JP6671661B2 - Film deterioration detection method - Google Patents

Description

  The present invention relates to a method for detecting deterioration of a coating film applied to a surface of a base material.

  BACKGROUND ART In a structure such as a bridge, a steel material is used as a base material in order to secure necessary strength and the like. A coating film is applied to the surface of the steel material to prevent rust from occurring.

  Patent Literature 1 below discloses a paint film deterioration diagnosis system that performs image processing on image data of a paint film surface photographed by photographing means and evaluates the state of deterioration of the paint film using the processed image data. ing. Specifically, the coating film deterioration diagnosis system described in Patent Literature 1 evaluates the deterioration state of the coating film based on at least one of a peeling state, a rust state, and a color state of the coating surface.

JP 2005-283519 A

  The coating film applied to the surface of the steel material is consumed by aging. Therefore, it is necessary to detect the wear of the coating film at an early stage and apply the coating film again to the area where the coating film has been consumed, thereby preventing rust from being generated in the steel material. In general, the coating film is composed of a plurality of layers. In this case, it is necessary to detect the wear of the outermost first layer of the coating film at an early stage. There is a problem that it is difficult to do. Specifically, the outermost first layer and the second layer immediately below the outermost layer of the coating film composed of a plurality of layers are formed in order to suppress the influence of the color of the second layer on the color of the first layer. Colors similar to each other are adopted as the colors of. Therefore, even if the coating film deteriorates and the first layer peels off to expose the second layer, it is difficult to visually confirm the exposure of the second layer. It is also difficult to confirm that the first layer is thin.

  Patent Literature 1 describes that the deterioration state of a coating film is evaluated based on the peeling state of the coating film surface. However, specific determination of a portion where the coating film remains and a portion where the coating film has peeled is described. No method is disclosed.

  Patent Literature 1 describes that a deterioration state of a coating film is evaluated based on a color state. However, this method monitors a temporal change in color itself of a coating film surface due to deterioration. However, there is no suggestion as to a specific method of determining the portion where the coating film remains and the portion where the coating film has peeled off.

  An object of the present invention is to provide a coating film deterioration detecting method capable of easily detecting a state in which the outermost layer among a plurality of coating films has been consumed.

  In order to achieve the above object, the inventors of the present application have studied by focusing on the spectral characteristics of the reflected light of the outermost first layer and the second layer immediately below the first layer. Was. As a result, in a specific wavelength region, there is a remarkable difference between the spectral characteristics of the reflected light of the first layer and the spectral characteristics of the reflected light of the second layer, as compared with the difference in color recognized by the naked eye. I found it. Further, since the light transmittance of the first layer increases as the thickness of the first layer decreases, the influence of the spectral characteristics of the reflected light of the second layer is greater than the spectral characteristics of the reflected light of the first layer. I also found out. Then, it has been found that by utilizing such characteristics, the consumption of the first layer can be easily detected. The present invention has been completed based on such findings.

  A method for detecting deterioration of a coating film according to the present invention comprises detecting deterioration of the first layer in a coating film having a first layer applied to a base material and located outermost and a second layer located immediately below the first layer. In the detection method, a spectral characteristic obtaining step of obtaining spectral characteristics of a wavelength region included in at least one of a visible region and a near-infrared region of the reflected light of the first layer and the second layer; Based on the spectral characteristics of the first layer and the second layer, the difference that occurs in the spectral characteristics of the first layer and the second layer in the wavelength region where the spectral characteristics of the first layer and the second layer is obtained. A detection wavelength region setting step of setting a detection wavelength region larger than the other wavelength regions, and a detection transmission filter preparing step of preparing a detection transmission filter that transmits light in a wavelength region included in the detection wavelength region. Through the detection transmission filter Based on the image of the photographed the coating film, and a detection step of detecting a depletion of the first layer.

  In the coating film deterioration detection method, the spectral characteristic of the reflected light of the first layer and the spectral characteristic of the reflected light of the second layer in the wavelength region of light transmitted through the transmission filter for detection are compared with those in other wavelength regions. Significant differences occur. Therefore, the influence of the spectral characteristics of the reflected light of the second layer easily changes according to the thickness of the first layer. As a result, the consumption of the first layer (that is, a decrease in the thickness of the first layer) can be detected from the image of the coating film taken through the transmission filter for detection.

  The detection step is preferably based on an image of the coating film taken through the transmission filter for detection, the second layer is exposed by depletion of the first layer until the first layer is peeled off. And detecting the presence of the user.

