JP2016188849A - Deterioration detection method and corrosion sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a degree of deterioration progress of a protective coating film in steel products to grasp a timing to apply protective coating material again.SOLUTION: There is provided a deterioration detection method that detects a degree of deterioration progress of a protective coating material applied to a steel product 60. The deterioration detection method includes at least the steps of: sticking an optical fiber sensor 62 on a surface of the steel product 60; applying a protective coating material to the steel product 60 on which the optical fiber sensor 62 is stuck, so as to have the optical fiber sensor 62 covered; and connecting a measuring device to the optical fiber sensor 62 and measuring a strain on the basis of variation of characteristics of a lightwave propagated through the optical fiber sensor 62. The degree of deterioration progress of the protective coating material applied to the steel product 60 is detected based on the measured strain.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for detecting the progress of deterioration of a protective coating applied to a steel material.

  Conventionally, in a structure using a steel material such as an iron bridge or a plant, a protective coating is used so that the steel material does not rust. This protective coating deteriorates over time due to penetration of corrosive factors and ultraviolet rays. For this reason, a method for detecting deterioration by measuring the thickness by fluorescent X-rays and a method for detecting deterioration by connecting a cable to a steel material and measuring a change in electrical characteristics accompanying corrosion have been proposed. . However, the former is not suitable for on-site measurement and has the disadvantage of being expensive, while the latter has the disadvantage of inferior sensitivity and accuracy. For these reasons, these methods are difficult to adopt, and conventionally, peeling of protective paint and inspection for rusting have been performed mainly by visual inspection. However, it is not easy to systematically repaint the protective paint and predict when it should be repainted in the future by the method of simply visual inspection. As a result, conventionally, the entire surface of the structure is regularly repainted with a protective coating.

JP 2013-053916 A JP 2012-208088 A

  However, since the deterioration of the protective coating of the structure does not progress uniformly, even if some deterioration has progressed, there may be places where other repainting is not yet required There is sex. In spite of this, since the entire surface of the structure has been regularly repainted with protective paint, unnecessary costs have been incurred. Since the soundness of steel is managed by the soundness of the protective paint, if it is possible to grasp the time for repainting at various locations in the structure, it is possible to reduce the life cycle cost while ensuring safety. It becomes. On the other hand, since the protective coating applied to the steel material is thin, it is not easy to grasp and manage the deterioration state of the coating.

  The present invention has been made in view of such circumstances, and provides a deterioration detection method and a corrosion sensor capable of detecting the progress of deterioration of a protective coating film of a steel material and grasping the time when the protective coating should be reapplied. The purpose is to provide.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the deterioration detection method of the present invention is a deterioration detection method for detecting the progress of deterioration of a protective coating applied to a steel material, the step of attaching an optical fiber sensor to the surface of the steel material, and the optical fiber sensor being attached. Applying a protective paint to the steel material so that the optical fiber sensor is coated, and connecting a measuring instrument to the optical fiber sensor, and changing the characteristics of light waves propagating through the optical fiber sensor. And measuring the strain, and detecting a progress of deterioration of the protective coating applied to the steel material based on the measured strain.

  As described above, since the optical fiber sensor having a small diameter is used, it can be installed between the protective coating film having a small thickness and the steel material. Also, there are few defects in the coating film. In addition, it is possible to detect the progress of the deterioration of the protective coating on steel and to know when to reapply the protective coating. As a result, it is possible to set an effective and efficient coating cycle. Thus, cost reduction can be achieved.

  (2) The degradation detection method of the present invention is a degradation detection method for detecting the progress of degradation of the protective coating applied to the steel material, the step of attaching an optical fiber sensor to the surface of a metal plate, and the light A step of affixing a metal plate to which a fiber sensor is affixed to a surface of a steel material; a step of applying a protective coating to the steel material to which the metal plate is affixed so as to cover the optical fiber sensor; and the optical fiber Connecting a measuring instrument to the sensor and measuring strain based on a change in characteristics of the light wave propagating through the optical fiber sensor, and the protection applied to the steel material based on the measured strain It is characterized by detecting the progress of paint deterioration.

