JP6944092B2 - Corrosion environment measurement method for structures, corrosion environment measurement system, repair plan formulation method and inspection plan formulation method using corrosion environment measurement results - Google Patents

Description

The present invention relates to a corrosion environment measurement method and a corrosion environment measurement system for quantitatively grasping the corrosion rate of a structure such as a lighting facility installed outdoors over a long period of time. Furthermore, a method of formulating a repair plan that enables repairs to be performed at the optimum timing according to the degree of deterioration, and an inspection plan that enables inspections of structures to be performed at the optimum timing according to the progress of corrosion and deterioration. It is about how to formulate.

As a method of grasping the progress of corrosion and deterioration of metal materials that make up structures such as lighting equipment installed outdoors, a method of exposing the ACM (Atmospheric Corrosion Monitor) sensor and measuring the atmospheric environment with an atmospheric corrosion monitor. Has been proposed.

For example, Japanese Patent Application Laid-Open No. 2008-224405 discloses a corrosion rate evaluation method for determining the corrosion rate in an area where the ACM sensor is not installed based on the corrosion rate at the location where the ACM sensor is installed.

Japanese Patent Application Laid-Open No. 2008-224405

Since the outdoor corrosive environment varies greatly depending on the location, the progress of deterioration differs depending on the location even for the same structure. Therefore, if the structures installed outdoors are uniformly repaired, the repair may be too late or unnecessary repairs may be performed. In addition, if the inspection work prior to repair is performed uniformly for each structure, the collection of deterioration information may be delayed in places where deterioration progresses quickly, and unnecessary inspection work may be performed in places where deterioration progresses slowly. be.

Therefore, a repair plan that can repair the structure at the optimum timing according to the degree of deterioration and an inspection performed prior to the repair are performed at the optimum timing according to the progress of corrosion and deterioration of the structure. It is necessary to formulate an inspection plan that can be carried out.

However, conventional techniques for measuring the atmospheric environment have not been able to accurately grasp the progress of corrosion and deterioration. For example, the conventional ACM sensor mainly measures the wetting time, and in the above corrosion rate evaluation method, the wetting time is measured in relation to the relative humidity and used as a guideline for corrosion, but the corrosion rate cannot be measured quantitatively. It was difficult.

In addition, since the ACM sensor has a structure that measures the current flowing between two types of metals, the sensor part deteriorates quickly and needs to be replaced frequently in places where the corrosive environment is severe, and continuous measurement over a long period of time. It was not suitable for.

Therefore, the present invention provides a corrosion environment measurement method and a corrosion environment measurement system that enable the corrosion rate of a structure installed outdoors to be quantitatively and continuously grasped, and repairs the degree of deterioration. We provide a method to formulate a repair plan that can be performed at the optimum timing according to the situation, and a method to formulate an inspection plan that can perform the inspection of the structure at the optimum timing according to the progress of corrosion and deterioration. The purpose is.

In the method for measuring a corrosive environment according to the present invention, in a road tunnel in which a plurality of structures are installed, an arbitrarily selected structure from the plurality of structures is set as a measurement target structure, and the measurement target structure is described as described above. A plurality of sensors having inspection surfaces in which a pair of electrodes formed of a material having a correlation with the structure to be measured and a material having a correlation in corrosion resistance are arranged at intervals are placed in the road tunnel at equal intervals, and the electrodes are the measurement target. It is possible to arrange the inspection surface in a state where it is not connected to a structure and expose the inspection surface to the atmosphere, and separate the resistance related to the ion conductivity of water droplets adhering to the inspection surface from the resistance of charge transfer on the surface of the electrode. The first inspection frequency, which is an arbitrary frequency within the possible frequency range, and the resistance related to the ion conductivity and the resistance of the charge transfer combined with time can be obtained, and the resistance related to the ion conductivity are The time course of impedance is measured at the obtained second inspection frequency.

The corrosion environment measurement system according to the present invention includes a plurality of sensors having inspection surfaces in which a pair of electrodes are arranged at intervals, and a measuring device for measuring impedance by applying an AC voltage to the electrodes. In a road tunnel in which a plurality of structures are installed, a structure arbitrarily selected from the plurality of structures is set as a measurement target structure, and a plurality of the sensors are measured at equal intervals in the road tunnel. The electrode is placed on the structure in a state where the inspection surface is exposed to the atmosphere without being connected to the structure to be measured. The electrode is formed of a material that correlates with the structure to be measured in terms of corrosion resistance. The measuring device applies the AC voltage at an arbitrary frequency within a frequency range capable of separating the resistance related to the ion conductivity of water droplets adhering to the inspection surface and the resistance of charge transfer on the surface of the electrode. Therefore, the voltage is applied at the first inspection frequency at which the resistance related to the ion conductivity and the resistance of the charge transfer combined with time can be obtained, and the second inspection frequency at which the resistance related to the ion conductivity can be obtained.

