JP2023114177A - Coated body inspection method - Google Patents

Abstract

To provide a coated body inspection method which enable accurate evaluation of damage to coated bodies.SOLUTION: A method of inspecting a coated body comprising an insulative coating film applied on a surface of a conductive base material is provided, the method comprising a preparation step (step S3) of preparing a reference sample, and an evaluation step (steps S6, S7) of measuring respective surface potentials of the coated body and the reference sample under the same temperature and relative humidity and evaluating damage to the coated body on the basis of a difference between the surface potentials.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method for inspecting a coated body having a coating film applied to a base material.

Generally, a technique is known for detecting damage to a coating film of an inspection object or corrosion of a base material under the coating film by measuring the surface potential of an inspection object such as a metal plate or a coated steel plate. Patent Literature 1 discloses a technique for periodically measuring the surface potential at the same location on the inspection object and evaluating the corrosion resistance of the inspection object base material based on the change in the surface potential over time. In addition, in Non-Patent Document 1, a coated steel plate of several cm square is placed on an XY stage, the XY stage is operated to measure the surface potential at each position of the coated steel plate, and from these surface potential distributions, the coating film A technique for relatively evaluating soundness is disclosed.

Japanese Patent No. 3158160

Hideki Katayama, Kengo Seki, Isao Shitanda, Masayuki Itagaki, Hiroyuki Masuda, "Non-destructive deterioration evaluation of coated steel sheets by surface potential measurement", Shikizai Kyokai, Vol. 85 (2012), pp. 235-239

However, in the conventional technique, the damage of the base material or coating film to be inspected is relatively evaluated from the temporal change of the surface potential at the same inspection point or from the potential distribution in the measurement surface of several cm square. For this reason, for example, when inspecting multiple locations on a wide surface to be inspected, such as a painted body used in an actual plant or vehicle, damage to the painted body such as deterioration of the coating film and corrosion of the base material can be accurately detected. There was room for improvement in terms of evaluation.

The present disclosure has been made in view of the above, and an object of the present disclosure is to provide a method for inspecting a coated body that can accurately evaluate damage to the coated body.

In order to solve the above-mentioned problems and achieve the object, the present disclosure provides a method for inspecting a coated body in which an insulating coating film is applied to the surface of a conductive base material, wherein a reference sample is created. and an evaluation step of evaluating damage to the coated body based on the difference in surface potential between the coated body and the reference sample under an environment of the same temperature and relative humidity.

Advantageous Effects of Invention According to the present disclosure, it is possible to accurately evaluate damage to a coated body such as deterioration of a coating film and corrosion of a base material.

FIG. 1 is a schematic diagram of a reference sample and a measuring device used when executing the method for inspecting a coated body according to the first embodiment. FIG. 2 is a flow chart showing the procedure of the coating body inspection method according to the first embodiment. FIG. 3 is a graph showing an example of the relationship between the surface potential and corrosion under the paint film due to deterioration of the paint film. FIG. 4 is a flow chart showing the procedure of the coating body inspection method according to the second embodiment. FIG. 5 is a flow chart showing the procedure of the coating body inspection method according to the third embodiment. FIG. 6 is a diagram showing an example of a data table obtained by measuring the surface potential of a reference sample under different conditions of temperature and relative humidity. FIG. 7 is a flow chart showing the procedure of the coating body inspection method according to the fourth embodiment.

A method for inspecting a coated body according to an embodiment will be described in detail below with reference to the drawings. Note that the present disclosure is not limited by this embodiment.
[First embodiment]

FIG. 1 is a schematic diagram of a reference sample and a measuring device used when executing the method for inspecting a coated body according to the first embodiment. In the present embodiment, the coated body 100 to be inspected constitutes, for example, a part of an actual plant or vehicle, and an insulating coating film 102 is applied to the surface of a base material 101 having conductivity. The substrate 101 is made of, for example, a metal plate of carbon steel, aluminum alloy, stainless steel, or the like. The coating film 102 protects the base material 101, and is made of, for example, an epoxy resin, a urethane resin, an acrylic resin, or the like. The body to be coated 100 is grounded via legs or the like.

