Corrosion sensor

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 first plate part 21 and a second plate part 22 extending intersecting each other; a linear coating flaw part 3 provided to the second plate part 22 so as to extend in the extension direction of the second plate part 22 including an intersecting part 23 of the first plate part 21 and the second plate part 22; a first resistance measurer 4 for measuring a first electrical resistance R1 between a first pair of points 61 provided to the first plate part 21 so that the coating flaw part 3 is located therebetween; and a second resistance measurer 5 for measuring a second electrical resistance R2 between a second pair of points 62 provided to the second plate part 22. Thus, the corrosion sensor 1 is constituted to obtain the width a and depth b of corrosion from the coating flaw part 3 from the first electrical resistance R1 and the second electrical resistance R2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a corrosion sensor 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 that can obtain more detailed information about how corrosion progresses from a paint defect and can improve the evaluation of the progression of corrosion from a paint defect. [Means for solving the problem]

[0009] In one embodiment, the corrosion sensor of the present invention comprises a sensor body made of a painted metal plate having a first plate portion and a second plate portion extending and intersecting each other, a linear paint defect portion provided on the second plate portion so as to extend in the extension direction of the second plate portion including the intersection of the first plate portion and the second plate portion, a first resistance meter for measuring a first electrical resistance between a first pair of points provided on the first plate portion spaced apart in the extension direction of the first plate portion so that the paint defect is located therebetween, and a second resistance meter for measuring a second electrical resistance between a second pair of points provided on the second plate portion spaced apart in the extension direction of the second plate portion, and is configured to obtain the width and depth of corrosion from the paint defect portion from the first electrical resistance and the second electrical resistance. [Effects of the Invention]

[0010] According to one embodiment of the corrosion sensor of the present invention, the width and depth of corrosion from a paint defect are obtained from the first electrical resistance and the second electrical resistance, so that it is possible to obtain more detailed information about how corrosion from a paint defect is progressing, thereby improving the evaluation of the progression of corrosion from a paint defect. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a plan view showing a corrosion sensor according to an 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 a plan view showing a first modified example of the corrosion sensor of FIG. [Figure 4] FIG. 2 is a plan view showing a second modified example of the corrosion sensor of FIG. [Figure 5] FIG. 10 is a plan view showing a third modified example of the corrosion sensor of FIG. [Figure 6] 4 is a graph showing the relationship between the rate of change in second electrical resistance and the depth of corrosion in an example. [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 an example. [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 an example. [Figure 9] 10 is a graph showing the relationship between the predicted value of corrosion depth and the set value in the example. [Figure 10] 10 is a graph showing the relationship between the predicted value of the corrosion width and the set value in the example. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] Fig. 1 is a plan view showing a corrosion sensor 1 according to an embodiment of the present invention, and Fig. 2 is an explanatory diagram showing corrosion from a paint defect 3 in Fig. 1. Fig. 3 is a plan view showing a first modified example of the corrosion sensor 1 in Fig. 1, Fig. 4 is a plan view showing a second modified example of the corrosion sensor 1 in Fig. 1, and Fig. 5 is a plan view showing a third modified example of the corrosion sensor 1 in Fig. 1. The corrosion sensor 1 shown in Fig. 1 has a sensor body 2, a paint defect 3, a first resistance meter 4, and a second resistance meter 5.

[0014] The sensor body 2 is made of a painted metal plate. 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 that forms the coating on the painted metal plate. The paint can be a commonly used paint resin, such as epoxy resin, urethane resin, vinyl resin, polyester resin, acrylic resin, alkyd resin, phthalic acid resin, butyral resin, melamine resin, or phenolic resin.

[0015] The sensor main body 2 has a first plate portion 21 and a second plate portion 22 that extend and intersect with each other. The first plate portion 21 and the second plate portion 22 may each be part of a painted metal plate that constitutes the sensor main body 2, and may extend on the same plane. The outer shapes of the first plate portion 21 and the second plate portion 22 may be any shape, but may be rectangular when viewed in a plane as shown in FIG. 1 . The intersection 23 of the first plate portion 21 and the second plate portion 22 may be understood to be part of both the first plate portion 21 and the second plate portion 22.