In the corrosive environment measuring method and the corrosive environment measuring system according to the present invention, the pair of the electrodes is a cylindrical first electrode and the first electrode having a diameter larger than that of the first electrode and surrounding the first electrode. It may be composed of a ring-shaped second electrode having an arrangement in which the axes coincide with each other.

In the repair plan formulation method according to the present invention, the corrosion rate of the measurement target structure is calculated based on the temporal change of the impedance obtained by the corrosion environment measurement method according to the present invention, and the measurement target structure and the measurement target structure and the above are described. Determine when to repair structures in a corrosive environment similar to the structure to be measured.

In the inspection plan formulation method according to the present invention, the corrosion rate of the measurement target structure is calculated based on the temporal change of the impedance obtained by the corrosion environment measurement method according to the present invention, and the measurement target structure and the measurement target structure and the above are described. Determine when to inspect structures in a corrosive environment similar to the structure to be measured.

According to the corrosion environment measurement method and the corrosion environment measurement system according to the present invention, the electrodes arranged at intervals on the inspection surface of the sensor are formed of a material that correlates with the structure to be measured in terms of corrosion resistance. On the inspection surface of the sensor, a corrosion phenomenon similar to the surface of the structure to be measured will occur. Then, the corrosion rate of the structure to be measured can be calculated based on the measured impedance. Therefore, not only the wetting time but also the corrosion rate of the structure can be quantitatively measured.

Moreover, since the electrodes placed on the inspection surface of the sensor are made of a material that corrodes with the structure to be measured in terms of corrosion resistance, they do not deteriorate extremely faster than the structure to be measured and are to be measured. Continuous measurement can be performed for a significant period to grasp the progress of deterioration in the structure. Therefore, it is possible to quantitatively and continuously grasp the corrosion rate of the structure installed outdoors.

When the corrosive environment measurement method and the corrosive environment measurement system according to the present invention are applied to a structure installed in a road tunnel, an arbitrarily selected structure is measured from a plurality of structures installed in the road tunnel. The target structure is a plurality of sensors arranged at equal intervals in the road tunnel. This makes it possible to more accurately grasp the corrosion rate of a plurality of structures installed in road tunnels having different corrosive environments depending on the location.

According to the present inventor, the antifreeze agent sprayed on the road surface near the tunnel opening and the exhaust gas from the vehicle are deeply involved in the corrosion of the structure installed in the tunnel, and the structure is corroded depending on the location even in the same tunnel. I found that the speeds are very different.

For example, in mountain tunnels, the corrosion rate may increase near the tunnel entrance where the antifreeze agent has a strong influence, and in tunnels in areas where the antifreeze agent is not sprayed, it is affected by exhaust gas and moisture in the tunnel. Corrosion rate may increase from the center of the tunnel to the exit. Therefore, in order to grasp the corrosion rate of a plurality of structures installed in the road tunnel, it is preferable to arrange a plurality of sensors at equal intervals in the road tunnel. In addition, it is preferable to relatively investigate the corrosion rate, and it is also preferable to measure the structure to be measured installed near the entrance or the exit outside the road tunnel.

The shape of the electrode may be optimized according to the usage conditions, but a cylindrical first electrode and an arrangement in which the diameter is larger than that of the first electrode and the axis of the first electrode coincides with that of the first electrode. Durability can be improved and the frequency of sensor replacement can be reduced by configuring the electrode with the ring-shaped second electrode.

In the repair plan formulation method according to the present invention, the progress of deterioration in the structure can be estimated with high accuracy by using the corrosion rate calculated based on the measured impedance. Therefore, by deciding the repair timing in consideration of the estimated deterioration situation, the repair can be performed at the optimum timing according to the degree of deterioration.

Similarly, in the inspection plan formulation method according to the present invention, the structure is inspected at the optimum timing according to the progress of corrosion and deterioration by deciding the inspection timing in consideration of the estimated deterioration situation. Can be done.

