JP6623326B2 - Corrosion sensor - Google Patents

Description

  The present invention relates to a corrosion sensor, and more particularly, to a corrosion sensor for evaluating a corrosion environment of a structure installed at a location susceptible to fluctuations in water level or splash of water.

Steel structures installed in rivers and oceans, such as sluices and piers, are exposed to severe corrosive environments. In particular, in a part affected by ebb and flow (tidal zone) due to a change in tide level and in a part subject to splashing (splash zone), the rate of corrosion of the structural material tends to increase due to frequent repetition of wet and dry conditions.
As a countermeasure against corrosion of a steel structure installed in such a corrosive environment, a portion immersed in water is often applied with electrolytic protection. However, since the cathodic protection does not function effectively in the gas phase, it is common to use a coating such as heavy anticorrosion coating.

In the case of cathodic protection, it is possible to suppress corrosion almost by properly managing it, and it is possible to evaluate the anticorrosion state by monitoring the potential and current. There is no other method but to evaluate it by observing external appearance such as accompanying discoloration.
Patent Document 1 discloses that a corrosive environment sensor in which a plurality of types of monitoring metal pieces are fixed is disposed in the same environment as a steel structure to cause corrosion, and a color change on the surface of each metal piece is measured. A method of evaluating a corrosive environment at a place where a steel structure is installed by measuring with a meter is disclosed.

JP 2006-64466 A

  However, in the method disclosed in Patent Document 1, since the color change of a plurality of types of metal pieces is measured, it is difficult to quantitatively evaluate a change in a corrosive environment over time, and the water level such as a change in tide level is also difficult. It was difficult to evaluate the change of the corrosive environment in the direction of the water level fluctuation of the structure installed in the place where the water fluctuated.

  The present invention has been made to solve such a conventional problem, and has as its object to provide a corrosion sensor capable of quantitatively evaluating a change in a corrosion environment in a predetermined direction of a structure. I do.

A corrosion sensor according to the present invention is a corrosion sensor for measuring a distribution of a corrosion rate of a structure to be measured in a predetermined direction, wherein the plurality of corrosion sensors are arranged in a predetermined direction and are respectively installed on the surface of the structure. A plurality of sample electrodes, a common counter electrode extending in a predetermined direction alongside the plurality of sample electrodes so as to include the arrangement positions of the plurality of sample electrodes in the predetermined direction, and a plurality of sample electrodes. The distribution of the corrosion rate in a predetermined direction is measured based on a plurality of corrosion currents flowing through a plurality of corrosion circuits formed by connecting the electrode and the common counter electrode and connecting the plurality of sample electrodes to the common counter electrode, respectively. A plurality of sample electrodes and a common counter electrode are arranged side by side on the same surface on the surface of the structure .

The plurality of sample electrodes are preferably made of the same material as the material constituting the structure.
Further, the common counter electrode can be formed from the same material as the plurality of sample electrodes. Alternatively, it is preferable that the common counter electrode is made of a material whose main component is the same material as the plurality of sample electrodes and which is more noble than the plurality of sample electrodes.
Further, it is preferable that the plurality of sample electrodes be attached on the surface of the structure via an insulating heat conductive sheet.
On the other hand, the common counter electrode may be stuck on the surface of the structure via an insulating heat conductive sheet, or the common counter electrode may be formed by the structure.
The measurement unit integrates the corrosion current flowing through the corrosion circuit formed by connecting the sample electrode to the common counter electrode for each of the plurality of sample electrodes, and integrates the structure at the location where the sample electrode is installed. It is preferable to measure the corrosion rate of steel.

  According to the present invention, a plurality of sample poles arranged in a predetermined direction and respectively installed on the surface of the structure, and aligned with the plurality of sample poles so as to include the arrangement positions of the plurality of sample poles in the predetermined direction. And a common counter electrode extending in a predetermined direction and disposed on the surface of the structure, wherein the measurement unit is connected to the plurality of sample electrodes and the common counter electrode, and connects the plurality of sample electrodes to the common counter electrode, respectively. Since the distribution of corrosion rate in a predetermined direction is measured based on a plurality of corrosion currents flowing through a plurality of corrosion circuits formed by performing the above, quantitatively evaluate changes in a corrosion environment in a predetermined direction of a structure. Becomes possible.