  As described above, since the optical fiber sensor is attached to the surface of the metal plate, the work of attaching the optical fiber at the site (site) is not required, and the work is simply performed by attaching the metal plate. In addition, the optical fiber can be attached to the metal plate with an appropriate tension in the room, not at the site, and the detection accuracy is increased. Therefore, construction on site is carried out as usual, and labor is not increased. Moreover, since it becomes possible to change the thickness of the protective coating film of a metal plate correctly in steps, it becomes possible to detect the progress of deterioration of the protective coating in steps.

  (3) Moreover, the deterioration detection method of this invention provides the dummy sensor which stuck the antirust coating on the surface of the steel material or the metal plate before sticking the optical fiber sensor on the surface of the steel material or the metal plate, The method further includes the step of detecting strain generated by factors other than corrosion and correcting the detected strain.

  With this configuration, it is possible to discriminate between distortion due to corrosion and other distortions, that is, distortion due to temperature or external force. Thereby, it becomes possible to remove the influence of strain due to temperature and external force. As a result, only distortion due to corrosion can be detected with high accuracy.

  (4) Moreover, the deterioration detection method of this invention provides the dummy sensor by which the anti-corrosion process which the corrosion factor did not permeate | penetrate was provided in the surface of the said stuck optical fiber sensor, and factors other than corrosion using a dummy sensor The method further includes the step of detecting the distortion generated in step 1 and correcting the detected distortion.

  With this configuration, it is possible to discriminate between distortion due to corrosion and other distortions, that is, distortion due to temperature or external force. Thereby, it becomes possible to remove the influence of strain due to temperature and external force. As a result, only distortion due to corrosion can be detected with high accuracy.

  (5) Further, the corrosion sensor of the present invention is a corrosion sensor for detecting the progress of deterioration of the protective coating applied to the steel material, the optical fiber sensor, the steel material holding the optical fiber sensor, and the optical fiber. And a protective paint for covering the steel material to which the optical fiber sensor is attached, and the characteristics of the light wave propagating through the optical fiber sensor change due to corrosion of the steel material.

  With this configuration, the work of attaching the sensor at the site (site) is not required, and the work is simply to install the sensor in the same environment as the object. In addition, the optical fiber can be stretched with an appropriate tension force in the room, not at the site, and the detection accuracy becomes high. Therefore, construction on site is carried out as usual, and labor is not increased. Furthermore, it can also be installed in a place where measurement is easy.

  According to the present invention, since an optical fiber sensor having a small diameter is used, it can be installed between a protective coating film having a small thickness and a steel material. Moreover, the defect | deletion part of a coating film also decreases. In addition, it is possible to detect the progress of the deterioration of the protective coating on steel and to know when to reapply the protective coating. As a result, it is possible to set an effective and efficient coating cycle. Thus, cost reduction can be achieved.

It is a figure which shows Embodiment 1 which concerns on this invention. It is a figure which shows a mode that the sensor was stuck on the side surface of H steel, and the protective coating was apply | coated. It is a figure which shows the usage example of the sensor which concerns on Embodiment 2. FIG. It is a figure which shows a mode that the metal plate which has an optical fiber sensor was stuck on steel materials, and the protective coating film was given. It is a figure which shows the test body which concerns on a verification example. It is a graph which shows the relationship between the elapsed time and distortion in a corrosive environment. It is a graph which shows the verification result which made the optical fiber sensor 3 turns to steel materials. It is a figure which shows the outline | summary of the test body which concerns on the verification example 2. FIG. It is a figure which shows a measurement result.

