a low frequency side voltage or current using a driving electromagnetic wave from an external activator 6, that is, a DC voltage or current is created. You can also. That is, by rectifying the low frequency on the basis of the driving electromagnetic wave from the activator 6 and substituting it with a direct current, one oscillation circuit can be omitted, and the electrochemical resistance measuring circuit, and thus the corrosion rate measuring sensor can be made compact. In addition, the accuracy of the polarization resistance is improved in principle by setting the low frequency side power source to DC. In particular, it is extremely effective for measuring polarization resistance in an environment where the corrosion rate is slow, for example, in concrete, soil, or the like.

  The principle of electrochemical resistance measurement for measuring the polarization resistance and the detailed method for calculating the corrosion rate from the polarization resistance will be described later. With the configuration and procedure as described above, the corrosion rate of the metal surface or the structure surface of the pair of measurement target electrodes 1 can be obtained without contact.

  Next, a fourth embodiment of the present invention will be described. FIG. 3 shows a configuration example of the electrode 1 to be measured when the corrosion rate measuring sensor 5 is applied in an actual environment. From the pair of metal rod electrodes 11, the electrode holding material 12 and the lead wire 13, FIG. It is made up. Here, although there is a pair of electrodes, it is not always necessary to have a pair, and generally there may be a plurality of electrodes. What is necessary is just to select and measure one pair from a plurality. It is also possible to measure by a plurality of combinations, average these values, and use the resistance value.

  Here, in FIG. 3, the exposed area of any metal bar is the same. This is because, as will be described later, when the exposed area is the same, the polarization resistance can be easily calculated. However, they are not necessarily the same. It is sufficient to prepare a conversion factor that takes into account the difference in area regarding resistance calculation through detailed current distribution calculations and experiments in advance.

  The electrode 1 to be measured in this example is made by using the metal used for the structure, and when the corrosion rate of the metal is measured in the environment of the structure, for example, in seawater, soil, concrete or mortar. Can be used.

  Next, a fifth embodiment of the present invention will be described. 4 and 5 show an example in which two rod-like electrodes 11 are installed on the surface of a structural member 14 having electrical conductivity such as a steel structure using an electrode holding member 12, and the structural member 14 is included. An electrode 1 to be measured is formed. 4 is a plan view and FIG. 5 is a cross-sectional view. The lead wire 13 is connected to the rod-shaped electrode 11 and the structural member 14. The number of rod-shaped electrodes is not necessarily two, but one or more rod-shaped electrodes are sufficient. In this configuration, two measurement methods are possible. In short, first, resistance measurement using a pair of rod-shaped electrodes 11 is possible. Second, resistance measurement can also be performed with the rod-shaped electrode 11 and the structural member 14 as a pair. When the structural member 14 is used, it is possible to directly measure the resistance of the structure surface. In this case, as in the case described above, it is sufficient to prepare a conversion coefficient in consideration of the difference in area regarding resistance calculation by calculation or experiment in advance.

  Next, a sixth embodiment of the present invention will be described. 6 and 7, the surface of the structural member 14 having electrical conductivity, such as a steel structure, is recessed, so that the surfaces of the four plate-like electrodes 15 are at the same level as the surface of the structural material. In this example, the electrode holding material 12 is removed. The lead wire 13 is connected to the plate electrode 15 and the structural member 14. Also in this case, the measurement target electrode 1 including the structural member 14 is formed. 6 is a plan view and FIG. 7 is a cross-sectional view. Even in this configuration, two measurement methods are possible as in the case of the fifth embodiment. In this case, the number of plate electrodes is not necessarily four, but may be one or more. In this figure, the surface level of the plate-like electrode is the same as the surface level of the structure, but this is not always necessary. However, this arrangement has the advantage that the environment of the structure surface is not disturbed or changed.