  According to this method, the first layer and the second layer can be clearly distinguished in the image of the coating film taken through the transmission filter for detection. The wear of the layer can be captured.

  Alternatively, the detection step preferably includes detecting the detection based on a relationship between a previously acquired thickness of the first layer and an influence of a spectral characteristic of reflected light of the first layer on an image of the coating film. Estimating the thickness of the first layer remaining in a state where the thickness is smaller than the initial thickness from an image of the coating film taken through a transmission filter for use.

  According to this method, since the area of the first layer having a different thickness can be clearly distinguished in the image of the coating film taken through the transmission filter for detection, the first image is obtained from the image of the coating film taken through the transmission filter for detection. The wear of the layer can be captured.

  In the aspect in which the thickness of the first layer is estimated from the image of the coating film captured through the transmission filter for detection, preferably, the detection step includes the step of determining the thickness of the first layer and the spectral characteristics of the reflected light of the first layer. The method further includes obtaining a relationship between the influence of the coating film on an image.

  In this method, the thickness of the first layer can be estimated using the acquired relationship.

  In the coating film deterioration detection method, preferably, in the spectral characteristic acquiring step, a spectral characteristic of a specific wavelength region included in at least the near infrared region of the reflected light of the first layer and the second layer is acquired. In the detection transmission filter preparing step, a near-infrared light transmission filter that transmits light in a wavelength region included in the specific wavelength region is prepared as the detection transmission filter. The consumption of the first layer is detected based on an image of the coating film taken through the near-infrared light transmission filter in an environment where the coating film is directly or indirectly irradiated.

  In this method, near-infrared light can be included in the reflected light of the coating film by using sunlight. As a result, the consumption of the first layer can be detected using the difference in the spectral characteristics of the first layer and the second layer in the near infrared region.

  The method for detecting the deterioration of the coating film, or alternatively, preparing a lighting device capable of irradiating infrared light, further comprising an infrared irradiation step of irradiating the coating film with infrared light using the lighting device, in the spectral characteristic obtaining step, The spectral characteristics of at least a specific wavelength region included in the near-infrared region of the reflected light of the first layer and the second layer are acquired, and in the detection transmission filter preparing step, the identification transmission filter is used as the detection transmission filter. Preparing a near-infrared light transmitting filter that transmits light in a wavelength region included in the wavelength region, and in the detecting step, the near-infrared light transmitting filter in an environment where the coating film is irradiated with infrared light from the lighting fixture. The consumption of the first layer is detected based on the image of the coating film taken through the camera.

  In this method, even in an environment where sunlight is not irradiated, near-infrared light can be included in the reflected light of the coating film by irradiating infrared rays from the lighting equipment. The consumption of the first layer can be detected by using the difference in the spectral characteristics between the first layer and the second layer in the outer region.

  Preferably, the coating film deterioration detection method includes the step of detecting the spectral characteristics of the first layer and the second layer based on the acquired spectral characteristics of the first layer and the second layer. A comparison wavelength region setting step of setting a comparison wavelength region in which the difference in the spectral characteristics of the first layer and the second layer is smaller than the wavelength region for comparison, and light in the wavelength region included in the comparison wavelength region. Further comprising a comparative transmission filter preparing step of preparing a comparative transmission filter to be transmitted, wherein in the detecting step, the image of the coating film photographed through the detection transmission filter and the photographed through the comparison transmission filter are photographed. The exhaustion of the first layer is detected by comparing with the image of the coating film.

  In this method, the image of the coating film in the detection wavelength region is compared with the image of the coating film in the comparison wavelength region in which the difference between the spectral characteristics of the first layer and the second layer is smaller than that in the detection wavelength region. This makes it possible to more reliably detect the consumption of the first layer as compared with the case where only the image of the coating film in the detection wavelength region is referred to.

  In the method for detecting deterioration of a coating film according to the present invention, the consumption of the first layer can be easily detected.

It is a schematic diagram which shows the steel material with which the coating film was applied as a detection target by the coating film deterioration detection method according to the embodiment of the present invention. 5 is a flowchart illustrating a method for detecting deterioration of a coating film according to an embodiment of the present invention. It is a graph which shows the spectral characteristic in the near-infrared region of a top coat layer and a middle coat layer acquired in a spectral characteristic acquisition process. It is the photograph of the test piece image | photographed without using any transmission filter. It is a photograph of the test piece image | photographed using the transmission filter for detection. It is a photograph of the test piece image | photographed using the transmission filter for a comparison. 9 is a flowchart illustrating a modification of the method for detecting deterioration of a coating film according to the embodiment of the present invention. It is explanatory drawing which shows several area | regions in a test piece. 9 is a graph showing a luminance value of an intermediate coating layer on the line shown in FIG. 8.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The coating film deterioration detection method according to the embodiment of the present invention is a method for detecting deterioration of a coating film having a plurality of layers applied to the surface of a steel material as a base material to be protected from corrosion. A steel material is used for a member constituting a structure. The structure is installed on the ground, for example. The structure may be one that can be removed while maintaining its function after installation, or one that cannot be removed while maintaining its function after installation. The structure may be, for example, a bridge, a storage tank for storing gas or liquid, or a pipe for transporting gas or liquid.