[0016] The paint defect 3 is provided on the second plate portion 22 in a linear shape extending in the extension direction Dy of the second plate portion 22, including the intersection 23 between the first plate portion 21 and the second plate portion 22. The extension direction Dy of the second plate portion 22 may be understood as the direction in which the first end 22a and the second end 22b of the second plate portion 22 are spaced apart. The extension direction Dy of the second plate portion 22 may be understood as the direction in which a straight line passing through the widthwise center position of the first end 22a and the widthwise center position of the second end 22b extends. The paint defect 3 may be a portion where the paint film has been removed to expose the base of the painted metal plate. The paint defect 3 may also be a scratch formed in the base of the painted metal plate after the paint film has been removed. The term "linear" refers to a long extension, and the width of the paint defect 3 is arbitrary. When the sensor body 2 is placed in a corrosive environment, corrosion progresses from the paint defect 3.

[0017] The first resistance meter 4 is a device for measuring a first electrical resistance R1 between a first pair of points 61 provided on the first plate portion 21 and spaced apart in the extension direction Dx of the first plate portion 21 so that the paint scratch portion 3 is located therebetween. The extension direction Dx of the first plate portion 21 may be understood as the direction in which the first end portion 21a and the second end portion 21b of the first plate portion 21 are spaced apart. The extension direction Dx of the first plate portion 21 may be understood as the direction in which a straight line passing through the widthwise center position of the first end portion 21a and the widthwise center position of the second end portion 21b extends. In FIG. 1 , the first pair of points 61 are shown as being provided at the first end portion 21a and the second end portion 21b of the first plate portion 21 (both ends of the first plate portion 21), but they may be provided at positions spaced apart from the first end portion 21a and the second end portion 21b of the first plate portion 21 in the extension direction Dx of the first plate portion 21.

[0018] The second resistance meter 5 is a device for measuring the second electrical resistance R2 between a second pair of points 62 provided on the second plate portion 22 and spaced apart in the extension direction Dy of the second plate portion 22. In Fig. 1, the second pair of points 62 are shown as being provided at the first end 22a and the second end 22b of the second plate portion 22 (both ends of the second plate portion 22), but may be provided at positions away from the first end 22a and the second end 22b of the second plate portion 22 in the extension direction Dy of the second plate portion 22.

[0019] The first resistance meter 4 and the second resistance meter 5 may be configured to measure the current values, a first voltage V1 between the first pair of points 61, and a second voltage V2 between the second pair of points 62, when currents are applied to the first plate portion 21 and the second plate portion 22, respectively. While not limited thereto, when the first pair of points 61 and the second pair of points 62 are provided at both ends of the first plate portion 21 and the second plate portion 22, the currents may be applied from the end faces of the first plate portion 21 and the second plate portion 22. The currents may be direct currents or alternating currents. When alternating currents are used, it is preferable to use a low frequency range of 100 kHz or less, taking into account the skin effect.

[0020] The corrosion sensor 1 of this embodiment is configured to obtain the width a and depth b (see FIG. 2) of corrosion from the paint defect 3 from the first electrical resistance R1 and the second electrical resistance R2.

[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 3. However, the inventors conducted various studies and discovered that the first electrical resistance R1 and the second electrical resistance R2 exhibit different values ​​depending on the width a and depth b of corrosion from the paint defect 3. 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 3 can be obtained. Obtaining the width a and depth b of corrosion using the corrosion sensor 1 of this embodiment allows for more detailed information on how corrosion from the paint defect 3 progresses, improving the evaluation of corrosion progression from the paint defect 3. 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 measured at any interval, preferably at regular intervals.

[0022] More specifically, 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 3 relative to the first initial electrical resistance R10 measured in the initial state of the corrosion sensor 1 (a state in which the paint scratch 3 has not yet formed on the sensor body 2, or a state before corrosion from the paint scratch 3 has occurred), and the rate of change (R2 / R20) of the second electrical resistance R2 measured when observing corrosion from the paint scratch 3 relative to the second initial electrical resistance R20 measured 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 3, 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 3 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 3 may not be constant in the width direction, a correlation can be found from values ​​obtained through 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] The first pair of points 61 and the second pair of points 62 may be arranged such that the intersection between the first line segment L1 connecting the first pair of points 61 and the paint defect 3 is different from the intersection between the second line segment L2 connecting the second pair of points 62 and the paint defect 3, and the first line segment L1 and the second line segment L2 are non-parallel to each other. 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 points 61, and the second line segment L2 may be a line segment connecting the centers of the second pair of points 62. The first angle θ1 and the second angle θ2 may be angles formed by a line L3 passing through the widthwise center position of the paint defect 3 with the first line segment L1 and the second line segment L2. The line L3 may be defined in the initial state of the corrosion sensor 1.

