Corrosion sensor and corrosion measurement method

Abstract

To provide a corrosion sensor with which it is possible to grasp in more detail the manner of progress of corrosion from a coating flaw part and improve evaluation of progress of corrosion from the coating flaw part.SOLUTION: A corrosion sensor 1 according to the present invention comprises: a sensor body 2 having a coating flaw part 20; a plurality of current application terminals 3 for applying a current to the sensor body 2; a first pair of voltage measuring terminals 41 and a second pair of voltage measuring terminals 42 for measuring a voltage when a current is applied from the current application terminals 3, in which the manner of intersection between a first line segment L1 linking the first pair of voltage measuring terminals 41 and the coating flaw part 20 is different from the manner of intersection between a second line segment L2 linking the second pair of voltage measuring terminals 42 and the coating flaw part 20, with the first line segment L1 and the second line segment L2 arranged to be non-parallel to each other. Thus, the corrosion sensor 1 is constituted to obtain the width and depth of corrosion from the coating flaw part 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a corrosion sensor and a corrosion measurement method for measuring corrosion of a metallic material. [Background technology]

[0002] For example, development of corrosion monitoring technology for steel materials is underway against the backdrop of needs for life estimation of metal materials such as steel materials and research and development of corrosion-resistant steel materials. As shown in Patent Documents 1 and 2 below, for example, one known corrosion monitoring method is a method of measuring the amount of corrosion based on an increase in electrical resistance that accompanies a decrease in plate thickness.

[0003] Due to its principle, corrosion monitoring methods that utilize changes in electrical resistance are used to evaluate uniform corrosion of metal materials. However, localized corrosion from paint defects is an issue for coated metal sheets, such as coated steel, and metallic materials that suppress the progression of corrosion in paint defects are being developed. To evaluate such metallic materials, a notch is made in a portion of the coated steel, and an exposure test in a real environment or a corrosion test in a corrosion testing machine is performed for a predetermined period of time. After that, the paint film in the corroded area caused by the paint defect on the target structure or test specimen is peeled off, the corrosion product is removed, and the peeling area ratio and corrosion depth are investigated.

[0004] However, the peeling area is an evaluation that captures the surface area two-dimensionally, and the measurement of corrosion depth is limited to a certain depth. Even when shape measurement is performed using a laser, the initial state is unclear and it is difficult to set a reference surface, making it difficult to perform a simple evaluation. In addition, since the paint film is peeled off during the evaluation, the test cannot be continued, and changes over time cannot be evaluated using the same test piece.

[0005] Patent Document 3 listed below proposes a corrosion sensor comprising "a measurement metal, a reference metal made of the same metal as the measurement metal, and an insulating coating covering the measurement metal and the reference metal, the coating having a notch in a portion that overlaps with the measurement metal, the measurement metal and the reference metal being shielded from the measurement environment except for the position of the notch in the coating, and configured to be able to measure the electrical resistance of each of the measurement metal and the reference metal." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-197102 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-3376 [Patent Document 3] Japanese Patent Publication No. 2022-151951 Summary of the Invention [Problem to be solved by the invention]

[0007] The corrosion sensor in Patent Document 3 can easily evaluate the amount of corrosion due to localized corrosion, but it cannot grasp in detail how corrosion progresses from a paint defect, and there is room for improvement in evaluating the progress of corrosion from a paint defect. More specifically, the corrosion sensor in Patent Document 3 cannot obtain the width and depth of corrosion from a paint defect.

[0008] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a corrosion sensor and a corrosion measurement method that can obtain more detailed information about how corrosion progresses from a paint defect and improve the evaluation of the progression of corrosion from a paint defect. [Means for solving the problem]

[0009] In one embodiment, the corrosion sensor according to the present invention comprises: a sensor body made of a painted metal plate having a linear paint defect; a plurality of current application terminals provided on the sensor body for applying current to the sensor body; and a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body for measuring voltage when current is applied from the current application terminals, wherein the first line segment connecting the first pair of voltage measurement terminals and the paint defect intersects with a different pattern than the second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are arranged non-parallel to each other. The corrosion sensor is configured to determine the width and depth of corrosion from the paint defect from the value of the current applied from the current application terminals, the first voltage measured by the first pair of voltage measurement terminals, and the second voltage measured by the second pair of voltage measurement terminals.