  The case where an optical fiber sensor is affixed on the surface of steel materials is illustrated as a corrosion detection method which concerns on this embodiment. In this corrosion sensor, it is possible to detect corrosion of the steel material itself. When the steel material is corroded, the optical fiber is stretched due to the volume expansion of the corrosion product. By detecting this elongation with a measuring instrument such as a data logger via an optical fiber sensor, it is diagnosed whether the steel is in a corrosive environment, whether a corrosive factor has entered, and whether the steel is corroded. It becomes possible to do. As the steel material, a steel material used in a structure may be used, or a steel material may be separately prepared and a sensor may be installed. Separately, when a sensor is installed by preparing a steel material, the sensor is installed so that the sensor does not move or drop out in the periphery where the measurement target and the environment are the same. When using the steel material used for the structure, it is not necessary to separately prepare or attach the steel material.

[Embodiment 1]
FIG. 1 is a diagram showing Embodiment 1 according to the present invention. In the first embodiment, the optical fiber sensor 62 is directly attached to the plane of the steel material 60. For example, as shown in FIG. 2, an optical fiber sensor 62 is attached to the side surface of H steel, and a protective coating is applied. As a result, the optical fiber sensor 62 can be provided directly on the steel material without processing the steel material. As a result, early detection of steel corrosion is possible. Further, it becomes possible to accurately detect strain due to corrosion.

  When applying protective paint to metal structures to be measured, such as steel bridges, plant equipment, street lamps, underground pipes, tanks, ships, etc., an optical fiber sensor 62 is placed on the surface of the metal material before application. Affix it. As the optical fiber sensor 62, an FBG sensor or the like can be used. When the optical fiber sensor 62 is attached to the steel material 60, it may be arranged in a straight line, but it may be bent. When the optical fiber sensor 62 is attached to the steel material 60, the optical fiber sensor 62 is wound so as to be in close contact, preferably with a tensile force applied, and both ends are fixed with an adhesive. Thereby, both the expansion side and the contraction side strain can be measured. Then, it protects so that it may not be damaged by a wind and rain etc. until a protective paint is applied. As a material to be protected, a film, a seal, or a material that dissolves with a paint may be covered.

  The length of the optical fiber sensor is preferably 5 mm to 500 mm. If the length of the optical fiber sensor is 500 mm or more, it is difficult to handle the optical fiber sensor and it may be damaged when the protective coating is applied. Further, when the length of the optical fiber sensor is 5 mm or less, the corrosion range to be detected is narrow and the strain is also small, so the detection accuracy is inferior.

  In the present embodiment, the optical fiber sensor and its end are exposed outside the protective coating and connected to the measuring instrument. Here, since the optical fiber sensor has a small diameter, the sensor can be installed without causing a coating film defect that occurs when the optical fiber sensor is pulled out. Alternatively, it may be taken out so that it can be connected to a measuring instrument or an optical fiber, or it may be wired so that it can be constantly monitored.

[Embodiment 2]
FIG. 3 is a diagram illustrating a usage example of the sensor according to the second embodiment. In the first embodiment described above, the optical fiber sensor is directly attached to the flat surface of the steel material. However, according to this embodiment, the optical fiber sensor 66 is attached to the metal plate 64 and the metal plate 64 is attached to the steel material. FIG. 4 is a view showing a state in which a protective metal coating 72 is applied by attaching a metal plate 64 having an optical fiber sensor 66 to a steel material 70. The material of the metal plate (or metal foil) 64 is preferably the same as that of the steel material 70 to be measured, but may be iron or zinc which is more easily rusted for early detection. When the optical fiber sensor 66 is attached to the metal plate 64, the optical fiber sensor 66 is wound so as to be in close contact with each other, preferably with a tensile force applied, and both ends are fixed with an adhesive. If the optical fiber sensor 66 is attached to the metal plate 64 so that an appropriate tensile force is applied in the room in advance, the corrosion sensor can be installed simply by attaching the metal plate 64 to the steel material to be installed. An adhesive is used to attach the metal plate 64 to the steel material 70.

