JP2017090399A - Test device and test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test device capable of easily and clearly comprehending the influences of macro corrosion on a metal structure which is buried across heterogeneous soils depending on combination of soils while controlling the soil circumstances.SOLUTION: The test device 1 includes: two or more cells 2 in which a soil S and a metal structure K are placed with a part or entire of which being berried in the soil S; pressurizing mechanism 4 that applies a pressure to the soil S in each of the cells 2; a water supply mechanism 5 for supplying water inside the cells 2; a gas supply mechanism 6 for supplying a gas other than oxygen inside the cells 2; and a potential measurement mechanism 3 for measuring a potential difference between the metal structures K each being placed in the different cells 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a test apparatus and a test method.

  Metal structures represented by infrastructure equipment such as steel pipe columns, supporting anchors and piping are used in a state where the whole or a part thereof is buried in the ground. Usually, a metal structure corrodes in contact with soil or groundwater, that is, soil corrodes, and decreases in thickness with the lapse of years (see Non-Patent Documents 1 to 3).

  If the metal structure is reduced in thickness due to soil corrosion, the function that the structure should originally exhibit may not be secured. For this reason, inspection / maintenance methods, anticorrosion methods, and methods for predicting corrosion progress are being studied.

  In order to perform appropriate inspection / maintenance, anticorrosion methods and highly accurate and reliable corrosion progress prediction, sufficient knowledge about the soil corrosion mechanism of metals is essential. In order to obtain such knowledge, it is necessary to investigate the corrosion thinning amount and corrosion products in a system in which each factor affecting soil corrosion is controlled, and to clarify the corrosion mechanism.

  The degree of soil corrosion varies markedly depending on the type and nature of the soil, the structure of the metal structure, the state of burial in the ground, and the weather conditions. Factors affecting soil corrosion include soil type, temperature, air temperature, pH, specific resistance, water content, soluble salt concentration, oxygen concentration, gases, and bacterial activity (see Non-Patent Documents 1 and 2). . Soil corrosion proceeds by a complex mechanism involving these factors.

  In particular, in a metal structure installed across multiple types of layered soil, macro-corrosion is often promoted and attention is required. Macro corrosion is corrosion that occurs when a potential difference occurs between metal structures in each soil, macroscopic separation occurs between the anode part and the cathode part, and a macro cell is formed. Many cases of severe corrosion progressing at a high rate have been confirmed. The occurrence of macro-corrosion is considered to be affected by differences in soil environment factors such as soil density, water content, and oxygen concentration in the depth direction of the ground.

Morio Kadoi, Shoaki Takahashi, Kotaro Yano, "Studies on soil corrosion of metal materials (1st report)", Corrosion protection technology, 1967, Vol.16, No.6, pp.10-18 Yoshikazu Miyata, Shuji Asakura, “Measurement of Soil Corrosion Focusing on Electrochemical Method (Part 2)”, Materials and Environment, 1997, Vol.46, pp.610-619 Naomi Emu and Yuka Takasawa, “Soil corrosion of steel bars by model experiment”, Materials and Environment, 1993, Vol.42, pp.136-143

  However, there is little information that is quantitatively grasped about differences in factors of the soil environment affecting macro corrosion. In order to confirm the influence of environmental factors affecting macro corrosion, for example, a test system is assumed in which a metal structure is embedded in a container in which different types of soil are stacked so as to straddle different types of soil. In this test system, the corrosion state of the metal structure can be analyzed using the metal structure taken out after being buried for a long time. However, in such a test system, the value of the natural potential measured for a metal structure as a conductor is one even if the soil is spread over different types of soil, and the potential difference generated in each different type of soil is not detected. I can't figure it out. Accordingly, it has been difficult to quantitatively grasp how much macro corrosion occurs in a metal structure embedded across different soil environments. Moreover, in this test system, it was difficult to control the soil density, water content, and oxygen concentration, which are factors of the soil environment, for each different type of soil.

  The present invention has been made in view of the above, and it is easy and clear to control the soil environment to influence the influence of soil combination on macro corrosion generated in metal structures embedded over different types of soil. The purpose is to understand.