In general, it is assumed that the coating body 100 is damaged over time, such as deterioration of the coating film 102 and corrosion of the base material 101 . The damage to the coated body 100 can be evaluated from the measured value of the surface potential of the coated body 100. However, in the case of inspecting a plurality of locations on a wide inspection target surface of the coated body 100, it is necessary to set evaluation criteria. There is For this reason, in this embodiment, the reference sample 200 is used when evaluating the presence or absence of damage to the coated body 100 , and this reference sample 200 serves as a standard for measuring the surface potential of the coated body 100 . Although the reference sample 200 is smaller than the coated body 100 , it includes a base material 201 and a coating film 202 and is made in the same manner as the coated body 100 . Specifically, the base material 201 and the coating film 202 of the reference sample 200 are made of the same materials as the base material 101 and the coating film 102 of the coated body 100, respectively. In addition, the coating film 202 of the reference sample 200 is adjusted to have the same film thickness as the coating film 102 of the coated body 100, and further, the same coating method as the coating film 102 (for example, brush coating, dip coating, airless spray coating etc.) is painted. Also, the reference sample 200 is grounded via a mounting table and lead wires (not shown).

The measuring device 10 measures the surface potentials of the coated body 100 and the reference sample 200, and evaluates the presence or absence of damage to the coated body 100 and the degree of damage based on the difference value of each surface potential. In this embodiment, the measuring device 10 includes, for example, a probe 11, a surface potential meter control device 12, and an arithmetic processing device 13. As shown in FIG. The probe 11 is a surface potential meter that measures the surface potentials of the coated body 100 and the reference sample 200 without contact, and includes a sensor electrode (not shown) built in the tip and a measurement surface (of the coated body 100 and the reference sample 200). Each surface) is used to measure the surface potential.

A surface potential meter controller 12 controls the operation of the probe 11 that measures the surface potential. The surface potential meter controller 12 also has a function of performing zero point calibration on the measured value of the surface potential. This surface potential meter control device 12 is grounded via the coated body 100, for example.

The arithmetic processing unit 13 is composed of, for example, a personal computer, and processes and stores data of the measured surface potential. Specifically, the arithmetic processing unit 13 associates and stores the positional information of the measurement point on the coated body 100 with the measured value of the surface potential. Further, the arithmetic processing unit 13 calculates a difference value between the surface potentials of the coated body 100 and the reference sample 200, compares this difference value with a predetermined evaluation reference value, and performs processing for evaluating damage to the coated body 100. conduct. The arithmetic processing unit 13 also has a function of storing values of the temperature T and the relative humidity RH of the environment in which the coated body 100 is installed, which are measured by the temperature/humidity sensor 14 .

Next, a method for inspecting the coated body 100 will be described. FIG. 2 is a flow chart showing the procedure of the coating body inspection method according to the first embodiment. First, a coated body 100 to be inspected is selected (step S1). For example, the processing unit 13 may periodically select the entire actual plant having the coated body 100, or the coated body 100 may be divided into a plurality of areas, and the processing unit 13 may periodically select each area. You may set the schedule to select.

Next, the coating specifications of the coated body 100 are investigated in order to prepare the reference sample 200 (step S2). Specifically, the type of base material 101 (for example, carbon steel, aluminum alloy, stainless steel, etc.) constituting the coated body 100 and the type of coating film 102 (for example, epoxy resin, urethane resin, acrylic resin, etc.) are investigated. do. In addition, the film thickness of the coating film 102 and the coating method of the coating film 102 (for example, brush coating, dip coating, airless spray coating, etc.) are investigated for each area of the coated body 100 . These investigations need to be conducted by the worker at the time of the first inspection, but the investigation data is recorded in the arithmetic processing unit 13, and at the time of the second and subsequent inspections, the arithmetic processing unit 13 reads out and uses the investigation data. You may

Next, a reference sample 200 is created with the same coating specifications as the coated body 100 (step S3; creation process). As described above, the reference sample 200 is made of the same material as the coated body 100 and has the same coating specifications, and serves as a reference for evaluating whether or not the coated body 100 is damaged. The prepared reference sample 200 is preferably stored, for example, in a sufficiently dry place (a place where the humidity is controlled to be low) to suppress damage over time of the reference sample 200 .