[0010] In one embodiment, a corrosion measurement method according to the present invention includes measuring voltage using a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body when a current is applied to the sensor body, which is made of a painted metal plate having a linear paint defect, wherein the first pair of voltage measurement terminals and the second pair of voltage measurement terminals are arranged so that the intersection pattern between a first line segment connecting the first pair of voltage measurement terminals and the paint defect is different from the intersection pattern between a second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are non-parallel to each other, and determining the width and depth of corrosion from the paint defect from the value of the current, the first voltage measured by the first pair of voltage measurement terminals, and the second voltage measured by the second pair of voltage measurement terminals. [Effects of the Invention]

[0011] According to one embodiment of the corrosion sensor and corrosion measurement method of the present invention, the width and depth of the paint defect are obtained from the value of the current applied from the current application terminal, the first voltage measured by the first pair of voltage measurement terminals, and the second voltage measured by the second pair of voltage measurement terminals, so that it is possible to obtain more detailed information about how corrosion from the paint defect is progressing, and to improve the evaluation of the progression of corrosion from the paint defect. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a plan view showing a corrosion sensor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory view showing corrosion from a paint defect in FIG. 1. [Figure 3] FIG. 2 is an enlarged view showing an area III in FIG. 1. [Figure 4] FIG. 10 is a plan view showing a corrosion sensor according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a plan view showing a corrosion sensor according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a plan view showing a corrosion sensor according to a fourth embodiment of the present invention. [Figure 7] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the rate of change in the second electrical resistance in Example 1. [Figure 8] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the ratio of the rate of change of the second electrical resistance to the rate of change of the first electrical resistance in Example 1. [Figure 9] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the rate of change in the second electrical resistance in Example 2. [Figure 10] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the ratio of the rate of change of the second electrical resistance to the rate of change of the first electrical resistance in Example 2. [Figure 11] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the rate of change in the second electrical resistance in Example 3. [Figure 12] 10 is a graph showing the relationship between the product of the width and depth of corrosion and the ratio of the rate of change of the second electrical resistance to the rate of change of the first electrical resistance in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0014] [About corrosion sensors] Embodiment 1 Fig. 1 is a plan view showing a corrosion sensor 1 according to a first embodiment of the present invention, Fig. 2 is an explanatory view showing corrosion from a paint defect 20 in Fig. 1, and Fig. 3 is an enlarged view showing an enlarged region III in Fig. 1. The corrosion sensor 1 shown in Fig. 1 has a sensor body 2, a plurality of current application terminals 3, a first pair of voltage measurement terminals 41, and a second pair of voltage measurement terminals 42.

[0015] The sensor body 2 is made of a painted metal plate having a linear paint scratch 20. Various metal plates can be used as the base metal plate for the painted metal plate. The metal plate may be, for example, a zinc plate, a copper plate, or an aluminum plate, but is typically a steel plate. Various paints can be used as the paint for forming the coating on the painted metal plate. Commonly used paint resins can be used, such as epoxy resin, urethane resin, vinyl resin, polyester resin, acrylic resin, alkyd resin, phthalate resin, butyral resin, melamine resin, or phenolic resin. While the outer shape of the illustrated sensor body 2 is rectangular in plan view, the outer shape of the sensor body 2 may be changed as desired.

[0016] The paint scratch 20 may be a portion where the paint film has been removed to reveal the base of the painted metal plate. The paint scratch 20 may also be a scratch formed in the base of the painted metal plate after the paint film has been removed. "Linear" means that it extends over a long distance, and the width of the paint scratch 20 is arbitrary. When the sensor main body 2 is placed in a corrosive environment, corrosion will progress from the paint scratch 20.

[0017] The multiple current application terminals 3 are provided on the sensor main body 2 and are used to apply current to the sensor main body 2. A current source 30 is connected to the current application terminals 3. The current may be either direct current or alternating current. When using alternating current, it is preferable to use a low frequency range of 100 kHz or less, taking into account the skin effect.

[0018] The first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 are each provided on the sensor main body 2, and are terminals for measuring a voltage when a current is applied from the current application terminals 3. A first voltmeter 51 is connected to the first pair of voltage measurement terminals 41, and the first voltmeter 51 measures a first voltage V1 between the first pair of voltage measurement terminals 41. Similarly, a second voltmeter 52 is connected to the second pair of voltage measurement terminals 42, and the second voltmeter 52 measures a second voltage V2 between the second pair of voltage measurement terminals 42.

[0019] The first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 are arranged such that the intersection between the first line segment L1 connecting the first pair of voltage measurement terminals 41 and the paint defect 20 is different from the intersection between the second line segment L2 connecting the second pair of voltage measurement terminals 42 and the paint defect 20, and the first line segment L1 and the second line segment L2 are non-parallel to each other. The different intersections may be understood to include different intersecting angles and differences in whether or not the lines intersect. The first line segment L1 may be a line segment connecting the centers of the first pair of voltage measurement terminals 41, and the second line segment L2 may be a line segment connecting the centers of the second pair of voltage measurement terminals 42. The first angle θ1 and the second angle θ2 may be angles formed by the first line segment L1 and the second line segment L2 with a line L3 (see FIG. 3 ) passing through the widthwise center position of the paint defect 20. The line L3 may be defined in the initial state of the corrosion sensor 1.