  In order to solve the above-described problems and achieve the object, a test apparatus according to the present invention includes two or more cells in which soil and a metal structure partially or entirely embedded in the soil are accommodated, Between a pressurizing mechanism that applies pressure to the soil in the cell, a water supply mechanism that supplies water into each cell, a gas supply mechanism that supplies a gas other than oxygen into each cell, and a metal structure housed in a different cell And a potential measuring mechanism for measuring a potential difference.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of the combination of the soil to the macro corrosion produced in the metal structure embed | buried over different soil can be grasped | ascertained simply and clearly by controlling soil.

FIG. 1 is a diagram for explaining an outline of an embodiment of the present invention. FIG. 2 is a schematic diagram showing a schematic configuration of the test apparatus of the present embodiment. FIG. 3 is a diagram illustrating the measurement result of the potential difference in the test processing of the present embodiment. FIG. 4 is a flowchart showing the test processing procedure of the present embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Moreover, in description of drawing, the same code | symbol is attached | subjected and shown to the same part.

  First, an outline of the present embodiment will be described with reference to FIG. In the test processing by the test apparatus according to the present embodiment, as illustrated in FIG. 1, macro corrosion that occurs in the metal structure K that is buried across different types of soil S1 and soil S2 stacked in the depth direction. Grasp the influence of soil S1 and soil S2. In the example shown in FIG. 1, it is known that the larger the difference between the potential of the metal structure K in the soil S1 and the potential of the metal structure K in the soil S2, the easier the macro corrosion occurs. Therefore, in this embodiment, the soil environment of the soil S1 and the soil S2 is individually controlled, and the difference between the potential of the metal structure K in the soil S1 and the potential of the metal structure K in the soil S2 is measured. Thus, the influence of the combination of the soil S1 and the soil S2 on the macro corrosion is grasped.

[Configuration of test equipment]
FIG. 2 is a schematic diagram showing a schematic configuration of the test apparatus according to the present embodiment. As shown in FIG. 2, the test apparatus 1 includes two or more cells 2 (21, 22) and a potential measurement mechanism 3.

  Each cell 2 accommodates one kind of soil S in which the metal structure K to be tested is embedded. The soil S1 accommodated in the cell 21 and the soil S2 accommodated in the cell 22 may be the same or different. The metal structure K1 embedded in the soil S1 and the metal structure K2 embedded in the soil S2 may be the same material or different materials. Here, metal structures having different alloy compositions and manufacturing / processing methods are made of different materials. In addition, the combination of soil S1 and soil S2 is mentioned later.

  Each soil S should just contain the granular material which consists of 1 or more types of oxide seed | species, and it does not specifically limit about the particle | grain size of the constituent species of a soil and a granular material. In order to approximate the soil environment of actual soil, for example, silicon dioxide, aluminum oxide, iron oxide, calcium oxide, and magnesium oxide, which are typical constituents of actual soil, may be mixed. In that case, you may control the mixing ratio and particle size of each component further. Thereby, it is expected that the reproducibility of the soil environment of the real soil is enhanced. Furthermore, you may mix a chloride, a sulfate, or nitrate.

  Alternatively, real soil may be used for each soil S. The location and conditions for collecting the actual soil are not particularly limited, but when using the actual soil in the present embodiment, it is preferable to sufficiently heat and remove the moisture beforehand in order to control the amount of water. Further, it is preferable to remove a mixture of grass, roots, insects or the like by sieving.

  The amount of soil S accommodated in each cell 2 is not particularly limited as long as the portion of the metal structure K to be checked for corrosion is buried. Moreover, the size and shape of each cell 2 are not particularly limited, and it is only necessary to accommodate the soil S in which the metal structure K is embedded in consideration of the size of the metal structure K and the amount of the soil S. Moreover, the material of each cell 2 should just have the intensity | strength and chemical stability which can be equal to the pressurization mechanism 4 mentioned later. For example, if a transparent plastic made of polyvinyl chloride or acrylic is used, the state in the cell 2 can be constantly confirmed.

