JP2019120549A - Method for detecting degradation of coating film - Google Patents

Abstract

To provide a method for detecting the deterioration of a coating film, capable of easily detecting a state that the first layer of the coating film consisting of a plurality of layers is deteriorated.SOLUTION: The method for detecting the deterioration of a coating film comprises: a spectral property acquisition step of acquiring spectral properties in a wavelength region included in at least one of a visible region and a near infrared region in light reflected on the first layer of the coating film and the second layer right thereunder; a detection wavelength region setting step of setting a detection wavelength region where a difference generated between the spectral properties of the first and second layers in a wavelength region acquiring the spectral properties of the first and second layers on the basis of the acquired spectral properties of the first and second layers is greater than that in the other wavelength region; a detection transmission filter preparation step of preparing a detection transmission filter for transmitting light having a wavelength region included in the detection wavelength region; and a detection step of detecting the consumption of the first layer on the basis of the image of the coating film imaged through the detection transmission filter.SELECTED DRAWING: Figure 1

Description

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

  In structures such as bridges, steel materials are used as a base material in order to secure necessary strength and the like. A coating is applied to the surface of the steel material to prevent the occurrence of rust.

  Patent Document 1 below discloses a coating film deterioration diagnostic system that performs image processing on image data of a coating film surface photographed by a photographing unit and uses the image data after the processing to evaluate the deterioration state of the coating film. ing. Specifically, the coating film deterioration diagnosis system described in Patent Document 1 evaluates the deterioration state of the coating film based on at least one of the peeling state of the coating film surface, the rusting state, and the color state.

JP, 2005-283519, A

  The coating applied to the surface of the steel material is consumed by aging. Therefore, it is necessary to prevent rusting of the steel material by detecting consumption of the coating film at an early stage and applying the coating film again to the area where the coating film has been consumed. The coating film is generally composed of a plurality of layers, in which case it is necessary to detect the consumption of the first layer located at the outermost side of the coating film at an early stage. There is a problem that it is difficult to do. Specifically, in order to suppress the influence of the color of the second layer on the color of the first layer, the first layer located at the outermost side of the coating film composed of a plurality of layers and the second layer directly under the first layer are both The colors close to each other are adopted as the color of. Therefore, even if the coating film is deteriorated and the first layer is peeled off to expose the second layer, it is difficult to visually check the exposure of the second layer. Also, it is difficult to confirm the state in which the first layer is thin.

  Although it is described in patent document 1 that the deterioration state of a coating film is evaluated based on the peeling state of a coating film surface, the specific discrimination | determination of the part from which the coating film remains, and the part from which the coating film peeled is described. Nothing is disclosed about the method.

  Further, Patent Document 1 describes that the deterioration state of the coating film is evaluated based on the color state, but this monitors the temporal change of the color of the coating film surface itself due to the deterioration. There is no suggestion as to how to specifically determine 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 detection method capable of easily detecting a state in which a layer located on the outermost side among a plurality of coating films is exhausted.

  In order to achieve the above-mentioned purpose, the inventors of the present application proceed the examination paying attention to the spectral characteristics of the reflected light of the first layer located on the outermost side of the coating film and the second layer located immediately below it. The As a result, in the specific wavelength region, there is a significant 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 to the difference in color recognized by the naked eye. I found it. Furthermore, since the light transmittance of the first layer increases as the thickness of the first layer decreases, the spectral characteristics of the reflected light of the second layer are greater than the spectral characteristics of the reflected light of the first layer. I also found it to be. Then, it has been found that it is possible to easily detect the consumption of the first layer by utilizing such characteristics. The present invention has been completed based on such findings.

  The coating film deterioration detection method according to the present invention is a coating film deterioration detecting a deterioration of the first layer in a coating film having a first layer applied to a base material and positioned outermost and a second layer positioned immediately below the first layer. A detection method of acquiring a spectral characteristic of a wavelength region included in at least one of a visible region and a near infrared region among reflected lights of the first layer and the second layer; The difference between the spectral characteristics of the first layer and the second layer in the wavelength range in which the spectral characteristics of the first layer and the second layer are obtained based on the spectral characteristics of the first layer and the second layer is A detection wavelength region setting step of setting a detection wavelength region larger than the other wavelength regions; and a detection transmission filter preparation step of preparing a detection transmission filter which transmits light in a wavelength region included in the detection wavelength region And the transmission filter for detection Based on the image of the photographed the coating film, and a detection step of detecting a depletion of the first layer.