[0020] The corrosion sensor 1 of this embodiment is configured to obtain the width a and depth b (see Figure 2) of corrosion from the paint defect 20 from the value of the current applied from the current application terminal 3, the first voltage V1 measured by the first pair of voltage measurement terminals 41, and the second voltage V2 measured by the second pair of voltage measurement terminals 42.

[0021] Conventional corrosion sensors, such as those described in Patent Document 3, were unable to measure the width a and depth b of corrosion from the paint defect 20. However, the inventors conducted various studies and discovered that when the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 are arranged as described above, the first electrical resistance R1 calculated from the first voltage V1 and the current value at that time and the second electrical resistance R2 calculated from the second voltage V2 and the current value at that time exhibit different values ​​depending on the width a and depth b of corrosion from the paint defect 20. Therefore, by observing the first electrical resistance R1 and the second electrical resistance R2, the width a and depth b of corrosion from the paint defect 20 can be obtained. Obtaining the width a and depth b of corrosion using the corrosion sensor 1 of the present embodiment allows for more detailed information on how corrosion from the paint defect 20 progresses, improving the evaluation of corrosion progression from the paint defect 20. Improving corrosion progression evaluation can contribute to elucidating corrosion mechanisms and developing corrosion-resistant metal materials (steel materials). The width a and depth b of corrosion may be obtained at any interval, but are preferably obtained at regular intervals.

[0022] More specifically, in the initial state of the corrosion sensor 1 (a state in which the paint scratch 20 has not yet formed on the sensor body 2, or a state before corrosion from the paint scratch 20 has occurred), the width a and depth b of the corrosion can be obtained from the rate of change (R1 / R10) of the first electrical resistance R1 measured when observing corrosion from the paint scratch 20 relative to the first initial electrical resistance R10 obtained from the first voltage V1 and the current value at that time, and the rate of change (R2 / R20) of the second electrical resistance R2 measured when observing corrosion from the paint scratch 20 relative to the second initial electrical resistance R20 obtained from the second voltage V2 and the current value at that time in the initial state of the corrosion sensor 1.

[0023] More specifically, by obtaining a correlation between the width a and depth b of corrosion and the rate of change of the first electrical resistance R1 (R1 / R10) and the rate of change of the second electrical resistance R2 (R2 / R20), a function expressing the width a and depth b of corrosion can be obtained in advance using the rate of change of the first electrical resistance R1 (R1 / R10) and the rate of change of the second electrical resistance R2 (R2 / R20) as variables, and the width a and depth b of corrosion can be obtained from this function and the rate of change of the first electrical resistance R1 (R1 / R10) and the rate of change of the second electrical resistance R2 (R2 / R20). The function may be obtained by simulation testing or numerical analysis.

[0024] The functions representing the width a and depth b of corrosion depend on the shape of the corrosion from the paint scratch 20, so numerical analysis is suitable. An example of numerical analysis is electromagnetic field analysis. In numerical analysis or electromagnetic field analysis, the first electrical resistance R1 and the second electrical resistance R2 are calculated from the shape of the corrosion (forward analysis). When using the corrosion sensor 1, the width a and depth b of the corrosion can be determined by performing an inverse analysis to determine the shape of the corrosion from the first electrical resistance R1 and the second electrical resistance R2. It is preferable to express the width a and depth b of the corrosion as a function as a simple method of calculating them. Examples of functions include the following:

[0025]

number

[0026]

number

[0027] As shown in Figure 2, the cross-sectional area of ​​corrosion from the paint scratch 20 decreases in the depth direction in an elliptical shape. Therefore, as in the first equation above, a function representing the product (ab) of the width a and depth b, which corresponds to the area of ​​the ellipse, can be obtained using the rate of change of the second electrical resistance R2 (R2 / R20) as a variable. Although the cross-sectional area of ​​corrosion from the paint scratch 20 may not be constant in the width direction, a correlation can be found from values ​​obtained by numerical analysis, as in the second equation above. Here, A, B, C, and D in the above equation are coefficients. The coefficients A, B, C, and D are determined arbitrarily depending on the shape of the sensor body 2, the arrangement of each terminal, and other factors. In other words, the function representing the width a and depth b of corrosion can be obtained for each shape of the sensor body 2 and the arrangement of each terminal.

[0028] In this embodiment, the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 are arranged so that the first angle θ1 at which the first line segment L1 intersects with the paint defect portion 20 is different from the second angle θ2 at which the second line segment L2 intersects with the paint defect portion 20.