Next, zero point calibration of the surface potential meter controller 12 is performed using the reference sample 200 in the same environment as the coating body 100 (step S4; calibration step). Specifically, the setting of the surface potential meter control device 12 is adjusted so that the measured value of the surface potential of the reference sample 200 placed in the same environment as the coated body 100 is displayed as 0 V. do. In this case, it is preferable to calibrate the zero point after the temperatures T of the reference sample 200 and the coated body 100 become the same. Also, if the measurement environment (temperature T or relative humidity RH) changes, the reference sample 200 is used again to perform zero point calibration again. The measured value of the surface potential usually depends on the temperature T and relative humidity RH of the measurement environment. Therefore, in the present embodiment, the reference sample 200 is zero-point calibrated to compensate for the influence of the temperature T and the relative humidity RH of the measurement environment, and to accurately evaluate changes in the surface potential due to damage to the coated body 100. can do.

Next, the temperature T and the relative humidity RH in the measurement environment are measured (step S5). Specifically, the temperature/humidity sensor 14 is used to measure the temperature T and the relative humidity RH in the measurement environment.

Next, the surface potential of the coated body 100 is measured, and the difference value between the surface potentials of the coated body 100 and the reference sample 200 is calculated (step S6). In this embodiment, since the surface potential of the reference sample 200 is calibrated at the zero point, when the surface potential of the coated body 100 is measured using the same probe 11, the surface potential of this coated body 100 is the above-described difference value. Become. Further, in this embodiment, since the probe 11 is used to measure the surface potential of the coated body 100, for example, an actual plant or vehicle can be inspected on site.

Next, the difference value is compared with a predetermined evaluation reference value to evaluate damage to the coated body 100 (step S7; evaluation step), and the process ends. This evaluation reference value S is a value that changes depending on the temperature T and the relative humidity RH, and is calculated by the formula S=Aexp(αT+βRH). In this formula, A, α, and β are constants defined by the coating specifications, respectively, and it is desirable to check the values of these constants A, α, and β in advance by experiments for each coating specification of the coated body 100. .

Here, the relationship between the surface potential and deterioration of the coating film will be described. FIG. 3 is a graph showing an example of the relationship between the surface potential and corrosion under the paint film due to deterioration of the paint film. In general, in a coated body in which a coating film is applied to a base material, corrosion of the base material under the coating progresses after the coating film deteriorates. In this case, as shown in FIG. 3, when the surface potential shows a decreasing tendency, the coating film deteriorates (range A in the figure), and when the surface potential shows an increasing tendency again, corrosion of the substrate occurs (see FIG. 3). It has been found that the middle range B).

Therefore, in this configuration, the difference value and the evaluation reference value S are compared, and if the difference value is smaller than the evaluation reference value S, the coating film 102 of the coated body 100 deteriorates due to the influence of water absorption and the like. When the difference value changes to a value larger than the evaluation reference value S, it can be evaluated that the substrate 101 is corroded under the coating film 102 . Therefore, it is possible to determine which of the coating film 102 and the substrate 101 is damaged based on the magnitude of the difference value and the evaluation reference value S, and the damage of the coated body 100 can be accurately evaluated. . For example, if the calculated difference value is smaller than the evaluation reference value and a decreasing tendency is observed, it can be determined that the coating film 102 has deteriorated. Corrosion can be minimized.