  Each cell 2 includes a pressurizing mechanism 4, a water supply mechanism 5, and a gas supply mechanism 6, and the soil environment of the soil S accommodated in each cell 2 is individually controlled. Each cell 2 includes a sensor 7 and measures factors of the soil environment of the soil S in the cell 2 in a timely manner. Examples of the sensor 7 include a thermometer, a moisture meter, a conductivity measuring device, a pH measuring device, or a pressure gauge.

  The pressurizing mechanism 4 applies pressure to the soil S in the cell 2. The pressurizing mechanism 4 is realized, for example, by pushing an inner lid provided in the cell 2 with a screw or the like or pressurizing with a gas. Thereby, the soil density of the soil S in the cell 2 can be controlled. In addition, it is preferable to monitor the pressure applied to the soil S with a pressure gauge as the sensor 7.

  The pressurizing mechanism 4 applies, for example, a pressure corresponding to a predetermined underground depth to the soil S in each cell 2. Here, the predetermined underground depth means the underground depth of the soil environment to be reproduced. In other words, the pressurizing mechanism 4 uses the weight of the upper soil S1 in the lower soil S2 in order to reproduce the positional relationship in the depth direction between the soil S1 and the soil S2 stacked as illustrated in FIG. Apply the corresponding pressure. That is, the cell 21 in which the soil S1 is stored is subjected to an atmospheric pressure condition of release pressure, that is, zero pressure, while the cell 22 in which the soil S2 is stored includes the thickness and density of the layer of the soil S1 and the bottom of the cell 2. A pressure corresponding to the weight calculated from the area is applied.

  In addition, it is preferable to place the metal structure K on the pedestal so that the position in the depth direction of the metal structure K embedded in the soil S does not change with the pressurization. The pedestal is preferably formed of a highly corrosion-resistant material such as vinyl chloride. Further, only the upper surface or the lower surface of the metal structure K may be exposed and embedded in the insulating resin so that the position in the depth direction where the metal structure K is exposed to the corrosive environment is limited. This insulating resin may be formed integrally with the base.

  Moreover, it is preferable to make the areas of the metal structure K and the pedestal facing the pressurizing mechanism 4 as small as possible. Thereby, the resistance of the metal structure K and the base is suppressed, and the uniform pressurization to the soil S is performed.

  The water supply mechanism 5 supplies water into the cell 2. For example, the water supply mechanism 5 includes a water supply port 51 and a drain port 52 into the cell 2, and is realized by supplying the adjusted amount of water into the cell 2. In the present embodiment, the water supply mechanism 5 includes a water container 53 connected to the water supply port 51, and adjusts the amount of water in the cell 2 according to the liquid level in the water container 53. That is, the amount of water is adjusted by making the liquid level in the water container 53 equal to the liquid level in the water supplied into the cell 2. In this case, the moisture content of the soil S in the vicinity of the metal structure K is adjusted to the position in the depth direction of the metal structure K in the cell 2 according to the relationship with the liquid level of the water container 53. For example, the water supply mechanism 5 supplies a predetermined amount of water in each cell 2, that is, a water amount corresponding to the depth of the soil environment to be reproduced.

The gas supply mechanism 6 supplies gas into the cell 2. For example, the gas supply mechanism 6 includes a gas supply port and an exhaust port provided in the cell 2, and circulates in the cell 2 by exhausting the gas supplied from the supply port from the exhaust port. The supplied gas is, for example, nitrogen N ₂ . By circulating a gas other than oxygen in the cell 2, the oxygen concentration in the soil S can be reduced. Thereby, the oxygen concentration in the soil S can be further lowered than the adjustment based only on the soil density and the water content. In addition, it is preferable that the supply pressure of gas is a grade which becomes a little higher than atmospheric pressure so that the soil density etc. of the soil S in the cell 2 may not be changed. For example, the gas supply mechanism 6 reduces the oxygen concentration in each cell 2 according to a predetermined underground depth, that is, an underground depth of a soil environment to be reproduced.

