JP6857710B2 - Soil corrosion evaluation device - Google Patents

Description

The present invention relates to a soil corrosiveness evaluation device for evaluating soil corrosiveness.

Various metal structures are used in a state where they are buried in the ground in whole or in part, as represented by infrastructure equipment such as steel pipe columns, support anchors and pipes. Metal structures are corroded because they come into contact with soil, and usually become thinner and deteriorate over time.

The degree of corrosion of metal structures buried in soil varies significantly depending on the type and properties of soil, the structure and burial conditions of metal structures, and differences in meteorological conditions. Factors that affect the corrosion of metal structures include soil type, air temperature and soil temperature, pH, specific resistance, water content, soluble salt concentration, oxygen concentration, gases, and bacterial activity. Soil corrosion proceeds by a complex mechanism involving these factors.

Therefore, it is necessary to take some measures such as repair and replacement before the metal structure can no longer perform its intended function. However, because underground structures are underground, it is often difficult to directly inspect them by humans or machines. Therefore, there is a method of evaluating the soil corrosiveness, which indicates the corrosiveness of the soil to the metal structure buried in the soil, based on a certain standard, and formulating a maintenance operation plan of the equipment based on the evaluation result of the soil corrosiveness.

Generally, it is said that, for example, corroded soil, peat soil, clay, and soil near rivers and coasts are highly corroded by metals in the ground, especially steel and cast iron materials. However, now that equipment is laid on a very wide area on a large scale, the laying environment is also diverse, and such qualitative and empirical indicators cannot be used.

Therefore, the idea of evaluating soil corrosiveness by using an electrochemical method is disclosed in, for example, Non-Patent Document 1.

Yoshikazu Miyata and one other person, "Soil Corrosion Measurement Focusing on Electrochemical Methods (Part 2)", Materials and Environment, 46, 610-619, 1997.

The conventional electrochemical method is, for example, a method of determining the polarization resistance of soil by an AC impedance method and evaluating soil corrosiveness. Since the method is complicated, it is performed exclusively in a laboratory or the like. Therefore, there is a problem that it is difficult to use it at the site where the metal structure is actually buried.

The present invention has been made in view of this problem, and an object of the present invention is to provide a soil corrosion evaluation device and a method thereof, which have a simpler configuration than the conventional one and can be conveniently used.

The soil corrosiveness evaluation device according to one aspect of the present embodiment is a soil corrosiveness evaluation device for evaluating the degree to which the soil corrodes the metal from the potential difference between two metals buried in the soil. The two metals embedded in the soil and a circuit connected between the two metals are provided, and the circuit includes a DC power source for connecting a negative power supply terminal to one of the metals constituting the anode, and the DC. the positive power supply terminal is connected to the anode electrode of the power source, a cathode electrode and a light emitting diode to be connected to the other of the metal, the potential difference in the case where the corrosion has proceeded before Kikin genus V1, the voltage of the DC power supply V2, and the forward voltage of the light emitting diode when the V3, a gist that you set the V2 such that V2 = V3-V1.

According to the present invention, it is possible to provide a soil corrosion evaluation device having a simpler structure than the conventional one and which can be conveniently used.

It is a figure which shows the functional composition example of the soil corrosiveness evaluation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the functional composition example of the soil corrosiveness evaluation apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the specific example of the measuring part of the soil corrosiveness evaluation apparatus shown in FIG. It is a figure which shows typically the relationship between evaluation time and natural potential. It is a figure which shows the functional composition example of the soil corrosiveness evaluation apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the functional composition example of the soil corrosiveness evaluation apparatus which concerns on 4th Embodiment of this invention. It is a figure which shows an example of the case of evaluation using a plurality of soil corrosiveness evaluation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows typically the relationship between evaluation time and natural potential. It is a figure which shows another example in the case of evaluation using a plurality of soil corrosiveness evaluation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the functional composition example of the modification of the soil corrosion property evaluation apparatus which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same objects in a plurality of drawings, and the description is not repeated.