  In the above coating film deterioration detection method, the spectral characteristics of the reflected light of the first layer and the spectral characteristics of the reflected light of the second layer in the wavelength region of light transmitted through the detection transmission filter are compared to other wavelength regions. Significant differences arise. 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, the decrease in the thickness of the first layer) can be captured from the image of the coating film taken through the detection transmission filter.

  In the detection step, preferably, the second layer is exposed by exhaustion of the first layer until the first layer is peeled off based on the image of the coating film taken through the transmission filter for detection. Detection of the condition.

  In this method, since the first layer and the second layer can be clearly distinguished in the image of the coating film taken through the detection transmission filter, the first image is obtained from the image of the coating film taken through the detection transmission filter. It can capture the exhaustion of layers.

  Alternatively, in the detection step, preferably, the detection step is performed based on a relationship between the thickness of the first layer acquired in advance and the influence of the spectral characteristics of the reflected light of the first layer on the image of the coating film. And estimating the thickness of the first layer remaining in a state in which the thickness is smaller than the original thickness from the image of the coating film photographed through the transmission filter.

  In this method, it is possible to clearly distinguish the region in which the thickness of the first layer is different in the image of the coating film taken through the detection transmission filter, so the first image from the image of the coating film taken through the detection transmission filter It can capture the exhaustion of layers.

  In the aspect of estimating the thickness of the first layer from the image of the coating film photographed through the transmission filter for detection, preferably, in the detection step, the thickness of the first layer and the spectral characteristic of the reflected light of the first layer are The method further includes acquiring a relationship with an influence on the image of the coating.

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

  In the above coating film deterioration detection method, preferably, 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. A near-infrared light transmission filter for transmitting light in a wavelength range included in the specific wavelength range is prepared as the detection transmission filter in the detection transmission filter preparation step, and sunlight is detected in the detection step. The consumption of the first layer is detected based on the image of the coating film photographed through the near infrared light transmission filter in an environment in which the coating film is irradiated directly or indirectly.

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

  Alternatively, the method for detecting deterioration of a coating film may further include an infrared irradiation step of preparing a lighting device capable of irradiating infrared light, and irradiating the coating film with infrared light using the lighting device, and in the spectral characteristic acquiring step, The spectral characteristics of a specific wavelength region included in at least the near infrared region among the reflected light of the first layer and the second layer are acquired, and in the detection transmission filter preparing step, the identification is performed as the detection transmission filter. A near-infrared light transmission filter for transmitting light in a wavelength range included in a wavelength range is prepared, and in the detection step, the near-infrared light transmission filter is produced under an environment where the coating film is irradiated with infrared light from the lighting device. The wear of the first layer is detected based on the image of the coating film taken through the method.

  In this method, even under an environment where sunlight is not irradiated, near infrared light can be included in the reflected light of the coating film by the irradiation of infrared radiation from the lighting equipment. The difference in spectral characteristics between the first layer and the second layer in the outer region can be used to detect the consumption of the first layer.

  The above-mentioned coating film deterioration detection method preferably detects 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, in the detection of the wavelength region. Wavelength range included in the comparison wavelength range, and a comparison wavelength range setting step of setting a comparison wavelength range in which the difference between the first layer and the second layer is smaller than the wavelength range. And a comparison transmission filter preparing step of preparing a comparison transmission filter to be transmitted, wherein, in the detection step, an image of the coating film photographed through the detection transmission filter and the image photographed through the comparison transmission filter The wear of the first layer is detected by comparing the image of the coating.

  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 of the detection wavelength region. Thus, the consumption of the first layer can be detected more reliably than when only the image of the coating film in the detection wavelength region is referred to.