It is a schematic block diagram of the corrosion environment measurement system which concerns on this invention. The configuration of the sensor is shown, (a) is a plan view, and (b) is a vertical sectional view. It is an equivalent electric circuit that is the principle of the measurement method. It is a Nyquist diagram of impedance to be measured. It is a figure which shows roughly the position where the sensor is arranged when the structure to be measured is a lighting device or an information board. It is a figure which shows roughly the position where the sensor is arranged when the structure to be measured is a tall gate. It is a figure which shows roughly the position where the sensor is arranged when the structure to be measured is a guardrail. It is a figure which shows roughly the position where the sensor is arranged when the structure to be measured is a tunnel lighting fixture. It is a figure which shows roughly the position where the sensor is arranged when the structure to be measured is a water spray pipe. When the structure to be measured is a jet fan, the position where the sensor is arranged is schematically shown, (a) is a side view, and (b) is a front view. The correlation between the frequency and the impedance obtained when the sensor whose inspection surface is left in the initial state is immersed in distilled water is shown, (a) is a Nyquist diagram, and (b) is a Bode diagram. The correlation between the frequency and the impedance obtained when the sensor with the inspection surface left in the initial state is immersed in the 3% NaCl solution is shown, (a) is a Nyquist diagram, and (b) is a Bode diagram. The correlation between the frequency and the impedance obtained when the sensor whose inspection surface is corroded is immersed in a 3% NaCl solution is shown, (a) is a Nyquist diagram, and (b) is a Bode diagram. It is a Nyquist diagram which shows the principle of calculating _{the charge transfer resistance Rct} of an electrode surface by modifying impedance measured on a low frequency side. It is a figure which shows the installation position of the sensor seen from the traveling direction of a vehicle at the point 180m from the entrance of the tunnel where the structure to be measured is installed. It is a graph which shows the time-dependent change of the reciprocal _{of the moisture resistance R sol} and the charge transfer resistance R _ct of the electrode surface at a point 180 m from the entrance of the tunnel where the structure to be measured is installed. It is a graph which shows the time-dependent change of the reciprocal _{of the moisture resistance R sol} and the charge transfer resistance R _ct of the electrode surface at the point 2155 m from the entrance of the tunnel where the structure to be measured is installed. A graph showing the time course of the reciprocal of _{the moisture resistance R sol} and the charge transfer resistance R _{ct on} the electrode surface during the measurement period after the measurement period shown in FIG. 16 at a point 180 m from the entrance of the tunnel where the structure to be measured is installed. Is.

1 and 2 show an embodiment of the corrosive environment measurement system according to the present invention. The corrosive environment measurement method according to the present invention can be carried out by this corrosive environment measurement system.

This corrosion environment measurement system includes a sensor 1 having an inspection surface 12 in which a pair of electrodes 11 are arranged at intervals, and a measuring device 2 for measuring impedance by applying an AC voltage to the electrodes 11.

The sensor 1 is arranged in the measurement target structure 4. It is necessary to perform repair or inspection on all structures, but it is not necessary to know the corrosion rate for all structures. A structure arbitrarily selected from a plurality of structures that are presumed to be exposed to almost the same corrosive environment can be designated as the measurement target structure 4.

In a road tunnel, the corrosion rate varies even within the same tunnel. Therefore, a structure arbitrarily selected from a plurality of structures installed in the road tunnel is set as the measurement target structure 4, and a plurality of sensors 1 are arranged at equal intervals in the road tunnel. This makes it possible to more accurately grasp the corrosion rate in a structure installed in a road tunnel having a different corrosive environment depending on the location. Further, it is preferable to relatively investigate the corrosion rate, and it is also preferable to measure the measurement target structure 4 installed near the entrance or the exit outside the road tunnel.

In the embodiment shown in FIG. 1, the structure installed inside and around the road tunnel 3 is the measurement target structure 4, but the measurement target structure is not limited. A lighting device, an information board, a tall gate, a guardrail, or the like may be used as the measurement target structure 4. Note that FIG. 1 is a representation of the configuration of the corrosion environment measurement system in a form that can be easily understood, and the sizes of the components of the system and the distance between installations are not accurate.

The installation interval of the sensors 1 inside the road tunnel 3 may be appropriately determined depending on the situation, and may be, for example, several hundred meters. Further, in a mountain tunnel, the structure near the tunnel entrance, which is strongly affected by the antifreeze agent, is exposed to the harshest corrosive environment. Can be.

The sensor 1 is composed of a cylindrical first electrode 11a, a ring-shaped second electrode 11b, and a synthetic resin coating material 13 that covers and hardens these electrodes 11a and 11b. The second electrode 11b has a larger diameter than the first electrode 11a, and is fixed around the first electrode 11a in an arrangement in which the axis line coincides with that of the first electrode 11a.