  Next, a seventh embodiment of the present invention will be described. FIG. 8 is a configuration example in which the measurement target electrode 1 is installed in an electrode installation hole previously opened in a structural member 14 having electrical conductivity such as a steel structure, and FIG. 8A is a plan view. 8 (b) is a sectional view. FIG. 8A is a view of the target electrode 11 in FIG. 8B as viewed from the left hand side of the drawing. The measurement target electrode 1 is characterized in that a ring-shaped and disk-shaped electrode 16 is embedded in the electrode holding material 12 so that only the exposed surface is exposed. The lead wire 13 is connected to the plate electrode 15 and the structural member 14. Even in this configuration, the measurement target electrode 1 including the structural member 14 is formed, and two measurement methods are possible as described above. Also in this case, the number of the ring-shaped electrode and the disk-shaped electrode is not necessarily one each, and one or more including both may be sufficient. In this figure as well, the surface level of the electrode is the same as the surface level of the structure, but it is not always necessary. In addition, the outer ring-shaped exposed area and the exposed area of the disc-shaped metal placed in the center are the same, but this is not necessarily required. In this example, since the metal holding member 12 has a cylindrical shape, it is also effective to measure the corrosion rate inside the pipe through which the solution flows by devising such as cutting the screw on the cylindrical surface or attaching it to the bolt screw tip. It becomes.

In the present invention described above, the metal holding member 12 is preferably an electrical insulating material. Although not specified in particular, a large electrical resistance is an essential requirement, and a resistivity of 10 ⁶ Ωcm or more is desirable. Furthermore, it is also important that processing is easy and durability and corrosion resistance are excellent, and epoxy resin, acrylic resin, urethane resin, vinyl chloride resin, polyethylene, polypropylene, polystyrene resin and the like can be used.

  Next, an eighth embodiment of the present invention will be described. FIG. 9 shows a configuration example in the case where the present patent technique is applied to the measurement of the electrochemical resistance of the coating film applied on the surface of the structural member 14 ′ or the rust coating generated on the structure surface. Reference numeral 17 denotes a counter electrode, 18 denotes an electrode cover, and 19 denotes a contact material impregnated with an electrolytic solution. This is used for the purpose of flowing an in-member current 35 through the structural member 14 ′ through the current 20 from the counter electrode 17 through the coating 20 on the surface of the structure. As this material, a gel material such as sponge, absorbent cotton or water-absorbing polymer is suitable.

  The lead wire 13 is connected to the two counter electrodes 17 and the structural member 14. Even in this configuration, the measurement target electrode 1 including the structural member 14 is formed, and two measurement methods are possible as described above. In the first method, the measurement current flows from one counter electrode 17 through the coating film or the rust film, through the path indicated by the arrow in the steel material, and to the other counter electrode 17. In the second method, the measurement current flows from one counter electrode 17 through the paint or rust film to the structural member 14 ′.

  Next, a ninth embodiment of the present invention is characterized by a corrosion rate measuring device comprising both the corrosion rate measuring sensor described above and an activator capable of driving them in a non-contact manner. Yes.

  That is, as an example, as shown in FIG. 1, the corrosion rate measuring device M according to the ninth embodiment of the present invention includes a corrosion rate measuring sensor 5 and a driving electromagnetic wave to the corrosion rate measuring sensor 5. And an activator 6 that can receive electrical resistance measurement data, polarization resistance calculation data, or corrosion rate calculation data converted into electromagnetic waves sent from the corrosion rate measurement sensor 5. .

  The tenth embodiment of the present invention is a method for measuring the corrosion rate using the apparatus described in the ninth embodiment.

  That is, as an example, a pair of electrodes to be measured are immersed in a medium in a corrosive environment, and voltages having two types of frequencies applied by the electrochemical resistance measurement circuit are applied between the pair of electrodes to be measured. Two different types of currents are passed, or currents of two types of frequencies applied by the electrochemical resistance measurement circuit are passed to generate two different types of voltages, and the two types of voltage values and The electrical resistance between the electrodes to be measured corresponding to the current value is measured, and using the measurement data of the measured electrical resistance, the polarization resistance is calculated in the electrochemical resistance measurement circuit, or the activator The corrosion rate is obtained by calculating the polarization resistance between the electrodes to be measured after transmitting measurement data of electrical resistance.

