JP7386958B1 - Method for evaluating the soundness of hot-dip galvanized structures - Google Patents

Abstract

The present invention provides a method that can more accurately evaluate the health of a hot-dip galvanized structure. The present invention is a method for evaluating the soundness of a hot-dip galvanized structure having a base steel plate/galvanized layer (alloy layer/zinc layer) at the beginning of construction. An electric drill is prepared which has a right circular conical tip and is rotatable around the axis of the right circular cone. With the tip of the electric drill rotated, the tip is pressed against the evaluation site of the hot-dip galvanized structure, thereby scraping the evaluation site with the tip, so that the evaluation site is A concave portion having an inverted right circular cone shape is formed to reach the base steel plate. As a result, the alloy layer and the zinc layer can be distinguished in magnified observation of the recess. Therefore, the soundness of the hot-dip galvanized structure is evaluated based on whether or not the zinc layer is identified around the alloy layer, separated from the alloy layer, in the enlarged observation of the recess. [Selection diagram] Figure 1

Description

The present invention relates to buildings with hot-dip galvanized specifications, such as bridges, steel towers, road ancillary equipment such as guardrails and signs, and structures in which hot-dip galvanizing is applied to base steel sheets (hereinafter referred to as "hot-dip galvanized structures"). related to methods for evaluating the soundness of

In order to prevent human damage that may occur due to bridge damage, collapse, collapse, etc., a ministerial ordinance of the Ministry of Land, Infrastructure, Transport and Tourism requires that bridges over 2 meters in length be inspected once every five years. Furthermore, with the aim of reducing the costs required for repairs, etc., structures such as bridges are required to periodically evaluate their health. Note that "healthiness" as used herein means the degree to which the main purpose of using the structure is maintained without being hindered.

Bridges are broadly classified into concrete bridges and steel bridges. Steel bridges are broadly classified into weather-resistant steel bridges (bare specification), painted specification bridges, and hot-dip galvanized specification bridges. The health evaluation of weathering steel bridges is performed based on external appearance inspection, rust thickness measurement, Cellotape (registered trademark) test, plate thickness measurement, and measurement of the amount of salt deposited. The health evaluation of painted bridges is conducted based on external appearance inspection, adhesion evaluation, glossiness/color difference measurement, coating thickness measurement using an electromagnetic coating thickness meter or cut-type coating thickness meter, and measurement of the amount of attached salt. be exposed. These soundness evaluation methods for weathering steel bridges and painted bridges have been established as reliable methods.

The health evaluation of hot-dip galvanized bridges has been conducted from 1963, when the first hot-dip galvanized bridge was constructed in Japan, to the present, by conducting external appearance surveys (surface appearance surveys) and measuring plating thickness using electromagnetic film thickness meters. It has been done based on. An electromagnetic film thickness meter is a tool that measures the distance to magnetic materials. The thickness of the galvanized layer can be determined by measuring the distance from the surface of the galvanized layer to the base steel plate (magnetic material) using an electromagnetic film thickness meter. However, since zinc corrosion products (white rust) and iron corrosion products (red rust) are non-magnetic substances except in special cases, if these corrosion products exist on the base steel plate, Since the value measured by the electromagnetic film thickness meter is the total thickness of the galvanized layer and corrosion products, it is not possible to determine the thickness of the galvanized layer alone. In addition, the galvanized layer includes an alloy layer of iron and zinc located on the base steel sheet and a zinc layer (hereinafter also referred to as "η layer") located on the alloy layer. It is also not possible to measure the thicknesses of the alloy layer and the zinc layer separately. As mentioned above, thickness measurement using an electromagnetic film thickness meter can only determine the total thickness of the alloy layer, zinc layer, zinc corrosion products, and iron corrosion products; can't figure it out.

Therefore, in the end, the health evaluation of hot-dip galvanized bridges relies only on surface appearance surveys. For example, if a beautiful plating appearance is maintained, or white rust (corrosion products of the zinc layer) is observed, red rust (corrosion products of the alloy layer or base steel sheet) is not observed. If the zinc layer clearly remains and the alloy layer and base steel plate are not exposed, the soundness is evaluated as good. On the other hand, when red rust is observed, the following steps are taken: (1) deterioration of the zinc layer progresses and the alloy layer is locally exposed; (2) deterioration of the zinc layer progresses and the alloy layer (3) When the deterioration of the alloy layer has progressed to the surface of the base steel sheet, (4) When the galvanized layer has disappeared and the surface of the base steel sheet is corroded, etc. being classified. Among these, in case (1), repairs such as painting are considered, and in cases (2) to (4), repairs are evaluated as necessary. However, in such a health evaluation method that relies on surface appearance, evaluation variations due to individual differences cannot be denied, and accurate evaluation cannot be performed. Further, even if red rust is observed on the surface, if the red rust is flowing rust from another part, a zinc layer may remain under the red rust. In such a case, the soundness should originally be evaluated as good. However, with the current surface appearance inspection alone, it is not possible to distinguish whether red rust is a corrosion product of the alloy layer, a corrosion product of the base steel plate, or flowing rust from other parts, and repair is not uniformly performed. The evaluation is that it is necessary. In other words, if the surface appearance is abnormal due to the influence of rust flowing from other parts, there is a possibility that unnecessary repairs will be performed even though a healthy plating layer remains. This is not preferable from the viewpoint of LCC (Life Cycle Cost).

As described above, a method that can accurately evaluate the soundness of hot-dip galvanized bridges has not been available to date, and has been desired for many years. In addition, from the perspective of health evaluation, accurate health evaluation is required not only for bridges but also for other buildings such as steel towers, road equipment such as guardrails and signs, and all hot-dip galvanized structures. In order to do this, a method is needed that can determine whether or not each of the alloy layer, zinc layer, and corrosion products exist on the base steel sheet, and the thickness of each layer. The inventors thought about this.