[0029] When the first angle θ1 is different from the second angle θ2 as in the configuration of this embodiment, either the first angle θ1 or the second angle θ2 may be 90°, and either the first angle θ1 or the second angle θ2 may be 0°.

[0030] In this embodiment, the first angle θ1 is set to 90°. From this perspective, the first voltage V1 between the first pair of voltage measurement terminals 41 may be referred to as a vertical voltage. Note that, in the present invention, "90°" does not only refer to the strict 90°, but also includes a substantial 90° that includes an allowable error in the technical field of the present invention. For example, when the angle formed by the first line segment L1 connecting the first pair of voltage measurement terminals 41 and the line L3 passing through the widthwise center position of the paint defect 20 is within the range of 90°±20° (70° or more and 110° or less), the first angle θ1 may be understood to be 90°.

[0031] In this embodiment, the second angle θ2 is set to 0°. In other words, the second line segment L2 and the paint defect 20 extend on the same straight line. From this perspective, the second voltage V2 between the second pair of voltage measurement terminals 42 may be referred to as a parallel voltage. Note that, in the present invention, "0°" may not only refer to the strict 0° but also to a substantial 0° that includes an allowable error in the technical field of the present invention. For example, when the angle formed by the second line segment L2 connecting the second pair of voltage measurement terminals 42 and the line L3 passing through the widthwise center position of the paint defect 20 is within the range of 0°±20° (when the angle is greater than or equal to -20° and less than or equal to +20°), the second angle θ2 may be understood to be 0°.

[0032] In the illustrated embodiment, the second pair of voltage measurement terminals 42 are shown to be provided on the paint defect portion 20, but the second pair of voltage measurement terminals 42 may also be positioned on an extension of the paint defect portion 20 (outside both longitudinal ends of the paint defect portion 20).

[0033] The distance between the first pair of voltage measurement terminals 41 and the distance between the second pair of voltage measurement terminals 42 may be set arbitrarily, but it is preferable to set them to 1 mm or more in order to reduce the effect of the resistance of each terminal on the voltage or resistance being measured.

[0034] The current supply terminals 3 of this embodiment include a first pair of current supply terminals 31 for supplying a current when measuring a voltage with the first pair of voltage measurement terminals 41, and a second pair of current supply terminals 32 for supplying a current when measuring a voltage with the second pair of voltage measurement terminals 42. The current source 30 may be configured to be connected sequentially to the first pair of current supply terminals 31 and the second pair of current supply terminals 32. As shown in the figure, the first pair of current supply terminals 31 may be located outside the first pair of voltage measurement terminals 41, i.e., on an extension of the first line segment L1. Similarly, the second pair of current supply terminals 32 may be located outside the second pair of voltage measurement terminals 42, i.e., on an extension of the second line segment L2. The first pair of current supply terminals 31 and the second pair of current supply terminals 32 may not be located strictly on the extensions of the first line segment L1 and the second line segment L2, but may be located at positions offset from each other.

[0035] Embodiment 2 4 is a plan view showing a corrosion sensor 1 according to a second embodiment of the present invention. In the first embodiment, the second pair of voltage measurement terminals 42 is described as being provided on the paint defect 20 or on an extension thereof, but the position of the second pair of voltage measurement terminals 42 may be changed as appropriate. As shown in FIG. 4, the second pair of voltage measurement terminals 42 may be disposed at diagonal positions on the sensor main body 2. In this case, the second angle θ2 at which the second line segment L2 connecting the second pair of voltage measurement terminals 42 intersects with the paint defect 20 may be changed as appropriate depending on the aspect ratio of the sensor main body 2.

[0036] Furthermore, in the first embodiment, the current application terminals 3 have been described as including a first pair of current application terminals 31 for applying a current when measuring a voltage with the first pair of voltage measurement terminals 41, and a second pair of current application terminals 32 for applying a current when measuring a voltage with the second pair of voltage measurement terminals 42. However, as shown in FIG. 4, only one pair of current application terminals 3 may be provided, and the pair of current application terminals 3 may be shared by the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42. In the illustrated embodiment, the pair of current application terminals 3 are arranged at diagonal positions on the sensor main body 2, but the position of the pair of current application terminals 3 may be changed as desired. The other configurations are the same as those of the first embodiment.