  Here, the medium is fresh water, seawater, cement, mortar, concrete, or air. These are media intended for steel structures, but are not necessarily limited to these, and there is no problem with other media such as chemical solutions.

  Next, a case where a plurality of electrodes to be measured are used will be described as one embodiment of the sensor for measuring corrosion rate of the present invention.

  An example of having a function of storing an identification code (hereinafter referred to as “identification code”) in the corrosion rate measurement sensor and further having a function of transmitting the identification code to the activator in a non-contact manner will be described. To do. An identification code unique to the measurement target electrode 29 is provided in the communication circuit, and the activator has a function of transmitting the measured liquid resistance value, polarization resistance value, and identification code of the measurement target electrode 29 in a non-contact manner. Can do. Thus, when a plurality of corrosion rate measuring devices are used, the identification code identifies which measurement target electrode the liquid resistance value and polarization resistance value data sent to the activator is sent from. It becomes possible.

  As a memory function of the identification code, for example, in the communication circuit of the present invention, for example, a circuit for storing an identification code number of 8 digits or more in hexadecimal can be stored. This makes it possible to individually recognize individual measured values of a plurality of installed corrosion rate measuring devices.

  In this case, specifically, a preset identification code number is transmitted as an electromagnetic wave via a transmission / reception antenna of the activator, which is received by the transmission / reception antenna of the corrosion rate measuring sensor and stored in a memory in the communication circuit.

  As another embodiment, as shown in FIG. 10, a plurality of measurement target electrodes 29 can be provided in the corrosion rate measuring sensor 5. In this case, an identification code may be assigned to each of the plurality of measurement target electrodes 29. When actually using a plurality of measurement target electrodes in the same management place, each measurement target electrode 29 is identified for each channel. It is also possible to determine the identification code number of the measurement target electrode 29 by connecting to the multiplexer 30 having the code number and assigning the identification number to each measurement target electrode 29.

  Then, by simultaneously transmitting the identification code number and the resistance value data, it is possible to recognize the electrical resistance value of each measurement target electrode.

  As an example of this, FIG. 10 shows an example in which a structure including a plurality of electrodes to be measured can be formed in one corrosion rate measuring sensor. In FIG. 10, four measurement target electrodes 29 are connected to the multiplexer 30. The multiplexer 30 sequentially switches each measurement target electrode 29, so that the electrical resistance value and the identification code number measured by the electrochemical resistance measurement circuit 2 for each measurement target electrode 29 are transmitted from the communication circuit 5 via the transmission / reception antenna 4. Send to activator.

  These identification codes can be stored in advance in the corrosion rate measuring sensor 1 at the time of factory shipment, for example. However, after the corrosion rate measuring sensor 5 is set on the structure to be measured, the activator Data can be transmitted and stored in the memory in the communication circuit 3 of the sensor 5 for corrosion rate measurement.

  Furthermore, a combination in which an identification code is assigned to each corrosion rate measuring sensor 5 and an identification code is also assigned to each of the measurement target electrodes 29 existing in the corrosion rate measuring sensor 5 is also possible. Further, it is necessary to individually identify a plurality of corrosion rate measuring sensors, but it is effective to store these identification numbers in a memory in the communication circuit. Also in this case, the pre-assigned identification number is transmitted as an electromagnetic wave through the transmitting / receiving antenna of the activator, and this is received by the transmitting / receiving antenna 4 of the sensor for corrosion rate measurement and stored in the memory in the communication circuit 3. Is possible.

  The structure to which the sensor for measuring corrosion rate is attached is a structure that may cause problems due to deterioration due to corrosion, such as land structures such as bridges, roads, tunnels, buildings, gymnasiums, stadiums, etc. This includes social capital represented by buildings, rivers, harbors, seawalls such as seawalls, and private capital structures such as ships, power plants, and factories.

  The part where the sensor for corrosion rate measurement is attached is a part where corrosion is a concern, a part with eaves or rain, a part that is highly likely to get wet due to the flow or condensation of drainage, a part immersed in seawater, Sites buried in the soil are appropriate. As a method of attaching to these structures, a method of attaching with an adhesive or a pressure-sensitive adhesive, bolt joining considering electric insulation, a method of directly embedding in the structure, or the like is appropriately selected.