Here, Patent Document 1 states, ``A cut is made at a certain angle in the coating layer, the cut surface is irradiated with light, and the reflected light is magnified by an optical magnification means of a certain magnification and placed on an imaging plate. 2. A method for measuring coating thickness, which comprises forming an image on the image and calculating the coating thickness from the length of the image. Moreover, paint layers, plating layers, etc. on metal plates such as steel plates and galvanized iron plates and other objects are described as measurement targets.

Japanese Unexamined Patent Publication No. 48-56161

The thickness measurement method of Patent Document 1 is related to thickness measurement using a so-called horizontal cut-type cut-type film thickness meter, and as mentioned above, it is commonly used to measure the coating thickness in the health evaluation of painted bridges. ing. Here, with reference to FIGS. 6(A) and 6(B), when measuring the thickness of a galvanized layer on a base steel sheet in a hot-dip galvanized structure using the thickness measurement method of Patent Document 1. I will explain about it. First, a worker manually marks the evaluation site of the hot-dip galvanized structure in a straight line using a knife with a V-shaped tip, and then scribes the base steel plate by penetrating the galvanized layer into the evaluation site. A straight recess (groove) with a V-shaped cross section reaching . When the recess is observed under magnification from the overhead direction z shown in FIG. 6(A), the boundary between the base steel sheet/galvanized layer and the surface of the galvanized layer can be visually recognized as shown in FIG. 6(B). Since the angle θ of the V-shaped groove is known, by measuring the distance s between the base steel plate/galvanized layer boundary and the galvanized layer surface in Fig. 6(B), the thickness d of the galvanized layer can be found. , d=s/tanθ.

However, according to the studies conducted by the present inventors, it was possible to determine the overall thickness of the galvanized layer with this method, as described in Patent Document 1, but the thickness of the galvanized layer It was found that the thickness of the alloy layer and the zinc layer could not be determined separately. This is because the zinc layer/alloy layer boundary (indicated by a broken line in FIG. 6(B)) cannot be identified when the recess is observed under magnification from the bird's-eye direction z. In addition, since the boundary between the zinc layer and the alloy layer is unknown, if red rust is observed on the base steel sheet, it is necessary to determine whether the red rust is a corrosion product of the alloy layer or flowing rust from another part. Can not. In other words, even if the surface appearance investigation was combined with the thickness measurement using the method described in Patent Document 1, it was still not possible to accurately evaluate the soundness of the hot-dip galvanized structure.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a method that can more accurately evaluate the soundness of a hot-dip galvanized structure.

In order to solve the above problems, the present inventors conducted extensive studies and obtained the following knowledge. First, an electric drill was prepared which had a right circular conical tip and was rotatable around the axis of the right circular cone. Then, while rotating the tip of the electric drill, the tip is pressed against the evaluation site of the hot-dip galvanized structure, thereby scraping the evaluation site with the tip. A concave portion in the shape of an inverted right cone was formed. By doing this, in the enlarged observation of the recess, the base steel plate, alloy layer, zinc layer, and corrosion products can each be visually recognized as different regions, that is, the base steel plate/alloy layer boundary, and the alloy layer. It has been found that the /zinc layer boundary, zinc layer/corrosion product boundary, alloy layer/corrosion product boundary, and base steel plate/corrosion product boundary can be identified. Therefore, the researchers discovered that by observing the recesses under magnification, it is possible to determine whether or not each of the alloy layer, zinc layer, and corrosion products exist on the base steel sheet, and the thickness of each layer. .

The gist of the present invention, which was completed based on the above knowledge, is as follows.
[1] At the beginning of construction, it has a base steel plate and a galvanized layer on the base steel plate, and the galvanized layer has an alloy layer on the base steel plate and a zinc layer on the alloy layer. A method for evaluating the soundness of a hot-dip galvanized structure comprising:
A first step of preparing an electric drill having a right circular conical tip, the tip being rotatable around the axis of the right circular cone;
With the tip of the electric drill being rotated, the tip is pressed against the evaluation site of the hot-dip galvanized structure to scrape the evaluation site with the tip, and the evaluation site is a second step of forming an inverted right conical concave portion reaching the base steel plate;
a third step of observing the concave portion under magnification;
In the enlarged observation of the recess, (i) evaluate the soundness of the hot-dip galvanized structure based on whether or not the alloy layer is identified around the base steel plate, separated from the base steel plate; , (ii) if the alloy layer is identified, the method of determining whether or not the zinc layer is identified around the alloy layer, separate from the alloy layer, of the hot-dip galvanized structure; A fourth step of further evaluating soundness;
A method for evaluating the soundness of a hot-dip galvanized structure, comprising:

[2] In the fourth step, if the alloy layer is identified around the base steel sheet in (i) and the zinc layer is identified around the alloy layer in (ii), the The hot-dip zinc according to [1] above, wherein both the alloy layer and the zinc layer remain on the base steel plate in the evaluated part, and the soundness of the hot-dip galvanized structure is evaluated to be good. Method for evaluating the health of plated structures.

[3] In (i) of the fourth step, the base steel plate and the alloy layer are identified based on one or both of the difference in brightness and the difference in pattern, and in (ii) of the fourth step, The method for evaluating the health of a hot-dip galvanized structure according to [2] above, wherein the alloy layer and the zinc layer are identified based on one or both of a difference in brightness and a difference in pattern.