  In addition, the thickness of the protective coating 72 can be changed by changing the thickness of the metal plate 64. By disposing a plurality of types of sensors having different thicknesses of the metal plate 64, the thickness of the protective coating 72 can be accurately changed, and stepwise deterioration detection can be performed. In this case, at the same time, it is possible to grasp the protective performance of the coating film in the actual local environment. Moreover, you may change the frequency | count of application | coating of the protective coating 72. FIG. For example, the invasion of the corrosion factor can be detected in advance by reducing the number of times of applying the undercoat only in the sensor attachment portion.

  For this reason, it becomes possible to grasp | ascertain the risk of corrosion earlier than the protective coating film 72 of the metal structure used as object. Furthermore, by changing the thickness of the metal plate 64 step by step and arranging a plurality of sensors having a plurality of types of thickness, it is possible to grasp the progress of deterioration in time series, and the durability of the coating film Preventive maintenance and management such as predicting systematic and systematic and efficient paint repainting.

  The thickness of the metal plate 64 according to the present embodiment is preferably 0.05 mm or more and 0.5 mm or less. For example, when the sensor is configured with the metal plate 64 having a thickness of 0.5 mm or less, it is particularly suitable when the sensor is embedded in the protective coating film 72. Since the thickness of the metal plate 64 (metal foil) is 0.5 mm or less, the metal plate 64 is flexible and can accommodate curved shapes such as pipes and tanks in a chemical factory plant or a spherical gas tank. In addition, it does not become an obstacle during application. If the thickness of the metal plate 64 (metal foil) is less than 0.05 mm, it may be damaged, and an appropriate tensile force cannot be applied. For example, by configuring the sensor with three types of thicknesses of the metal plate 64 (metal foil) of 0.05 mm, 0.1 mm, and 0.15 mm, and arranging these three types of sensors on the surface of the steel structure, It becomes possible to detect the progress of deterioration of the protective coating film in stages.

  The metal plate 64 may be stuck on the protective coating film 72 of the metal structure. In this case, the same protective coating as that of the metal structure is applied to the corrosion sensor.

[Embodiment 3]
This embodiment is a mode in which an optical fiber sensor is installed according to the above-described embodiment, and is installed with a dummy sensor that has been subjected to rust prevention treatment so as not to detect corrosion. In other words, the strain caused by factors other than corrosion is detected using a dummy sensor, and the strain detected by the optical fiber sensor is corrected, so that the strain due to corrosion can be accurately detected. Thereby, for example, it becomes possible to remove the influence such as shrinkage strain of the steel material due to temperature.

  As a manufacturing method of the dummy sensor, after placing an optical fiber sensor on the surface of a steel material or a metal plate, a resin (for example, an epoxy resin) or a paint (for example, an epoxy resin) that prevents the neutralization or invasion of deterioration factors from the protective coating used. There is a method to prevent corrosion of the internal steel material by coating with zinc rich paint) or plating. This method is suitable for attaching an optical fiber sensor directly to a steel material.

  As a method for manufacturing the dummy sensor, a metal plate such as titanium or a noble metal is attached to a steel material, and then the optical fiber sensor is attached to the metal plate. This method is suitable for attaching an optical fiber sensor to a metal foil.

 Moreover, when there exists a part which does not produce corrosion, such as the inside of a steel pipe or a round steel, an optical fiber sensor may be installed in the part, and a dummy sensor may be used.

