Method and apparatus for evaluating the adhesion of a coating film.

Abstract

To provide a coating film adhesion evaluation method and evaluation device that can evaluate the adhesion of a coating film simply and accurately without depending on the direction of the coating film surface.SOLUTION: An evaluation device includes: a reference plate made of a metal block with a through hole that penetrates the top and bottom surfaces in the normal direction; a wedge-shaped tool that is movable back and forth along and fitted to the through hole; fixing members fixed onto a steel bridge and spans an area to be evaluated of a coating film; a spring load application mechanism that controls the spring load on the wedge-shaped tool; and a locking mechanism that switches between locking and unlocking the movement of the wedge-shaped tool. By using the evaluation device, an evaluation method includes steps of: fixing the fixing members at each position across the area to be evaluated of the coating film; fixing the reference plate on the fixing member so as to be parallel to and spaced apart from the coating film; bringing a wedge-shaped end of the tip of the wedge-shaped tool into contact with the area to be evaluated to lock the wedge-shaped tool and the reference plate; and applying a predetermined spring load to the wedge-shaped tool, and releasing the lock and pressing the wedge-shaped end into the area to be evaluated of the coating film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for evaluating the adhesion of a coating film of a painted steel bridge, and particularly to a method and an apparatus for evaluating the adhesion of a coating film of a painted steel bridge that enable on-site work.

Background Art

[0002] When deterioration occurs in a part of the coating film of a painted steel bridge, the deteriorated part is peeled off and repainting is performed. At this time, it is necessary to evaluate the partial soundness of the coating film. Regarding such a soundness evaluation test of the coating film, a cross-cut test according to JIS K 5600-5-6, in which a cut is made partially in the coating film to generate a shearing force in the coating film for peel evaluation, is used.

[0003] For example, Patent Document 1 discloses a cutting line forming tool for making grid-shaped cuts on the coating film surface of a cross-cut test. An operator presses a cutting line forming tool provided with a plurality of cutter blades held at intervals by a spacer against the coating film and moves the cutting edge along the coating film surface.

[0004] In a test method such as the cross-cut test, in which an operator introduces a scratch into the coating film and applies a shearing force to the coating film for peel evaluation, variations in test results due to operator dependence are likely to occur.

[0005] Therefore, Non-Patent Document 1 proposes a method for performing peel evaluation by applying a shearing force to the coating film by mechanically pressing a wedge-shaped tool into the coating film based on the cross-cut test. Here, an abutment jig is installed on the coating film, a wedge-shaped tool is inserted into the insertion opening thereof, a predetermined weight is loaded from above, and the wedge-shaped tool is vertically pressed into the target location for evaluation. Since the operation only involves loading the weight without relatively moving the tool along the coating film surface as in the cross-cut test, operator dependence on the test results can be eliminated.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-220183 [Non-patent literature]

[0007] [Non-Patent Document 1] Kei Suzuki, Tatsuro Sakamoto, Hayato Suzuki; "Evaluation of coating integrity focusing on shear adhesion of coatings," Railway Technical Research Institute Report, Vol. 35, No. 11, 2021. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The method described in Non-Patent Document 1 is simple and can suppress variations in test results due to operator dependence. On the other hand, in cases where the painted surface is oriented in various directions, such as on a painted steel bridge, it is necessary to push the wedge-shaped tool in a direction different from the direction of gravity, making on-site work impossible.

[0009] The present invention has been made in view of the above circumstances, and its purpose is to provide a method and apparatus for evaluating the adhesion of a coating film that can evaluate the adhesion of a coating film simply and accurately, without being dependent on the direction of the coating film surface. [Means for solving the problem]

[0010] The present invention relates to a method for evaluating the adhesion of a paint film on a steel bridge, using an apparatus that includes a reference plate made of a metal block having a pair of parallel upper and lower surfaces and through holes penetrating these upper and lower surfaces in the normal direction, and a wedge-shaped tool fitted into the through holes and reciprocally movable along the through holes, wherein fixing members are fixed on the steel bridge at positions that straddle the portion of the paint film to be evaluated, and the opening of the lower surface of the through holes is positioned to span the portion of the paint film to be evaluated The method is characterized by fixing the reference plate on the fixing member, facing the lower surface, and spaced apart so that the coating film and the lower surface are parallel to each other, bringing the wedge-shaped end of the tip of the wedge-shaped tool into contact with the part to be evaluated, fixing the wedge-shaped tool and the reference plate by operating a locking mechanism, applying a predetermined spring load to the wedge-shaped tool so as to push it out from the opening in the lower surface, releasing the locking mechanism and pressing the wedge-shaped end into the coating film in the part to be evaluated.