The end faces of the first electrode 11a and the second electrode 11b are exposed to the atmosphere on the inspection surface 12 of the sensor 1. The contour of the end face of the first electrode 11a and the contour of the end face of the second electrode 11b when viewed from the inspection surface 12 side appear as concentric circles. Further, the areas of the first electrode 11a and the second electrode 11b exposed to the atmosphere are the same.

The distance between the contour of the end face of the first electrode 11a and the contour inside the end face of the second electrode 11b on the inspection surface 12 of the sensor 1 (hereinafter referred to as the inter-electrode gap G) is the distance between the water droplets adhering to the inspection surface 12. The diameter may be smaller than the diameter, and the optimum dimensions may be used according to the manufacturing conditions and the properties of the constituent members.

An electric wire 14 is connected to each of the end faces of the first electrode 11a and the second electrode 11b covered with the synthetic resin. The electric wire 14 penetrates the covering material 13 and is led out to the outside, and is connected to the measuring device 2.

As the synthetic resin that is the material of the covering material 13, for example, an epoxy resin can be adopted. However, the material of the covering material 13 is not limited as long as it has the insulating property and workability necessary for providing the gap G between the electrodes and has the water resistance to prevent the intrusion of moisture into the sensor 1. The optimum one should be selected according to the usage environment and cost.

If the materials of the first electrode 11a and the second electrode 11b are the same as those of the structure 4 to be measured, it can be regarded as the same as the corrosion rate of the structure 4 to be measured. can. On the other hand, when it is necessary to extend the life of the sensor 1, for example, a small amount of chromium or nickel may be added to make the sensor less corrosive. In this case, the corrosion rate can be obtained by making appropriate corrections to the measurement results.

However, if the corrosion resistance of the first electrode 11a and the second electrode 11b is extremely higher than the corrosion resistance of the structure 4 to be measured, the deterioration of the structure 4 to be measured is progressing. Nevertheless, the sensor 1 may not be able to detect it. Therefore, the materials of the first electrode 11a and the second electrode 11b are assumed to have a correlation with the structure 4 to be measured in terms of corrosion resistance.

Moisture such as dew condensation and rainwater caused by fluctuations in temperature adheres to the structure 4 to be measured, and if this moisture contains chloride ions or the like, corrosion of the structure 4 to be measured is promoted. For example, in the vicinity of the entrance in the tunnel, when the droplets of the antifreeze agent sprayed on the road surface outside the road tunnel 3 that are generated as the vehicle travels dissolve in the water, chloride ions are contained. Then, the inspection surface 12 of the sensor 1 arranged on the measurement target structure 4 also has the same corrosive environment as the surface of the measurement target structure 4.

The state in which water adheres to the inspection surface 12 can be expressed as an equivalent electric circuit when an AC voltage is applied to the electrode 11. As shown in FIG. 3, the equivalent circuit at this time is represented by the electrode surface resistance R _ct , the electric double layer capacitance C _dl , and the moisture resistance R _sol .

The electrode surface resistance R _ct changes depending on the type and state of rust on the surface of the electrode 11, and the water droplet resistance R _sol becomes smaller when chloride ions or the like, which are antifreeze agents, are contained. Therefore, the AC voltage of an arbitrary frequency (hereinafter referred to as the inspection frequency) within the frequency range in which the resistance related to the ion conductivity of the moisture adhering to the inspection surface 12 and the resistance of charge transfer on the electrode surface can be separated. The impedance measured when is applied varies depending on the corrosive environment. That is, the state of the corrosive environment can be grasped by measuring the change of impedance with time.

The inspection frequency can be appropriately determined according to the material and installation condition of the structure 4 to be measured for measuring the progress of corrosion and deterioration, but the frequency can be set from a frequency of 10 kHz or more to a frequency of 10 MHz or less. It is preferable to scan to create and analyze a Nyquist diagram or a Bode diagram before making a decision.

