JP5571711B2 - Corrosion sensor - Google Patents

Description

  The present invention relates to a corrosion sensor for measuring a surrounding corrosion environment.

In a structure such as a bridge or a plant, it is necessary to periodically check the corrosion state in order to maintain a predetermined durability over a long period of time. However, the corrosion of the structure proceeds locally according to the difference in corrosive environmental properties such as oxygen concentration, pH, temperature and humidity existing in the vicinity thereof, and there is a possibility that it may be overlooked by inspection depending on the corrosion location.
As corrosion that is difficult to check, for example, ground corrosion that occurs near the base of a structure that is difficult to check from the outside, that is, near the boundary between the atmosphere and the ground, is known. This is because the corrosive environment is different in the atmosphere and in the ground, so there is a potential difference across the ground between structures from the atmosphere to the ground, and water such as rainwater is stagnant in the ground. By doing so, the ground portion of the structure is electrically short-circuited to generate a macrocell corrosion current, and the ground portion of the structure is corroded by the battery action. In order to cope with such corrosion that occurs in places that are difficult to confirm from the appearance, it is required to measure the corrosive environment around the structure.

  Therefore, as a technique for evaluating the corrosive environmental properties in the ground, for example, as disclosed in Patent Document 1, by inserting a metal specimen into the ground and measuring the macrocell corrosion current generated in the metal specimen, It has been proposed to evaluate the underground corrosive environment.

JP 2008-298688 A

  However, although the macrocell corrosion current is generated at portions where the corrosion environment properties are different from each other, it is difficult to accurately measure the corrosion environment property when the change in the environment occurs in a minute region.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a corrosion sensor that can solve such conventional problems and can measure the corrosion environment at the ground and underground with high accuracy.

The corrosion sensor according to the present invention includes an insulating frame, an electrode unit that is attached to the insulating frame and includes a plurality of unit electrodes each including a sample electrode and a counter electrode disposed in proximity to the sample electrode, A current measuring device connected to each of the plurality of unit electrodes of the electrode unit and measuring a current flowing between the sample electrode and the counter electrode in each unit electrode; and disposed inside the insulating frame, An electric wire connecting the sample electrode of the unit electrode and the counter electrode to the current measuring device, the sample electrode and the counter electrode each have a flat plate shape, and the sample electrode is wider in width than the counter electrode and The counter electrode is joined to a central portion of the sample electrode via an insulating material, and the electric wire extending from the current measuring device to the sample electrode is distributed and connected to both side portions of the sample electrode sandwiching the counter electrode. It is those that.

Here, it is preferable that the sample electrodes included in the plurality of unit electrodes are made of the same material, and the counter electrodes included in the plurality of unit electrodes are made of the same material. In each unit electrode, the sample electrode is preferably made of a metal material, and the counter electrode is preferably made of a metal material that is more noble than the metal material of the sample electrode . Also, the sample electrode is composed of steel or aluminum or the like, the counter electrode may be composed of silver, nickel or copper.

The current measuring device is preferably a non-resistance type multi-channel ammeter.
The insulating frame may have a plurality of recesses arranged in a row, and the plurality of unit electrodes may be arranged in the recesses so as not to protrude outside from the insulating frame.

The plurality of unit electrodes may be installed and used so that a part of them enters the ground.
Further, the plurality of unit electrodes may be installed and used so that the arrangement direction of the unit electrodes is along a structure containing metal. The sample electrode is preferably subjected to the same surface treatment as the structure.

  According to the present invention, each of the current measuring devices connected to the plurality of unit electrodes arranged in a row measures the current flowing between the sample electrode and the counter electrode arranged close to each other in each unit electrode. Moreover, it becomes possible to measure the corrosive environmental properties at the ground and underground with high accuracy.

The structure of the corrosion sensor which concerns on one embodiment of this invention is shown, (A) is side surface sectional drawing of a corrosion sensor, (B) is a front view of a corrosion sensor. It is a figure which shows a mode that the sample electrode and the counter electrode were short-circuited with the water | moisture content. It is a figure which shows the corrosion sensor installed so that a part of several unit electrode may enter the ground. It is side surface sectional drawing which shows the modification of the corrosion sensor which concerns on this Embodiment. The Example which measured the corrosion current in sand using the corrosion sensor which concerns on this Embodiment is shown, (A) is a current value in 100% of moisture addition rates, (B) is a current value in 80% of moisture addition rates. FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1A and 1B show the configuration of a corrosion sensor according to an embodiment of the present invention. The corrosion sensor includes an insulating frame 1 made of an insulating material, an electrode portion 2 attached to the insulating frame 1, and a current measuring device 3 electrically connected to the electrode portion 2.
The insulating frame 1 has an elongated flat plate shape, and a plurality of recesses 4 are formed on the surface of the insulating frame 1 in a line in the longitudinal direction. The insulating frame 1 is formed with a connection path 5 extending in the longitudinal direction and a communication path 6 extending from the bottom surface of the recess 4 to the connection path 5 to communicate the both.