[0037] Embodiment 3 FIG. 5 is a plan view showing a corrosion sensor 1 according to a third embodiment of the present invention. In the first embodiment, the first angle θ1 at which the first line segment L1 connecting the first pair of voltage measurement terminals 41 intersects with the paint defect 20 is 90°, and the second angle θ2 at which the second line segment L2 connecting the second pair of voltage measurement terminals 42 intersects with the paint defect 20 is 0°. However, as shown in FIG. 5, the first angle θ1 and the second angle θ2 may be changed as desired. In the illustrated embodiment, the first angle θ1 is 80°, and the second angle θ2 is 30°. The remaining configuration is the same as in the first and second embodiments.

[0038] Embodiment 4 FIG. 6 is a plan view showing a corrosion sensor 1 according to a fourth embodiment of the present invention. In the first embodiment, both the first line segment L1 connecting the first pair of voltage measurement terminals 41 and the second line segment L2 connecting the second pair of voltage measurement terminals 42 intersect with the paint defect 20. However, the first line segment L1 connecting the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 may be arranged so that one of the first line segment L1 and the second line segment L2 intersects with the paint defect 20 and the other does not intersect with the paint defect 20. In the illustrated embodiment, the first line segment L1 intersects with the paint defect 20 and the second line segment L2 does not intersect with the paint defect 20. The shortest distance between the other of the first line segment L1 and the second line segment L2 that does not intersect with the paint defect 20 and a straight line L3 passing through the paint defect 20 or its center in the width direction is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. Additionally and / or alternatively, it is preferable that the other of the first line segment L1 and the second line segment L2 that does not intersect with the paint defect portion 20 is positioned within a range that intersects with one of the first line segment L1 and the second line segment L2 that intersects with the paint defect portion 20.

[0039] As in the configuration of the fourth embodiment, when one of the first line segment L1 and the second line segment L2 intersects with the paint defect 20 and the other does not intersect with the paint defect 20, the angle at which one of the line segments L1 and L2 intersects with the paint defect 20 may be 90°. In this case, the other line segment L2 may be parallel to the paint defect 20.

[0040] In the illustrated embodiment, the first line segment L1 intersects with the paint defect 20 at an angle of 90°, and the second line segment L2 is disposed parallel to the paint defect 20. In the present invention, "parallel" does not only mean "strictly parallel," but also includes "substantially parallel," which includes an error that is acceptable in the technical field of the present invention. For example, when the angle formed by the extension of the second line segment L2 connecting the second pair of voltage measurement terminals 42 and the line L3 passing through the center position of the paint defect 20 in the width direction is within the range of 0°±20° (when the angle is greater than or equal to -20° and less than or equal to +20°), the second line segment L2 can be understood to be disposed parallel to the paint defect 20. Other configurations are the same as those of the first to third embodiments.

[0041] [Corrosion measurement method] The corrosion measurement method of the present embodiment includes: When a current is applied to a sensor body (2) made of a painted metal plate having a linear paint defect (20), voltage is measured by a first pair of voltage measurement terminals (41) and a second pair of voltage measurement terminals (42) provided on the sensor body (2), and the first pair of voltage measurement terminals (41) and the second pair of voltage measurement terminals (42) are arranged so that the intersection between a first line segment (L1) connecting the first pair of voltage measurement terminals (41) and the paint defect (20) is different from the intersection between a second line segment (L2) connecting the second pair of voltage measurement terminals (42) and the paint defect (20), and the first line segment (L1) and the second line segment (L2) are not parallel to each other; and This includes obtaining the width a and depth b of corrosion from the paint defect 20 from the current value, the first voltage V1 measured by the first pair of voltage measurement terminals 41, and the second voltage V2 measured by the second pair of voltage measurement terminals 42.

[0042] The corrosion measurement method of this embodiment can be carried out using the corrosion sensor 1 as explained in Embodiments 1 to 4. The first voltage V1 and the second voltage V2 may be measured sequentially or simultaneously.

[0043] The corrosion measurement method of the present embodiment includes: In an initial state of the corrosion sensor 1, a first initial electrical resistance R10 is obtained from the first voltage V1 and the current value at that time, and a second initial electrical resistance R20 is obtained from the second voltage V2 and the current value at that time; When observing corrosion from the paint scratch portion 20, a first electric resistance R1 is obtained from the first voltage V1 and the current value at that time, and a second electric resistance R2 is obtained from the second voltage V2 and the current value at that time; and After obtaining the first electrical resistance R1 and the second electrical resistance R2, obtain the rate of change (R1 / R10) of the first electrical resistance R1 relative to the first initial electrical resistance R10 and the rate of change (R2 / R20) of the second electrical resistance R2 relative to the second initial electrical resistance R20. It may further include:

[0044] The initial state of the corrosion sensor 1 may be a state in which the paint defect 20 is not formed on the sensor body 2, or a state in which corrosion from the paint defect 20 has not yet occurred.