  For example, in the case of a steel girder, it is appropriate to apply it directly to the surface of the lower flange steel while being insulated from the steel with an adhesive or adhesive material. When the steel surface is one of the electrodes, the lead wire may be directly attached to the steel surface in the vicinity of which the corrosion rate measuring sensor is attached by soldering or welding. For reinforcing bars embedded in concrete, the electrode for the corrosion rate measurement sensor is fixed to the surface of the reinforcing bar in the concrete with adhesive tape or a binding band, and the corrosion rate measuring circuit is waterproof. It is appropriate to embed in a concrete surface part in a plastic case.

  In the case where a reinforcing bar which is a structure is used as one of the electrodes, a lead wire may be attached to the surface of the reinforcing bar in the vicinity where the corrosion rate measuring sensor is attached by welding. Similarly, when attaching to a structure having electrical conductivity other than the reinforcing bar, the lead wire may be welded to the structure surface.

  Measurement is performed by an activator at the time when the corrosion has progressed after the sensor for measuring the corrosion rate has been installed or when the corrosion is considered to have progressed. FIG. 18 shows how the measurement is performed. In this case, measurement is performed by an activator 33 that has a sensor 34 installed on the bridge. The distance between the sensor and the activator varies depending on the frequency used and the situation of surrounding radio waves, and is usually from a state close to contact to about 50 cm.

  If the measurement target electrode of the sensor for corrosion rate measurement is at a high location, extend the lead wire and install only the circuit for corrosion rate measurement or the transmission / reception antenna as much as possible so that the operator can access it. Is desirable. If this is difficult, it is also effective to attach only the activator's transmission / reception antenna to a rod-shaped auxiliary jig so as to be close to the transmission / reception antenna of the corrosion rate measuring sensor.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  Next, the measurement principle of the corrosion rate using the corrosion rate measurement circuit and the measurement sensor of the present invention will be described. FIG. 11 is an explanatory diagram for explaining electrochemical resistance measurement using a two-frequency method. In FIG. 11, 21 is an exposed metal, 22 is an electrochemical resistance measuring device (corresponding to an electrochemical resistance circuit), and 23 is a solution (corresponding to a medium).

  FIG. 12 schematically shows the electrical characteristics of a circuit including the lead wire 13 and the exposed metal 21 as an electrically equivalent circuit. Here, the exposed metal surface in the solution is a parallel circuit of the polarization resistance element 25 and the capacitor element 26, and the solution between the pair of exposed metals is simulated by the solution resistance element 24. In the figure, the current flowing through this circuit is ΔI, and the voltage generated at that time is ΔE.

  FIG. 13 illustrates a method for calculating the polarization resistance 25 (Rp) by an electrochemical resistance measurement method using a rectangular-wave current-controlled two-frequency method.

  First, as a first step, measurement is performed by applying a high-frequency rectangular wave current. In the case of a high-frequency current, the resistance of the capacitor element Cp becomes zero in the equivalent circuit of FIG. 12, and the total circuit resistance Rt = solution resistance Rs as shown in Expression (1). Next, the measurement which applied the low frequency rectangular current as a 2nd step is performed. In this case, the resistance of the capacitor element Cp is significantly larger than the polarization resistance Rp, and the total circuit resistance can be regarded as Rt = Rs + 2Rp as shown in Equation (2). Then, as a third step, the polarization resistance value Rp is finally calculated by subtracting the solution resistance value Rs obtained from the equation (1) from the resistance value Rt = Rs + 2Rp obtained from the equation (2). become.

  Here, the high frequency is suitably 10 Hz or more from the viewpoint of reducing the resistance component of the capacitor element capacitance. However, at present, the AC frequency used for power transmission / reception and communication of the activator 6 and the corrosion rate measurement sensor 5 is mostly in the 125 kHz band and 13.56 MHz band according to regulations of the Radio Law, etc. Can do.