  The potential measurement mechanism 3 measures a potential difference between the metal structures K accommodated in different cells 2. For example, the potential measuring mechanism 3 is realized by connecting the metal structure K1 accommodated in the cell 21 and the metal structure K2 accommodated in the cell 22 with a conductive wire via a voltmeter. In this case, it is preferable that the internal resistance of the voltmeter is as high as possible. The measurement of the potential difference may be performed constantly or periodically.

  In the test apparatus 1 configured as described above, the soil environment of the soil S in each cell 2 is individually controlled by the pressurization mechanism 4, the water supply mechanism 5, and the gas supply mechanism 6. And the electrical potential difference between the metal structure K1 and the metal structure K2 each embed | buried in soil S1 and soil S2 from which soil environment differs is measured. It is determined that macro corrosion is more likely to occur as the measured potential difference is larger.

  FIG. 3 is a diagram illustrating the measurement result of the potential difference. In the example of FIG. 3, when the shapes and materials of the metal structure K1 and the metal structure K2 are the same, the combination of soil S1 and soil S2 is changed to change soil 1 and soil 2, soil 3 and soil 4 The potential difference for three different combinations of soil 5 and soil 6 has been measured. As illustrated in FIG. 3, if the combination of the soil S1 and the soil S2 is different, the potential difference is different and the likelihood of macro corrosion is different.

  In the present embodiment, the potential difference is measured by the potential measuring mechanism 3, but an ammeter may be installed instead of the potential measuring mechanism 3. In this case, by connecting the metal structure K1 accommodated in the cell 21 and the metal structure K2 accommodated in the cell 22 via an ammeter, the macro of the metal structure K exposed to different environments. The magnitude of the reaction related to corrosion can be measured in the form of current value. In this case, the internal resistance of the ammeter is preferably close to zero.

  As described above, if the shape, material, and burying position in the cell 2 of the metal structure K1 and the metal structure K2 are the same, and the soil S1 and the soil S2 are different, the macro in the same metal structure K It becomes possible to grasp the influence of the combination of the soil S1 and the soil S2 on the corrosion.

  Moreover, soil S1 and soil S2 are made the same type, and only one cell 22 is added with a pressure corresponding to the weight of the soil S1 in the other cell 21 and a moisture amount according to the depth of the ground, and nitrogen is added. If gas concentration is supplied and oxygen concentration is reduced, the soil environment according to underground depth can be reproduced. That is, the soil environment on the ground surface side is reproduced in the soil S1 in the cell 21, and the deep soil environment is reproduced in the soil S2 in the cell 22. In this case, it is preferable to control the soil environment of the soil S in each cell 2 according to the measured values of soil density, water content, and oxygen concentration according to the surface depth of the actual soil. This increases the accuracy and reliability of the test process.

  If a metal structure K having the same shape and material is embedded in each of the cells 21 and 22 in which the same kind of soil S is accommodated and the soil environment according to the depth of the ground is reproduced, the underground surface side in the ground It is possible to grasp the tendency of whether or not macro corrosion is likely to occur in the metal structure K embedded toward the deep layer. Or it can also be grasped | ascertained whether the macro corrosion tends to occur in the metal structure K from which a shape or a material differs with depth in the ground. For example, each of the cell 21 and the cell 22 in which the soil S of the same kind is accommodated and the soil environment according to the depth of the ground is reproduced, the metal structures K1, K2 having a shape or material according to the depth of the ground. Should be buried.

[Test processing]
Next, the test processing procedure in the test apparatus 1 will be described with reference to the flowchart of FIG. As illustrated in FIG. 4, first, the soil environment in each cell 2 is individually controlled by the pressurizing mechanism 4, the water supply mechanism 5, and the gas supply mechanism 6. That is, the pressurizing mechanism 4 applies pressure to the soil in each cell 2 (step S101), the water supply mechanism 5 supplies water to each cell 2 (step S102), and the gas supply mechanism 6 is in each cell 2. A gas other than oxygen is supplied (step S103). Note that the processing order of steps S101 to S103 may be interchanged.