[0045] The corrosion measurement method of the present embodiment includes: A process of investigating the correlation between the width a and depth b of corrosion and the rate of change of the first electrical resistance R1 (R1 / R10) and the rate of change of the second electrical resistance R2 (R2 / R20) to obtain a function representing the width a and depth b of corrosion using the rate of change of the first electrical resistance R1 (R1 / R10) and the rate of change of the second electrical resistance R2 (R2 / R20) as variables; When obtaining the width a and depth b of corrosion from the paint scratch portion 20, a step of substituting the obtained values ​​of the rate of change (R1 / R10) of the first electrical resistance R1 and the rate of change (R2 / R20) of the second electrical resistance R2 into the function. The step of obtaining the function may further include performing a simulation test or a numerical analysis. A function representing the product (ab) of the width a and the depth b may be obtained using the rate of change (R2 / R20) of the second electrical resistance R2 as a variable. The function representing the width a and depth b of corrosion may be obtained for each shape of the sensor body 2 and each arrangement of the terminals.

[0046] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0048] Example 1 The inventors carried out a corrosion test simulation using a finite difference method program written in C language. The basic conditions for the simulation were as follows: a steel specimen (volume resistivity: 1×10) measuring 50 mm wide x 75 mm long x 0.5 mm thick was used. -7 A model of the sensor body 2 with a resistance of Ω·m was created, and a paint defect 20 was formed on the model of the sensor body 2. The paint defect 20 was formed at the center position in the width direction of the model of the sensor body 2, extending in the length direction of the sensor body 2, and had a length of 50 mm.

[0049] As described with reference to FIG. 1 , the current application terminals 3 (first pair of current application terminals 31 and second pair of current application terminals 32), first pair of voltage measurement terminals 41, and second pair of voltage measurement terminals 42 were arranged. That is, the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 were arranged so that the first angle θ1 formed by the first line segment L1 connecting the first pair of voltage measurement terminals 41 and the paint defect 20 was 90°, and the second angle θ2 formed by the second line segment L2 connecting the second pair of voltage measurement terminals 42 and the paint defect 20 was 0°. The first pair of voltage measurement terminals 41 was arranged on both sides of the paint defect 20, and the second pair of voltage measurement terminals 42 was arranged above the paint defect 20. The distance between the first pair of voltage measurement terminals 41 and the distance between the second pair of voltage measurement terminals 42 were both 10 mm. The first pair of current application terminals 31 was arranged on an extension of the first line segment L1, and the second pair of current application terminals 32 was arranged on an extension of the second line segment L2.

[0050] Then, while changing the width a and depth b of the corrosion from the paint scratch 20, the first voltage V1 (vertical voltage) measured by the first pair of voltage measurement terminals 41 and the second voltage V2 (parallel voltage) measured by the second pair of voltage measurement terminals 42 were calculated using electromagnetic field analysis. The current value was kept constant at 1 A. The width a and depth b of the corrosion were changed between 0.05 and 0.45 mm.

[0051] The basic equations used in the electromagnetic field analysis are as follows: ▽·εE=0 i=ρE where E is the electric field, i is the current density, ε is the permittivity, and ρ is the conductivity.

[0052] The initial state of the corrosion sensor 1 was a state in which no paint scratches 20 had formed on the sensor body 2. In this state, the first initial electrical resistance R10 (initial perpendicular resistance) was calculated from the first voltage V1 and the current value at that time, and the second initial electrical resistance R20 (initial parallel resistance) was calculated from the second voltage V2 and the current value at that time. Furthermore, when the width a and depth b of the corrosion were changed as described above, the first electrical resistance R1 (perpendicular resistance) was calculated from the first voltage V1 and the current value at that time, and the second electrical resistance R2 (parallel resistance) was calculated from the second voltage V2 and the current value at that time.

[0053] FIG. 7 is a graph showing the relationship between the product (ab) of the width a and depth b of the corrosion and the rate of change (R2 / R20) of the second electrical resistance R2 in Example 1, and FIG. 8 is a graph showing the relationship between the product (a(0.0005-b)) of the width a and depth b of the corrosion in Example 1 and the rate of change (R2 / R20) of the second electrical resistance R2 in Example 1. 2 8 is a graph showing the relationship between the ratio [{(R2 / R20)-1} / {(R1 / R10)-1}] of the rate of change of the second electrical resistance R2 (R2 / R20) and the rate of change of the first electrical resistance R1 (R1 / R10). After examining various values ​​for the corrosion width a and depth b, as well as the calculated first initial electrical resistance R10, second initial electrical resistance R20, first electrical resistance R1, and second electrical resistance R2, the results were organized as shown in the graphs shown in FIGS. 7 and 8. The following approximate formula was obtained from the relationships shown in FIGS. 7 and 8. In the approximate formula, A, B, C, and D are coefficients. The coefficients A, B, C, and D vary depending on the shape of the sensor body 2 and the arrangement of each terminal.