  The coating film 20 applied to the surface of the steel material 10 will be described with reference to FIG. FIG. 1 is a schematic diagram showing a steel material 10 and a coating film 20.

  The steel material 10 is used, for example, as a member forming a bridge. The steel material 10 exists in an environment where sunlight is directly or indirectly irradiated.

  The coating film 20 is applied to the surface of the steel material 10 to suppress rust on the surface of the steel material 10. The coating film 20 is composed of a plurality of layers, and includes a sacrificial anticorrosion layer 21, an undercoat layer 22, an intermediate coat layer 23, and an overcoat layer 24.

  Here, the overcoat layer 24 is the outermost layer of the coating film 20, that is, the first layer. Therefore, the overcoat layer 24 first deteriorates under the influence of the environment in which the steel material 10 exists. The deterioration factor of the overcoat layer 24 is, for example, sunlight irradiated on the overcoat layer 24 or fine particles that collide with the overcoat layer 24 due to wind.

  The intermediate coating layer 23 is a layer located immediately below the upper coating layer 24 as a first layer, that is, a second layer. The color of the middle coat layer 23 is similar to the color of the top coat layer 24. Thereby, the color of the upper coating layer 24 is less affected by the color of the intermediate coating layer 23. That is, it is difficult to visually recognize the state in which the top coat layer 24 is peeled off and the middle coat layer 23 is exposed.

  Hereinafter, a plurality (four in this embodiment) of the layers constituting the coating film 20 will be described.

  The sacrificial anticorrosion layer 21 directly covers the surface of the steel material 10 and protects the surface of the steel material 10. The sacrificial anticorrosion layer 21 is set to have a higher ionization tendency than the steel material 10 so as to corrode before the steel material 10. That is, the sacrificial anticorrosion layer 21 has excellent anticorrosion properties due to the electric anticorrosion action. The sacrificial anticorrosion layer 21 functions as a base for suppressing the generation of rust on the surface of the steel material 10. The sacrificial anticorrosion layer 21 is, for example, an inorganic zinc-rich paint.

  It is difficult to repaint the sacrificial anticorrosion layer 21 in a state where a structure made of the steel material 10 is installed. Therefore, in order to prevent the sacrificial anticorrosion layer 21 from deteriorating, the undercoat layer 22 covers the sacrificial anticorrosion layer 21.

  The undercoat layer 22 protects the sacrificial anticorrosion layer 21 by directly covering the sacrificial anticorrosion layer 21. The undercoat layer 22 has water resistance and the like. The undercoat layer 22 has a greater thickness than the sacrificial anticorrosion layer 21. The undercoat layer 22 is, for example, an epoxy resin paint.

  The middle coat layer 23 is located between the top coat layer 24 and the undercoat layer 22, and functions as an adhesive for bonding the top coat layer 24 and the undercoat layer 22. The intermediate coating layer 23 covers the undercoat layer 22. The intermediate coating layer 23 has a thickness smaller than that of the undercoat layer 22. The color of the middle coat layer 23 is set to a color similar to the color of the top coat layer 24 so that the influence on the color of the top coat layer 24 is reduced. The intermediate coating layer 23 is, for example, an epoxy resin paint.

  The overcoat layer 24 is located on the most front side in a plurality (four in the present embodiment) of the layers constituting the coating film 20. That is, it is the overcoat layer 24 that is easily affected by the environment in the coating film 20. In other words, the first thing that deteriorates in the coating film 20 is the overcoat layer 24. Therefore, the overcoat layer 24 has better weather resistance than other layers. That is, the overcoat layer 24 is less likely to deteriorate than other layers. The top coat layer 24 covers the middle coat layer 23. The top coat layer 24 has a slightly smaller thickness than the middle coat layer 23. The overcoat layer 24 may be, for example, a fluororesin paint or a polyurethane resin paint.