FIG. 1 is a diagram showing a configuration of a corrosion sensor according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view showing a plurality of sample electrodes arranged on the surface of a structure and a common counter electrode. It is sectional drawing which shows the state where the counter electrode common to a sample electrode was immersed in water. It is a figure which shows a flood gate typically. It is a perspective view which shows the door body of a floodgate. FIG. 3 is a diagram showing a door of a floodgate where the corrosion sensor according to the first embodiment is installed. FIG. 9 is a diagram showing a configuration of a corrosion sensor according to a second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1
FIG. 1 shows a configuration of the corrosion sensor according to the first embodiment. This corrosion sensor includes a plurality of sample electrodes 2 installed on a surface of a structure 1 to be evaluated for a corrosive environment, and a common sample electrode 2 arranged on the surface of the structure 1 and in the vicinity of the plurality of sample electrodes 2. The measuring unit 5 has a counter electrode 3 and is electrically connected to the common counter electrode 3 with each of the plurality of sample electrodes 2 via a cable 4.

On the surface of the structure 1, the plurality of sample electrodes 2 are arranged in a row in a predetermined direction D in which a change in the corrosive environment is to be evaluated. The plurality of sample electrodes 2 extend in a predetermined direction D so as to include all the arrangement positions of the sample electrodes 2.
Here, the predetermined direction D is, for example, when the structure 1 is a structure installed in a place such as a pier, a floodgate, or the like that is exposed to seawater or river water whose water level fluctuates with time, It can be set in the vertical direction which is the water level fluctuation direction.

The plurality of sample electrodes 2 and the common counter electrode 3 are each formed of a material having the same composition as the material constituting the structure 1. For example, when the structure 1 is made of a steel material having a certain composition, each sample electrode 2 and the common counter electrode 3 are formed of a steel material having the same composition as the structure 1.
The plurality of sample electrodes 2 are separated from each other and are independent of each other. As shown in FIG. 2, each of the plurality of sample electrodes 2 is attached to the surface of the structure 1 via an insulating heat conductive sheet 6. Similarly to the plurality of sample electrodes 2, the common counter electrode 3 is attached to the surface of the structure 1 via the insulating heat conductive sheet 7.

The plurality of sample electrodes 2 and the common counter electrode 3 are preferably not formed by film formation but formed of a bulk material.
Further, as the heat conductive sheets 6 and 7, commercially available heat conductive sheets having an adhesive material adhered to both surfaces can be used. The sample electrode 2 and the common counter electrode 3 can be stuck on the surface of the structure 1 using the adhesive attached to the heat conductive sheet.

The measurement unit 5 measures a plurality of corrosion currents Ic flowing through a plurality of corrosion circuits formed by connecting the plurality of sample electrodes 2 connected via the cable 4 to the common counter electrode 3, respectively. Specifically, the measuring unit 5 measures the corrosion current Ic flowing through one corrosion circuit formed by connecting one sample electrode 2 of the plurality of sample electrodes 2 to the common counter electrode 3, The sample electrode 2 is cut off from the common counter electrode 3 and the corrosion current Ic flowing through the next corrosion circuit formed by connecting the next sample electrode 2 to the common counter electrode 3 is measured. In this way, the plurality of sample electrodes 2 are sequentially connected to the common counter electrode 3, and the corrosion current Ic flowing through each formed corrosion circuit is measured.
The measuring unit 5 further calculates the corrosion rates at the plurality of sample electrodes 2 by time-integrating the plurality of corrosion currents Ic flowing through the plurality of corrosion circuits, respectively, and determines a predetermined direction D based on the corrosion rates. The distribution of the corrosion rate at is measured.

Next, the operation of the corrosion sensor according to the first embodiment will be described.
For example, it is assumed that the structure 1 is a steel structure installed at a location exposed to seawater, river water, or the like, and the predetermined direction D is set to a vertical direction which is a water level fluctuation direction. Since the common counter electrode 3 extends in the predetermined direction D so as to include all of the arrangement positions of the plurality of sample electrodes 2 in the predetermined direction D, the common counter electrode 3 has a plurality of sample electrodes 2 arranged on the surface of the structure 1. When the lowest sample electrode 2 is immersed in water, the common counter electrode 3 corresponding to the position where the sample electrode 2 is arranged is also immersed in water.