[Embodiment 4]
In the above embodiment, the optical fiber sensor is installed on the steel material of the target structure. However, this embodiment is a mode in which the steel material to which the optical fiber sensor is separately attached is installed as a corrosion sensor. . That is, the steel material of the above embodiment is replaced with a small steel material. For example, an optical fiber sensor is attached to a small iron bar or iron plate made of the same material as the object, and a protective paint is applied. The attachment method is the same as in the above embodiment. The sensor manufactured in the present embodiment is only installed by taking measures so that it does not move or drop out to the periphery of an object whose environment is the same as the object to be measured. The sensor of this embodiment can be used if it is precisely manufactured indoors and transported to a measurement location without being manufactured on site. Therefore, construction on site is carried out as usual, and labor is not increased, and no additional work such as attaching a sensor to the structure is required. It can also be installed in a place where measurement is easy.

[Verification example]
FIG. 5 is a view showing a test body used for verifying whether the optical fiber sensor detects strain due to corrosion of metal. As shown in FIG. 5, the test body 40 is configured by winding an optical fiber sensor 51 around a steel bar 50 and covering with a hardened cement body 52 such as mortar. With respect to the test body 40, the vertical fog is 20 mm, and the horizontal fog is 10 mm. In FIG. 5, an example in which the optical fiber sensor 51 is wound once with respect to the steel bar 50 is shown. Next, a specific verification example of the test body 40 is shown.

  JIS G 3108 SGD3M was used as the polished steel bar. The method of winding the optical fiber around the polished steel bar is under certain tension, for example, after confirming that some tensile strain has occurred during winding, and then winding the wire with CN (manufactured by Tokyo Sokki). Fixed. An optical fiber sensor (FBG sensor) having the specifications shown in Table 2 was used. In addition, it is preferable to detect corrosion based on the difference in strain behavior of the dummy sensor, and it is expected that the influence of volume change and moisture content of the coated mortar will appear in the strain. The body was made.

Next, the covering mortar will be described. The materials used for the mortar are as shown in the following table.

なお、上記の表中、「Ｂ」とは、「Ｃ」と「Ｌ」とを混合したものである。 Next, the composition of the mortar is as shown in the following table.

In the above table, “B” is a mixture of “C” and “L”.

[Mortar mixing method]
The mortar used for the test body was kneaded using a “Maruto Seisakusho mortar mixer (2 L kneading)”. The mixing procedure is as follows. The mortar was kneaded in a constant temperature and humidity chamber at 20 ± 2 ° C. and a humidity of 50% or more.

  Placing mortar into a PVC mold (inner diameter φ40 mm x height 50 mm, or inner diameter φ40 mm x height 65 mm), placing a steel bar wrapped with an optical fiber in the center, and then 3 hours in the same constant temperature and humidity chamber After curing, it was cured at 20 ° C. and humidity of 95% or more for 7 days and demolded.

  Specimen 40 under corrosive environment (temperature 40 ° C., immersed in NaCl: 10% aqueous solution for 1 day, humidity 60% dried for 3 days, again immersed in NaCl: 10% aqueous solution for 1 day, and thereafter dried at 60% humidity) The change in wavelength was measured using a measuring instrument (manufactured by Watanabe Seisakusho Co., Ltd.) In the immersion of the NaCl: 10% aqueous solution, a portion of 30 mm from the lower end of the test specimen (45 mm from the lower end of the test specimen in the case of three windings) was so immersed that the NaCl aqueous solution did not enter from the optical fiber lead-out portion. . The dummy specimen used here was the same specimen as the corrosion sensor without using a steel bar that does not corrode experimentally, and was immersed in pure water that does not corrode instead of using the NaCl aqueous solution.

ここで、ε：ひずみ（μ）、λ：測定時の波長（ｎｍ）、λ^*：初期波長（ｎｍ）である。 Using the following equation, the wavelength was converted to strain, and the change in strain due to corrosion was confirmed.

Here, ε: strain (μ), λ: wavelength at the time of measurement (nm), and λ ^* : initial wavelength (nm).

  FIG. 6 is a graph showing the relationship between elapsed time and strain in a corrosive environment. In the verification example with one winding shown in FIG. 6, since it was immersed in salt water or water on the 1st and 4th, the strain temporarily changed due to temperature change or mortar water absorption, but the dummy specimen also changed in the same way This is not due to corrosion. On the 16th, the strain amount of the test specimen and the dummy test specimen deviated. Then, when the covering mortar of the test body was removed, it was confirmed that the steel bar was corroded.