[0029] In the embodiment shown in FIG. 1, the first pair of points 61 and the second pair of points 62 are arranged so that the first angle θ1 at which the first line segment L1 intersects with the paint defect portion 3 is different from the second angle θ2 at which the second line segment L2 intersects with the paint defect portion 3.

[0030] In this embodiment, the first angle θ1 is set to 90°. From this perspective, the first electrical resistance R1 between the first pair of points 61 may be referred to as the vertical electrical resistance. In the present invention, "90°" may refer not only to the strict 90° but also to 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 points 61 and the straight line L3 passing through the widthwise center position of the paint defect portion 3 is within the range of 90°±20° (when the angle is greater than or equal to 70° and less than or equal to 110°), 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 3 extend on the same straight line. From this perspective, the second electrical resistance R2 between the second pair of points 62 may be referred to as a parallel electrical resistance. The second pair of points 62 may be located on an extension of the paint defect 3. Alternatively, the first pair of points 61 may be located on the paint defect 3. Note that, in the present invention, "0°" does not only mean strict 0°, but also includes a substantial 0° that includes an error acceptable 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 points 62 and the straight line L3 passing through the widthwise center position of the paint defect 3 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] The first angle θ1 and the second angle θ2 may be changed arbitrarily as shown in Fig. 3. In the embodiment shown in Fig. 3, the first angle θ1 is set to 76°, and the second angle θ2 is set to 6°.

[0033] As shown in FIG. 4, a first line segment L1 connecting a first pair of points 61 may intersect with the paint defect 3, while a second line segment L2 connecting a second pair of points 62 may be arranged so as not to intersect with the paint defect 3. The shortest distance between the second line segment L2 that does not intersect with the paint defect 3 and a line L3 passing through the paint defect 3 or its widthwise center is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. Additionally and / or alternatively, the second line segment L2 is preferably arranged within a range where it intersects with the first line segment L1. The second line segment L2 may be arranged parallel to the paint defect 3. In the present invention, "parallel" may include not only strict parallelism but also substantial parallelism, including tolerances acceptable in the technical field of the present invention. For example, when the angle formed by the extension line of the second line segment L2 connecting the second pair of points 62 and the straight line L3 passing through the widthwise center position of the paint scratch portion 3 is within the range of 0°±20° (when it is greater than -20° and less than +20°), it can be understood that the second line segment L2 is arranged parallel to the paint scratch portion 3.

[0034] The distance between the first pair of points 61 and the distance between the second pair of points 62 may be set arbitrarily, but is preferably set to 1 mm or more to reduce the effect of the resistance of each point or terminal on the measured resistance.

[0035] 1, the first plate portion 21 and the second plate portion 22 may intersect to form a cross. The center position of the first plate portion 21 in the extension direction Dx of the first plate portion 21 may coincide with the center position of the second plate portion 22 in the extension direction Dx of the first plate portion 21, or these center positions may be offset. In the illustrated embodiment, the center position of the second plate portion 22 in the extension direction Dx of the first plate portion 21 is offset toward the first end portion 21a of the first plate portion 21 in the extension direction Dx of the first plate portion 21 (the upper end portion side in FIG. 1).

[0036] Alternatively, as shown in FIG. 5, the first plate portion 21 and the second plate portion 22 may intersect to form a T-shape.

[0037] The first plate portion 21 and the second plate portion 22 may extend perpendicular to each other. When a line passing through the center position of the first plate portion 21 in the extension direction Dy of the second plate portion 22 intersects at 90° with a line passing through the center position of the second plate portion 22 in the extension direction Dx of the first plate portion 21, the first plate portion 21 and the second plate portion 22 may be understood to extend perpendicular to each other. From another perspective, when a side end 21s of the first plate portion 21 in the extension direction Dy of the second plate portion 22 intersects at 90° with a side end 22s of the second plate portion 22 in the extension direction Dx of the first plate portion 21, the first plate portion 21 and the second plate portion 22 may be understood to extend perpendicular to each other. As described above, the term "90°" in the present invention may not only refer to a strict 90° but also to a substantial 90° that includes an error acceptable in the technical field of the present invention. For example, when the angle between the above-mentioned straight lines or side ends 21s, 22s is within the range of 90°±20° (greater than 70° and less than 110°), the first plate portion 21 and the second plate portion 22 may be understood to extend perpendicular to each other.