[4] In the fourth step, when the alloy layer is identified around the base steel plate in (i) and the zinc layer is identified around the alloy layer in (ii), ( Even if in ii) another area is identified around the zinc layer, separate from the zinc layer, and it is assessed that corrosion products are present on the zinc layer, the integrity of the hot-dip galvanized structure is The method for evaluating the soundness of a hot-dip galvanized structure according to [2] or [3] above, which evaluates that the structure is good.

[5] In (ii) of the fourth step, the melting according to [4] above identifies the zinc layer and the other region based on one or both of a difference in brightness and a difference in pattern. Method for evaluating the integrity of galvanized structures.

[6] Evaluation that the soundness of the hot-dip galvanized structure is good means that the evaluated portion of the hot-dip galvanized structure can continue to be used as is, [2] to [2] above. 5]. The method for evaluating the soundness of a hot-dip galvanized structure according to any one of [5].

[7] In the fourth step, if the alloy layer is identified around the base steel plate in (i) and the zinc layer is not identified in (ii), the base steel plate is Although the alloy layer remains on the hot-dip galvanized structure, the zinc layer does not remain, and the hot-dip galvanized structure is evaluated to have poor soundness. A method for evaluating the soundness of things.

[8] The molten zinc according to [7] above, wherein in (i) of the fourth step, the base steel sheet and the alloy layer are identified based on one or both of a difference in brightness and a difference in pattern. Method for evaluating the health of plated structures.

[9] The evaluation that the soundness of the hot-dip galvanized structure is poor means that the evaluated portion of the hot-dip galvanized structure requires repair; A method for evaluating the soundness of a hot-dip galvanized structure.

[10] In the fourth step, if the alloy layer is not identified in (i), the alloy layer and the zinc layer do not remain on the base steel plate in the evaluation site, and the molten zinc The method for evaluating the health of a hot-dip galvanized structure according to [1] above, which evaluates that the health of the galvanized structure is particularly poor.

[11] Evaluation that the health of the hot-dip galvanized structure is particularly poor means that the evaluated portion of the hot-dip galvanized structure requires repair or is unusable. 10], the method for evaluating the soundness of a hot-dip galvanized structure.

[12] The method for evaluating the health of a hot-dip galvanized structure according to any one of [1] to [11] above, wherein the third step is performed while the recess is illuminated with visible light.

[13] The method for evaluating the health of a hot-dip galvanized structure according to any one of [1] to [12] above, wherein the third step is performed using a microscope.

[14] The method according to any one of [1] to [13] above, wherein in the third step, an enlarged image of the recess is obtained, and the fourth step is performed using the enlarged image of the recess. Method for evaluating the soundness of hot-dip galvanized structures.

[15] The method for evaluating the health of a hot-dip galvanized structure according to [14] above, wherein the enlarged image is acquired using a solid-state imaging device.

[16] The method for evaluating the soundness of a hot-dip galvanized structure according to any one of [1] to [15] above, wherein the tip of the electric drill is made of tungsten carbide steel.

[17] The hot-dip galvanized structure according to any one of [1] to [16] above, wherein the hot-dip galvanized structure is one or more types selected from the group consisting of bridges, steel towers, and road ancillary equipment. A method for evaluating the soundness of things.

[18] Soundness evaluation of the hot-dip galvanized structure according to any one of [1] to [17] above, wherein the hot-dip galvanized structure has a coating film on the zinc layer at the beginning of construction. Method.

According to the method for evaluating the health of a hot-dip galvanized structure of the present invention, the health of a hot-dip galvanized structure can be evaluated more accurately.

FIG. 2 is a schematic diagram of a recess (part to be evaluated) in the first embodiment of the present invention, (A) is a cross-sectional view of the recess (II cross-sectional view in (B)), and (B) is a cross-sectional view of the recess. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of a recess (part to be evaluated) in a second embodiment of the present invention, (A) is a cross-sectional view of the recess (II cross-sectional view in (B)), and (B) is a cross-sectional view of the recess. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of a recess (part to be evaluated) in a third embodiment of the present invention, (A) is a cross-sectional view of the recess (II cross-sectional view in (B)), and (B) is a cross-sectional view of the recess. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of the recessed part (part to be evaluated) in the fourth embodiment of the present invention, (A) is a sectional view of the recessed part (II sectional view in (B)), and (B) is a schematic diagram of the recessed part. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of the recessed part (part to be evaluated) in the fifth embodiment of the present invention, (A) is a sectional view of the recessed part (II sectional view in (B)), and (B) is a schematic diagram of the recessed part. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). FIG. 3 is a schematic diagram of a recess (part to be evaluated) in a conventional example, in which (A) is a cross-sectional view of the recess (II cross-sectional view in (B)), and (B) is a top view of the recess ((A ) is a view seen from the bird's-eye view direction z). In Example 1, (A) is an external photograph of the sample, (B) is an enlarged image of the recessed part of the sample taken with a digital camera, and (C) is an image of the recessed part of the sample taken with a cut-type film thickness measuring device. This is an enlarged image taken with a CCD camera installed in the building. In Example 1, these are optical microscope images of the cross section of the sample, (A) is an image without etching treatment, and (B) is an image with etching treatment. In Example 1, this is an image in which the outer periphery of the recess, the zinc layer/alloy layer boundary, and the alloy layer/base steel plate boundary are specified with respect to the enlarged image of FIG. 7(C). This is an external image of evaluated parts 1 to 3 of real bridge A in Example 2. In Example 2, it is an enlarged image of the concave portion of the evaluation site 1 of the real bridge A. This is an external image of evaluated parts 4 to 6 of real bridge A in Example 3. In Example 3, it is an enlarged image of the concave portion of the evaluation site 4 of the real bridge A. In Example 4, it is an external image of the evaluated parts 7 and 8 of real bridge B. In Example 4, it is an enlarged image of the concave portion of the evaluation site 7 of the real bridge B. In Example 4, it is an enlarged image of the concave portion of the evaluation site 8 of the real bridge B. In Example 5, it is an enlarged image of the recessed part of the evaluation site 9 of sample C which was subjected to hot-dip galvanizing. It is a schematic diagram of the recessed part (part to be evaluated) in the sixth embodiment of the present invention, (A) is a sectional view of the recessed part (II sectional view in (B)), and (B) is a schematic diagram of the recessed part. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of the recessed part (part to be evaluated) in the seventh embodiment of the present invention, (A) is a cross-sectional view of the recessed part (II cross-sectional view in (B)), and (B) is a schematic diagram of the recessed part. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). It is a schematic diagram of the recessed part (part to be evaluated) in the eighth embodiment of the present invention, (A) is a cross-sectional view of the recessed part (II cross-sectional view in (B)), and (B) is a schematic diagram of the recessed part. FIG. 2 is a top view (a view seen from the bird's-eye direction z in (A)). In Example 6, it is an enlarged image of the recessed part of the evaluation site 10 of sample D which was subjected to hot-dip galvanizing and painting.