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

It is a schematic diagram which shows the steel materials by which the coating film as a detection target by the coating-film deterioration detection method which concerns on embodiment of this invention was apply | coated. It is a flowchart which shows the coating-film deterioration detection method by embodiment of this invention. It is a graph which shows the spectral characteristics in the near-infrared area | region of the top coat layer and middle coat layer which were acquired at the spectral characteristic acquisition process. It is a photograph of the test piece taken without using any transmission filter. It is a photograph of a test piece photographed using a transmission filter for detection. It is a photograph of a test piece photographed using a comparative transmission filter. It is a flowchart which shows the modification of the coating film deterioration detection method by embodiment of this invention. It is an explanatory view showing a plurality of fields in a test piece. It is a graph which shows the luminance value of the middle coat layer on the line segment shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the attached 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 of a plurality of layers applied to the surface of a steel material as a base material to be subjected to corrosion protection. A steel material is used for the member which comprises a structure. The structure is installed, for example, on the ground or the like. For example, the structure may be one that can be removed while maintaining its function after installation, or it may be one that can not 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 piping 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. 1. FIG. 1 is a schematic view showing a steel material 10 and a coating film 20. As shown in FIG.

  The steel material 10 is used for the member which comprises a bridge, for example. The steel material 10 is present 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 the occurrence of rust on the surface of the steel material 10. The coating film 20 is composed of a plurality of layers, and includes a sacrificial anticorrosive layer 21, an undercoat layer 22, an intermediate coating layer 23 and an overcoat layer 24.

  Here, the top coat layer 24 is the outermost layer of the coating film 20, that is, the first layer. Therefore, the top coat layer 24 first deteriorates under the influence of the environment in which the steel material 10 is present. The deterioration factor of the top coat layer 24 is, for example, sunlight emitted to the top coat layer 24 or fine particles which collide with the top coat layer 24 by wind.

  The middle coat layer 23 is a layer located immediately below the top coat 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. As a result, the color of the top coat layer 24 is less likely to be affected by the color of the middle coat layer 23. That is, it is difficult to visually distinguish the state in which the upper coating layer 24 is peeled off and the middle coating layer 23 is exposed.

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

  The sacrificial anticorrosive layer 21 directly covers the surface of the steel material 10 and protects the surface of the steel material 10. The sacrificial anticorrosive layer 21 is set to have a larger ionization tendency than the steel material 10 so as to corrode the steel material 10 earlier. That is, the sacrificial anticorrosive layer 21 has excellent anticorrosion by the electrical anticorrosion effect. The sacrificial anticorrosive layer 21 functions as a base that suppresses the occurrence of rust on the surface of the steel material 10. The sacrificial anticorrosive layer 21 is, for example, an inorganic zinc rich paint.

  It is difficult to repaint the sacrificial anticorrosive layer 21 in the state where the structure constituted by the steel material 10 is installed. Therefore, in order to prevent deterioration of the sacrificial anticorrosive layer 21, the undercoat layer 22 covers the sacrificial anticorrosive layer 21.

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

  The intermediate layer 23 is located between the overcoat layer 24 and the undercoat layer 22 and functions as an adhesive for adhering the overcoat layer 24 and the undercoat layer 22. The middle coat layer 23 covers the undercoat layer 22. The middle coat 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 color of the top coat layer 24 is less affected. The middle coat layer 23 is, for example, an epoxy resin paint.

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

  A method for detecting such deterioration of the coating film 20 will be described with reference to FIG. FIG. 2 is a flow chart showing a method of detecting deterioration of the coating film 20 under 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 the upper coating layer 24 is peeled off and the middle coating layer 23 is 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, visually finding the state in which the top coat layer 24 is peeled off 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 the state in which the upper coating layer 24 is peeled off and the middle coating layer 23 is exposed. Specifically, the method for detecting deterioration of the coating film 20 according to the present embodiment uses the remarkable difference between the spectral characteristics of the upper coating layer 24 and the intermediate coating layer 23 in a specific wavelength range to This enables clear discrimination regardless of the color approximation of the paint layer 23.

  The deterioration detection method 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.

  Spectroscopic characteristic acquisition step S11 is a step of acquiring the spectral characteristic of the wavelength region included in at least one of the visible region and the near infrared region among the reflected light of the upper coating layer 24 and the intermediate coating layer 23. In the present embodiment, the spectral characteristics acquisition step S11 is a step of acquiring the spectral characteristics of a specific wavelength region included in at least the near infrared region among the reflected lights of the upper coating layer 24 and the middle coating layer 23. In the near infrared region, for example, the wavelength of light is a region of 800 nm to 2500 nm.