[0038] The width Wx of the second plate portion 22 in the extension direction Dx of the first plate portion 21 is preferably at least twice the initial width W30 of the paint defect portion 3 in the extension direction Dx of the first plate portion 21. By adopting such a configuration, the second electrical resistance R2 can be measured more reliably. The width Wx of the second plate portion 22 can be several mm to several cm.

[0039] It is preferable that the distance D1 from the side end 22s of the second plate portion 22 to the first pair of points 61 in the extension direction Dx of the first plate portion 21 be equal to or greater than the width Wy of the first plate portion 21 in the extension direction Dy of the second plate portion 22. By adopting such a configuration, the current in the paint defect portion 3 can be more reliably made uniform.

[0040] The width Wy of the first plate portion 21 in the extension direction Dy of the second plate portion 22 is preferably equal to the width Wx of the second plate portion 22 in the extension direction Dx of the first plate portion 21. If the width Wy is too wide, the current density may spread near the intersection 23 during measurement of the second electrical resistance R2 (parallel electrical resistance), resulting in a decrease in electrical resistance. To prevent this, it is preferable to reduce the width Wy, but if the width Wy is too small, the width Wx will have a significant effect on the measurement of the first electrical resistance R1 (perpendicular electrical resistance). For this reason, it is preferable that the width Wy is equal to the width Wx, as described above.

[0041] It is preferable that the distance D2 from the side end 21s of the first plate portion 21 in the extension direction Dy of the second plate portion 22 to the second pair of points 62 be equal to or greater than the width Wx of the second plate portion 22 in the extension direction Dx of the first plate portion 21. By adopting such a configuration, the current in the paint defect portion 3 can be more reliably made uniform.

[0042] 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]

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0044] The inventors carried out a corrosion test simulation using a finite difference method program written in C language. The basic conditions for the simulation are as follows: As shown in FIG. 1, a steel plate (volume resistivity: 1×10) having a first plate portion 21 and a second plate portion 22 was used. -7 A model of a sensor body 2 with a resistance of Ω·m was created, and a paint defect 3 was formed on the second plate portion 22 of the sensor body 2. The first plate portion 21 was a rectangle measuring 10 mm wide x 50 mm long x 0.5 mm thick, and the second plate portion 22 was a rectangle measuring 10 mm wide x 75 mm long x 0.5 mm thick, with the first plate portion 21 and second plate portion 22 extending perpendicularly to form a cross. The paint defect 3 was formed at the center of the width of the second plate portion 22, extending in the extension direction Dy of the second plate portion 22, and having a length of 50 mm.

[0045] The first pair of points 61 are arranged at both ends of the first plate portion 21 in the widthwise center of the first plate portion 21, and the second pair of points 62 are arranged at both ends of the second plate portion 22 in the widthwise center of the second plate portion 22. The first pair of points 61 and the second pair of points 62 are arranged so that a first angle θ1 at which a first line segment L1 connecting the first pair of points 61 intersects with the paint defect portion 3 is 90°, and a second angle θ2 at which a second line segment L2 connecting the second pair of points 62 intersects with the paint defect portion 3 is 0°.

[0046] The initial state of the corrosion sensor 1 was a state in which no paint scratches 3 had formed on the sensor body 2. In this state, the first initial electrical resistance R10 (initial perpendicular electrical resistance) and the second initial electrical resistance R20 (initial parallel electrical resistance) were calculated using electromagnetic field analysis. The first electrical resistance R1 (perpendicular electrical resistance) and the second electrical resistance R2 (parallel electrical resistance) were calculated while varying the width a and depth b of the corrosion from the paint scratch 3. The current value was kept constant at 1 A. The width a and depth b of the corrosion were varied between 0.05 and 0.45 mm.

[0047] 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.

[0048] Fig. 6 is a graph showing the relationship between the rate of change of the second electrical resistance R2 {(R2 / R20)-1} and the depth of corrosion b in the example. As shown in Fig. 6, it is clear that it is difficult to measure the depth of corrosion b based on the rate of change of the second electrical resistance R2 alone. Note that the reason that multiple rates of change of the second electrical resistance R2 {(R2 / R20)-1} are obtained at the same depth of corrosion b is thought to be due to differences in the width a of the corrosion.

[0049] Next, 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 the example, 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 the example. 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.

[0050]

number

[0051]

number

[0052] The cross-sectional area of ​​corrosion from the paint scratch 3 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 width a and depth b, which corresponds 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 3 in the width direction was not constant, but after various investigations, the second equation above was obtained.