[0011] With these characteristics, the shear force generated in the coating of the area being evaluated is not constrained, and there are no restrictions on the direction of the load. Therefore, the adhesion of the coating can be evaluated simply and accurately, regardless of the direction of the coating surface.

[0012] In the above-described invention, the spring load may be corrected in accordance with the orientation of the wedge-shaped tool from the vertical when the locking mechanism is operated, and the coating film may be evaluated accordingly. With this feature, the adhesion of the coating film can be evaluated simply and accurately, regardless of the orientation of the coating film surface.

[0013] Furthermore, the present invention relates to a device for evaluating the adhesion of a paint film on a steel bridge, and includes a reference plate made of a metal block having a pair of parallel upper and lower surfaces and through holes penetrating these upper and lower surfaces in the normal direction, and a wedge-shaped tool fitted into the through holes and combined to be reciprocally movable along the through holes, a fixing member fixed on the steel bridge at each position straddling the portion of the paint film to be evaluated, a spring load application mechanism that variably controls the spring load in the direction of pushing the wedge-shaped tool out from the opening on the lower surface, and a switch for fixing or releasing the movement of the wedge-shaped tool along the through holes. The invention further includes a locking mechanism, wherein the opening on the lower surface of the through hole is positioned opposite the portion to be evaluated, and the reference plate is fixed on the fixing member with a gap between the coating film and the lower surface so that they are parallel to each other, the wedge-shaped end of the tip of the wedge-shaped tool is brought into contact with the portion to be evaluated, and the wedge-shaped tool and the reference plate are fixed by operating the locking mechanism, the spring load application mechanism applies a predetermined spring load to the wedge-shaped tool so as to push the wedge-shaped tool out of the opening on the lower surface, and the locking mechanism is released to push the wedge-shaped end into the coating film at the portion to be evaluated.

[0014] With these characteristics, the shear force generated in the coating of the area being evaluated is not constrained, and there are no restrictions on the direction of the load. Therefore, the adhesion of the coating can be evaluated simply and accurately, regardless of the direction of the coating surface.

[0015] In the invention described above, the spring load application mechanism may be characterized by including a movable part that faces the upper surface of the reference plate and whose distance from it is variable, a spring elastic part disposed between the movable part and the wedge-shaped tool, and an adjustment part that moves the movable part to change the distance. Furthermore, the spring elastic part may include a coil spring and be at its natural length when the distance of the movable part is maximized. With such features, the adhesion of the coating can be evaluated simply and accurately, regardless of the direction of the coating surface.

[0016] In the above-described invention, the fixing member may be characterized in that it is previously fixed to the reference flat plate. Further, the fixing member may be characterized in that it is fixed to the steel bridge by magnetic force. According to such a feature, the adhesion of the coating film can be evaluated simply and accurately without depending on the direction of the coating film surface.

Brief Description of the Drawings

[0017] [Figure 1] It is a perspective view of an evaluation apparatus in one embodiment of the present invention. [Figure 2] It is a side view near the spring elastic part. [Figure 3] It is a side cross-sectional view near the movable part of the evaluation apparatus. [Figure 4] It is a side view around the fixing member of the evaluation apparatus. [Figure 5] It is a flowchart showing a method for evaluating the adhesion of a coating film using the evaluation apparatus. [Figure 6] It is a cross-sectional view of the coating film showing a state where the wedge-shaped end is pushed into the coating film. [Figure 7] It is a graph showing the relationship between the amount of pushing into the coating film and the load. [Figure 8] It is a graph showing the relationship between the load at the time of crack generation and the remaining area ratio by the checkerboard test.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, a method for evaluating the adhesion of a coating film and an adhesion evaluation apparatus according to the present invention will be described.

[0019] First, the adhesion evaluation apparatus will be described with reference to FIGS. 1 to 3.

[0020] As shown in Figure 1, the evaluation device 1 includes a reference plate 2 made of a metal block and a wedge-shaped tool 3 fitted into a through hole 23 located approximately in the center of the reference plate 2. The reference plate 2 has a pair of parallel upper and lower surfaces 21 and 22, with the through hole 23 passing through it in the direction normal to its upper and lower surfaces. The wedge-shaped tool 3 is assembled to reciprocate along the through hole 23. In other words, the wedge-shaped tool 3 is movable vertically along the normals to the upper and lower surfaces of the reference plate 2. The length of the through hole 23 is secured by making the reference plate 2 a block-like body so that the direction of movement of the wedge-shaped tool 3 can be stabilized. The wedge-shaped tool 3 also includes a wedge-shaped portion 31 that hangs down from the lower surface 22 of the reference plate 2 and has a lower wedge shape, and a shaft portion 32 that fits into the through hole 23 and moves inside it.