  Then, the potential difference between the metal structure K1 and the metal structure K2 embedded in each of the soil S1 and the soil S2 that are housed in the different cells 21 and 22 and whose soil environment is controlled is measured. (Step S104).

  As described above, the test apparatus 1 of this embodiment includes two or more cells 2 in which the soil S and the metal structure K partially or entirely embedded in the soil S are accommodated, and each cell 2. Stored in a different cell 2, a pressurizing mechanism 4 that applies pressure to the soil S inside, a water supply mechanism 5 that supplies water into each cell 2, a gas supply mechanism 6 that supplies a gas other than oxygen into each cell 2, and And a potential measuring mechanism 3 that measures a potential difference between the metal structures K.

  Thereby, the soil environment of the soil S accommodated in each cell 2 can be controlled according to, for example, the depth of the ground, and the potential difference generated by the combination of different soil environments can be measured. Therefore, the potential difference is large and macro corrosion easily occurs. The combination of soil environment can be grasped. Therefore, the test apparatus 1 of the present embodiment can easily and clearly grasp the influence of the combination of soils on the macro-corrosion generated in the metal structure K embedded over different kinds of soils by controlling the soil environment. Can do.

  Moreover, the pressurization mechanism 4 applies the pressure according to the predetermined underground depth to the soil S in each cell 2. Further, the water supply mechanism 5 supplies water in each cell 2 according to a predetermined underground depth. Moreover, the gas supply mechanism 6 reduces the oxygen concentration in each cell 2 according to a predetermined underground depth. Thereby, the soil environment of the laminated soil S is reproduced according to the underground depth.

  A water container 53 connected to the cell 2 is provided, and the liquid level in the cell 2 is adjusted by the liquid level in the water container 53. Thereby, the moisture content in the cell 2 can be adjusted easily.

  Note that the test apparatus 1 may include three or more cells 2. In this case, the potential measuring mechanism 3 measures the potential difference between the metal structures K in any two of the three or more cells 2. Further, two or more metal structures K may be embedded in each cell 2. In this case, the potential measuring mechanism 3 measures the potential difference between any one of the two or more metal structures K in the same cell 2 and any one of the metal structures K in the other cell 2. To do. You may measure the electrical potential difference of the combination of the other metal structure K by the several electrical potential measurement mechanism 3 simultaneously.

  As mentioned above, although embodiment which applied the invention made | formed by this inventor was described, this invention is not limited with the description and drawing which make a part of indication of this invention by this embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Test apparatus 2,21,22 Cell 3 Potential measurement mechanism 4 Pressurization mechanism 5 Water supply mechanism 51 Water supply port 52 Drain port 53 Water container 6 Gas supply mechanism 7 Sensor K, K1, K2 Metal structure S, S1, S2 Soil

Claims (6)

Two or more cells in which the soil and a metal structure partly or entirely embedded in the soil are accommodated;
A pressure mechanism that applies pressure to the soil in each cell;
A water supply mechanism for supplying water into each cell;
A gas supply mechanism for supplying a gas other than oxygen into each cell;
A potential measuring mechanism for measuring a potential difference between metal structures housed in different cells;
A test apparatus comprising:   The test apparatus according to claim 1, wherein the pressurizing mechanism applies a pressure corresponding to a predetermined underground depth to the soil in each cell.   The test apparatus according to claim 1 or 2, wherein the water supply mechanism supplies a water amount corresponding to a predetermined underground depth into each cell.   The test apparatus according to claim 1, wherein the gas supply mechanism reduces the oxygen concentration in each cell according to a predetermined underground depth.   The said water supply mechanism is equipped with the water container connected with the said cell, The water content in the said cell is adjusted with the liquid level height in this water container, The any one of Claims 1-4 characterized by the above-mentioned. The test apparatus described in 1. A housing step of housing the soil and a metal structure partially or entirely embedded in the soil in different cells;
A pressurizing step of applying pressure to the soil in each cell;
A water supply process for supplying water into each cell;
A gas supply step of supplying a gas other than oxygen into each cell;
A potential measurement step for measuring a potential difference between metal structures housed in different cells;
The test method characterized by including.

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