  The spectral characteristics of the top coat 24 and the middle coat 23 are obtained, for example, by measuring samples of the top coat 24 and the middle coat 23 by a spectrophotometer. For example, a diffuse reflection method is used to obtain spectral characteristics.

  FIG. 3 is a graph showing an example of the spectral characteristics in the near infrared region of the upper coating layer 24 and the middle coating layer 23 acquired in the spectral characteristic acquiring step S11. FIG. 3 shows diffuse reflectance spectra of the top coat layer 24 and the middle coat layer 23. In FIG. 3, the horizontal axis indicates the wavelength (unit: nm), and the vertical axis indicates the 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 top coat layer 24 and the middle coat layer 23 is attributed to the respective components of the top coat layer 24 and the middle coat layer 23. That is, unless the respective components of the top coat layer 24 and the middle coat layer 23 are exactly the same, the difference in the spectral characteristics of the top coat 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. In addition, a coating-film component is a component of a coating material which remains as a coating film even after the coating material is dried.

  The wavelength range setting step S12 is a step of setting a wavelength range to be a reference when determining the wavelength range of light transmitted by the transmission filter prepared in the filter preparation step S13. The wavelength region setting step S12 is performed based on the spectral characteristics of the upper coating layer 24 and the middle coating layer 23 acquired in the spectral characteristic acquisition step S11.

  The wavelength range setting step S12 includes a detection wavelength range setting step S121 and a comparison wavelength range setting step S122. In the detection wavelength region setting step S121, based on the spectral characteristics of the upper coating layer 24 and the middle coating layer 23 acquired in the spectral characteristic acquisition step S11, the upper coating layer 24 and the intermediate coating in the wavelength region in which the spectral characteristics are acquired. This is a step of setting a detection wavelength region in which the difference in the spectral characteristics of the layer 23 is larger than that of the other wavelength regions. In the comparative wavelength region setting step S122, based on the spectral characteristics of the upper coating layer 24 and the middle coating layer 23 acquired in the spectral characteristic acquisition step S11, the wavelength region in which the spectral characteristics are acquired is higher than the detection wavelength region. This is a step of setting a comparative wavelength region in which the difference between the spectral characteristics of the coating layer 24 and the intermediate coating layer 23 is small. The difference which arises in the spectral characteristics of top coat layer 24 and middle coat layer 23 is the difference of the light absorbency of top coat layer 24 and middle coat layer 23, for example.

  In the case of the spectral characteristics shown in FIG. 3, a region shorter than 1500 nm is set as the detection wavelength region, and a region 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 largely different from each other at the 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 exhibit similar spectral characteristics. That is, in the region where the wavelength is longer than 1500 nm, the top coat 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 upper coating layer 24 and the middle coating layer 23 is larger than in the region where the wavelength is longer than 1500 nm. 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 top coat layer 24 looks darker than the middle coat layer 23.

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

  The filter preparation step S13 is a step of preparing a transmission filter that transmits light in the wavelength range included in the wavelength range set in the wavelength range setting step S12. The transmission filter may be newly manufactured or may be appropriately 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 preparation 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 preparation 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 for transmitting light in a region shorter than 1450 nm is prepared as a transmission filter for detection, and light in a region longer than 1400 nm is transmitted as a transmission filter for comparison. Transmission filters are prepared.

  In the detection step S14, 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 upper coating layer 24 is peeled off and the intermediate coating layer 23 is exposed. Is a process of detecting the The image of the coating film 20 is taken by a camera. As the camera, for example, an appropriate one is used depending on 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 employed as the camera. The difference between the top coat layer 24 and the middle coat layer 23 may be confirmed visually, for example, or may be confirmed by performing appropriate image processing on the photographed image of the coating film 20.

  The result of detecting the state in which the upper coating layer 24 is peeled off and the middle coating layer 23 is exposed will be described using the test piece with reference to FIGS. 4, 5 and 6. FIG. 4 shows an image of a test strip taken without using any transmission filter. FIG. 5 shows an image of a test piece taken through a detection transmission filter. FIG. 6 shows an image of a test piece taken through a comparison transmission filter.

  Referring to FIG. 4, of the test pieces, the coating on the wide-width portion (upper portion in the figure) is the same as the top coat layer 24 and the white color on the narrow-width portion (lower portion in the figure) The coating film of the part is the same as the intermediate coating layer 23.