As described above, the method for inspecting the coated body 100 according to the present embodiment is a method for inspecting the coated body 100 in which the insulating coating film 102 is applied to the surface of the conductive base material 101, and the preparation process for creating the reference sample 200. and an evaluation step of evaluating damage to the coated body 100 based on the difference in surface potential between the coated body 100 and the reference sample 200 in an environment with the same temperature T and relative humidity RH. According to this configuration, damage to the coated body 100 can be accurately evaluated using the surface potential of the reference sample 200 as a reference.

In addition, according to the present embodiment, the reference sample 200 is prepared with the same coating specifications using the base material 201 and the coating film 202 of the same type as those of the coated body 100. Therefore, the coated body 100 and the reference sample 200 each Damage to the coated body 100 can be easily evaluated by comparing the surface potentials.

Further, according to the present embodiment, in the evaluation step, when the difference value is smaller than the predetermined evaluation reference value S, the coating film 102 is evaluated as deteriorated, and when the difference value is greater than the evaluation reference value S is evaluated as corrosion of the base material 101, the degree of damage to the coated body 100 can be accurately evaluated.

Further, according to the present embodiment, before the evaluation step, the reference sample 200 is arranged in the same environment as the coated body 100, and the reference sample 200 is subjected to zero point calibration of the surface potential. It is possible to compensate for the effects of environmental temperature T and relative humidity RH, and to accurately evaluate changes in surface potential that accompany damage to the coated body 100 .

[Second embodiment]
Next, a method for inspecting a coated body according to the second embodiment will be described. FIG. 4 is a flow chart showing the procedure of the coating body inspection method according to the second embodiment. The same steps as in the above-described first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

As in the first embodiment, a coated body 100 to be inspected is selected (step S1), and the coating specifications of this coated body 100 are investigated (step S2). Then, a reference sample 200 is created with the same coating specifications as the coated body 100 (step S3).

Next, the surface potential meter controller 12 is zero-point calibrated in the same environment as the coating body 100 (step S4), and the temperature T and the relative humidity RH in the measurement environment are measured (step S5).

Next, the surface potentials of the coated body 100 and the reference sample 200 are simultaneously measured, and the difference value between these surface potentials is calculated (step S6A). In this embodiment, for example, the measuring device 10 is configured to include two probes 11, one probe 11 measures the surface potential of the reference sample 200, and the other probe 11 measures the surface potential of the coated body 100. can be done. In this case, it is assumed that all the probes 11 are subjected to the same zero point calibration in step S4. Therefore, compared with the first embodiment, there is an advantage that the surface potentials of the reference sample 200 and the coated body 100 can be compared on time. Alternatively, one probe 11 may be formed integrally with the reference sample 200 so that the surface potential of the reference sample 200 can always be measured.

Next, the difference value is compared with a predetermined evaluation reference value to evaluate damage to the coated body 100 (step S7), and the process ends. In this second embodiment, steps S6A and S7 are included in the evaluation process.

In the second embodiment, in addition to the effects of the first embodiment described above, the surface potentials of the coated body 100 and the reference sample 200 are simultaneously measured in the evaluation step, and the difference value is calculated. The calculation can be performed quickly, and the damage to the coated body 100 can be quickly evaluated.

[Third embodiment]
Next, a method for inspecting a coated body according to the third embodiment will be described. FIG. 5 is a flow chart showing the procedure of the coating body inspection method according to the third embodiment. FIG. 6 is a diagram showing an example of a data table obtained by measuring the surface potential of a reference sample under different conditions of temperature and relative humidity. The same steps as in the above-described first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

As in the first embodiment, a coated body 100 to be inspected is selected (step S1), and the coating specifications of this coated body 100 are investigated (step S2). Then, a reference sample 200 is created with the same coating specifications as the coated body 100 (step S3).