[0021] The reference plate 2 is fixed to fixing members 4a and 4b on its left and right sides, straddling the through hole 23, at its lower surface 22. In other words, the reference plate 2 has a wedge portion 31 hanging down between the fixing members 4a and 4b. The fixing members 4a and 4b are designed to be fixed to the painted steel bridge so that the lower surface 22 of the reference plate 2 is parallel to the paint film P (see Figure 4) to be evaluated. For example, in this embodiment, the paint film painted on a flat part of the steel bridge is to be evaluated, and it is made possible to fix it to this plane by magnetic force. Specifically, the fixing members 4a and 4b are rectangular parallelepipeds of the same height and are magnet holder bases that can switch the magnetic force ON and OFF.

[0022] The lower surface 22 of the reference plate 2 is provided with a locking mechanism 24 that switches between fixing or releasing the vertical movement of the wedge-shaped tool 3. As the locking mechanism 24, for example, a known shaft clamp can be used, which can switch between fixing and releasing the movement of the shaft portion 32 by rotating the lower lever 25.

[0023] A spring load application mechanism 5 is provided on the upper surface 21 of the reference plate 2 to apply a spring load to the wedge-shaped tool 3. The spring load application mechanism 5 can be any mechanism that can apply a desired spring load to the wedge-shaped tool 3 from above with variable control, but it can be configured as follows, for example.

[0024] As an example, the spring load application mechanism 5 includes columns 51a and 51b fixed to the upper surface 21 of the reference plate 2 and extending upward, a plate body 52 fixed to the upper ends of the columns 51a and 51b and extending substantially horizontally, a rotating body 53 attached to the plate body 52, and a spring elastic part 40 connected to the upper end of the wedge-shaped tool 3. The columns 51a and 51b are positioned on the left and right sides of the spring elastic part 40 and fix the distance between the plate body 52 and the reference plate 2.

[0025] As shown in Figure 2, the spring elastic part 40 is equipped with a compression coil spring 41 that is compressed in the vertical direction, and a cover body 42 attached to the upper end 41a of the compression coil spring 41 is in contact with the lower end of the movable part 53b of the rotating body 53, which will be described later. The cover body 42 is slidable relative to the movable part 53b.

[0026] Furthermore, the compression coil spring 41 is positioned on the upper part of the wedge-shaped tool 3. As described above, the wedge-shaped tool 3 has a shaft portion 32 that extends vertically, but a shaft body 33 with a smaller diameter than the shaft portion 32 extends further upward from the stepped upper part 32a of the shaft portion 32. The compression coil spring 41 abuts its lower end 41b against the stepped upper part 32a, and the shaft body 33 is inserted inside it. This allows the spring load due to the compression deformation of the compression coil spring 41 to be applied to the wedge-shaped tool 3, and also suppresses the lateral deformation of the compression coil spring. The length of the shaft body 33 is such that its upper end does not come into contact with the cover body 42 due to the deformation of the compression coil spring 41.

[0027] On the other hand, as shown in Figure 3, the rotating body 53 includes an adjustment part 53a, which is disc-shaped with its central axis oriented vertically and has a handle 53c attached to its upper surface, and a movable part 53b consisting of a shaft that hangs down from its center. The lower part of the movable part 53b has threads cut on its outer circumference and is screwed into a vertically extending screw hole 52a provided in the plate body 52, passing through it. By operating the handle 53c and rotating the adjustment part 53a, the movable part 53b can be moved up and down. The movable part 53b faces the upper surface 21 of the reference plate 2, so the distance between them is variable. This distance is the distance between the cover body 42, the compression coil spring 41, and the shaft portion 32 of the wedge-shaped tool 3 that protrudes from the upper surface 21. In other words, the deformable compression coil spring 41 can be compressed by changing the distance of the movable part 53b relative to the reference plate 2. Furthermore, it is preferable to set the natural length of the compression coil spring 41 so that when this distance is maximized, the position when no load is applied can be easily manipulated and adjusted.