The low frequency can be regarded as Rt = Rs + 2Rp. 1 Hz or less, preferably 0.25 Hz or less, or DC is desirable.
Rt = ΔEs / ΔI = Rs ------ (1)
Rt = (ΔEs + ΔEp) / ΔI = Rs + 2Rp ------ (2)

The above-mentioned polarization resistance is theoretically inversely proportional to the corrosion rate, but the following equation is used to obtain the corrosion rate.
V = α · K / Rp ---- (3)
Where V: corrosion rate (mm / year), α: constant (mm / year · A ⁻¹ cm ² ), K: constant (V),
Rp: Polarization resistance (Ωcm ² )

As the value of α, 11.6 × 10 ³ is used in the case of iron corrosion. Use 10.8 × 10 ^{3 for} aluminum, 14.9 × 10 ^{3 for} zinc, and 11.6 × 10 ³ for copper. As the value of K, an appropriate value needs to be selected depending on the metal and the corrosive environment, but is usually determined by an experiment for determining the relationship between the polarization resistance measurement and the weight loss. However, under neutral conditions, 0.03 is used for active corrosion, 0.052 for passive state, etc., based on previous research results. In order to improve accuracy, it is better to determine an appropriate numerical value in advance by a corrosion experiment simulating an actual corrosive environment.

Example 1
A round steel having a length of 30 mm and a diameter of 5 mm was cut from the deformed reinforcing bar D13, and this surface was polished with No. 400 polishing paper. Eight of these were prepared, and a lead wire was soldered to the upper end. The distance between the two pairs of round steel bars was 5 mm, and the upper and lower portions were embedded and fixed in the epoxy resin 36 to produce a total of four pieces. The exposed length of round steel was 20 mm. Thereafter, four types of specimens shown in Table 1 were prepared in which mortar was filled between the epoxy resins 36 whose upper and lower sides were fixed. That is, four types of mortars having a combination of water cement ratio (W / C = 0.5 and 0.7) and NaCl concentration (0%, 3%) were prepared as cement kneading water. The round steel was measured in advance and the results shown in Table 1. An electrode to be measured was prepared. This schematic diagram is shown in FIG. The left side of this figure is a bird's-eye view of the measurement target electrode as viewed obliquely from above. A cross-sectional view is shown on the right.

  The specimen was dried in a room for 20 days after filling with mortar, and then allowed to stand in the atmosphere for 120 days. During that period, the polarization resistance Rp was monitored using the corrosion rate measuring circuit and activator of the present invention. At this time, a handy reader / writer (RX2100) manufactured by RF System was used as an activator. The driving electromagnetic wave was 125 kHz, the high frequency used in the measurement was 125 kHz, and the low frequency side was DC.

  By setting the high frequency side to the same frequency as that of the driving electromagnetic wave and the low frequency side to direct current, the two oscillation circuits can be omitted, and the size of the corrosion rate measuring circuit is 10 cm long × 7 cm wide × 2 cm high. It was possible to make it compact. In addition, the electrochemical resistance measurement circuit in Example 1 applied the voltage of the applied two types of frequency, and used the type which passes two different types of electric current. Daily measurement results are shown in FIG. When the NaCl concentration is 3%, the polarization resistance is always smaller than 0%, indicating that the corrosion rate is high.

  After the test, the specimen was broken, the round steel was taken out, rust was removed by pickling, the mass was measured, the corrosion weight loss was measured, and the corrosion mass per unit area was determined. On the other hand, the corrosion rate was calculated from the polarization resistance Rp that was constantly monitored and measured by the equation (3), and further integrated over time to obtain a calculated value of corrosion weight loss. These obtained data were plotted as shown in FIG. 16 for four specimens. As a result, there was a sufficient correlation between the two. This is because the corrosion rate calculated by the polarization resistance measured by the corrosion rate measuring sensor according to the present invention sufficiently captures the actual phenomenon, and the metal corrosion rate in the actual environment can be stably measured without contact. Show.