[Hot-dip galvanized structure to be evaluated]
In this embodiment, the hot-dip galvanized structure to be evaluated includes a base steel plate and a galvanized layer on the base steel plate at the initial stage of construction, as shown in FIG. 1(A), for example. The galvanized layer includes an alloy layer on the base steel sheet and a zinc layer (η layer) on the alloy layer.

The steel type, composition, structure, mechanical properties, etc. of the base steel sheet are appropriately selected depending on the type of hot-dip galvanized structure and are not particularly limited. The galvanized layer is formed by hot-dip galvanizing a base steel sheet by a conventional method, and is not particularly limited. Usually, the galvanized layer has a zinc layer (η layer) having a composition close to that of pure zinc, and an alloy layer formed at the interface between the base steel sheet and the galvanized layer. The composition of the alloy layer can include, for example, a ζ layer (FeZn13), a δ ₁ layer (FeZn7), a Γ ₁ layer (Fe5Zn21), and a Γ layer (Fe3Zn10), and the alloy layer is selected from these. It shall consist of at least one layer.

In this embodiment, as shown in FIG. 18A, for example, the hot-dip galvanized structure to be evaluated includes a base steel plate, a galvanized layer on the base steel plate, and a galvanized layer on the base steel plate. It may have a coating film on a galvanized layer, and the galvanized layer may have an alloy layer on the base steel sheet and a zinc layer (η layer) on the alloy layer. A coating film is formed on the zinc layer (η layer).

The type of hot-dip galvanized structure is not particularly limited, and examples thereof include buildings such as bridges, steel towers, and road accessories such as guardrails and signs. As mentioned above, bridges are clearly classified into those with painted specifications and bridges with hot-dip galvanized specifications, and the bridges with hot-dip galvanized specifications, which are the subject of evaluation in this embodiment, are not painted. First, the layer structure is as shown in FIG. 1(A). However, some hot-dip galvanized structures other than bridges, such as steel towers and buildings, have the layer structure shown in FIG. 18(A) by coating the galvanized layer. As detailed below, in this embodiment, the soundness of such a painted hot-dip galvanized structure can also be evaluated.

[Surface condition of hot-dip galvanized structure without coating]
After construction, a hot-dip galvanized structure without a coating can take on various surface conditions depending on the environment and the period of use. Typical examples will be explained below.

(First aspect)
Referring to FIG. 1(A), the first embodiment has a configuration of base steel plate/alloy layer/zinc layer, and no corrosion products are generated on the surface of the zinc layer. This condition is equivalent to the condition at the time of construction and should be evaluated as the highest in soundness.

(Second aspect)
Referring to FIG. 2(A), the second embodiment has a configuration of base steel plate/alloy layer/zinc layer, and red rust is present on the surface of the zinc layer. Since a zinc layer exists directly below the red rust, this red rust is not a corrosion product of the alloy layer or a corrosion product of the base steel plate, but is flowing rust from other parts. In this state, since the zinc layer remains, the soundness should originally be evaluated as good. However, in conventional health evaluations based only on surface appearance inspections, if there is an abnormality in surface appearance due to red rust, it is uniformly evaluated as requiring repair.

(Third aspect)
Referring to FIG. 3(A), the third embodiment has a configuration of base steel plate/alloy layer/zinc layer, and white rust (corrosion product of the η layer) is present on the zinc layer. . This is a stage where corrosion of the galvanized layer has progressed slightly and white rust, which is a corrosion product of zinc, has occurred, and compared to the initial appearance, the metallic luster is reduced and the overall appearance is whitish. In this state, since the zinc layer remains, the soundness should be evaluated as good.

(Fourth aspect)
Referring to FIG. 4(A), the fourth aspect is a base steel plate/alloy layer configuration, and red rust (corrosion product of the alloy layer) is present on the alloy layer. This is a state in which the corrosion of the galvanized layer further progresses, the zinc layer disappears, and the alloy layer is exposed. When the alloy layer is exposed, red dots of rust begin to appear, and as corrosion progresses, the entire surface turns red. In this state, since the zinc layer has disappeared, the integrity should be evaluated as poor, that is, it is necessary to repair the relevant part of the hot-dip galvanized structure.