[First Embodiment]
FIG. 1 shows an example of the functional configuration of the soil corrosiveness evaluation device 1 according to the first embodiment. The soil corrosion evaluation device 1 includes two metals 11 and 12, a circuit 20, and a measuring unit 21.

The metal 11 and the metal 12 are made of different materials and are buried in the soil 100. The metals 12 and 13 need to generate an electromotive force when they are electrically connected via the circuit 20 in a state of being buried in the soil 100. Therefore, the metals 12 and 13 form a dissimilar metal pair 10 in which metals having different natural potentials (corrosion potentials) in the soil are combined.

As the combination of metals, for example, a combination of iron and zinc, silver and iron, copper and iron, iron and magnesium, and the like can be considered. The metal does not have to have a single composition, and for example, a metal subjected to hot dip galvanizing may be used. That is, as a combination of dissimilar metals to 10, for example, a steel material and a hot-dip galvanized steel material may be used. Further, the shape including the size and thickness of the metal is not particularly limited.

The circuit 20 is connected between the metals 11 and 12 forming the dissimilar metal pair 10. The measuring unit 21 measures the current flowing through the circuit 20.

The measuring unit 21 is, for example, an ammeter. As will be described later, the measuring unit 21 may be a voltmeter that measures the potential difference between the metals 11 and 12. Further, it may be a charge amount measuring device.

In the present embodiment, the corrosiveness (soil corrosiveness) of the soil of the soil 100 is determined by utilizing so-called galvanic corrosion, which is generated when dissimilar metal pairs 10 are buried in the soil and the metals 11 and 12 are electrically connected to each other. evaluate.

As shown in FIG. 1, when dissimilar metal pairs 10 are buried in soil 100 and the metals 11 and 12 are electrically connected, a galvanic corrosion current flows. For example, when a combination of iron and zinc is embedded in general Kanto loam soil or the like, a natural potential of about 0.3 to 0.4 V is generated between the metals 11 and 12, although it depends on the water content of the soil 100. This galvanic corrosion has a different mechanism from the corrosion of metals independently existing in soil 100, but is known to show a high correlation with the corrosion rate in soil 100.

By connecting the two metals 11 and 12 with a circuit 20, galvanic corrosion occurs, and the corrosion of the metals 11 and 12 progresses. After a certain period of time, one metal, for example zinc, which constitutes the dissimilar metal pair 10, disappears, and a corrosion generating portion is formed on the surface of the other metal, for example, iron.

As the corrosion progresses and the states of the metals 11 and 12 change, the magnitude of the potential difference generated between the metals 11 and 12 changes. By visualizing this change with the measuring unit 21, the soil corrosiveness of the soil 100 to the metals 11 and 12 can be evaluated.

As described above, the soil corrosiveness evaluation device 1 of the present embodiment has a simple configuration of two metals 11, 12, a circuit 20, and a measuring unit 21, and is a metal 11 for evaluating the soil corrosiveness of the soil 100. The change in the magnitude of the potential difference that occurs between and 12 is displayed. As described above, the soil corrosiveness evaluation device 1 enables a simple evaluation of soil corrosiveness. Therefore, it is possible to evaluate soil corrosiveness at the site where the metal structure is actually buried.

[Second Embodiment]
FIG. 2 shows an example of the functional configuration of the soil corrosiveness evaluation device 2 according to the first embodiment. The soil corrosion evaluation device 2 includes a measuring unit 22 which is a voltmeter connected between the metals 11 and 12 in place of the measuring unit 21.

In this way, the measuring unit 22 may be configured by a voltmeter. The voltmeter may be a general one.

It is possible to measure the voltage between the metals 11 and 12 with a simpler configuration than a general voltmeter. FIG. 3 shows a specific example of the measuring unit 22.

FIG. 3 shows an example in which the measuring unit 22 is composed of the DC power supply 23 and the light emitting diode 24.

The negative electrode of the DC power supply 23 is connected to the metal 11, the positive electrode of the DC power supply 23 is connected to the anode electrode of the light emitting diode 24, and the cathode electrode of the light emitting diode 24 is connected to the metal 12. That is, the DC power supply 23 and the light emitting diode 24 are connected in series between the metals 11 and 12.