  A method for detecting the deterioration of the coating film 20 will be described with reference to FIG. FIG. 2 is a flowchart illustrating a method for detecting deterioration of the coating film 20 in an environment where sunlight is directly or indirectly irradiated.

  In the present embodiment, when the deterioration of the coating film 20 is detected, it is confirmed whether or not the top coat layer 24 has been peeled and the intermediate coat layer 23 has been exposed. Here, as described above, since the color of the middle coat layer 23 is similar to the color of the top coat layer 24, it is necessary to visually check the state where the top coat layer 24 is peeled and the middle coat layer 23 is exposed. Although it is difficult, according to the method for detecting deterioration of the coating film 20 according to the present embodiment, it is possible to easily detect a state in which the top coat layer 24 is peeled off and the middle coat layer 23 is exposed. Specifically, the method for detecting the deterioration of the coating film 20 according to the present embodiment utilizes the remarkable difference in the spectral characteristics between the overcoat layer 24 and the middle coat layer 23 in a specific wavelength region, and thereby allows the middle coat layer 24 and the middle coat layer 23 to have the same characteristics. Regardless of the color approximation of the coating layer 23, the distinction can be made clearly.

  The method for detecting the deterioration of the coating film 20 includes a spectral characteristic acquisition step S11, a wavelength region setting step S12, a filter preparation step S13, and a detection step S14. These steps are performed in this order. Hereinafter, these steps will be described.

  The spectral characteristic acquiring step S11 is a step of acquiring spectral characteristics of a wavelength region included in at least one of a visible region and a near-infrared region in the reflected light of the topcoat layer 24 and the middle coat layer 23. In the present embodiment, the spectral characteristic acquiring step S11 is a step of acquiring spectral characteristics of a specific wavelength region included in at least a near-infrared region of the reflected light of the top coat layer 24 and the middle coat layer 23. The near-infrared region is, for example, a region where the wavelength of light is 800 nm to 2500 nm.

  The spectral characteristics of the top coat layer 24 and the middle coat layer 23 can be obtained, for example, by measuring samples of the top coat layer 24 and the middle coat layer 23 with a spectrophotometer. For obtaining the spectral characteristics, for example, a diffuse reflection method is used.

  FIG. 3 is a graph showing an example of the spectral characteristics in the near-infrared region of the overcoat layer 24 and the middle coat layer 23 acquired in the spectral characteristic acquisition step S11. FIG. 3 shows the diffuse reflection spectrum of the top coat layer 24 and the middle coat layer 23. In FIG. 3, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents absorbance. In FIG. 3, graph 1 shows the spectral characteristics of the top coat layer 24, and graph 2 shows the spectral characteristics of the middle coat layer 23.

  The difference in spectral characteristics between the topcoat layer 24 and the middle coat layer 23 is caused by the respective components of the topcoat layer 24 and the middle coat layer 23. That is, unless the components of the overcoat layer 24 and the middle coat layer 23 are exactly the same, the difference in spectral characteristics between the topcoat layer 24 and the middle coat layer 23 occurs in any wavelength region. Components that affect the difference in spectral characteristics are, for example, coating components such as pigments, resins, and additives. The coating film component is a component of the paint that remains as a paint film even after the paint is dried.

  The wavelength region setting step S12 is a step of setting a wavelength region that serves as a reference when determining the wavelength region of light transmitted by the transmission filter prepared in the filter preparing step S13. The wavelength region setting step S12 is performed based on the spectral characteristics of the overcoat layer 24 and the intermediate coating layer 23 acquired in the spectral characteristic acquisition step S11.

  The wavelength region setting step S12 includes a detection wavelength region setting step S121 and a comparison wavelength region setting step S122. The detection wavelength region setting step S121 is based on the spectral characteristics of the top coat layer 24 and the middle coat layer 23 acquired in the spectral characteristic acquisition step S11, and the upper coat layer 24 and the middle coat layer in the wavelength region where the spectral characteristics are acquired. This is a step of setting a detection wavelength region in which a difference in the spectral characteristics of the layer 23 is larger than other wavelength regions. The comparison wavelength region setting step S122 is based on the spectral characteristics of the overcoat layer 24 and the middle coating layer 23 acquired in the spectral characteristic acquisition step S11, and is located above the detection wavelength region in the wavelength region in which the spectral characteristics have been acquired. This is a step of setting a comparison wavelength region in which a difference in spectral characteristics between the coating layer 24 and the intermediate coating layer 23 is small. The difference occurring in the spectral characteristics between the topcoat layer 24 and the middle coat layer 23 is, for example, a difference in absorbance between the topcoat layer 24 and the middle coat layer 23.