The electrode part 2 is composed of a plurality of unit electrodes 7 arranged in a line in the longitudinal direction of the insulating frame 1 by being attached to the plurality of recesses 4 of the insulating frame 1. Each of the unit electrodes 7 has a flat plate shape extending in a direction perpendicular to the longitudinal direction of the insulating frame 1, and a sample electrode 8 and a counter electrode 9 made of a metal material are parallel to each other via an insulating adhesive 10. It is formed by joining. The sample electrode 8 is wider than the counter electrode 9 and has a through hole 11 formed in the center. The counter electrode 9 is joined to the central portion of the sample electrode 8 so as to close the through hole 11. By attaching such a unit electrode 7 to the insulating frame 1 so that the sample electrode 8 side is in contact with the bottom surface of the recess 4, the sample electrode 8 is exposed to the communication path 6 formed in the insulating frame 1. . Further, the communication path 6 communicates with the through hole 11 and the counter electrode 9 is exposed to the communication path 6.
In this way, the unit electrode 7 in which the sample electrode 8 and the counter electrode 9 are arranged close to each other is attached on the surface of the insulating frame 1. Here, it is assumed that the sample electrode 8 is made of steel, and the counter electrode 9 is made of a metal material that is more potential than the sample electrode 8.

  The current measuring devices 3 are respectively connected to the unit electrodes 7 through electric wires drawn into the communication passage 6 through the connection path 5 of the insulating frame 1. Specifically, as shown in FIG. 2, the current measuring device 3 connects the sample electrode 8 and the counter electrode 9 of each unit electrode 7 through an electric wire, and the water W in the surrounding environment is arranged close to each other. The corrosion current A flowing from the counter electrode 9 to the sample electrode 8 is measured by short-circuiting the sample electrode 8 and the counter electrode 9 that have been formed. The current measuring device 3 is preferably a non-resistance type multi-channel non-resistance ammeter. In addition, as shown in FIG. 1B, the connection between the current measuring device 3 and the sample electrode 8 of each unit electrode 7 is such that the sample electrode 8 sandwiches the counter electrode 9 in the arrangement direction of the plurality of unit electrodes 7. It is preferable that the electric wires connecting the current measuring device 3 and each sample electrode 8 are distributed to the left and right to prevent the electric wires from being densely arranged in a limited space.

Next, an example of measuring the corrosivity of the surrounding environment using the corrosion sensor shown in FIG. 1 will be described.
First, by installing a corrosion sensor so that a part of the plurality of unit electrodes 7 enters the ground, as shown in FIG. 3, the plurality of unit electrodes 7 arranged in a row are arranged in the atmosphere. It is divided into a part 12, a ground part 13 located on the ground, and a ground part 14 located in the ground. That is, the atmospheric part 12 is exposed to an atmospheric corrosive environment, the ground part 13 is exposed to an underground corrosive environment, and the underground part 14 is exposed to an underground corrosive environment. In each unit electrode 7 exposed to each corrosive environment, as shown in FIG. 2, the moisture W in the corrosive environment adheres to the sample electrode 8 and the counter electrode 9 that are insulated from each other, so that both are short-circuited.

As a result, the anode electrode (oxidation reaction) represented by, for example, the following formula (1) occurs on the sample electrode 8 side that is low in potential, and the iron atom Fe emits an electron e ⁻ to the sample electrode 8, It dissolves in the form of iron ions Fe ²⁺ and diffuses into the water W.
Fe → Fe ²⁺ + 2e ⁻ (1)
On the other hand, at the potential noble counter electrode 9 side, the electron e ⁻ generated at the sample electrode 8 is supplied to cause a cathode reaction (reduction reaction) as shown in the following formula (2), and water H ₂ O, oxygen O ₂ and the electron e ⁻ supplied from the sample electrode 8 react to generate a hydroxide ion OH ⁻ .
_{H 2 O + O 2/2} + 2e - → 2OH - (2)

As described above, the anodic reaction and the cathodic reaction occur at the sample electrode 8 and the counter electrode 9 respectively, whereby electrons e ⁻ are sequentially supplied from the sample electrode 8 to the counter electrode 9 and the corrosion current A is generated from the counter electrode 9 to the sample electrode 8. Flowing. This corrosion current depends on the reaction rate of the anode reaction and the cathode reaction.