At this time, as shown in FIG. 3, the surface of the sample electrode 2 and the surface of the common counter electrode 3 are electrically connected via the water W, and the measuring unit 5 is connected to the sample electrode 2 via the cable 4. By connecting the counter electrode 3 to the counter electrode 3, a corrosion circuit returning from the measuring section 5 to the measuring section 5 via the sample electrode 2, the water W and the common counter electrode 3 is formed.
Here, when a corrosion reaction (anode reaction) occurs in the sample electrode 2 and iron ions Fe ²⁺ are dissolved and diffused in the water W from the surface of the sample electrode 2, electrons e ⁻ generated in the sample electrode 2 are measured by the measuring unit. 5, water molecules H ₂ O, which are supplied to the common counter electrode 3 and constitute water W on the surface of the common counter electrode 3, oxygen molecules O ₂ dissolved in the water, and electrons e ⁻ react (cathode reaction). ) To form hydroxide ions OH ⁻ .

In this way, the anodic reaction and the cathodic reaction occur at the sample electrode 2 and the common counter electrode 3 respectively, so that the corrosion current Ic flows from the common counter electrode 3 to the sample electrode 2 through the measuring unit 5. The corrosion current Ic are those that depend on the reaction rate of the anodic reaction and the cathodic reaction, i.e., becomes dependent on the amount of components such as iron atoms Fe and molecular oxygen O ₂ involved in these reactions.

Similarly, the corrosion current Ic flowing through the plurality of corrosion circuits formed by sequentially connecting the plurality of sample electrodes 2 to the common counter electrode 3 is measured by the measurement unit 5.
In the sample electrode 2 which is frequently submerged in water or arranged in a position susceptible to water splash, the speeds of the anodic reaction and the cathodic reaction are increased, and a large corrosion current Ic flows. On the other hand, in the sample electrode 2 which is not immersed in water even when the water level rises and is located at a high position where the influence of water splash does not affect, the speeds of the anode reaction and the cathode reaction are slow. And the corrosion current Ic becomes smaller.
As described above, the corrosion current Ic corresponding to the corrosive environment of the arrangement position flows through each of the plurality of sample electrodes 2, and the corrosion current Ic is measured by the measuring unit 5.

Here, as described above, the plurality of sample electrodes 2 and the common counter electrode 3 are formed of materials having the same composition as each other, and are configured so that acceleration of electrons due to a potential difference does not occur.
Therefore, the corrosion current Ic measured for each sample electrode 2 corresponds to the amount of generated electrons. Then, the amount of electrons is calculated from the corrosion current Ic, and the corrosion reaction formula Fe → Fe 2 ⁺⁺ 2e ⁻
, The number of moles of consumed Fe, that is, the weight can be calculated. Further, the corrosion rate can be obtained by dividing the weight of consumed Fe by time.

In this way, the measuring section 5 calculates the corrosion rate in each of the plurality of sample electrodes 2 and measures the distribution of the corrosion rate in the predetermined direction D.
Since each of the plurality of sample electrodes 2 is formed from a material having the same composition as the material constituting the structure 1, the corrosion rate calculated for each sample electrode 2 is the same as that of the sample electrode 2. It can be regarded as the corrosion rate of the structure 1 at the site located at the position.
Therefore, the distribution of the corrosion rate in the structure 1 is obtained, and it becomes possible to quantitatively evaluate the change in the corrosion environment in the predetermined direction D of the structure 1.

  In general, it is known that the corrosion rate greatly changes depending on the temperature of an object. However, in the corrosion sensor according to the first embodiment, the plurality of sample electrodes 2 are attached to the surface of the structure 1 via the heat conductive sheet 6, and the common counter electrode 3 is also connected to the structure via the heat conductive sheet 7. Since it is attached to the surface of the structure 1, a large temperature difference between the plurality of sample electrodes 2 and the common counter electrode 3 and the structure 1 is suppressed, and the corrosion rate can be obtained with high accuracy.

  The measuring unit 5 can obtain a distribution of corrosion rates under various conditions, for example, a corrosion rate during rainfall, an average of the corrosion rates during one week or one month, and compare and evaluate the distribution to evaluate the structure. It can be used for evaluation of the corrosion life of the object 1 and formulation of a maintenance plan.