[0028] Furthermore, as described above, the lower end of the movable part 53b contacts the cover body 42, which is the upper end of the spring elastic part 40, allowing the upper end 41a of the compression coil spring 41 to move downward. This movement of the upper end 41a corresponds to the change in the distance of the movable part 53b from the upper surface 21 of the reference plate 2, as described above. This movement compresses and deforms the compression coil spring 41, and a load corresponding to this deformation can be applied to the wedge-shaped tool 3. As described above, the cover body 42 is slidable relative to the movable part 53b, absorbing the rotation of the rotating body 53 and preventing a torsional force from being applied to the compression coil spring 41.

[0029] The plate body 52 is provided with an upper locking mechanism 54 that switches between fixing and releasing the rotation of the rotating body 53, covering the periphery of the upper portion of the movable part 53b. The upper locking mechanism 54 may use a known shaft clamp that can be switched between fixing and releasing by rotating an upper lever 55 (see Figure 1). The upper locking mechanism 54 can maintain a desired load by stopping the rotation of the rotating body 53, which has been deformed to generate a load in the spring elastic part 40. Preferably, the movable part 53b is provided with a scale indicating the amount of movement (amount of deformation of the compression coil spring) corresponding to the load generated in the spring elastic part 40, and this allows adjustment by the adjustment part 53a to apply a predetermined load.

[0030] As shown in Figure 4, the bottom surfaces of the fixing members 4a and 4b are on the same plane, and the wedge-shaped end 31a of the wedge portion 31 can be positioned on this plane as its initial position. As will be described later, at the start of use, the wedge-shaped end 31a is brought into contact with the evaluation target portion P1 of the coating P. Therefore, this arrangement is used when the evaluation surface 61 of the steel bridge 60 to which the coating P is applied is flat. Also, the wedge-shaped end 31a is brought into contact with the surface of the evaluation target portion P1 from a direction perpendicular to it as its initial position. Therefore, the coating P and the lower surface 22 of the reference plate 2 are fixed while being spaced apart so that they are parallel to each other. Note that if the evaluation surface 61 is not flat, the shape and fixing method of the fixing members 4a and 4b may be changed to match its shape.

[0031] Next, the method for evaluating the adhesion of the coating film using the evaluation device 1 will be explained in accordance with Figure 5, with reference to Figures 4, 6 to 8.

[0032] Referring to Figure 4 in conjunction with Figure 5, first, the evaluation device 1 is fixed to the steel bridge 60 including the evaluation target portion P1 of the coating film (S1). That is, the fixing members 4a and 4b of the evaluation device 1 are fixed on the steel bridge 60 at positions that straddle the evaluation target portion P1. At this time, the opening 23' of the lower surface 22 of the through hole 23 of the reference plate 2 is positioned facing the evaluation target portion P1, and the coating film P and the lower surface 22 are spaced apart so that they are parallel to each other. In other words, the direction of vertical movement of the wedge-shaped tool 3 is perpendicular to the surface of the coating film P, and the wedge-shaped end 31a is positioned so that it can come into contact with the evaluation target portion P1 by the vertical movement of the wedge-shaped tool 3. In this embodiment, the fixing members 4a and 4b are fixed to the reference plate 2 in advance. However, it is sufficient to position them spaced apart so that their lower surfaces 22 are parallel to the coating P, and to have the wedge-shaped end 31a in contact with the evaluation target portion P1. Other fixing methods, such as clamping with spacers, may also be used.

[0033] Next, the wedge-shaped tool 3 is fixed to the reference plate 2 (S2). At this time, the initial position of the wedge-shaped tool 3 is such that the wedge-shaped end 31a is in contact with the evaluation target portion P1. Then, with the wedge-shaped end 31a in contact with the evaluation target portion P1, the locking mechanism 24 is activated to fix the wedge-shaped tool 3 to the reference plate 2.

[0034] Next, a predetermined spring load is applied to the wedge-shaped tool 3 (S3). Here, the handle 53c is operated to rotate the rotating body 53, which lowers the movable part 53b and applies a downward load to the spring elastic part 40. The spring elastic part 40 then compresses the compression coil spring 41 and transmits the reaction force to the wedge-shaped tool 3. As a result, the wedge-shaped tool 3 is subjected to a spring load so that it is pushed downward from the opening 23' in the lower surface 22 of the reference plate 2. At this time, the load applied to the wedge-shaped tool 3 is adjusted to a predetermined value using the adjustment part 53a. Since the locking mechanism 24 is activated, the wedge-shaped end 31a is not pressed into the coating P while the load to be applied to the wedge-shaped tool 3 is being adjusted.