For this reason, each unit electrode 7 flows a corrosion current A according to the corrosive environmental properties such as the surrounding oxygen concentration and humidity. For example, the atmospheric part 12 exposed to the atmosphere having a high oxygen concentration and a low humidity, and In the underground part 14 exposed to the ground where the oxygen concentration is low and the humidity is high, the corrosion current A is small. On the other hand, the corrosion current A becomes large in the subsurface portion 13 exposed to the subsurface where both the oxygen concentration and the humidity are high.
Thus, the corrosion current A corresponding to the surrounding corrosive environment flows through each unit electrode 7, and this corrosion current A is measured by the current measuring device 3. Then, the corrosive environment in the atmosphere is based on the current value of the atmospheric portion 12, the corrosive environmental property is based on the current value of the underground portion 13, and the underground corrosion is based on the current value of the underground portion 14. Each environmental property is evaluated, and the distribution of corrosive environmental properties over the atmosphere, the ground, and the ground is evaluated.

  According to the present embodiment, since the plurality of unit electrodes 7 each capable of detecting the surrounding corrosive environment property are arranged in a line, the distribution of the corrosive environment property in the arrangement direction can be evaluated. Further, each unit electrode 7 has a corrosion current A when the sample electrode 8 and the counter electrode 9 having different natural potentials are short-circuited with moisture by using a sample electrode 8 and a counter electrode 9 having different natural potentials, even if there is no potential difference due to the surrounding corrosive environment. Since it flows, it becomes possible to evaluate the corrosive environment property with high resolution even when the corrosive environment property is uniform. Further, by using the sample electrode 8 and the counter electrode 9 having different natural potentials, a larger corrosion current A flows to each unit electrode 7 and the corrosion environment can be evaluated with high sensitivity.

In the above embodiment, the sample electrode 8 is made of steel. However, the sample electrode 8 is not limited to this as long as it is a lower-potential metal material than the counter electrode 9. For example, the sample electrode 8 is made of aluminum or the like. It can also be configured. The counter electrode 9 can also be composed of silver, nickel, copper, or the like.
Further, the sample electrode 8 and the counter electrode 9 of each unit electrode 7 are joined in parallel with each other by the adhesive 10. However, the unit electrode 7 is not limited to this as long as the sample electrode 8 and the counter electrode 9 are arranged close to each other and can be short-circuited by the moisture W. .

In addition, the recess 4 of the insulating frame 1 can be formed to such a depth that each unit electrode 7 of the electrode portion 3 does not protrude outside from the insulating frame 1, so that the surface of the counter electrode 9 is accommodated in the recess 4. In this way, each unit electrode 7 can be attached to the insulating frame 1. For example, as shown in FIG. 4, the recess 4 can be formed such that the surface of the counter electrode 9 of each unit electrode 7 attached to the insulating frame 1 is at the same height as the surface of the insulating frame 1. Further, the recess 4 can be formed so that the surface of the counter electrode 9 is lower than the surface of the insulating frame 1, and each unit electrode 7 can be embedded in the insulating frame 1.
Thereby, when inserting and installing a corrosion sensor in the ground, it can suppress that each unit electrode 7 is damaged by friction.

  In addition, the corrosion sensor can be installed and used so that the arrangement direction of the unit electrodes 7 is along a structure containing metal. For example, the corrosion sensor is installed so that the atmospheric part 12, the ground part 13 and the underground part 14 of the plurality of unit electrodes 7 exist in the vicinity of the atmospheric part, the ground part and the underground part of the structure, respectively. In each unit electrode 7, a corrosion current A corresponding to the surrounding corrosive environment property flows, and this corrosion current A is measured by the current measuring device 3.

The current values from the plurality of unit electrodes 7 thus obtained represent the corrosive environmental properties to which each part of the structure is exposed. The current value from the atmospheric part 12 and the current value from the ground part 13 Based on the above, it is possible to relatively evaluate the corrosion state of the ground portion from the corrosion state of the atmospheric portion of the structure. Furthermore, by adding and comparing the current value from the underground portion 14, the corrosion state of the ground portion of the structure can be evaluated with higher accuracy.
In this way, it is possible to accurately evaluate the corrosion state of the ground portion of the structure where it is difficult to confirm the progress of corrosion from the appearance. In addition, the remaining life of the structure can be estimated based on the corrosive environment around the structure.
In addition, by subjecting the sample electrode 8 of each unit electrode 7 to the same surface treatment as the structure, the corrosion state of the structure can be evaluated with higher accuracy.
The corrosion sensor is not limited to a structure installed on the soil, and can be installed along a structure such as a sign post, a lighting pole, and a bridge pier installed on concrete. The corrosion sensor can also be installed such that each electrode array extends from the atmosphere to the liquid. For example, it can be installed along a structure such as a marine structure installed from seawater to the atmosphere, a river structure installed from fresh water to the atmosphere, or a plant tank containing a chemical solution or the like. Furthermore, the corrosion sensor can be installed such that each electrode array extends from a solid such as concrete into a liquid. For example, install on concrete parts such as foundations of offshore structures installed in seawater and foundations of river structures installed in fresh water, and evaluate the corrosion status of steel materials extending from concrete into liquids. Can do.