When time elapses with the measuring unit 22 connected, for example, the surface of the metal 11 (for example, iron) is rusted, and the metal 12 (for example, zinc) is thinned. As a result, the potential difference between the metals 11 and 12 becomes small.

FIG. 4 schematically shows how the natural potential decreases with the passage of time. If the potential difference between the magnitudes of soil corrosiveness is defined as V1, for example, the soil corrosiveness of the soil 100 that follows the change in pattern α in FIG. 4 is set to be small, and the soil corrosion of the soil 100 that follows the change in pattern β. Gender can be classified as large.

In this case, assuming that the forward voltage of the light emitting diode 24 is V3 and the voltage of the DC power supply 23 is V2, if V2 = V3-V1 is set, soil corrosion is caused by the presence or absence of lighting of the light emitting diode 24. The size can be identified. That is, since V3 = V2 + V1, when the natural potential between the metals 11 and 12 becomes smaller than V1, the voltage applied to the light emitting diode 24 becomes equal to or less than the forward voltage, and the light emitting diode 24 is turned off.

The measuring unit 22 of the present embodiment is configured by connecting the light emitting diode 24 and the DC power supply 23 in series. According to this configuration, the light emitting diode 24 is turned off when the corrosion progresses and the natural potential becomes smaller than V1. As a result, it can be known that the potential difference has decreased to V1 (corrosion has progressed). That is, the operator who confirms that the light is turned off can determine that the soil is highly corrosive.

As described above, the soil corrosiveness evaluation device 2 of the present embodiment can display the magnitude of soil corrosiveness with a simple configuration of the DC power supply 23 and the light emitting diode 24.

[Third Embodiment]
FIG. 5 shows an example of the functional configuration of the soil corrosiveness evaluation device 3 according to the third embodiment. The soil corrosiveness evaluation device 3 differs from the soil corrosiveness evaluation device 1 (FIG. 1) in that a support portion 30 is provided.

The support portion 30 supports, for example, rod-shaped metals 11 and 12 with one end of the rod-shaped metal on the surface portion of the soil 100. By providing the support portion 30, it is possible to facilitate the burying of the metals 11 and 12 in the soil 100.

Further, since the support portion 30 fixes the distance between the metals 11 and 12 at a predetermined distance, it is possible to save the trouble of making the distance between the metals 11 and 12 constant for each evaluation site. Also, metal 11
By fixing the lengths of, 12 and pushing the support portion 30 to the surface of the soil 100, the conditions in the depth direction of the metals 11 and 12 can be matched.

The metals 11 and 12 of the present embodiment and the circuit 20 may be separated from each other. By making it possible to separate the metals 11 and 12 from the circuit 20, it is not necessary to provide the circuit 20 in all the soil corrosiveness evaluation devices 3. Therefore, the cost of the soil corrosiveness evaluation device 3 can be reduced.

When the circuit 20 is separated from the metals 11 and 12, the metals 11 and 12 are in an insulated state except for the soil 100. In that state, galvanic corrosion does not occur, so there is a problem that the progress rate of corrosion is slowed down. Next, a fourth embodiment that solves this problem will be described.

[Fourth Embodiment]
FIG. 6 shows an example of the functional configuration of the soil corrosiveness evaluation device 4 according to the fourth embodiment. The soil corrosiveness evaluation device 4 is different from the soil corrosiveness evaluation device 3 (FIG. 5) in that a short-circuit portion 31 is provided.

The short-circuit portion 31 short-circuits between the metals 11 and 12 when the metals 11 and 12 and the circuit 20 are separated. The short-circuit portion 31 can be easily realized by, for example, a convex portion provided in the circuit 20 and a contact provided in the support portion 30. That is, the convex portion of the circuit 20 may be inserted between the contacts of the contacts that conduct when the circuit 20 is disconnected. The notation of the configuration (convex portion and contact point) is omitted.