(Fifth aspect)
Referring to FIG. 5(A), the fifth aspect is a state in which red rust (corrosion product of the base steel plate) is present on the base steel plate. This is a state where the entire galvanized layer has disappeared and the base steel sheet is exposed. When the base steel plate is exposed, red rust, which is a corrosion product of iron, can be observed. In this condition, the integrity of the galvanized structure should be evaluated as particularly poor since the entire galvanized layer has disappeared, meaning that the area of the hot-dip galvanized structure should be immediately repaired or replaced. It needs to be replaced immediately. In particular, as corrosion of the base steel plate progresses, the strength of the structure decreases, leading to the possibility of breakage, damage, and collapse. Therefore, it is necessary to perform repairs (new anti-corrosion treatment) before the base steel plate begins to corrode (before the fifth aspect occurs). However, it may be difficult to distinguish between a state in which corrosion of the alloy layer has progressed (fourth embodiment) and a state in which the base steel plate has corroded (fifth embodiment) based only on the surface appearance. Therefore, there is also a need for a soundness evaluation method that accurately discriminates between the fourth aspect and the fifth aspect.

[Method for evaluating the soundness of hot-dip galvanized structures]
In the method for evaluating the health of a hot-dip galvanized structure according to the present embodiment, first, an electric drill is prepared which has a right circular conical tip and is rotatable around the axis of the right circular cone. Then, while rotating the tip of the electric drill, the tip is pressed against the evaluation site of the hot-dip galvanized structure, thereby scraping the evaluation site with the tip. A concave portion having an inverted right circular cone shape is formed. By doing so, the base steel plate, the alloy layer, the zinc layer, and the corrosion products can each be visually recognized as different regions in an enlarged observation of the recess. That is, it is possible to identify the base steel sheet/alloy layer boundary, alloy layer/zinc layer boundary, zinc layer/corrosion product boundary, alloy layer/corrosion product boundary, and base steel sheet/corrosion product boundary. can. Therefore, by observing the recesses under magnification, it is possible to determine whether or not each of the alloy layer, zinc layer, and corrosion product is present on the base steel sheet, or how thick each layer is.

The present inventors believe that the principle by which such an effect is obtained is as follows. Comparing the hardness of each layer of a hot-dip galvanized structure, the zinc layer, the base steel plate, and the alloy layer are found in descending order of hardness. Moreover, when the fracture toughness values of each layer are compared, it becomes the zinc layer, the alloy layer, and the base steel sheet in descending order of fracture toughness value. The corrosion products also have hardness and fracture toughness values that are different from those of the zinc layer, alloy layer, and base steel sheet. Thus, the zinc layer, the alloy layer, the base steel sheet, and the corrosion products have different physical property values. Here, if a concave portion is formed by scraping the evaluation site little by little using an electric drill having a right circular cone-shaped tip as in this embodiment, the difference in physical property values of each layer as described above will occur. Therefore, differences occur in the fine surface shape of the recesses for each layer. The most obvious example is that on the surface of the recess, the surface profile was rougher in the zinc layer than in the alloy layer. In this way, since differences occur in the fine surface shapes of the recesses for each layer, it is thought that each layer can be visually recognized (optically distinguished) as a different region in magnified observation of the recesses. On the other hand, in the method described in Patent Document 1 shown in FIGS. The recesses are formed by scribing straight lines on the part to be evaluated. However, with this method, it is not possible to create differences in the minute surface shape of the recesses for each layer. It is considered that these areas cannot be visually recognized as different areas.

Hereinafter, a description will be given of how each of the first to fifth aspects described above can be evaluated using the soundness evaluation method according to the present embodiment.

[First step: Preparation of electric drill]
First, an electric drill is prepared which has a right circular conical tip and is rotatable around the axis of the right circular cone. From the viewpoint of creating a difference in the minute surface shape of the recess for each layer, the tip of the electric drill should be made of at least one of high speed steel such as tungsten carbide steel, superalloy steel, diamond sintered body, etc. is preferred.

[Second step: Formation of recesses]
Subsequently, with the tip of the electric drill being rotated, the tip is pressed against the evaluation site of the hot-dip galvanized structure to scrape the evaluation site with the tip, and the evaluation site is removed. A concave portion having an inverted right circular cone shape is formed. That is, the tip of the electric drill is pressed against the region to be evaluated while maintaining the state in which the axis of the right circular cone at the tip is perpendicular to the surface of the region to be evaluated before the recess is formed. In addition, "the axis of the right circular cone at the tip is perpendicular to the surface of the area to be evaluated before the recess is formed" means that the electric drill should not be intentionally pressed diagonally against the surface of the area to be evaluated. This does not mean purely mathematical verticality, and errors that inevitably occur when an operator operates an electric drill are naturally allowed.

The diameter of the recess and the angle of the recess (θ in Fig. 1(A)) are determined by the shape of the tip of the electric drill and the cutting depth, and may be determined as appropriate depending on the type of structure and the desired measurement accuracy. , not particularly limited. However, the diameter of the recess can be, for example, in the range of 1 to 4 mm. If the diameter is 1 mm or more, each layer can be sufficiently identified as a different region by magnifying observation of the recess, and if the diameter is 4 mm or less, the recess will not significantly impair the integrity of the structure. The angle of the recess (θ in FIG. 1(A)) can be in the range of 45 to 85 degrees (°), for example. If the angle of the recess is within this range, each layer can be sufficiently identified as a different region.

Regarding the depth of the recess, in order to appropriately evaluate the soundness in all of the above-mentioned first to fifth aspects, (through the zinc layer and alloy layer, if each exists) Form a recess that reaches the base steel plate. However, if it appears that a zinc layer clearly remains as a result of the surface appearance investigation, a recess should be formed so that it at least penetrates the zinc layer and reaches the alloy layer, even if it does not reach the base steel sheet. You can. In this way, at least the zinc layer and the alloy layer can be distinguished.