Next, a data table is prepared by measuring the surface potential of the reference sample 200 under different conditions of temperature T and relative humidity RH (step S4A; data table preparation step). Specifically, the reference sample 200 is placed in a laboratory (chamber) in which the temperature T and the relative humidity RH can be changed independently, and the surface of the reference sample 200 is changed while changing the temperature T and the relative humidity RH. Measure the potential respectively. Then, as shown in FIG. 5, a data table 300 is created in which the measured surface potential (V) is associated with the measurement conditions (temperature T (° C.) and relative humidity RH (%)). The created data table 300 is stored in the arithmetic processing unit 13, for example. In the example of FIG. 5, the data table 300 is created by dividing the temperature T into 5° C. intervals and the relative humidity RH into 10% intervals, but these intervals may be changed as appropriate.

Next, the temperature T and the relative humidity RH in the measurement environment are measured (step S5). In this case, the processing unit 13 reads the surface potential of the reference sample 200 corresponding to the measured temperature T and relative humidity RH from the data table 300 . Next, the surface potential of the coated body 100 is measured, and the difference value between the surface potential of this coated body 100 and the surface potential of the reference sample 200 read out from the data table 300 is calculated (step S6B). In this configuration, the surface potential of the reference sample 200 read from the data table 300 can be used. Therefore, compared with the first embodiment and the second embodiment, there is an advantage that it is not necessary to actually measure the surface potential of the reference sample 200 at the inspection site.

Next, the difference value is compared with a predetermined evaluation reference value to evaluate damage to the coated body 100 (step S7), and the process ends. In this third embodiment, steps S6B and S7 are included in the evaluation process.

This third embodiment includes a data table creating step of creating a data table 300 in which the surface potentials of the reference sample 200 are measured under different conditions of temperature T and relative humidity RH. Further, in the evaluation step, the temperature T, the relative humidity RH, and the surface potential of the coated body 100 of the environment in which the coated body 100 is placed are measured, and the surface of the reference sample 200 corresponding to the measured temperature T and relative humidity RH The potential is read from the data table 300, and the difference value is calculated from the read surface potential of the reference sample 200 and the measured surface potential of the coated body 100. FIG. For this reason, in addition to the effects of the first embodiment described above, there is no need to actually measure the surface potential of the reference sample 200 at the inspection site, and calculation of the difference value and evaluation of damage to the coated body 100 can be performed easily. It can be carried out.

[Fourth embodiment]
Next, a method for inspecting a coated body according to the fourth embodiment will be described. FIG. 7 is a flow chart showing the procedure of the coating body inspection method according to the fourth embodiment. The same reference numerals are assigned to the same configurations and procedures as those of the above-described first embodiment, and the description thereof is omitted. First, a reference sample is created (step S11). In the above-described first to third embodiments, the reference sample 200 uses the same base material and coating film as the coated body 100 to be inspected, and is created according to the same coating specifications. On the other hand, in the fourth embodiment, the reference sample is different in that there are no restrictions on materials and coating specifications. This reference sample is made of, for example, a metal substrate without a coating film. Specifically, the base material is made of a material (eg, titanium, platinum, stainless steel, etc.) whose surface potential is less likely to change over time due to corrosion.

Next, after completing the coating of the coated body 100, the surface potential of the coated body 100 is measured (step S12). Here, the term "after completion of coating" refers to the initial state in which the coating is applied to the coated body 100, and not only the new state in which the coated body 100 is coated for the first time, but also the coated body 100 to which repair coating is applied. state.

Next, the surface potential of the reference sample is measured in the same environment (step S13). The surface potential of this reference sample is also measured immediately after the coating of the body 100 is completed. Then, an initial difference value between the surface potentials of the coated body 100 and the reference sample is calculated, and this initial difference value is stored in the arithmetic processing unit 13 (step S14; storage step). This initial difference value serves as a reference for evaluating damage to the coated body 100 . Further, in the present embodiment, steps S11 to S14 described above are steps of determining the initial difference value in advance.