In the first embodiment, the plurality of sample electrodes 2 and the common counter electrode 3 are formed of materials having the same composition as each other. However, this influences the value of the corrosion rate calculated by the measuring unit 5. An insignificant potential difference can be formed between the plurality of sample electrodes 2 and the common counter electrode 3. In this way, it is possible to avoid the possibility that the common counter electrode 3 is corroded by itself and that the anode reaction and the cathode reaction are reversed between the sample electrode 2 and the common counter electrode 3.
In this case, the common counter electrode 3 for the sample electrode 2 is preferably made of a noble material. Specifically, the common counter electrode 3 can be formed from a material containing the same material as the plurality of sample electrodes 2 as a main component and more noble than the plurality of sample electrodes 2.

  For example, in the case of alloy steel in which chromium or nickel is added to iron, the spontaneous potential increases as the amount of chromium or nickel added increases. Therefore, when the structure 1 is made of ordinary steel, a plurality of sample electrodes 2 are commonly used. By forming the common counter electrode 3 from alloy steel to which chromium or nickel is added while forming the common counter electrode 3 from steel, the common counter electrode 3 with respect to the sample electrode 2 can be a noble material.

  According to Japanese Industrial Standards (JIS), the maximum amount of chromium added to chromium molybdenum steel (SCM) is 1.5%, and the maximum amount of chromium added to nickel chromium molybdenum steel (SNCM) is 3. 5%, and the maximum addition amount of nickel is also described as 3.5%. Therefore, alloy steel to which chromium or nickel is added within the maximum addition amount of 3.5% or chromium is added within the maximum addition amount of 3.5% and the maximum addition amount is within the range of 3.5%. When the common counter electrode 3 is formed by using an alloy steel to which nickel is added by the above method, a potential difference that does not affect the value of the corrosion rate calculated by the measuring unit 5 is set to a common counter electrode with the plurality of sample electrodes 2. 3 can be formed.

The structure 1 is exposed to seawater or river water whose water level fluctuates with time, or is susceptible to water droplets, such as a marine structure such as a pier, a river structure such as a sluice gate or a gutter, or a bridge. Structures can be suitably mentioned.
For example, the door 12 of the floodgate facility 11 as shown in FIG. 4 may be used as the structure 1, and the corrosion sensor according to the first embodiment may be installed on the door 12.
As shown in FIG. 5, the door body 12 is suspended by a pair of wires 13 and moves up and down. However, since the door body 12 is located underwater or above the water as it moves up and down, it often repeats wet and dry. Corrosion rates tend to be higher than at other sites.

Therefore, as shown in FIG. 6, the predetermined direction D is set to the vertical direction, a plurality of sample electrodes 2 and a common counter electrode 3 are attached on the surface of the door body 12, and the plurality of sample electrodes 2 and The corrosion sensor is formed by electrically connecting the measuring unit 5 to the common counter electrode 3 via the cable 4.
As described above, the corrosion sensor according to the first embodiment is installed on the door body 12, the corrosion current Ic corresponding to the plurality of sample electrodes 2 is measured by the measurement unit 5, and the corrosion rate at each sample electrode 2 is calculated. By doing so, a distribution of the corrosion rate in the vertical direction can be obtained.

  In the corrosion sensor according to the first embodiment, the plurality of sample electrodes 2 are separated and independent from each other, are respectively attached to the surface of the structure 1 via the insulating heat conductive sheet 6, and the common counter electrode 3 is provided. Is also attached to the surface of the structure 1 via the insulating heat conductive sheet 7 independently of the plurality of sample electrodes 2, regardless of the structure and shape of the structure 1. And the common counter electrode 3 can be easily arranged on the surface of the structure 1.

  For example, as shown in FIG. 5, the door body 12 of the floodgate facility 11 generally has a back surface structure divided into a plurality of parts by a plurality of girders or beams. There is a possibility that the environment is likely to remain susceptible to corrosion. However, if the corrosion sensor according to the first embodiment is used, it is possible to arrange the sample electrodes 2 individually in the divided portions and evaluate the distribution of the corrosion rate. It becomes. However, the common counter electrode 3 needs to extend in the predetermined direction D so as to include all the arrangement positions of the plurality of sample electrodes 2 in the predetermined direction D.