  In the case of the spectral characteristics shown in FIG. 3, a region whose wavelength is shorter than 1500 nm is set as the detection wavelength region, and a region whose wavelength is longer than 1500 nm is set as the comparison wavelength region. The reason is as follows.

  As shown in FIG. 3, the spectral characteristics of the top coat layer 24 and the middle coat layer 23 are significantly different from each other at a position where the wavelength is about 1500 nm. Specifically, in the region where the wavelength is longer than 1500 nm, the difference in absorbance between the top coat layer 24 and the middle coat layer 23 is small, and the top coat layer 24 and the middle coat layer 23 show similar spectral characteristics. That is, in a region where the wavelength is longer than 1500 nm, the topcoat layer 24 and the middle coat layer 23 appear to have substantially the same brightness. On the other hand, in the region where the wavelength is shorter than 1500 nm, the difference in absorbance between the top coat layer 24 and the middle coat layer 23 is larger than in the region where the wavelength is longer than 1500 nm, and the top coat layer 24 and the middle coat layer 23 are different. Show completely different spectral characteristics. Specifically, the absorbance of the top coat layer 24 is considerably larger than the absorbance of the middle coat layer 23. That is, in the region where the wavelength is shorter than 1500 nm, the topcoat layer 24 looks darker than the middle coat layer 23.

  Therefore, the wavelength region for detection is set to a wavelength region where the difference in absorbance between the top coat layer 24 and the middle coat layer 23 is large, that is, a region where the wavelength is shorter than 1500 nm. The wavelength region for comparison is set to a wavelength region where the difference in absorbance between the top coat layer 24 and the middle coat layer 23 is small, that is, a region where the wavelength is longer than 1500 nm.

  The filter preparing step S13 is a step of preparing a transmission filter that transmits light in the wavelength region included in the wavelength region set in the wavelength region setting step S12. The transmission filter may be newly manufactured, or an appropriate one may be selected from those already manufactured.

  The filter preparation step S13 includes a detection transmission filter preparation step S131 and a comparison transmission filter preparation step S132. The detection transmission filter preparing step S131 is a step of preparing a detection transmission filter that transmits light in the wavelength region included in the detection wavelength region set in the detection wavelength region setting step S121. The comparison transmission filter preparing step S132 is a step of preparing a comparison transmission filter that transmits light in the wavelength region included in the comparison wavelength region set in the comparison wavelength region setting step S122.

  In the case of the spectral characteristics shown in FIG. 3, a transmission filter that transmits light in a region shorter than 1450 nm is prepared as a transmission filter for detection, and a transmission filter that transmits light in a region longer than 1400 nm is used as a comparison transmission filter. A transmission filter is prepared.

  The detection step S14 compares the image of the coating film captured through the transmission filter for detection with the image of the coating film captured through the transmission filter for comparison, whereby the topcoat layer 24 is peeled off and the intermediate coating layer 23 is exposed. This is a step of detecting the state of the vehicle. The image of the coating film 20 is taken by a camera. As the camera, for example, an appropriate camera is used according to the wavelength region of light transmitted by the transmission filter. For example, if the transmission filter transmits light in the near infrared region, an infrared camera is used as the camera. The difference between the top coat layer 24 and the middle coat layer 23 may be confirmed, for example, by visual observation or by performing appropriate image processing on the photographed image of the coating film 20.

  With reference to FIGS. 4, 5 and 6, a description will be given of a result of detecting a state in which the top coat layer 24 has been peeled and the middle coat layer 23 has been exposed using a test piece. FIG. 4 shows an image of a test piece taken without using any transmission filters. FIG. 5 shows an image of a test piece taken through a transmission filter for detection. FIG. 6 shows an image of a test piece taken through a comparative transmission filter.

  Referring to FIG. 4, in the test piece, the coating film of the wide portion (upper portion in the drawing) is the same as the overcoat layer 24, and the white portion of the narrow width portion (the lower portion in the drawing) is white. Is the same as the middle coat layer 23.

  In the image shown in FIG. 5 (that is, the image of the test piece photographed through the transmission filter for detection), the difference between the top coat layer 24 and the middle coat layer 23 is clearer than the images shown in FIGS. . That is, when the transmission filter for detection is used (see FIG. 5), the overcoat layer 24 and the intermediate coating layer 23 can be easily distinguished as compared with the case where the transmission filter for detection is not used (see FIG. 4). is there. Also, by comparing the image photographed through the transmission filter for detection (see FIG. 5) with the image photographed through the transmission filter for comparison (see FIG. 6), the top coat layer 24 and the middle coat layer 23 can be more reliably formed. It can be determined.