  The image shown in FIG. 5 (that is, the image of the test strip taken through the detection transmission filter) has a clear difference between the top coat layer 24 and the middle coat layer 23 as compared with the images shown in FIG. 4 and FIG. . That is, when the detection transmission filter is used (see FIG. 5), the upper coating layer 24 and the middle coating layer 23 can be easily distinguished as compared with the case where the detection transmission filter is not used (see FIG. 4) is there. Also, by comparing the image taken through the detection transmission filter (see FIG. 5) with the image taken through the comparison transmission filter (see FIG. 6), the upper coat layer 24 and the middle coat layer 23 can be made more reliably. It can be determined.

  In such a method for detecting deterioration of the coating film 20, the difference in the spectral characteristics of the upper coating layer 24 and the intermediate coating layer 23 is larger than in the other wavelength regions in the wavelength region of light transmitted through the detection transmission filter. . Therefore, in the image of the coating film 20 photographed through the transmission filter for detection, the upper coating layer 24 and the middle coating layer 23 are different from each other in comparison with the color difference of the upper coating layer 24 and the middle coating layer 23 recognized by the naked eye. The difference is very clear. That is, the above method makes it possible to easily distinguish the top coat layer 24 and the middle coat layer 23 even when the top coat layer 24 and the middle coat layer 23 have similar colors. .

  In addition, in the method for detecting deterioration of the coating film 20 as described above, since the solar light is directly or indirectly irradiated to the steel material 10 in the environment, the top coat layer 24 and the middle coat layer 23 in the near infrared region The top coat layer 24 and the middle coat layer 23 can be distinguished by utilizing the difference in the spectral characteristics of

  Further, in such a method for detecting the deterioration of the coating film 20, when detecting that the upper coating layer 24 is peeled off and the middle coating layer 23 is exposed, an image of the coating film in the detection wavelength region; The image of the coating film in the comparative wavelength region in which the difference between the spectral characteristics of the upper coating layer 24 and the intermediate coating layer 23 is smaller than the detection wavelength region is compared. Therefore, the top coat layer 24 and the middle coat layer 23 can be more reliably distinguished.

[Modification 1 of Embodiment]
Referring to FIG. 7, when the sunlight 10 does not irradiate the steel material 10 directly or indirectly, 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 to A coating film deterioration detection method 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 detection method according to the present modification further includes an infrared irradiation step S10 as compared to the coating film deterioration detection method according to the above-described 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. . The irradiation of the 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. In addition, the lighting fixture which can irradiate infrared rays is a halogen heater, a xenon heater, a quartz heater etc., for example.

[Modification 2 of the embodiment]
In the above embodiment, the state in which the middle coat layer 23 is exposed is detected by 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). A state in which the thickness of the upper coating layer 24 is reduced may be detected.

  In this case, based on the relationship between the thickness of the upper coating layer 24 and the influence of the spectral characteristics of the reflected light of the upper coating layer 24 on the image of the coating film 20, a coating film photographed through the detection transmission filter Estimating the thickness of the upper coating layer 24 remaining in a state in which the thickness is smaller than the initial value from the 20 images and determining the deterioration of the coating film 20 from the estimated thickness of the upper coating layer 24 Including.

  The influence of the spectral characteristics of the reflected light of the upper coating layer 24 on the image of the coating film 20 can be an index of the thickness of the upper coating layer 24 in the image of the coating film 20. What can be an index of the thickness of the top coat layer 24 in the image of the coating film 20 is, for example, the intensity of the reflected light of the top coat layer 24. The intensity of the reflected light of the top coat layer 24 appears, for example, as the brightness of the top coat layer 24 in the image of the coating film 20.

  The relationship between the thickness of the upper coating layer 24 and the influence of the spectral characteristics of the reflected light of the upper coating layer 24 on the image of the coating film 20 is, for example, a plurality of regions of different thicknesses of the upper coating layer 24 and the middle coating layer 23 The influence of the spectral characteristics of the reflected light of the overcoat layer 24 on the image of the coating film 20 is measured in each region using a sample having exposed regions, and the reflected light of the overcoat layer 24 in each region is measured. These spectral characteristics can be obtained by examining the relationship between the influence of the spectral properties of the coating film 20 on the image and the thickness of the top coat layer 24.