(Example 2)
From a JIS-SM400B steel plate with a thickness of 5 mm, a ring-shaped metal with an outer shape of 20 mm and an inner shape of 17.3 mm and a disk-shaped metal with a diameter of 10 mm are cut out, soldered with lead wires and embedded in epoxy resin, as shown in FIG. One measurement object electrode as shown was created. This outer surface was polished with No. 400 polishing paper as in Example 1. This measurement target electrode was immersed in artificial seawater in a bucket for 3 months to conduct a corrosion experiment. The water temperature was constant at 40 ° C. During the test period, the polarization resistance was measured once a week using the corrosion rate measuring circuit and activator according to the present invention as in Example 1. At this time, a handy reader / writer (RX2100) manufactured by RF System was used as an activator. The driving electromagnetic wave was 125 kHz, the high frequency used in the measurement was 125 kHz, and the low frequency side was DC.

  By setting the high frequency side to the same frequency as that of the driving electromagnetic wave and the low frequency side to direct current, the two oscillation circuits can be omitted, and the size of the corrosion rate measuring circuit is 10 cm long × 7 cm wide × 2 cm high. It was possible to make it compact. In addition, the electrochemical resistance measurement circuit in Example 2 used a type in which two different types of currents were passed by applying voltages of two kinds of applied frequencies (one is a DC voltage).

From the measured polarization resistance Rp, the corrosion rate was calculated by equation (3), and further integrated over time to obtain a calculated value of corrosion weight loss. The calculated values of corrosion weight loss after 1 month, 2 months, and 3 months were 11.3, 22.3, and 23.6 mg / cm ² , respectively.

In addition, in this experiment, as a comparative material, separately processed from a steel material taken from the same lot as the electrode to be measured, three 50mm x 50mm x 1.5t corrosion samples were produced and immersed in the same bucket as the electrode to be measured. Similarly, a corrosion experiment was conducted. This corrosion sample was taken out after 1 month, 2 months, and 3 months, and then pickled and weighed. The corrosion weight loss per surface area of each sample was 15.2, 22.8, 26.1 mg / cm ² .

  These obtained data were plotted as shown in FIG. 17 for the above three corrosion samples. As a result, although there was some variation between the two, a sufficient correlation was shown. This indicates that the corrosion rate calculated by the polarization resistance measured by the corrosion rate measuring sensor according to the present invention is in good agreement with the experimental value, and the corrosion rate of metals in a real environment can be measured stably without contact. It shows what you can do.

  The present invention is useful when evaluating the corrosion deterioration environment of a structure.

It is an example of composition of a corrosion rate measuring device. It is a detailed block diagram of the sensor and activator for corrosion rate measurement. It is the example 1 of a structure example of the measuring object electrode by a rod-shaped metal. It is the example 2 of a structure of the measuring object electrode by a rod-shaped metal, and has shown the top view. It is the example 2 of a structure of the measuring object electrode by a rod-shaped metal, and has shown sectional drawing. It is a structural example figure of the measuring object electrode by a plate-shaped metal, and has shown the top view. It is a structural example figure of the measuring object electrode by a plate-shaped metal, and has shown sectional drawing. It is a structural example figure of the measuring object electrode by a ring shape and a disk-shaped metal, (a) is a top view, (b) has shown sectional drawing. It is a structural example figure of the measuring object electrode which made the steel material surface film target. It is a block diagram of the sensor for corrosion rate measurement which measures a some measuring object electrode. It is explanatory drawing explaining an electrochemical resistance measurement. It is a conceptual diagram of the equivalent circuit of electrochemical resistance measurement. It is a conceptual diagram of the current application and potential response of electrochemical resistance measurement. It is a figure of a mortar filling specimen. It is a graph of resistance value measurement. 2 is a comparison graph between experimental values and calculated values of the corrosion amount of Example 1. FIG. It is a comparison graph of the experimental value and calculated value of the corrosion amount of Example 2. It is a field measurement situation figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode to be measured 2 Electrochemical resistance measurement circuit 3 Communication circuit 4 Transmission / reception antenna 5 Corrosion rate measurement sensor 5 'Corrosion rate measurement circuit 6 Activator 7 Transmission / reception antenna 8 Transmission / reception circuit 9 2 frequency application circuit 10 Impedance measurement circuit 11 Rod electrode DESCRIPTION OF SYMBOLS 12 Electrode holding material 13 Lead wire 14 Structural member 14 'Structural member with a film | membrane 15 Plate-shaped metal member 16 Ring-shaped and disk-shaped electrode 17 Counter electrode 18 Electrode cover 19 Soaked electrolyte solution Contact material 20 Coating 21 Exposed metal member 22 Electricity Chemical resistance measuring instrument 23 Solution 24 Liquid resistance element 25 Polarization resistance element 26 Capacitor element 27 Internal memory 28 Internal memory 29 Electrode to be measured 30 Multiplexer 31 Round steel 32 Mortar 33 Activator 34 Corrosion rate sensor 35 Current in member 36 Epoxy resin M Corrosion Speed measuring device