  The verification example with 3 windings shown in FIG. 7 is an example in which measurement is started after the temperature becomes constant and measurement is continued after corrosion. Corrosion cracks occurred on the 45th measurement day. It has been proved that it is possible to continuously capture the expansion due to corrosion until cracking occurs.

[Verification Example 2]
In order to confirm whether or not the strain increases according to the corrosion situation, the corrosion situation was confirmed and the strain was measured with the optical fiber in the case where the optical fiber was wrapped around the steel material. As shown in FIG. 8, the test specimen was a φ20 mm steel bar 50 and one turn of the optical fiber sensor 51 in a measurement area height of 25 mm at the center. FIG. 9 is a diagram showing measurement results. Since it was in the atmosphere at 20 ° C. until the second day of measurement, as shown in circle 1, there was almost no corrosion, and immediately after that, salt water was applied to the center of the test body of the fiber 1 roll. After that, the strain increased rapidly, and the corrosion range in round 2 was 10% by visual judgment, and in round 3, the corrosion range was 35% by visual judgment. From the above results, it can be seen that the strain increases corresponding to the degree of corrosion.

  Thereby, it becomes possible to detect the progress of deterioration of the protective coating locally. As a result, an effective and efficient coating cycle can be set, and the life cycle cost can be reduced.

40 Specimen 50 Steel bar 51 Optical fiber sensor 52 Cement hardened body (mortar)
60 Steel 62 Optical fiber sensor 64 Metal plate (metal foil)
66 Optical fiber sensor 70 Steel 72 Protective coating

Claims (5)

A deterioration detection method for detecting the progress of deterioration of a protective coating applied to a steel material,
Attaching the optical fiber sensor to the surface of the steel material;
Applying a protective coating to the steel material to which the optical fiber sensor is attached so that the optical fiber sensor is coated;
Connecting a measuring instrument to the optical fiber sensor, and measuring strain based on a characteristic change of a light wave propagating in the optical fiber sensor,
A degradation detection method, comprising: detecting a progress of degradation of the protective coating applied to the steel material based on the measured strain. A deterioration detection method for detecting the progress of deterioration of a protective coating applied to a steel material,
Attaching the optical fiber sensor to the surface of the metal plate;
Attaching the metal plate to which the optical fiber sensor is attached to the surface of the steel material;
Applying a protective coating to the steel material to which the metal plate is attached so that the optical fiber sensor is coated;
Connecting a measuring instrument to the optical fiber sensor, and measuring strain based on a characteristic change of a light wave propagating in the optical fiber sensor,
A degradation detection method, comprising: detecting a progress of degradation of the protective coating applied to the steel material based on the measured strain.   Before applying the optical fiber sensor to the surface of the steel or metal plate, a dummy sensor with a rust-proof coating applied to the surface of the steel or metal plate is provided, and the dummy sensor is used to detect strains caused by factors other than corrosion. The deterioration detection method according to claim 1, further comprising a step of correcting the detected distortion.   On the surface of the affixed optical fiber sensor, a dummy sensor that has been subjected to a rust prevention treatment that does not allow corrosion factors to permeate is provided, and the strain generated by factors other than corrosion is detected using the dummy sensor, and the detected strain is detected. The deterioration detection method according to claim 1, further comprising a correction step. A corrosion sensor that detects the progress of deterioration of the protective coating applied to steel,
An optical fiber sensor;
A steel material for holding the optical fiber sensor;
A protective paint for covering the optical fiber sensor and the steel material to which the optical fiber sensor is attached,
A corrosion sensor characterized in that a change occurs in characteristics of a light wave propagating through an optical fiber sensor due to corrosion of the steel material.

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