  The relationship between the thickness of the upper coating layer 24 and the influence of the spectral characteristics of the reflected light of the upper coating layer 24 on the image of the coating film 20 may be acquired before the detection step, or acquired in the detection step May be

  The criteria for determining the deterioration of the coating film 20 from the estimated thickness of the upper coating layer 24 is, for example, when the estimated thickness of the upper coating layer 24 becomes half or less of the thickness of the initial upper coating layer 24 .

  Referring to FIGS. 8 and 9, the thickness of the upper coating layer 24 and the spectral characteristics of the reflected light of the upper coating layer 24 affect the image of the coating film 20 with the brightness value of the upper coating layer 24 in the image. An example of the relationship will be described. FIG. 8 is an explanatory view 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 detection transmission filter. The test piece 30 has a plurality of (in this embodiment, three) areas 32, 33, 34 in which the area 31 where the intermediate coating layer 23 is exposed and the thickness of the upper coating layer 24 covering the intermediate coating layer 23 are different. Have. The thickness of the overcoat 24 in the region 32 is 14 μm, the thickness of the overcoat 24 in the region 33 is 20 μm, and the thickness of the overcoat 24 in the region 34 is 25 μm. In FIG. 8, each of the plurality of regions 32, 33, 34 has a mesh. The larger the thickness of the upper coating layer 24, the larger the mesh. FIG. 9 is a graph showing the luminance value of the upper coating layer 24 in the image, which is the influence of the spectral characteristics of the reflected light of the upper coating layer 24 on the line segment SL shown in FIG. .

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

The energy of light irradiated to the upper coating layer 24 is E, and the reflectance, absorptivity and transmittance of the upper coating layer 24 are respectively _{1 1} , α ₁ and τ _1, and the reflectance and absorptivity of the middle coating layer 23 And the transmittances are ρ ₂ , α ₂ and τ ₂ respectively.

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

Further, the energy E2 of the light emitted from the upper coating layer 24 after being incident on the upper coating layer 24 and reflected by the intermediate coating layer 23 is represented by the following formula (2).
E2 = ρ ₂ (τ ₁ E) −α ₁ {ρ ₂ (τ ₁ E)} (2)

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

Here, the absorptivity α ₁ and the transmittance τ ₁ of the top coat layer 24 included in the formula (2) representing the energy E 2 depend on the thickness of the top coat layer 24. That is, the energy E2 changes in accordance with the thickness of the top coat layer 24. Therefore, the luminance value of the top coat layer 24 in the image of the coating film 20 changes according to the thickness of the top coat layer 24. The correlation between the brightness value of the upper coating layer 24 and the thickness of the upper coating layer 24 in the image of the coating film 20 can be expressed using, for example, a linear function or a quadratic function.

  In this modification, the luminance value of the upper coating layer 24 is acquired from the image of the coating film 20 photographed using the transmission filter for detection, and the correlation between the acquired luminance value and the thickness of the upper coating layer 24 is obtained. The thickness of the top coat layer 24 can be estimated. Moreover, deterioration of the coating film 20 can be determined from the estimated thickness of the top coat layer 24.

  Note that the present modification is not limited to the aspect of estimating the thickness of the upper coating layer 24 after acquiring in advance the correlation that exists between the thickness of the upper coating layer 24 and the luminance value of the upper coating layer 24. For example, even if the correlation existing between the thickness of the upper coating layer 24 and the brightness value of the upper coating layer 24 is obtained in advance and then the degree of consumption of the upper coating layer 24 is estimated from the brightness value of the upper coating layer 24 Good.

  As mentioned above, although the embodiment of the present invention has been described in detail, these are merely examples, and the present invention is not construed as being limited in any way by the description of the embodiment described above.

  For example, in the above embodiment, the upper coating layer 24 is peeled off by comparing the image of the coating film taken through the detection transmission filter with the image of the coating film taken through the comparison transmission filter. Detects the state in which the upper coating layer 24 is peeled off and the intermediate coating layer 23 is exposed, using only the image of the coating film taken through the detection transmission filter. May be In addition, when only the image of the coating film photographed through the transmission filter for detection is used when detecting the state in which the upper coating layer 24 is peeled off and the middle coating layer 23 is exposed, the wavelength region for comparison is set. It is not necessary, nor is it necessary to prepare a comparison transmission filter.