Embodiment 2
In the first embodiment, the common counter electrode 3 extending in the predetermined direction D is attached on the surface of the structure 1 so as to include all the arrangement positions of the plurality of sample electrodes 2 arranged in the predetermined direction D. However, the present invention is not limited to this, and a common counter electrode can be formed by a structure.
The corrosion sensor according to the second embodiment shown in FIG. 7 differs from the corrosion sensor according to the first embodiment in that the common counter electrode 3 arranged on the surface of the structure 1 is omitted, and the measurement unit 5 is connected to the measurement unit 5 via the cable 4. The structures 1 are electrically connected to each other.

Even in such a configuration, the measuring unit 5 measures the corrosion current Ic flowing through the corrosion circuit formed by sequentially connecting the plurality of sample electrodes 2 to the structure 1 as a common counter electrode, thereby realizing the implementation. In the same manner as in Embodiment 1, it is possible to calculate the corrosion rate in each sample electrode 2 and obtain the distribution of the corrosion rate in the predetermined direction D.
In the second embodiment, it is not necessary to attach a common counter electrode on the surface of the structure 1, and the installation of the corrosion sensor on the structure 1 is further facilitated.

  For example, even if the structure 1 has a structure divided into a plurality of portions by a plurality of beams or beams as in the door body 12 shown in FIG. 5, a plurality of sample electrodes 2 are separated from each other. The corrosion sensor can be installed simply by sticking on the surface of the object 1 and electrically connecting the plurality of sample electrodes 2 and the structure 1 to the measuring unit 5, and the corrosion rate of the structure 1 can be easily determined. The distribution can be evaluated.

In FIGS. 1, 6 and 7, five sample electrodes 2 are arranged in the predetermined direction D. However, the number of sample electrodes 2 is not limited to five, and a plurality of arbitrary number The sample electrodes 2 are arranged in a predetermined direction D, and these sample electrodes 2 are connected to the measuring unit 5 to measure the distribution of the corrosion rate.
The predetermined direction D in which the plurality of sample electrodes 2 are arranged is not limited to the vertical direction, and may be set to any direction in which a change in the corrosive environment is to be evaluated.

  1 structure, 2 sample electrodes, 3 common counter electrodes, 4 cables, 5 measuring units, 6,7 heat conductive sheet, 11 sluice facility, 12 door body, 13 wires, D predetermined direction, W water, Ic corrosion current.

Claims (8)

In a corrosion sensor for measuring the distribution of corrosion rate in a predetermined direction of the structure to be measured,
A plurality of sample poles arranged in the predetermined direction and each placed on the surface of the structure,
A common counter electrode that extends in the predetermined direction along with the plurality of sample electrodes so as to include the arrangement position of the plurality of sample electrodes in the predetermined direction, and is disposed on the surface of the structure;
The predetermined direction based on a plurality of corrosion currents flowing through a plurality of corrosion circuits connected to the plurality of sample electrodes and the common counter electrode and formed by connecting the plurality of sample electrodes to the common counter electrode, respectively. and a measuring unit for measuring the distribution of the corrosion rate in,
The corrosion sensor according to claim 1, wherein the plurality of sample electrodes and the common counter electrode are arranged on the same surface on the surface of the structure .   The corrosion sensor according to claim 1, wherein the plurality of sample electrodes are made of the same material as a material constituting the structure.   The corrosion sensor according to claim 2, wherein the common counter electrode is made of the same material as the plurality of sample electrodes.   3. The corrosion sensor according to claim 2, wherein the common counter electrode is mainly composed of the same material as the plurality of sample electrodes and is made of a material which is more noble than the plurality of sample electrodes. 4.   The corrosion sensor according to claim 1, wherein the plurality of sample electrodes are attached to a surface of the structure via an insulating heat conductive sheet.   The corrosion sensor according to any one of claims 1 to 5, wherein the common counter electrode is attached to a surface of the structure via an insulating heat conductive sheet.   The corrosion sensor according to claim 1, wherein the common counter electrode is formed by the structure.   The measurement unit is provided with the sample electrode by time-integrating a corrosion current flowing through a corrosion circuit formed by connecting the sample electrode to the common counter electrode for each of the plurality of sample electrodes. The corrosion sensor according to any one of claims 1 to 7, wherein a corrosion rate of the structure at a location where the corrosion has occurred is measured.

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