As shown in the Nyquist diagram of FIG. 4, the impedance measured when an AC voltage is applied to the electrode 11 is the resistance related to the ion conductivity of the moisture adhering to the inspection surface 12 and the charge transfer on the electrode surface. At any frequency within the frequency range in which the resistance can be separated _{, both the charge transfer resistance Rct} and the moisture resistance R _{sol on} the electrode surface affect the low frequency side, whereas the electrode surface on the high frequency side. The influence of the charge transfer resistance R _ct of the above becomes low, and the influence of the moisture resistance R _sol becomes dominant. Therefore, the frequency on the low frequency side shown in FIG. 4 where the value on the vertical axis is small (hereinafter referred to as the first inspection frequency) and the frequency on the high frequency side shown in FIG. 4 where the value on the vertical axis is small (hereinafter referred to as the first inspection frequency). By setting both of (hereinafter referred to as the second inspection frequency) as the inspection frequency _{, changes in the charge transfer resistance R ct} and the moisture resistance R _{sol on} the electrode surface can be accurately grasped.

In an actual corrosive environment, the impedance on the low frequency side is affected by factors other than the _{charge transfer resistance R ct} and the water resistance R _{sol on the electrode surface.} For example, the cathode portion is affected by the resistance (Worldsburg impedance) associated with oxygen diffusion.

The cathode portion is also affected by the reaction represented by the following formula (1) due to the action of β-FeOOH and γ-FeOOH formed in the presence of chloride ions as an oxidizing agent.

Further, in the anode part, if an intermediate adsorption product is generated in the corrosion reaction, it will be affected by the intermediate adsorption product. For example, when the intermediate adsorption product ^{acts as a catalyst for producing FeOH −} , it is affected by the following reaction.

However, by treating the impedance measured by the result received for these effects as a charge transfer resistance R _ct of the electrode surface, in the first inspection frequency the combined charge transfer resistance R _ct moisture resistance R _sol and electrode surface resistance The change with time is obtained, and the moisture resistance R _sol is obtained at the second inspection frequency. Therefore, the charge transfer resistance R _ct on the electrode surface obtained from the difference should be the reciprocal (corrosion rate I _cor = K / R _ct ). Therefore, the state of the corrosive environment can be grasped.

The first inspection frequency is approximately 1 Hz or less, and the second inspection frequency is approximately 1 kHz or more, but it differs depending on the material and installation status of the measurement target structure 4 for which the progress of corrosion and deterioration is to be measured. Further, since it takes time to measure at a low frequency, it is preferable to determine the first inspection frequency in consideration of the measurement time.

The change with time of impedance can be measured by applying an AC voltage a plurality of times at a predetermined timing for a predetermined period. For example, by continuing the application once every 12 hours for one year, it is possible to grasp the change with time for one year. In FIG. 3, the low frequency means the alternating current of the first inspection frequency, and the high frequency means the alternating current of the second inspection frequency.

The position where the sensor 1 is arranged is preferably the position where the corrosive environment is the most severe in the measurement target structure 4. Further, when the measured value obtained by using the sensor 1 alone is treated as a representative value of the surrounding environment, it is preferable that the inspection surface 12 of the sensor 1 is exposed to rainwater and new water flows so as to circulate. These conditions can be satisfied by setting the angle of attack of the sensor 1 between an angle at which rainwater is likely to be applied (upward in the vertical direction) and an angle at which moisture is likely to flow (horizontal direction), for example, 45 degrees. However, the angle of attack of the sensor 1 can be appropriately determined depending on the situation in which the sensor 1 is arranged.

The position where the sensor 1 is arranged is illustrated in FIGS. 5-10. It should be noted that FIGS. 5 to 10 show the position where the sensor 1 is arranged in a form that can be easily understood, and the dimensional correlation is not accurate. The white arrow lines shown in FIGS. 5 to 10 are the traveling directions of the vehicle.

As shown in FIG. 5, when the measurement target structure 4 is a lighting device or an information board, it is preferable to arrange the structure 4 in the inspection port 41 of the pole 4a of the lighting device or the information board and in the ground portion 42. Then, in the inspection port 41, it is preferable that the height is about 10 cm from the ground surface, 45 degrees upward, and upstream of the lane at the vicinity of the lower end of the inspection port and 45 degrees downward.

As shown in FIG. 6, when the structure 4 to be measured is the tall gate 4b, the back of the radio wave absorber 43 and the outlet lane most upstream column ground portion 44 are preferable. Then, it is preferable that the position behind the radio wave absorber 43 is stagnant due to poor air flow, and the position is upward. preferable. At Tallgate 4b, there is little grass that grows on the ground surface, so it is preferable to place it as close to the ground as possible.

When it is desired to pinpoint a specific portion of the structure 4 to be measured, it is preferable that the facing surface of the portion and the inspection surface 12 of the sensor 1 are oriented in the same direction. Therefore, behind the radio wave absorber 43, it is preferable that the sensor 1 faces upward so that the inspection surface 12 faces the same direction as the radio wave absorber 43. Further, when there is a place where the air flow is poor and stagnant around the structure 4 to be measured, it is preferable to arrange the structure 4 upward in the same place as the radio wave absorber 43.