Claims (7)

A corrosion rate measurement sensor comprising a pair of electrodes to be measured, an electrochemical resistance measurement circuit, a communication circuit, and a corrosion rate measurement circuit having a transmission / reception antenna that transmits and receives electromagnetic waves between external activators. And
  The electrochemical resistance measurement circuit measures electrical resistance by applying a voltage or current through a lead wire between the pair of electrodes to be measured, or polarization from the measured electrical resistance in addition to the measurement of the electrical resistance. In addition to the calculation of resistance or the measurement of the electrical resistance and the calculation of the polarization resistance, the impedance measurement circuit calculates the corrosion rate from the calculated polarization resistance, and the impedance measurement circuit has at least two types of frequencies. A two-frequency application circuit that can apply a voltage of 2 or a current of two types of frequencies,
  The two-frequency application circuit is a driving electromagnetic wave that is sent from the activator with one of the voltages having at least two types of frequencies to be applied or one of the current having at least two types of frequencies to be applied. Or a DC voltage generated from a driving electromagnetic wave sent from the activator, or one of the applied currents of at least two frequencies is generated from the driving electromagnetic wave sent from the activator. A sensor for measuring corrosion rate, characterized in that the generated direct current is used. The sensor for corrosion rate measurement according to claim 1, wherein a plurality of the measurement target electrodes are present, and a voltage or a current is loaded through a lead wire between a pair of measurement target electrodes selected from them. The corrosion rate measurement sensor according to claim 1 or 2, wherein at least one of the pair of measurement target electrodes is a structure itself of a corrosion rate measurement target. The corrosion rate measurement sensor according to any one of claims 1 to 3, and the electric wave converted to the electromagnetic wave sent from the corrosion rate measurement sensor while being able to transmit a driving electromagnetic wave to the corrosion rate measurement sensor. An apparatus for measuring a corrosion rate, comprising: an activator capable of receiving measurement data of resistance, calculation data of the polarization resistance, or calculation data of the corrosion rate. 5. A corrosion rate measurement method using the corrosion rate measurement device according to claim 4, wherein the pair of measurement target electrodes are immersed in a medium of a corrosive environment, and the electrochemical is interposed between the pair of measurement target electrodes. Apply two different frequency voltages applied in the resistance measurement circuit and pass two different currents, or pass two different frequency currents applied in the electrochemical resistance measurement circuit, Two different types of voltage are generated,
The electrical resistance between the electrodes to be measured corresponding to the two types of voltage value and current value is measured, and the polarization resistance is calculated in the electrochemical resistance measurement circuit from the measured electrical resistance, or to the activator A method of measuring a corrosion rate, wherein the corrosion rate is obtained by calculating a polarization resistance between the electrodes to be measured after transmitting measurement data of the electrical resistance. The method for measuring a corrosion rate according to claim 5, wherein the medium of the corrosive environment is fresh water, seawater, cement, mortar, concrete, or air. One of the two types of frequency voltages or currents is a high frequency voltage or current of 10 Hz or more, and the other is a low frequency voltage or DC voltage of 0.25 Hz or less, or the other is a low frequency of 0.25 Hz or less. The method according to claim 5 or 6, wherein the corrosion rate is a frequency current or a direct current.

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