[0035] Then, when the wedge-shaped tool 3 is released by the locking mechanism 24 (S4), the wedge-shaped end 31a moves to be pushed into the evaluation target portion P1 of the coating film P with a predetermined load. Since the wedge-shaped end 31a is pushed in from a position that has been previously in contact with the evaluation target portion P1, no impact force is generated, which contributes to quantitative evaluation.

[0036] As shown in Figure 6, the wedge-shaped end 31a is then pressed into the evaluation target portion P1 of the coating film P to a depth corresponding to the load applied to the wedge-shaped tool 3. In the evaluation target portion P1, the wedge shape of the pressed-in wedge-shaped end 31a causes a shear force along the surface in a direction away from the wedge-shaped end 31a (left-right direction on the plane of the paper). This shear force is uniquely determined by the shape of the wedge-shaped end 31a and the amount of indentation, and is quantitative. In this way, in order to apply a shear force to the coating film according to the amount of indentation, the angle of the cross-sectional shape that widens upwards from the wedge-shaped end 31a is made larger than that of a cutter blade intended for cutting.

[0037] Furthermore, the fixing members 4a and 4b of the evaluation device 1 are spaced apart across the evaluation target portion P1, and the reference plate 2 is also spaced apart from the evaluation target portion P1, so the shear force generated in the coating P of the evaluation target portion P1 is not restrained. Also, as described above, the load applied to the wedge-shaped tool 3 is predetermined, and the load on the wedge-shaped end 31a can also be controlled to be constant. In addition, since the wedge-shaped end 31a is pressed into the coating P by the spring load, it is independent of the direction of gravity, and there are no restrictions on the direction of the evaluation device 1. In other words, the evaluation device 1 causes little disturbance to the coating P of the evaluation target portion P1, has little variation in test results due to repetition or operator error, and can be used without restriction on the direction of the coating P of the evaluation target portion P1 on the steel bridge 60.

[0038] Next, in order to evaluate the adhesion of the coating, the coating of the part P1 to be evaluated is observed, and the amount of deformation of the compression coil spring 41 corresponding to the load applied to the wedge-shaped tool 3 is recorded, along with whether or not cracks have formed (S5). As described above, the wedge-shaped end 31a is pressed into the coating to a depth corresponding to the load, and a shear force is generated in the coating according to the amount of pressing. In other words, a shear force corresponding to the load can be generated in the coating. And if we consider that the adhesion of the coating corresponds to the shear force that causes cracks, then it also corresponds to the load that causes cracks. In other words, the adhesion of the coating can be evaluated by the load that causes cracks or the amount of deformation of the compression coil spring 41 corresponding to it.

[0039] As shown in Figure 7, the relationship between the amount of indentation of the wedge-shaped end 31a into the coating and the load (test force) was accurately measured in the laboratory. As a result, it was found that the load and the amount of indentation when cracks (fissures) occurred in the coating remained constant with good reproducibility.

[0040] Furthermore, as shown in Figure 8, the relationship between the load at which the coating film of a steel bridge failed (cracked) according to this embodiment and the remaining area ratio obtained by the conventional grid test was investigated. It was found that the change in the relationship between the two was approximately proportional. In other words, this embodiment allows for accurate evaluation of the adhesion of the coating film.

[0041] As described above, the evaluation method using the evaluation device 1 according to this embodiment is a simple method that only requires recording the load at which cracks occur in the coating film, and it is possible to evaluate the adhesion of the coating film accurately regardless of the direction of the coating film and the operator.

[0042] As described above, in this embodiment, the wedge-shaped end 31a has a wider angle than a cutter blade, allowing a large shear force to be applied to the coating film, which is significantly different from the grid test, at least when making cuts. Furthermore, in this embodiment, adhesion is evaluated based on whether or not cracks have formed in the coating film, whereas in the grid test, adhesion is evaluated based on the state of peeling of the coating film. Thus, although the two evaluation methods are quite different, it was found that they can evaluate the adhesion of the coating film equally well, as described above (see Figure 8). From this, it can be said that both of these methods are able to evaluate the adhesion of the coating film well.

[0043] Furthermore, in conventional grid-pattern tests, the effort required to make incisions increases as the thickness of the coating increases, and variations in incision depth due to the operator's habits and skill level also increase. For this reason, coatings with a thickness of 250 μm or more are outside the scope of the grid-pattern test standard. On the other hand, according to this embodiment, the wedge-shaped end 31a can be pressed into the coating with a constant load, so there is no variation in test results due to repetition or operator differences, and accurate evaluation is possible even when the coating thickness is 250 μm or more.