As shown in FIG. 7, when the structure 4 to be measured is a guardrail 4c, it is preferable that the guardpost ground portion 45 has a height of about 15 cm from the ground surface, an upward direction of 45 degrees, and a lane upstream direction. In the guardrail 4c, there are many grasses that grow on the ground surface, and it is necessary to mow them regularly. Therefore, it is preferable that the height is set so as not to interfere with the mowing machine.

As shown in FIG. 8, when the structure 4 to be measured is a tunnel lighting lamp 4d, it is arranged at 45 degrees upward on the metal fitting 47 for fixing the lamp main body 46 to the wall surface, which is arranged on the upstream lower side. Is preferable.

As shown in FIG. 9, when the measurement target structure 4 is the water spray pipe 4e arranged in the road tunnel, it is preferable to arrange it at the branch portion of the spray nozzle 48 at an upward angle of 45 degrees.

As shown in FIG. 10, when the structure 4 to be measured is a jet fan 4f arranged in a road tunnel, a hanging metal fitting 50 for suspending and fixing the fan body 49 to the upper wall surface while avoiding a position on the roadway. Of these, it is preferable to arrange the one on the shoulder side of the road at an upward angle of 45 degrees.

Other structures installed on the wall of the road tunnel, such as fire alarms, are preferably placed at the lowest position at an upward 45 degree.

The measuring device 2 is composed of a known potentiometer and an FRA (Frequency Response Analoger). Further, it is connected to an arithmetic processing unit (not shown) installed in the management center 8 via a communication cable 7. Then, the measurement data of the measuring device 2 is collected in the arithmetic processing unit of the management center 8.

The management center 8 monitors the progress of corrosion and deterioration based on the measurement data collected in the arithmetic processing unit, that is, the change over time of impedance. Further, the time for inspection work or the time for repair is determined from the corrosion rate of the structure 4 to be measured, which is calculated based on the change in impedance with time.

For example, the corrosion rate is higher than that of the structure to be measured 4 which is exposed to the same corrosive environment as the structure whose inspection work is performed once every three years based on the rule of thumb (inspection cycle is three years). If it is three times as early, the inspection work should be done every year (the inspection cycle is one year).

On the other hand, the structure to be measured 4 is exposed to the same corrosive environment as the structure with the inspection cycle of 3 years based on the experience side, and the structure is exposed to the same corrosive environment as the structure with the inspection cycle of 5 years based on the rule of thumb. If the corrosion rates are the same, the inspection cycle, which used to be 3 years, is changed to 5 years. The same applies to repairs.

In measuring the corrosive environment in the road tunnel 3, first, a confirmation test was conducted to confirm that the temporal change of impedance can be measured at the selected first inspection frequency and second inspection frequency.

<Test 1>
The sensor 1 was immersed in distilled water, and an AC voltage having a potential amplitude of 10 mV was applied by scanning the frequency from 10 kHz to 10 MHz, and the impedance was measured. The potentiometer used was a solartron type 1287, and the FRA used a solartron type 1255B. The measurement results are shown in FIG.

<Test 2>
The sensor 1 was immersed in a 3% NaCl solution, and the impedance was measured under the same conditions as in Test 1. The measurement results are shown in FIG.

<Test 3>
After spraying salt water on the inspection surface 12 for 2 hours and drying it for 4 hours, the process of keeping the wet state for 2 hours was repeated three times, and the sensor 1 in which the inspection surface 12 was in a rusted state was immersed in a 3% NaCl solution. Then, the impedance was measured under the same conditions as in Test 1. The measurement result is shown in FIG.

<Change in moisture resistance R _sol>
In this confirmation test, the resistance of the solution in which the sensor 1 is immersed _{corresponds to the moisture resistance R sol.} Therefore, in the following description, it is expressed as the _{solution resistance R sol.} As described above, the solution resistance R _sol is dominant on the high frequency side, so when focusing on the impedance of the highest frequency of 10 kHz, it is 432.4 Ω in test 1, whereas it is 3.7 Ω in test 2. In test 3, it was 4.1Ω. That is, the impedance is low in the 3% NaCl solution that promotes corrosion. Therefore, the sensor 1 of this embodiment can measure the change with time of the impedance caused by the water droplets adhering to the inspection surface 12 with 10 kHz as the second inspection frequency.