  In such a method for detecting the deterioration of the coating film 20, the difference in the spectral characteristics between the top coat layer 24 and the middle coat layer 23 in the wavelength region of light transmitted through the transmission filter for detection is larger than in other wavelength regions. . Therefore, in the image of the coating film 20 photographed through the transmission filter for detection, the difference between the colors of the top coat layer 24 and the middle coat layer 23 recognized by the naked eye, The differences are remarkably clear. That is, the above-described method enables the topcoat layer 24 and the middle coat layer 23 to be easily distinguished from each other even when the topcoat layer 24 and the middle coat layer 23 have similar colors. .

  In addition, since such a method for detecting deterioration of the coating film 20 is performed in an environment in which sunlight is directly or indirectly applied to the steel material 10, the overcoat layer 24 and the middle coating layer 23 in the near infrared region are used. The top coat layer 24 and the middle coat layer 23 can be distinguished by utilizing the difference in the spectral characteristics of.

  In addition, in such a method for detecting deterioration of the coating film 20, when detecting that the topcoat layer 24 is peeled off and the intermediate coating layer 23 is exposed, an image of the coating film in the detection wavelength region is provided, The comparison is made between the image of the coating film in the comparative wavelength region where the difference in the spectral characteristics between the top coat layer 24 and the middle coat layer 23 is smaller than the wavelength region for detection. Therefore, the top coat layer 24 and the middle coat layer 23 can be distinguished more reliably.

[Modification 1 of Embodiment]
Referring to FIG. 7, when the sunlight is not directly or indirectly applied to the steel material 10, the difference between the spectral characteristics of the top coat layer 24 and the middle coat layer 23 in the near infrared region is utilized. A method for detecting deterioration of the coating film for detecting the exposure of the coating layer 23 will be described. FIG. 7 is a flowchart showing such a coating film deterioration detection method.

  The coating film deterioration detecting method according to the present modification further includes an infrared irradiation step S10 as compared with the coating film deterioration detecting method according to the above embodiment. The infrared irradiation step S10 is a step of preparing a lighting device capable of irradiating infrared light so that the reflected light of the coating film 20 includes near-infrared light, and irradiating the coating film 20 with infrared light using the lighting device. . Irradiation of infrared rays in the infrared irradiation step S10 may be performed when the detection step S14 is performed. That is, the infrared irradiation step S10 is performed simultaneously with or before the detection step S14. In the example shown in FIG. 7, the infrared irradiation step S10 is performed immediately before the detection step S14. Illumination equipment that can emit infrared rays is, for example, a halogen heater, a xenon heater, a quartz heater, or the like.

[Modification 2 of Embodiment]
In the above-described embodiment, the state in which the middle coat layer 23 is exposed due to the consumption of the top coat layer 24 until the top coat layer 24 is peeled off (that is, the top coat layer 24 disappears) is detected. The state where the thickness of the overcoat layer 24 is small may be detected.

  In this case, the detection step is performed based on the relationship between the thickness of the overcoat layer 24 and the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20. Estimating the thickness of the overcoat layer 24 remaining in a state in which the thickness is smaller than the initial thickness from the image of No. 20 and determining the deterioration of the coating film 20 from the estimated thickness of the overcoat layer 24 Including.

  The effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20 can be an index of the thickness of the overcoat layer 24 in the image of the coating film 20. What can be an index of the thickness of the overcoat layer 24 in the image of the coating film 20 is, for example, the intensity of the reflected light of the overcoat layer 24. The intensity of the reflected light of the overcoat layer 24 appears as, for example, the luminance of the overcoat layer 24 in the image of the coating film 20.

  The relationship between the thickness of the overcoat layer 24 and the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20 is, for example, that the plurality of regions having different thicknesses of the overcoat layer 24 and the middle coat layer 23 are different. Using a sample having an exposed area, the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20 in each area was measured, and the reflected light of the overcoat layer 24 in each area was measured. Can be obtained by examining the relationship between the influence of the spectral characteristics of the coating film 20 on the image of the coating film 20 and the thickness of the overcoat layer 24.

  The relationship between the thickness of the overcoat layer 24 and the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20 may be acquired before the detection step, or may be acquired in the detection step. You may.

  The criterion for determining the deterioration of the coating film 20 from the estimated thickness of the overcoat layer 24 is, for example, when the estimated thickness of the overcoat layer 24 is equal to or less than half the thickness of the initial overcoat layer 24. .