Moreover, you may use a magnet. The short-circuit portion 31 can be configured by arranging a magnet for turning off the relay provided on the support portion 30 in the circuit 20. When the circuit 20 is disconnected, the relay connecting between the metals 11 and 12 is turned on, and galvanic corrosion occurs.

By providing the short-circuit portion 31, the soil corrosion evaluation device 4 of the present embodiment can cause galvanic corrosion between the metals 11 and 12 even when the circuit 20 is disconnected. Further, the short-circuit portion 31 can pass a large current (galvanic corrosion current) between the metals 11 and 12 as compared with connecting the metals 11 and 12 with a voltmeter. Therefore, the soil corrosion evaluation device 4 of the present embodiment can shorten the evaluation time as compared with the case where the voltmeter (measurement unit 22) is always connected.

(Application Example I)
A plurality of soil corrosiveness evaluation devices of the present embodiment may be used to evaluate soil corrosiveness. FIG. 7 shows Application Example I using three soil corrosiveness evaluation devices 1.

In FIG. 7, the three soil corrosion evaluation devices 1, 72, and 73 are arranged side by side. The soil corrosiveness evaluation device 1 at one end is the same as the above-mentioned soil corrosiveness evaluation device 1 as is clear from the reference reference numerals.

Since the metal 11 and 12 and the circuit 20 may be separated from each other as described above, the soil corrosion evaluation apparatus of the present embodiment may be composed of only dissimilar metal pairs in Application Example I. That is, it may be a soil corrosiveness evaluation device composed of two metals 11, 12, two metals 14, 15 and two metals 16, 17 buried in the soil 100.

The soil corrosiveness evaluation device 72 in the middle has a different voltage of the DC power supply 723 from the soil corrosiveness evaluation device 1. Further, the material of one metal 14 of the soil corrosiveness evaluation device 72 is the same as that of the metal 11, and the thickness is thinner than that of the metal 11. Further, the material of the other metal 15 of the soil corrosion evaluation device 72 in the middle is the same as that of the metal 12, and the thickness is thinner than that of the metal 12. The thickness of the metal 15 is the same as that of the metal 14.

In the soil corrosion evaluation device 73 at the other end, the voltage of the DC power supply 733 is different from that of the soil corrosion evaluation devices 1 and 72. Further, the material of one metal 16 of the soil corrosiveness evaluation device 73 is the same as that of the metal 14, and the thickness is thinner than that of the metal 14. Further, the material of the other metal 17 of the soil corrosion evaluation device 73 at the other end is the same as that of the metal 15, and the thickness is thinner than that of the metal 15. The thickness of the metal 17 is the same as that of the metal 16.

That is, Application Example I includes two or more sets of metal pairs composed of two metals, and the metal of each metal pair has a unique thickness.

In this way, by making the combination of the two metals the same and making the thickness different, it is possible to adjust the change over time in the potential difference between the two metals. When the thickness of each metal is increased and when the thickness is reduced, the period until the potential difference becomes smaller is shorter when the thickness is reduced.

FIG. 8 schematically shows a change in the potential difference between three metals having different slopes with respect to the evaluation time. γ represents the change in the potential difference between the two metals of the soil corrosion evaluation device 73 in which the thicknesses of the metals 16 and 17 are also the thinnest. β represents the change in the potential difference between the two metals of the soil corrosion evaluation device 72 with the thicknesses of the metals 14 and 15 set to the middle. α represents the change in the potential difference between the two metals of the soil corrosion evaluation device 1 in which the thicknesses of the metals 11 and 12 are the thickest.

The voltage of the DC power supply 733 of the soil corrosion evaluation device 73 showing the largest change in potential difference is Vα, the voltage of the DC power supply 723 of the soil corrosion evaluation device 72 showing the change of medium potential difference is Vβ, and the voltage of the smallest potential difference. Let Vγ be the voltage of the DC power supply 23 of the soil corrosiveness evaluation device 1 showing a change. By changing the respective voltages of the DC power supplies 23, 723, and 733 in this way, the soil corrosiveness can be displayed in multiple stages.