<Change in charge transfer resistance _{Rct on the electrode surface>}
As described above, the charge transfer resistance _Rct on the electrode surface is dominant on the low frequency side. Therefore, when focusing on the impedance of the lowest measured frequency, in Test 1, it is 124770 Ω at a frequency of 39.8 Hz. On the other hand, in Test 2, it was 2074.3 Ω at a frequency of 10 MHz, and in Test 3, it was 84.6 Ω at a frequency of 10 MHz. That is, the impedance is low in the 3% NaCl solution that promotes corrosion, and the impedance is further lowered in the state where rust is generated. Therefore, the sensor 1 of this embodiment can measure the change with time of the impedance due to _{the charge transfer resistance Rct} of the electrode surface of the electrode 11 with 10 MHz as the first inspection frequency.

In the Bode diagram of Test 1 shown in FIG. 11B, the plot of 100 Hz is off, but this is considered to be noise that tends to appear in a multiple of 50 Hz of the power supply.

Further, in the Nyquist curve of Test 1 shown in FIG. 11A, the chevron portion appearing on the low frequency side is the influence of the Worldsburg impedance in the cathode portion. In an actual corrosive environment affected by factors other than the charge transfer resistance R _ct and the moisture resistance R _sol on the electrode surface, the shape on the low frequency side in the Nyquist diagram varies, and thus the impedance at a frequency of 10 MHz is not always present. It may not be said that it corresponds to the sum of the charge transfer resistance R _ct and the water resistance R _sol.

That is, the result measured at a frequency of 10 MHz is obtained by the real part Re [Z] and the imaginary number Im [Z], and may be in the middle of the semicircle in the Nyquist diagram. Therefore, in such a case, _{in obtaining the charge transfer resistance Rct} on the electrode surface, as shown in FIG. 14, the value x obtained by the following equation (3) is added to _{Re [Z] -R sol.} do.

Then, the charge transfer resistance _Rct on the electrode surface can be obtained by the following equation (4).

<Example>
A one-way road tunnel 3 with an extension of 2925 m, 180 m from the entrance (corresponding to point A shown in FIG. 1, hereinafter referred to as measurement point P1) and 2155 m (770 m from the exit, corresponding to point B shown in FIG. 1). The sensor 1 was placed on the measurement target structure 4 installed at the measurement point P2), and the corrosive environment was measured.

The sensor 1 was arranged in three measurement target structures 4 installed at different heights at each point. FIG. 15 is a diagram showing the installation position of the sensor 1 at the measurement point P1 as seen from the traveling direction of the vehicle. Sensors 1 were placed on a fire detector 4g installed at a low position, a jet fan 4f installed at a high position, and a cable rack 4h installed at a height between them. Note that FIG. 15 shows the position where the sensor 1 is arranged in a form that can be easily understood, and the dimensional correlation is not accurate. Further, all the sensors 1 were set to 45 degrees upward.

Similarly, at the measurement point P2, the sensors 1 were arranged at each of the fire detector 4g and the cable rack 4h. Further, the sensor 1 was also arranged in a cross pipe (not shown) installed at a height similar to that of the jet fan 4f at the measurement point P1. In the following description, the sensor 1 arranged in the fire detector 4g is referred to as CH1, the sensor 1 arranged in the cable rack 4h is referred to as CH2, and the sensor 1 arranged in the jet fan 4f or the cross pipe is referred to as CH3.

Using the same measuring device 2 as the confirmation test, the impedance at a frequency of 10 kHz (moisture resistance R _sol ) and the impedance at a frequency of 10 MHz (charge transfer resistance R _ct on the electrode surface) are measured every hour. The test was performed at point P1 for 554 days and at measurement point P2 for 48 days. The results are shown in FIGS. 16, 17, and 18.

_{The reciprocal of the charge transfer resistance Rct on} the electrode surface at the measurement point P1 shown in FIG. 16 is larger than the reciprocal _{of the charge transfer resistance Rct on} the electrode surface at the measurement point P2 shown in FIG. Therefore, it was confirmed that the structure installed near the tunnel entrance was exposed to a harsher corrosive environment than the structure installed at the measurement point P2.

In addition, when the temperature difference from the dew point decreases, the moisture resistance R _sol decreases and the reciprocal of the charge transfer resistance R _ct on the electrode surface increases, confirming that there is a relationship between the ease of dew condensation and the progress of corrosion. Was done. It should be noted that the measurement point P1 and the measurement point P2 are located near the tunnel entrance because there is a difference in the reciprocals of _{the moisture resistance R sol} and the charge transfer resistance R _{ct on the electrode surface even when the temperature difference from the dew point is almost the same.} It can be seen that the installed structure is exposed to a harsher corrosive environment than the structure installed at the measurement point P2.