The rotational speed of the tip of the electric drill (torque setting value of the electric drill) is not particularly limited, but is preferably in the range of 60 to 240 rpm from the viewpoint of creating differences in the fine surface shape of the recesses for each layer. . Furthermore, the rotational speed of the tip of the electric drill during the process of forming the recess may be constant or may vary. However, from the viewpoint of producing differences in the fine surface shapes of the recesses for each layer, it is preferable that the rotation speed is constant. Note that the "rotational speed of the tip of the electric drill" here means the rotational speed as the torque setting value of the electric drill, that is, the rotational speed when there is no resistance at the tip of the drill. do. Therefore, when the rotational speed is "constant", it means that the rotational speed as the torque setting value of the electric drill is constant during the process of forming the recess. Of course, it is acceptable that the actual drill rotational speed may vary somewhat due to the fact that the tip of the drill receives resistance from the portion to be evaluated.

The pressing load of the electric drill on the evaluation site is preferably constant, and preferably in the range of 30 to 80 N, from the viewpoint of creating differences in the fine surface shape of the recess for each layer. It is more preferable to set it in the range of ~60N.

The first and second steps as described above can be realized using, for example, a commercially available drill-cut film thickness meter (Paint Boreer 518PC, manufactured by Erichsen). Since this device is portable, it can be suitably used for on-site health evaluation of structures. Note that the drill-cut type cut-type film thickness meter, like the straight-line cut-type film thickness meter described in Patent Document 1, has conventionally been used to measure coating film thickness. It has not been applied to measuring the thickness of plating layers.

In the present invention, an inverted right cone-shaped recess is formed in the evaluation site using an electric drill having a right cone-shaped tip. However, the shape of the tip of the drill and the shape of the recess are not limited to those of the present invention, as long as the fine surface shape of the recess can be made different for each layer.

[Third step: Enlarged observation of recess]
Next, the recess is observed under magnification. As mentioned above, the diameter of the recess is several mm at most, so it is necessary to observe the recess under magnification in order to visually recognize the base steel sheet, alloy layer, zinc layer, and corrosion products as different regions. It is.

The enlarged observation of the recess is preferably performed while the recess is illuminated with visible light. Thereby, the base steel sheet, the alloy layer, the zinc layer, and the corrosion product can be more clearly seen as different regions. In other words, the boundaries between the base steel sheet and the alloy layer, the boundaries between the alloy layer and the zinc layer, the boundaries between the zinc layer and the corrosion products, the boundaries between the alloy layer and the corrosion products, and the boundaries between the base steel sheet and the corrosion products can be identified with more precision. can do.

The enlarged observation of the recess can be performed by, for example, obtaining an optically enlarged image of the recess using an arbitrary microscope such as an enlargement mode of a digital camera, a scope, or an optical microscope, and observing the image visually.

Furthermore, it is preferable to obtain an enlarged image of the recess. Thereby, the fourth step (evaluation of soundness), which will be described later, can be performed using the enlarged image of the recess. In this case, by visually observing the acquired enlarged image, health evaluation can be performed without being subject to time constraints. Furthermore, by analyzing the enlarged image, it is possible to perform a more detailed and quantitative evaluation of the health, such as identifying the boundaries between each layer and measuring the thickness of each layer in the enlarged image.

The enlarged image can be acquired using any solid-state imaging device, such as a digital camera, a CCD camera installed in a cut-type film thickness meter, or a camera installed in various types of microscopes.

[Fourth step: Soundness evaluation]
In the fourth step, the soundness of the hot-dip galvanized structure is evaluated based on the enlarged observation of the recess. Hereinafter, each of the first to fifth aspects described above will be specifically explained.

Referring to FIGS. 1(A) and 1(B), in the first embodiment, a concave portion having an inverted right circular cone shape reaching the base steel plate is formed in the evaluation site. When the recess is observed under magnification from the bird's-eye direction z shown in FIG. 1(A), the base steel plate, the alloy layer, and the zinc layer can be visually recognized as different regions, as shown in FIG. 1(B). That is, the boundary between the base steel sheet and the alloy layer and the boundary between the alloy layer and the zinc layer can be specified. Therefore, by magnifying observation of the recessed portion, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate at the evaluation site, and it can be evaluated that the soundness is good. In addition, since the angle θ of the recess is known, if the extension length s ₁ of the zinc layer is measured in the enlarged image of the recess, the thickness d ₁ of the zinc layer can be calculated by calculating d ₁ = s ₁ /tan θ. You can ask for it. Similarly, the thickness d ₂ of the alloy layer can be determined by calculating d ₂ =s ₂ /tanθ. In this manner, in this embodiment, the zinc layer and the alloy layer can be separated and identified, and then the thickness of each layer can be determined.

Referring to FIGS. 2(A) and 2(B), in the second embodiment, an inverted right conical recess that reaches the base steel plate is formed in the evaluation site. When the concave portion is magnified and observed from the bird's-eye direction z shown in FIG. 2(A), the base steel plate, the alloy layer, the zinc layer, and the red rust can be visually recognized as different regions, as shown in FIG. 2(B). That is, the boundary between the base steel sheet and the alloy layer, the boundary between the alloy layer and the zinc layer, and the boundary between the zinc layer and the red rust can be specified. Therefore, although red rust is observed in the surface appearance investigation, magnified observation of the recesses reveals that both the alloy layer and the zinc layer remain on the base steel plate in the area being evaluated, and the soundness is good. It can be evaluated as follows. Further, in the same manner as in the first embodiment, the thicknesses of the zinc layer, alloy layer, and corrosion product (red rust) can be determined individually. In this manner, in this embodiment, the thickness of each layer can be determined after separating and identifying the zinc layer, alloy layer, and corrosion product (red rust). This embodiment is preferable in that it can eliminate the possibility of performing unnecessary repairs.