[0044] Furthermore, as mentioned above, there are no restrictions on the direction of the load, but it is preferable to correct the spring load in accordance with the orientation of the wedge-shaped tool 3 from the vertical when the locking mechanism 24 is in operation. In other words, the load due to the self-weight of the wedge-shaped tool 3 and the compression coil spring 41, which affects the load applied to the wedge-shaped end 31a, is corrected in accordance with the direction of gravity. This makes it possible to evaluate the adhesion of the coating with greater accuracy, regardless of the orientation of the coating surface.

[0045] Although representative embodiments of the present invention and their variations have been described above, the present invention is not necessarily limited thereto and can be modified as appropriate by those skilled in the art. That is, those skilled in the art will be able to find various alternative embodiments and modifications without departing from the scope of the attached claims. [Explanation of Symbols]

[0046] 1. Evaluation device 2 Reference plate 3. Wedge-shaped tool 4a, 4b Fixing members 5. Spring load application mechanism 24 Locking mechanism 25 Lower lever 55 Upper lever

Claims

1. A reference plate made of a metal block having a pair of parallel upper and lower surfaces and through holes penetrating these upper and lower surfaces in the normal direction, A method for evaluating the adhesion of a paint film on a painted steel bridge using an apparatus that includes a wedge-shaped tool fitted into the through-hole and arranged to reciprocate along the through-hole, Fixing members are fixed to the steel bridge at positions that straddle the portion of the coating to be evaluated. The opening on the lower surface of the through hole is positioned opposite the portion to be evaluated, and the reference plate is fixed on the fixing member with a gap between it and the coating film and the lower surface so that they are parallel to each other. The wedge-shaped end of the wedge-shaped tool is brought into contact with the part to be evaluated, and the wedge-shaped tool and the reference plate are fixed together by activating the locking mechanism. A predetermined spring load is applied to the wedge-shaped tool so as to push it out from the opening on the lower surface. A method for evaluating the adhesion of a paint film on a steel bridge, characterized by releasing the locking mechanism and pressing the wedge-shaped end into the paint film in the portion to be evaluated.

2. The method for evaluating the adhesion of a paint film on a steel bridge according to claim 1, characterized in that the spring load is corrected in accordance with the orientation of the wedge-shaped tool from the vertical direction when the locking mechanism is in operation, and the paint film is evaluated.

3. A device for evaluating the adhesion of paint films on painted steel bridges, A reference plate made of a metal block having a pair of parallel upper and lower surfaces and through holes penetrating these upper and lower surfaces in the normal direction, Includes a wedge-shaped tool fitted into the through hole and assembled to be reciprocable along the through hole, A fixing member is fixed to the steel bridge at each position that straddles the portion of the coating to be evaluated, A spring load application mechanism that variably controls the spring load in the direction of pushing the wedge-shaped tool out from the opening on the lower surface, The invention further includes a locking mechanism for switching the movement of the wedge-shaped tool along the through hole between fixed and unlocked, The opening on the lower surface of the through hole is positioned opposite the portion to be evaluated, and the reference plate is fixed on the fixing member with a gap between it and the coating film and the lower surface so that they are parallel to each other. The wedge-shaped end of the wedge-shaped tool is brought into contact with the part to be evaluated, and the wedge-shaped tool and the reference plate are fixed together by activating the locking mechanism. The spring load application mechanism applies a predetermined spring load to the wedge-shaped tool so as to push the wedge-shaped tool out of the opening on the lower surface. An apparatus for evaluating the adhesion of a paint film on a steel bridge, characterized by releasing the locking mechanism and operating to press the wedge-shaped end into the paint film in the portion to be evaluated.

4. The device for evaluating the adhesion of a coating on a steel bridge according to claim 3, characterized in that the spring load application mechanism includes a movable part that faces the upper surface of the reference plate and whose distance from it is variable, a spring elastic part disposed between the movable part and the wedge-shaped tool, and an adjustment part that moves the movable part so as to change the distance.

5. The device for evaluating the adhesion of a coating on a steel bridge according to claim 4, characterized in that the spring elastic part includes a coil spring and is at its natural length when the distance of the movable part is maximized.

6. The apparatus for evaluating the adhesion of a coating film on a steel bridge according to claim 3, characterized in that the fixing member is fixed in advance to the reference plate.

7. The apparatus for evaluating the adhesion of a coating film on a steel bridge according to claim 6, characterized in that the fixing member is fixed to the steel bridge by magnetic force.

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