  For example, in the above embodiment, the exposure of the middle coat layer 23 was detected using the difference in the spectral characteristics of the top coat layer 24 and the middle coat layer 23 in the near infrared region. The difference in spectral characteristics of the layer 24 and the middle coat layer 23 may be used to detect the exposure of the middle coat layer 23.

  For example, in the above embodiment, the coating has a coating layer (the undercoating layer 22 and the sacrificial anticorrosive layer 21) in addition to the first layer (upper coating layer 24) and the second layer (middle coating layer 23). However, the coating film may be configured to have only the first layer and the second layer.

DESCRIPTION OF SYMBOLS 10 Steel materials 20 Coating film 21 A sacrificial-corrosion layer 22 Under-coating layer 23 Inter-coating layer 24 Over-coating layer

Claims (7)

A coating film deterioration detecting method for detecting deterioration of a first layer in a coating film having a first layer applied to a base material and located at the outermost side and a second layer positioned immediately below the first layer,
A spectral characteristic acquisition step of acquiring spectral characteristics of a wavelength region included in at least one of a visible region and a near infrared region among reflected lights of the first layer and the second layer;
In 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 acquired based on the acquired spectral characteristics of the first layer and the second layer A detection wavelength range setting step of setting a detection wavelength range having a larger difference than the other wavelength ranges;
A detection transmission filter preparation step of preparing a detection transmission filter that transmits light in a wavelength region included in the detection wavelength region;
And detecting the consumption of the first layer based on the image of the coating film captured through the detection transmission filter. It is a coating film deterioration detection method according to claim 1,
The detection step is a state in which the second layer is exposed by the first layer being consumed until the first layer is peeled off based on the image of the coating film taken through the transmission filter for detection. A method for detecting coating film deterioration, comprising detecting. It is a coating film deterioration detection method according to claim 1,
In the detection step, photographing is performed through the detection transmission filter based on the relationship between the thickness of the first layer acquired in advance and the influence of the spectral characteristics of the reflected light of the first layer on the image of the coating film. The coating film deterioration detection method including estimating the thickness of the said 1st layer which has remained in the state which thickness became smaller than the beginning from the image of the said coating film. It is a 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 the thickness of the first layer and the influence of the spectral characteristics of the reflected light of the first layer on the image of the coating film. It is a coating film deterioration detection method in any one of Claims 1-4, Comprising:
In the spectral characteristic acquisition step, spectral characteristics of a specific wavelength region included in at least the near infrared region among the reflected light of the first layer and the second layer are acquired,
In the detection transmission filter preparation step, a near infrared light transmission filter for transmitting light in a wavelength range included in the specific wavelength range is prepared as the detection transmission filter,
In the detection step, the first layer is formed 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 irradiated to the coating film. Coating film deterioration detection method for detecting consumption. It is a coating film deterioration detection method in any one of Claims 1-4, Comprising:
A lighting device capable of emitting infrared light is further provided, and the method further comprises an infrared irradiation step of irradiating the coating film with infrared light using the lighting device,
In the spectral characteristic acquisition step, spectral characteristics of a specific wavelength region included in at least the near infrared region among the reflected light of the first layer and the second layer are acquired,
In the detection transmission filter preparation step, a near infrared light transmission filter for transmitting light in a wavelength range included in the specific wavelength range is prepared as the detection transmission filter,
In the detection 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 under an environment in which the coating film is irradiated with infrared light from the lighting device. , Coating film deterioration detection method. It is a coating film deterioration detection method in any one of Claims 1-6, Comprising:
The first layer and the first layer are more than the wavelength region for detection among the wavelength regions in which the spectral characteristics of the first layer and the second layer are acquired based on the acquired spectral characteristics of the first layer and the second layer. A comparative wavelength region setting step of setting a comparative wavelength region in which the difference in the spectral characteristics of the second layer is small;
A comparative transmission filter preparation step of preparing a comparative transmission filter that transmits light in a wavelength region included in the comparison wavelength region,
In the detection step, the consumption of the first layer is detected by comparing the image of the coating film taken through the detection transmission filter with the image of the coating film taken through the comparison transmission filter. Coating film deterioration detection method.

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