Referring to FIGS. 3(A) and 3(B), in the third embodiment, a concave portion having an inverted right circular cone shape reaching the base steel plate is formed in the evaluation site. When the concave portion is magnified and observed from the bird's-eye direction z shown in FIG. 3(A), the base steel plate, the alloy layer, the zinc layer, and the white rust can be visually recognized as different regions, as shown in FIG. 3(B). That is, it is possible to specify the base steel plate/alloy layer boundary, the alloy layer/zinc layer boundary, and the zinc layer/white rust boundary. Therefore, by magnifying observation of the recessed portion, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate at the evaluation site, and it can be evaluated that the soundness is good. Further, similarly to the first embodiment, the thicknesses of the zinc layer, alloy layer, and corrosion product (white rust) can be determined individually. In this manner, in this embodiment, the thickness of each layer can be determined after separating and identifying the zinc layer, alloy layer, and corrosion product (white rust).

Referring to FIGS. 4(A) and 4(B), in the fourth embodiment, a concave portion having an inverted right circular cone shape reaching the base steel plate is formed in the evaluation site. When the concave portion is magnified and observed from the bird's-eye direction z shown in FIG. 4(A), the base steel plate, the alloy layer, and the red rust can be visually recognized as different regions, as shown in FIG. 4(B). That is, the boundary between the base steel sheet and the alloy layer and the boundary between the alloy layer and red rust can be specified. Therefore, by magnifying observation of the recess, it can be seen that the zinc layer has disappeared although the alloy layer remains in the evaluation site, and it can be evaluated that the soundness is poor. Further, in the same manner as in the first embodiment, the thicknesses of the alloy layer and the corrosion product (red rust) can be determined individually. In this manner, in this embodiment, the thickness of each layer can be determined after separating and identifying the alloy layer and the corrosion product (red rust).

Referring to FIGS. 5(A) and 5(B), in the fifth embodiment, a concave portion having an inverted right circular cone shape reaching the base steel plate is formed in the evaluation site. When the recess is observed under magnification from the bird's-eye direction z shown in FIG. 5(A), the base steel plate and the red rust can be visually recognized as different regions, as shown in FIG. 5(B). That is, the boundary between the base steel plate and red rust can be specified. Therefore, by magnifying observation of the recess, it can be seen that the entire galvanized layer has disappeared at the evaluated site, and the health can be evaluated as being particularly poor.

(Evaluation of soundness based on presence or absence of alloy layer and presence or absence of zinc layer)
Based on the above, in an embodiment of the present invention, in an enlarged observation of a recess, (i) based on whether or not the alloy layer is identified around the base steel plate, separated from the base steel plate, Evaluate the soundness of the hot-dip galvanized structure, and (ii) if the alloy layer is identified, determine whether the zinc layer is identified around the alloy layer and separate from the alloy layer. Based on this, the health of the hot-dip galvanized structure can be further evaluated. Specifically, it is as follows.

If an alloy layer is identified around the base steel plate in (i), and a zinc layer is identified around the alloy layer in (ii), the alloy layer and zinc layer are formed on the base steel plate at the location to be evaluated. Both remain, and the soundness of the hot-dip galvanized structure is evaluated to be good. This applies to the examples in FIGS. 1A and 1B, FIGS. 2A and 2B, and 3A and 3B.

In addition, as in the examples of FIGS. 2 (A) and (B) and the examples of FIGS. 3 (A) and (B), the alloy layer is identified around the base steel plate in (i), and the alloy layer is identified around the base steel plate in (ii). If a zinc layer is identified around the alloy layer, a separate area is identified around the zinc layer and separate from the zinc layer, even if corrosion products are assessed to be present on the zinc layer. Since both the alloy layer and the zinc layer remain on the base steel plate in the evaluated area, the soundness of the hot-dip galvanized structure is evaluated to be good. In the case of red rust as shown in Figures 2 (A) and (B), this corrosion product is flowing rust from other parts, and in the case of white rust as in Figures 3 (A) and (B), this corrosion product is If present, it is a corrosion product of the zinc layer. In any case, if the zinc layer remains, the soundness may be evaluated as good.

In addition, if an alloy layer is identified around the base steel plate in (i), and a zinc layer is not identified in (ii), although the alloy layer remains on the base steel plate in the area to be evaluated, zinc No layer remains and the integrity of the hot-dip galvanized structure is rated as poor. This corresponds to the examples in FIGS. 4(A) and 4(B).

In addition, if the alloy layer is not identified in (i), there is no alloy layer or zinc layer remaining on the base steel plate in the evaluated area, and the integrity of the hot-dip galvanized structure is evaluated to be particularly poor. do. This corresponds to the examples in FIGS. 5(A) and 5(B).

Therefore, according to the present embodiment, it is possible to accurately discriminate between a state in which corrosion of the alloy layer has progressed (fourth embodiment) and a state in which the base steel plate is corroded (fifth embodiment).

(Definition of soundness evaluation)
Evaluation that the health of the hot-dip galvanized structure is good means that the evaluated portion of the hot-dip galvanized structure can continue to be used as is. Furthermore, an evaluation that the health of the hot-dip galvanized structure is poor means that the evaluated portion of the hot-dip galvanized structure requires repair. Repair is any treatment that reinforces the corrosion resistance of the portion of the structure to be evaluated, and includes, for example, painting, metal spraying, and the like. Evaluation that the health of the hot-dip galvanized structure is particularly poor means that the evaluated portion of the hot-dip galvanized structure requires repair or is unusable. In particular, in the case of a defective evaluation, it is necessary to immediately repair or replace the evaluated part immediately.