[0054]

number

[0055]

number

[0056] The cross-sectional area of ​​corrosion from the paint scratch 20 in the depth direction decreases in an elliptical shape. Utilizing this, as in the first equation above, a function was obtained that expresses the product (ab) of the width a and depth b, which correspond to the area of ​​the ellipse, using the rate of change of the second electrical resistance R2 (R2 / R20) as a variable. On the other hand, the cross-sectional area of ​​corrosion from the paint scratch 20 in the width direction was not constant, but after various investigations, the second equation above was obtained.

[0057] These approximate formulas can be rearranged for the width a and depth b of corrosion as follows:

[0058]

number

[0059]

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[0060] Therefore, the width a and depth b of corrosion can be obtained from these two equations. From these results, it can be seen that the corrosion sensor 1 of the present invention is configured to be able to obtain the width a and depth b of corrosion from the paint flaw 20 from the value of the current applied from the current application terminals 3, the first voltage V1 measured by the first pair of voltage measurement terminals 41, and the second voltage V2 measured by the second pair of voltage measurement terminals 42.

[0061] Example 2. The inventors performed a similar corrosion test simulation by changing the arrangement of the current application terminals 3 (first pair of current application terminals 31 and second pair of current application terminals 32) and the first pair of voltage measurement terminals 41 and second pair of voltage measurement terminals 42 from the above-mentioned Example 1. Specifically, as shown in FIG. 4, the second pair of voltage measurement terminals 42 and the current application terminals 3 were arranged at diagonal positions on the sensor main body 2.

[0062] As in Example 1, various studies were conducted on the width a and depth b of the corrosion, as well as the calculated first initial electrical resistance R10, second initial electrical resistance R20, first electrical resistance R1, and second electrical resistance R2, and the results were organized as shown in the graphs in Figures 9 and 10. Figure 9 is a graph showing the relationship between the product (ab) of the width a and depth b of the corrosion in Example 2 and the rate of change (R2 / R20) of the second electrical resistance R2, and Figure 10 is a graph showing the relationship between the product {a(0.0005-b)} of the width a and depth b of the corrosion in Example 2. 2} and the ratio [{(R2 / R20)-1} / {(R1 / R10)-1}] of the rate of change of the second electrical resistance R2 (R2 / R20) to the rate of change of the first electrical resistance R1 (R1 / R10).

[0063] 9 and 10 of Example 2 and the graphs of Example 1 in Figures 7 and 8, a correlation similar to that of Example 1 is observed when the terminals are arranged as shown in Figure 4. This result shows that the width a and depth b of corrosion from the paint defect 20 can be obtained even if the terminal arrangement is changed.

[0064] Example 3. The inventors performed a similar corrosion test simulation by changing the arrangement of the current application terminals 3 (the first pair of current application terminals 31 and the second pair of current application terminals 32) and the first pair of voltage measurement terminals 41 and the second pair of voltage measurement terminals 42 from Example 1 described above. Specifically, as shown in Fig. 6, the first pair of current application terminals 31 and the second pair of current application terminals 32 were arranged so that the first line segment L1 intersected the paint defect 20 while the second line segment L2 did not intersect the paint defect 20. The second line segment L2 extended parallel to the paint defect 20 at a position 5 mm away from the paint defect 20.

[0065] As in Example 1, various studies were conducted on the width a and depth b of the corrosion, as well as the calculated first initial electrical resistance R10, second initial electrical resistance R20, first electrical resistance R1, and second electrical resistance R2, and the results were organized as shown in the graphs in Figures 11 and 12. Figure 11 is a graph showing the relationship between the product (ab) of the width a and depth b of the corrosion in Example 3 and the rate of change (R2 / R20) of the second electrical resistance R2, and Figure 12 is a graph showing the relationship between the product {a(0.0005-b)} of the width a and depth b of the corrosion in Example 3. 2} and the ratio [{(R2 / R20)-1} / {(R1 / R10)-1}] of the rate of change of the second electrical resistance R2 (R2 / R20) to the rate of change of the first electrical resistance R1 (R1 / R10).

[0066] 11 and 12 for Example 3 and the graphs of Example 1 in Figures 7 and 8, a correlation similar to that in Example 1 is observed when the terminals are arranged as in Figure 6. This result shows that the width a and depth b of corrosion from the paint scratch 20 can be obtained even if the terminal arrangement is changed.