Next, according to a predetermined inspection schedule, the surface potential of the coated body 100 is measured (step S15), and the surface potential of the reference sample is measured in the same environment (step S16). Then, a difference value between the surface potentials of the coated body 100 and the reference sample is calculated, and this difference value is stored in the arithmetic processing unit 13 (step S17). In this embodiment, the surface potential of the reference sample is measured in the same environment for each inspection, and the difference value between the surface potential of the reference sample and the surface potential of the coated body 100 is calculated. can be compensated for, and the change in surface potential caused by the damage of the coated body 100 can be accurately evaluated.

Next, the difference value and the initial difference value recorded in the arithmetic processing unit 13 are read out, and the difference value and the initial difference value are compared to evaluate the damage of the coated body 100 (step S18). Specifically, when the difference value is smaller than the initial difference value, the coating film 102 of the coated body 100 has deteriorated due to the influence of water absorption, etc., and when the difference value turns to a value larger than the initial difference value , it can be evaluated that the substrate 101 is corroded under the coating film 102 . Therefore, it is possible to determine which of the coating film 102 and the substrate 101 is damaged by the magnitude of the difference value and the initial difference value, and the damage of the coated body 100 can be accurately evaluated. For example, when the calculated difference value is smaller than the initial difference value and a decreasing tendency is observed, it can be determined that the coating film 102 has deteriorated. Corrosion can be minimized. In this embodiment, steps S15 to S18 are steps for inspecting the coating body for damage.

This fourth embodiment includes a recording step of recording the initial difference values of the surface potentials of the coated body 100 and the reference sample under the same environment and in the initial state. Damage to the coated body 100 is evaluated based on the potential difference value and the initial difference value. Therefore, in addition to the effects of the first embodiment described above, damage to the coated body 100 can be accurately evaluated without preparing a reference sample of the same type as the coated body 100 . In addition, since the surface potential of the coated body 100 when the coating is in a new state is used as an evaluation criterion, changes (deterioration) of the coated body 100 over time can be accurately detected.

The components described above include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the above configurations can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration are possible without departing from the gist of the present disclosure. For example, by preparing a plurality of test pieces with different degrees of deterioration for each coating specification of the coated body 100 and obtaining the surface potential data of these test pieces in advance through experiments, it is possible to determine the deterioration of the coated body 100 from the measured values of the surface potential. You can also judge the degree.

As described above, the method for inspecting a coated body according to the present embodiment can be grasped, for example, as follows.

A method for inspecting a coated body according to the first aspect is a method for inspecting a coated body 100 in which an insulating coating film 102 is applied to the surface of a conductive base material 101, and a reference sample 200 is created. A step (step S3) and an evaluation step (step S6) of evaluating damage to the coated body 100 based on the difference in surface potential between the coated body 100 and the reference sample 200 in an environment with the same temperature T and relative humidity RH. and including.

According to this configuration, damage to the coated body 100 can be accurately evaluated using the surface potential of the reference sample 200 as a reference.

As a second aspect, the reference sample 200 is prepared with the same coating specifications as the coated body 100 using the same type of base material 201 and coating film 202 . According to this configuration, damage to the coated body 100 can be easily evaluated by comparing the surface potentials of the coated body 100 and the reference sample 200 .

As a third aspect, in the evaluation step (steps S6 and S7), if the difference value is smaller than the predetermined evaluation reference value S, it is evaluated as deterioration of the coating film 102, and the difference value is lower than the evaluation reference value S If it is large, it is evaluated as corrosion of the base material 101 . According to this configuration, the degree of damage to the coated body 100 can be accurately evaluated based on the relationship between the difference value and the evaluation reference value S.

As a fourth aspect, before the evaluation process (steps S6 and S7), the reference sample 200 is placed in the same environment as the coated body 100, and the calibration process (step S4). According to this configuration, it is possible to compensate for the influence of the temperature T and the relative humidity RH of the measurement environment, and to accurately evaluate the change in the surface potential due to the damage of the body 100 to be coated.