  Referring to FIGS. 8 and 9, the relationship between the thickness of the overcoat layer 24 and the luminance value of the overcoat layer 24 in the image, which is the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20, is shown. An example of the relationship will be described. FIG. 8 is an explanatory diagram showing a plurality of regions 31 to 34 formed on the test piece 30 to which the light of the halogen lamp is irradiated using the transmission filter for detection. The test piece 30 has a plurality (three in the present embodiment) of regions 32, 33, and 34 in which the thickness of the top coat layer 24 covering the middle coat layer 23 is different from the region 31 where the middle coat layer 23 is exposed. Having. The thickness of the overcoat layer 24 in the region 32 is 14 μm, the thickness of the overcoat layer 24 in the region 33 is 20 μm, and the thickness of the overcoat layer 24 in the region 34 is 25 μm. In FIG. 8, each of the plurality of regions 32, 33, and 34 is meshed. The mesh increases as the thickness of the overcoat layer 24 increases. FIG. 9 is a graph showing the luminance value of the overcoat layer 24 in the image, which is the effect of the spectral characteristics of the reflected light of the overcoat layer 24 on the line segment SL shown in FIG. .

  As shown in FIG. 9, when the thickness of the overcoat layer 24 is different, the luminance value of the overcoat layer 24 changes. That is, there is some correlation between the thickness of the overcoat layer 24 and the luminance value of the overcoat layer 24. This will be described below. Note that the following description is conceptual.

The energy of the light irradiated to the overcoat layer 24 and E, the reflectivity of the overcoat layer 24, and the absorption ratio and transmittance, respectively [rho _1, and alpha ₁ and tau _1, the reflectivity of the intercoat layer 23, absorption rate And the transmittance are ρ ₂ , α ₂ and τ ₂ , respectively.

In this case, the energy E1 of light reflected by the overcoat layer 24 is represented by the following equation (1).
E1 = ρ ₁ E (1)

In addition, the energy E2 of light that enters the overcoat layer 24, is reflected by the middle coat layer 23, and then exits from the overcoat layer 24 is represented by the following equation (2).
E2 = ρ ₂ (τ ₁ E) −α ₁ {ρ ₂ (τ ₁ E)} (2)

  The luminance value of the overcoat layer 24 in the image of the coating film 20 has a correlation with the sum of the energies E1 and E2. This correlation can be expressed using, for example, a linear function or a quadratic function.

Here, the absorption α ₁ and the transmittance τ ₁ of the overcoat layer 24 included in the expression (2) representing the energy E2 depend on the thickness of the overcoat layer 24. That is, the energy E2 changes according to the thickness of the overcoat layer 24. Therefore, the luminance value of the overcoat layer 24 in the image of the coating film 20 changes according to the thickness of the overcoat layer 24. The correlation between the luminance value of the overcoat layer 24 and the thickness of the overcoat layer 24 in the image of the coating film 20 can be represented using, for example, a linear function, a quadratic function, or the like.

  In the present modification, the luminance value of the overcoat layer 24 is acquired from the image of the coating film 20 captured using the transmission filter for detection, and based on the correlation between the acquired luminance value and the thickness of the overcoat layer 24. , The thickness of the overcoat layer 24 can be estimated. Further, the deterioration of the coating film 20 can be determined from the estimated thickness of the overcoat layer 24.

  The present modification is not limited to a mode in which the thickness of the overcoat layer 24 is estimated after the correlation existing between the thickness of the overcoat layer 24 and the luminance value of the overcoat layer 24 is acquired in advance. For example, even if the correlation existing between the thickness of the overcoat layer 24 and the luminance value of the overcoat layer 24 is obtained in advance, and the degree of consumption of the overcoat layer 24 is estimated from the luminance value of the overcoat layer 24. Good.

  Although the embodiments of the present invention have been described in detail above, these are merely examples, and the present invention is not to be construed as being limited by the description of the above embodiments.

  For example, in the above embodiment, by comparing the image of the coating film taken through the transmission filter for detection with the image of the coating film taken through the transmission filter for comparison, the top coat layer 24 is peeled off and the middle coat layer 23 is removed. Was detected, but only the image of the coating film photographed through the transmission filter for detection was used to detect a state in which the topcoat layer 24 was peeled off and the middle coat layer 23 was exposed. You may. If only the image of the coating film photographed through the transmission filter for detection is used to detect the state in which the topcoat layer 24 is peeled off and the intermediate coating layer 23 is exposed, a wavelength region for comparison is set. There is no need to prepare a transmission filter for comparison.