[0067] The invention described in this specification can also be described as follows. [1] a sensor body made of a painted metal plate having a linear paint scratch; a plurality of current application terminals provided on the sensor main body for applying a current to the sensor main body; a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body for measuring a voltage when a current is applied from the current application terminals, wherein an intersection between a first line segment connecting the first pair of voltage measurement terminals and the paint defect is different from an intersection between a second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are arranged so as to be non-parallel to each other; Equipped with and determining a width and depth of corrosion from the paint defect based on a value of a current applied from the current application terminals, a first voltage measured by the first pair of voltage measurement terminals, and a second voltage measured by the second pair of voltage measurement terminals. Corrosion sensors. [2] The first pair of voltage measurement terminals and the second pair of voltage measurement terminals are The first line segment and the paint defect are arranged so that a first angle at which the first line segment intersects with the paint defect is different from a second angle at which the second line segment intersects with the paint defect; or One of the first line segment and the second line segment intersects with the paint defect portion, and the other is arranged so as not to intersect with the paint defect portion. 2. The corrosion sensor according to claim 1. [3] When the first angle is different from the second angle, either the first angle or the second angle is 90°; When one of the first line segment and the second line segment intersects with the paint defect portion and the other does not intersect with the paint defect portion, the angle at which the one line segment intersects with the paint defect portion is 90°. 3. The corrosion sensor according to claim 2. [4] When the first angle is different from the second angle, either the first angle or the second angle is 0°; When one of the first line segment and the second line segment intersects with the paint defect portion and the other does not intersect with the paint defect portion, the other line segment is parallel to the paint defect portion. 4. The corrosion sensor according to claim 2 or 3. [5] When a current is applied to a sensor body made of a painted metal plate having a linear paint defect, voltage is measured by a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body, wherein the first pair of voltage measurement terminals and the second pair of voltage measurement terminals are arranged so that an intersection between a first line segment connecting the first pair of voltage measurement terminals and the paint defect differs from an intersection between a second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are not parallel to each other; and and obtaining a width and depth of corrosion from the paint defect from the value of the current, a first voltage measured by the first pair of voltage measurement terminals, and a second voltage measured by the second pair of voltage measurement terminals. Including, Corrosion measurement methods. [Explanation of symbols]

[0068] 1: Corrosion sensor 2: Sensor body 3: Current application terminal 20: Paint damage 41: First pair of voltage measurement terminals 42: Second pair of voltage measurement terminals

Claims

1. a sensor body made of a painted metal plate having a linear paint scratch; a plurality of current application terminals provided on the sensor body for applying a current to the sensor body; a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body for measuring a voltage when a current is applied from the current application terminals, wherein an intersection between a first line segment connecting the first pair of voltage measurement terminals and the paint defect is different from an intersection between a second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are arranged so as to be non-parallel to each other; Equipped with and determining a width and depth of corrosion from the paint defect based on a value of a current applied from the current application terminals, a first voltage measured by the first pair of voltage measurement terminals, and a second voltage measured by the second pair of voltage measurement terminals. Corrosion sensors.

2. The first pair of voltage measurement terminals and the second pair of voltage measurement terminals are The first line segment and the paint defect are arranged such that a first angle at which the first line segment intersects with the paint defect is different from a second angle at which the second line segment intersects with the paint defect; or one of the first line segment and the second line segment intersects with the paint defect portion, and the other is arranged so as not to intersect with the paint defect portion; The corrosion sensor according to claim 1 .

3. When the first angle is different from the second angle, either the first angle or the second angle is 90°; When one of the first line segment and the second line segment intersects with the paint defect portion and the other does not intersect with the paint defect portion, the angle at which the one line segment intersects with the paint defect portion is 90°. The corrosion sensor according to claim 2 .

4. When the first angle is different from the second angle, either the first angle or the second angle is 0°; When one of the first line segment and the second line segment intersects with the paint defect portion and the other does not intersect with the paint defect portion, the other line segment is parallel to the paint defect portion. The corrosion sensor according to claim 2 or 3.

5. When a current is applied to a sensor body made of a painted metal plate having a linear paint defect, voltage is measured by a first pair of voltage measurement terminals and a second pair of voltage measurement terminals provided on the sensor body, wherein the first pair of voltage measurement terminals and the second pair of voltage measurement terminals are arranged so that an intersection between a first line segment connecting the first pair of voltage measurement terminals and the paint defect differs from an intersection between a second line segment connecting the second pair of voltage measurement terminals and the paint defect, and the first line segment and the second line segment are not parallel to each other; and and obtaining a width and depth of corrosion from the paint defect from the value of the current, a first voltage measured by the first pair of voltage measurement terminals, and a second voltage measured by the second pair of voltage measurement terminals. Including, Corrosion measurement methods.

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