FIG. 18 shows the time course of impedance in a period after the measurement period shown in FIG. 16 at the measurement point P1. In the measurement period shown in FIG. 18, _{the reciprocal of the charge transfer resistance Rct on} the electrode surface has been changing at a high value from the beginning. It shows that once affected by chloride, the corrosion rate remains at a high level even after spring when the antifreeze is not sprayed.

Further, at the beginning of the measurement period shown in FIG. 18, the moisture resistance R _sol is lowered, and corrosion is likely to proceed. It is thought to indicate the effect of the rainy season.

Further, assuming that the corrosion environment of the structure installed in the road tunnel 3 in this embodiment is substantially the same as that of the measurement point P2, the corrosion rate of the structure installed at the measurement point P1 is at another point. It can be seen that the corrosion rate of the structure increases on the order of several tens of times. Therefore, it is necessary to shorten the inspection cycle, and there is a high possibility that repairs must be performed at the same time as the inspection, and it is judged that it is safe to make the inspection cycle and the repair cycle the same.

1 Sensor 2 Measuring device 3 Road tunnel 4 Measurement target structure 7 Communication cable 8 Management center 11 Electrode 12 Inspection surface 13 Coating material 14 Electric wire

Claims (6)

In a road tunnel in which a plurality of structures are installed, an arbitrarily selected structure from the plurality of structures is used as a measurement target structure, and the measurement target structure correlates with the measurement target structure in terms of corrosion resistance. A plurality of sensors having an inspection surface in which a pair of electrodes made of a certain material are arranged at intervals are arranged in the road tunnel at equal intervals, and the electrodes are not connected to the measurement target structure and the inspection surface is formed. Arranged in an exposed state to the atmosphere, at an arbitrary frequency within a frequency range in which the resistance related to the ion conductivity of water droplets adhering to the inspection surface and the resistance of charge transfer on the surface of the electrode can be separated. Therefore, the time-dependent impedance is obtained at the first inspection frequency at which the resistance related to the ion conductivity and the resistance of the charge transfer combined with time change can be obtained, and the second inspection frequency at which the resistance related to the ion conductivity can be obtained. A corrosive environment measurement method characterized by measuring changes. The pair of the electrodes is a cylindrical first electrode and a ring-shaped second electrode having a diameter larger than that of the first electrode and having an arrangement in which the axis coincides with the first electrode around the first electrode. The method for measuring a corrosive environment according to claim 1. It is provided with a plurality of sensors having inspection surfaces in which a pair of electrodes are arranged at intervals, and a measuring device for measuring impedance by applying an AC voltage to the electrodes.
In a road tunnel in which a plurality of structures are installed, a structure arbitrarily selected from the plurality of structures is set as a measurement target structure, and a plurality of the sensors are measured at equal intervals in the road tunnel. The electrode is placed on the structure in a state where the inspection surface is exposed to the atmosphere without being connected to the structure to be measured.
The electrode is formed of a material that correlates with the structure to be measured in terms of corrosion resistance.
The measuring device applies the AC voltage at an arbitrary frequency within a frequency range capable of separating the resistance related to the ion conductivity of water droplets adhering to the inspection surface and the resistance of charge transfer on the surface of the electrode. Therefore, the voltage is applied at the first inspection frequency at which the resistance related to the ion conductivity and the resistance of the charge transfer combined with time can be obtained, and the second inspection frequency at which the resistance related to the ion conductivity can be obtained. A corrosive environment measurement system featuring. The pair of the electrodes is a cylindrical first electrode and a ring-shaped second electrode having a diameter larger than that of the first electrode and having an arrangement in which the axis coincides with the first electrode around the first electrode. The corrosive environment measurement system according to claim 3, further comprising. Based on the time course of the impedance obtained by the corrosion environment measurement method according to claim 1 or 2, the corrosion rate of the measurement target structure is calculated, and the same as that of the measurement target structure and the measurement target structure. A repair plan formulation method characterized by determining when to repair a structure in a corroded environment. Based on the time course of the impedance obtained by the corrosion environment measurement method according to claim 1 or 2, the corrosion rate of the measurement target structure is calculated, and the same as that of the measurement target structure and the measurement target structure. An inspection plan formulation method characterized by determining when to perform inspection work on structures in a corroded environment.

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