Next, an embodiment in which the corrosion environment distribution is actually evaluated using a corrosion sensor will be described. A corrosion sensor was installed in a container containing a predetermined amount of sand so that a part of the plurality of unit electrodes 7 entered the sand, and a 0.1 wt% NaCl aqueous solution was added. Then, when the water surface reaches the interface between the sand and the atmosphere, the moisture addition rate is 100%, and the corrosion current A flowing through each unit electrode 7 in the state where the moisture addition rate is 100% is measured in FIG. ) And the corrosion current A flowing through each unit electrode 7 in a state where the water addition rate is 80% is shown in FIG. 4B.
As a result, in FIG. 4A, the sensor height is the highest near the interface between the sand and the atmosphere, that is, the upper surface position of the moisture added to the container, and the sensor height increases as the sensor height increases. The current value decreased as the value decreased. Also in FIG. 4B, the current value becomes the largest near the position where the sensor height is 80% from the bottom with respect to the thickness of the sand, that is, the upper surface position of the moisture added to the container. The current value decreased as the sensor height increased or the sensor height decreased.
Thus, the corrosion current A was the highest at the upper surface of the moisture rich in oxygen along with the moisture, and the corrosion current A was reduced in the atmospheric environment with little moisture and the sand environment with little oxygen. From this, it can be seen that these measured values represent the corrosion environment around each unit electrode 7, that is, the distribution of the corrosion environment from the atmosphere to the sand.

  DESCRIPTION OF SYMBOLS 1 Insulation frame, 2 electrode part, 3 Current measuring device, 4 Recessed part, 5 Connection path, 6 Communication path, 7 Unit electrode, 8 Sample electrode, 9 Counter electrode, 10 Adhesive, 11 Through-hole, 12 Air | atmosphere part, 13 Ground Part, 14 Underground part, W moisture, A Corrosion current.

Claims (9)

An insulation frame;
An electrode portion in which a plurality of unit electrodes each including a sample electrode and a counter electrode disposed in proximity to the sample electrode are arranged in a row and are attached to the insulating frame;
A current measuring device that is connected to each of the plurality of unit electrodes of the electrode unit and measures a current flowing between the sample electrode and the counter electrode in each unit electrode ;
An electric wire disposed inside the insulating frame and connecting the sample electrode and the counter electrode of each unit electrode to the current measuring device ;
The sample electrode and the counter electrode each have a flat plate shape, and the sample electrode is wider in width than the counter electrode, and the counter electrode is joined to a central portion of the sample electrode via an insulating material,
The corrosion sensor , wherein the electric wire extending from the current measuring instrument to the sample electrode is distributed and connected to both side portions of the sample electrode sandwiching the counter electrode . 2. The corrosion sensor according to claim 1, wherein the sample electrodes included in the plurality of unit electrodes are made of the same material, and the counter electrodes included in the plurality of unit electrodes are made of the same material. 3. The corrosion sensor according to claim 1, wherein in each unit electrode, the sample electrode is formed of a metal material, and the counter electrode is formed of a metal material that is more potential than the metal material of the sample electrode.   The corrosion sensor according to any one of claims 1 to 3, wherein the sample electrode is made of steel or aluminum, and the counter electrode is made of silver, nickel, or copper.   The corrosion sensor according to any one of claims 1 to 4, wherein the current measuring instrument is a non-resistance type multi-channel ammeter. The insulating frame has a plurality of recesses arranged in a row,
The corrosion sensor according to any one of claims 1 to 5, wherein the plurality of unit electrodes are respectively disposed in the recesses so as not to protrude outward from the insulating frame.   The corrosion sensor according to any one of claims 1 to 6, wherein the corrosion sensor is installed and used so that a part of the plurality of unit electrodes enters the ground.   The corrosion sensor according to any one of claims 1 to 7, wherein the corrosion sensor is installed and used so that an arrangement direction of the plurality of unit electrodes is along a structure including a metal.   The corrosion sensor according to claim 8, wherein the sample electrode is subjected to the same surface treatment as that of the structure.

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