For example, all of the light emitting diodes 24,724,734 are lit (corrosion degree A), only the light emitting diode 734 is turned off (corrosion degree B), the light emitting diodes 734 and 724 are turned off (corrosion degree C), and the light emitting diodes 24,724, Soil corrosiveness can be expressed in four stages of turning off all 734s (corrosion degree D).

(Application Example II)
The type of metal combination of dissimilar metals to 10 of a plurality of soil corrosion evaluation devices may be different. When three soil corrosion evaluation devices 1, 74, 75 are used as in Application Example I, the combination of materials of each dissimilar metal to 10 is different.

FIG. 9 shows Application Example II using three soil corrosiveness evaluation devices 1. Application Example II is unique in the combination of metal materials in a metal pair consisting of two metals. Application Example II has the same effect as Application Example I.

In Application Example II, for example, when it is desired to evaluate soil corrosiveness to different metals, each of the target metals and a metal having a higher (higher) natural potential are combined. Doing so allows for simultaneous evaluation of different metals.

(Modification example)
FIG. 10 shows a functional configuration example of a modified example of the soil corrosiveness evaluation device 3. In the modified example of the soil corrosiveness evaluation device 3, the shapes of the metals 42 and 43 are different from those of the soil corrosiveness evaluation device 2 (FIG. 4).

The metals 42 and 43 are tapered rods whose cross-sectional area decreases from one end toward the tip on the soil 100 side.

By forming the metals 42 and 43 in this way, the metals 42 and 43 can be easily buried in the soil 100. That is, since the resistance when the support portion 30 provided with the metals 42 and 43 is pushed into the soil 100 can be reduced, the metals 42 and 43 can be easily embedded in the soil 100.

As described above, the soil corrosiveness evaluation devices 1, 2, 3 and 4 of the present embodiment enable simple evaluation of soil corrosiveness. Therefore, it is possible to evaluate soil corrosiveness at the site where the metal structure is actually buried.

The shapes of the metals 11, 12 and the like have been described by taking a rod shape as an example, but the shape is not limited to the rod shape. The shape of the metals 11, 12, etc. may be any shape. Further, the soil corrosiveness evaluation device 3 of the third embodiment has been described with a configuration in which the support portion 30 is added to the soil corrosiveness evaluation device 1 (FIG. 1), but the present invention is not limited to this example. The support portion 30 may be added to the soil corrosiveness evaluation device 2 of the second embodiment.

Further, although the application examples I and II have been described by using three soil corrosiveness evaluation devices 1 (FIG. 1), a plurality of soil corrosiveness evaluation devices 2 and 3 may be used. As described above, the present invention is not limited to the above-described embodiment, and can be modified within the scope of the gist thereof.

1, 2, 3, 72, 73, 74, 75: Soil corrosion evaluation device 10: Dissimilar metal pairs 11, 12, 14, 15, 16, 17, 18, 19, 40, 41, 42, 43: Metal 20 : Circuits 21, 22: Measuring units 23, 723, 733: DC power supply 24, 724,734: Light emitting diode 30: Support part 31: Short circuit part 100: Soil α, β, γ: Change pattern of natural potential

Claims (2)

A soil corrosiveness evaluation device for evaluating the degree to which the soil corrodes the metal from the potential difference between two metals buried in the soil.
The two metals buried in the soil and
The circuit connected between the two metals and
With
The circuit
A DC power supply that connects a negative power supply terminal to one of the metals that make up the anode,
With a light emitting diode in which an anode electrode is connected to the positive power supply terminal of the DC power supply and the cathode electrode is connected to the other metal.
With
The potential difference in the case where the corrosion has proceeded before Kikin genus V1, the voltage of the DC power supply V2, and the forward voltage of the light emitting diode when the V3, so that the V2 and V2 = V3-V1 Ru set Teisu to
Soil corrosion evaluation apparatus according to claim and this. The soil corrosiveness evaluation device according to claim 1, wherein the metal and the circuit can be separated from each other.

Images