  For example, in the above-described embodiment, the exposure of the middle coat layer 23 is detected by using the difference in spectral characteristics between the top coat layer 24 and the middle coat layer 23 in the near infrared region. Exposure of the intermediate coating layer 23 may be detected by using a difference in spectral characteristics between the layer 24 and the intermediate coating layer 23.

  For example, in the above embodiment, a configuration in which the coating film has a coating layer (undercoat layer 22 and sacrificial anticorrosion layer 21) in addition to the first layer (overcoat layer 24) and the second layer (intermediate coating layer 23). However, the coating film may have a configuration having only the first layer and the second layer.

DESCRIPTION OF SYMBOLS 10 Steel material 20 Coating film 21 Sacrificial anticorrosion layer 22 Undercoat layer 23 Intermediate coating layer 24 Top coating layer

Claims (7)

A coating film deterioration detection method for detecting deterioration of the first layer in a coating film having a first layer located on the outermost side and a second layer located immediately below the first layer, the method being applied to a base material,
A spectral characteristic acquiring step of acquiring spectral characteristics of a wavelength region included in at least one of a visible region and a near-infrared region of the reflected light of the first layer and the second layer;
Based on the obtained spectral characteristics of the first layer and the second layer, the spectral characteristics of the first layer and the second layer in the wavelength region in which the spectral characteristics of the first layer and the second layer are obtained. A detection wavelength region setting step of setting a detection wavelength region in which the difference that occurs is larger than the other wavelength regions,
A detection transmission filter preparing step of preparing a detection transmission filter that transmits light in the wavelength region included in the detection wavelength region,
Detecting a consumption of the first layer based on an image of the coating film taken through the transmission filter for detection. A coating film deterioration detection method according to claim 1,
The detecting step includes, based on an image of the coating film taken through the detection transmission filter, a state in which the second layer is exposed by depletion of the first layer until the first layer is peeled off. A method for detecting deterioration of a coating film, including detecting. A coating film deterioration detection method according to claim 1,
The detection step is performed through the detection transmission filter based on a relationship between a previously acquired thickness of the first layer and an influence of a spectral characteristic of reflected light of the first layer on an image of the coating film. A method for detecting deterioration of a coating film, comprising estimating a thickness of the first layer remaining in a state in which the thickness is smaller than the initial thickness from an image of the coating film. The coating film deterioration detection method according to claim 3,
The coating film deterioration detection method according to claim 1, wherein the detecting step further includes acquiring a relationship between a thickness of the first layer and an influence of a spectral characteristic of reflected light of the first layer on an image of the coating film. A coating film deterioration detection method according to any one of claims 1 to 4,
In the spectral characteristic acquiring step, the spectral characteristic of a specific wavelength region included in at least the near-infrared region of the reflected light of the first layer and the second layer is acquired,
In the detection transmission filter preparation step, as the detection transmission filter, prepare a near infrared light transmission filter that transmits light in the wavelength region included in the specific wavelength region,
In the detecting step, based on an image of the coating film taken through the near-infrared light transmission filter in an environment where sunlight is directly or indirectly applied to the coating film, the first layer A coating film deterioration detection method that detects wear. A coating film deterioration detection method according to any one of claims 1 to 4,
Prepare a lighting fixture capable of irradiating infrared, further comprising an infrared irradiation step of irradiating the coating film with infrared using the lighting fixture,
In the spectral characteristic acquiring step, the spectral characteristic of a specific wavelength region included in at least the near-infrared region of the reflected light of the first layer and the second layer is acquired,
In the detection transmission filter preparation step, as the detection transmission filter, prepare a near infrared light transmission filter that transmits light in the wavelength region included in the specific wavelength region,
In the detecting step, the consumption of the first layer is detected based on an image of the coating film taken through the near-infrared light transmission filter in an environment where the coating film is irradiated with infrared light from the lighting fixture. , Coating film deterioration detection method. A coating film deterioration detection method according to any one of claims 1 to 6,
Based on the acquired spectral characteristics of the first layer and the second layer, the wavelength range for which the spectral characteristics of the first layer and the second layer are acquired is more than the wavelength region for detection, the first layer and the wavelength region. A comparison wavelength region setting step of setting a comparison wavelength region in which a difference occurring in the spectral characteristics of the second layer is small;
Further comprising a comparison transmission filter preparation step of preparing a comparison transmission filter that transmits light in the wavelength region included in the comparison wavelength region,
In the detecting step, the consumption of the first layer is detected by comparing an image of the coating film captured through the detection transmission filter with an image of the coating film captured through the comparison transmission filter. Coating film deterioration detection method.

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