[0053] These approximate formulas can be rearranged for the width a and depth b of corrosion as follows:

[0054]

number

[0055]

number

[0056] 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 obtain the width a and depth b of corrosion from the paint defect 3 from the first electrical resistance R1 and the second electrical resistance R2.

[0057] Next, Fig. 9 is a graph showing the relationship between the predicted value and the set value of corrosion depth b in the example, and Fig. 10 is a graph showing the relationship between the predicted value and the set value of corrosion width a in the example. The set values ​​of corrosion width a and depth b shown in Figs. 9 and 10 are set values ​​in the simulation, and the predicted values ​​of corrosion width a and depth b are values ​​calculated from the above-mentioned formulas for corrosion width a and depth b. As shown in Figs. 9 and 10, the predicted values ​​roughly correspond to the set values, and it can be seen that corrosion width a and depth b can be obtained using the above-mentioned formulas.

[0058] The invention described in this specification can also be described as follows. [1] a sensor body made of a painted metal plate having a first plate portion and a second plate portion extending to intersect with each other; A linear paint scratch portion provided on the second plate portion so as to extend in the extension direction of the second plate portion, including an intersection portion of the first plate portion and the second plate portion; a first resistance meter for measuring a first electrical resistance between a first pair of points provided on the first plate portion and spaced apart in the extension direction of the first plate portion so that the paint defect portion is located therebetween; a second resistance meter for measuring a second electrical resistance between a second pair of points provided on the second plate portion and spaced apart in the extending direction of the second plate portion; and Equipped with The width and depth of corrosion from the paint defect are obtained from the first electrical resistance and the second electrical resistance. Corrosion sensors. [2] The first plate portion and the second plate portion intersect to form a cross. 2. The corrosion sensor according to claim 1. [3] The width of the second plate portion in the extension direction of the first plate portion is at least twice the initial width of the paint defect portion in the extension direction of the first plate portion. 3. The corrosion sensor according to claim 1 or 2. [4] The distance from the side end of the second plate portion in the extension direction of the first plate portion to the first pair of points is equal to or greater than the width of the first plate portion in the extension direction of the second plate portion. 4. The corrosion sensor according to any one of claims 1 to 3. [5] The width of the first plate portion in the extension direction of the second plate portion is equal to the width of the second plate portion in the extension direction of the first plate portion. 5. The corrosion sensor according to any one of claims 1 to 4. [6] The distance from the side end of the first plate portion in the extension direction of the second plate portion to the second pair of points is equal to or greater than the width of the second plate portion in the extension direction of the first plate portion. 6. The corrosion sensor according to any one of claims 1 to 5. [Explanation of symbols]

[0059] 1: Corrosion sensor 2: Sensor body 3: Paint damage 4: First resistance measuring instrument 5: Second resistance measuring instrument 21: 1st plate part 22: 2nd plate part 23: Intersection

Claims

1. a sensor body made of a painted metal plate having a first plate portion and a second plate portion extending to intersect with each other; a linear paint scratch portion provided on the second plate portion so as to extend in the extension direction of the second plate portion, including an intersection portion of the first plate portion and the second plate portion; a first resistance meter for measuring a first electrical resistance between a first pair of points provided on the first plate portion and spaced apart in the extension direction of the first plate portion so that the paint defect portion is located therebetween; a second resistance meter for measuring a second electrical resistance between a second pair of points provided on the second plate portion and spaced apart in the extending direction of the second plate portion; Equipped with The width and depth of corrosion from the paint defect portion are obtained from the first electrical resistance and the second electrical resistance. Corrosion sensors.

2. The first plate portion and the second plate portion intersect to form a cross. The corrosion sensor according to claim 1 .

3. The width of the second plate portion in the extension direction of the first plate portion is at least twice the initial width of the paint defect portion in the extension direction of the first plate portion. The corrosion sensor according to claim 2 .

4. a distance from a side end of the second plate portion in the extension direction of the first plate portion to the first pair of points is equal to or greater than a width of the first plate portion in the extension direction of the second plate portion; The corrosion sensor according to claim 2 or 3.

5. The width of the first plate portion in the extension direction of the second plate portion is equal to the width of the second plate portion in the extension direction of the first plate portion. The corrosion sensor according to claim 2 or 3.

6. a distance from a side end of the first plate portion in the extension direction of the second plate portion to the second pair of points is equal to or greater than a width of the second plate portion in the extension direction of the first plate portion; The corrosion sensor according to claim 2 or 3.

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