As a fifth aspect, in the evaluation step (steps S6A and S7), the surface potentials of the coated body 100 and the reference sample 200 are simultaneously measured to calculate the difference value. According to this configuration, the difference value can be quickly calculated, and damage to the coated body 100 can be quickly evaluated.

As a sixth aspect, a data table creation step (step S4A) is provided for creating a data table 300 in which the surface potentials of the reference sample 200 are measured under different conditions of temperature T and relative humidity RH. In the evaluation step (steps S6B and S7), the temperature T and relative humidity RH of the environment in which the coated body 100 is placed and the surface potential of the coated body 100 are measured, and the measured temperature T and relative humidity RH correspond to The surface potential of the reference sample 200 is read from the data table 300, and the difference value is calculated from the read surface potential of the reference sample 200 and the measured surface potential of the coated body 100. FIG. According to this configuration, there is no need to actually measure the surface potential of the reference sample 200 at the inspection site, and it is possible to easily calculate the difference value and evaluate the damage of the coated body 100 .

As a seventh aspect, a recording step (step S14) of recording the initial difference value of each surface potential of the coated body 100 and the reference sample under the same environment and in the initial state is provided, and in the evaluation step (step S18), the coated body The damage of the coated object 100 is evaluated based on the difference value and the initial difference value of the surface potentials of the sample 100 and the reference sample. According to this configuration, damage to the coated body 100 can be accurately evaluated without preparing a reference sample of the same type as the coated body 100 . In addition, since the surface potential of the coated body 100 when the coating is in a new state is used as an evaluation criterion, changes (deterioration) of the coated body 100 over time can be accurately detected.

REFERENCE SIGNS LIST 10 measuring device 11 probe 12 surface potential meter control device 13 arithmetic processing device 14 temperature and humidity sensor 100 coated body 101 base material 102 coating film 200 reference sample 201 base material 202 coating film 300 data table

Claims (7)

A method for inspecting a coated body in which an insulating coating film is applied to the surface of a conductive base material,
A creation process for creating a reference sample;
An evaluation step of evaluating damage to the coated body based on the difference in surface potential between the coated body and the reference sample in an environment with the same temperature and relative humidity;
A method for inspecting a painted body including 2. The method for inspecting a coated body according to claim 1, wherein the reference sample is prepared with the same coating specifications using the same type of the base material and the coating film as the coated body. In the evaluation step, when the difference value is smaller than a predetermined evaluation reference value, the coating film is evaluated as deteriorated, and when the difference value is greater than the evaluation reference value, the substrate is corroded. The method for inspecting a coated body according to claim 1 or 2, which is evaluated as. 4. The method according to any one of claims 1 to 3, further comprising a calibration step of placing the reference sample in the same environment as the coated body and performing zero point calibration of the surface potential of the reference sample before the evaluation step. The inspection method of the painted body of. 4. The method for inspecting a coated body according to claim 1, wherein in said evaluation step, the surface potentials of said coated body and said reference sample are simultaneously measured to calculate said difference value. A data table creation step of creating a data table in which the surface potential of the reference sample is measured under different conditions of temperature and relative humidity,
In the evaluation step, the temperature and relative humidity of the environment in which the coated body is placed, and the surface potential of the coated body are measured, and the surface potential of the reference sample corresponding to the measured temperature and relative humidity is obtained from the data table. 4. The method of inspecting a coated body according to claim 1, wherein the differential value is calculated from the read surface potential of the reference sample and the measured surface potential of the coated body. A recording step of recording an initial difference value of each surface potential of the coated body and the reference sample in the same environment and in the initial state,
4. The coating according to any one of claims 1 to 3, wherein in the evaluation step, damage to the coated body is evaluated based on a difference value of surface potentials between the coated body and the reference sample and the initial difference value. body examination method.

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