When painting as part of repair work, surface preparation may be performed before painting in order to remove deteriorated paint or plating and improve the adhesion of the paint. Regarding substrate preparation, it is preferable to leave as much of the plating or coating film (referred to as active film) as possible while maintaining its performance. Further, from the viewpoint of workability and cost, it is preferable that the surface preparation be as simple as possible. By performing soundness evaluation using the method of the present invention, for example, understanding the depth of rust that has developed during plating, and determining the type of substrate preparation and target values for the thickness of grinding based on this information, You can perform simple surface preparation.

(Identification of each layer)
In the enlarged observation of the recess, (A) discrimination between the alloy layer and the zinc layer, (B) discrimination between the zinc layer and corrosion products on the zinc layer, and (C) discrimination between the base steel sheet and the alloy layer are as follows: Both can be performed based on one or both of the difference in brightness and the difference in pattern. For example, when a healthy galvanized layer (alloy layer and zinc layer) is cut with a drill, the cut marks have a pattern depending on the layer, giving it a shiny appearance, whereas corrosion products have a metallic luster. is not observed. That is, the zinc layer has an appearance with metallic luster, whereas the corrosion product (white rust) of the zinc layer has a dull appearance without metallic luster. Further, the zinc layer has a relatively whitish and bright appearance, whereas the alloy layer has a metallic luster but a relatively dark appearance. Further, when performing magnified observation of the recess under light irradiation, the halation pattern may differ depending on the region of each layer, and each layer can be identified based on the difference in pattern.

[Surface condition of hot dip galvanized structure to be coated]
After construction of a hot-dip galvanized structure having a coating film, the galvanized layer under the coating film can take various states depending on the environment and the period of use. In the case of a hot-dip galvanized structure having a coating film, corrosion of the galvanized layer basically progresses under the coating film, and the manner of corrosion is the same as in the case where there is no coating film. Typical examples will be explained below.

(Sixth aspect)
Referring to FIG. 18(A), the sixth embodiment has a structure of base steel plate/alloy layer/zinc layer/paint film, and no corrosion products are generated on the surface of the zinc layer. This condition is equivalent to the condition at the time of construction and should be evaluated as the highest in soundness. This corresponds to the first aspect (FIG. 1(A)) where there is no coating film.

(Seventh aspect)
Referring to FIG. 19(A), the seventh embodiment has a structure of base steel plate/alloy layer/zinc layer/paint film, and red rust is present on the surface of the paint film. Since there is a zinc layer under the paint film, this red rust is not a corrosion product of the alloy layer or a corrosion product of the base steel plate, but is flowing rust from other parts. In this state, since the zinc layer remains, the soundness should originally be evaluated as good. However, in conventional health evaluations based only on surface appearance inspections, if there is an abnormality in surface appearance due to red rust, it is uniformly evaluated as requiring repair. This corresponds to the second aspect (FIG. 2(A)) where there is no coating film.

(Eighth aspect)
Referring to FIG. 20(A), the eighth aspect has a structure of base steel plate/alloy layer/zinc layer/paint film, and under the paint film, white rust (corrosion formation of η layer) is formed on the zinc layer. is the state in which a thing) exists. This is a stage where corrosion of the galvanized layer has progressed slightly and white rust, which is a corrosion product of zinc, has formed under the coating film. In this state, since the zinc layer remains, the soundness should be evaluated as good. This corresponds to the third aspect (FIG. 3(A)) where there is no coating film.

Although not shown in the figure, as the corrosion under the paint film further progresses, the alloy layer becomes exposed under the paint film, which corresponds to the fourth aspect (Fig. 4(A)) when there is no paint film. In this case, the base steel sheet is exposed under the coating film, corresponding to the state in which red rust (corrosion product of the alloy layer) is present, or the fifth embodiment (Fig. 5 (A)) in which there is no coating film. may be exposed and red rust (corrosion products of the base steel plate) may be present.

[Method for evaluating the soundness of hot-dip galvanized structures with coatings]
In the method for evaluating the health of a hot-dip galvanized structure according to the present embodiment, the same method is applied to a hot-dip galvanized structure having a coating film as in the case of a hot-dip galvanized structure without a coating film, as described above. Health can be evaluated. This is because the coating film can also be visually recognized as an area different from other layers when observing the recess under magnification. Therefore, the matters explained as the health evaluation for hot-dip galvanized structures without a paint film are also applied to the soundness evaluation of hot-dip galvanized structures that have a paint film. Hereinafter, a specific example of performing soundness evaluation based on enlarged observation of the recessed portion will be described in accordance with each of the sixth to eighth aspects.

Referring to FIGS. 18(A) and 18(B), in the sixth embodiment, an inverted right conical recess that reaches the base steel plate is formed in the evaluation site. When the concave portion is magnified and observed from the bird's-eye direction z shown in FIG. 18(A), the base steel plate, the alloy layer, the zinc layer, and the coating film can each be visually recognized as different regions as shown in FIG. 18(B). That is, the boundary between the base steel sheet and the alloy layer, the boundary between the alloy layer and the zinc layer, and the boundary between the zinc layer and the coating film can be specified. Therefore, by magnifying observation of the recessed portion, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate at the evaluation site, and it can be evaluated that the soundness is good. In addition, since the angle θ of the recess is known, if the extension length s ₁ of the zinc layer is measured in the enlarged image of the recess, the thickness d ₁ of the zinc layer can be calculated by calculating d ₁ = s ₁ /tan θ. You can ask for it. Similarly, the thickness d ₂ of the alloy layer can be determined by calculating d ₂ =s ₂ /tanθ. In this manner, in this embodiment, the zinc layer and the alloy layer can be separated and identified, and then the thickness of each layer can be determined.

Referring to FIGS. 19(A) and 19(B), in the seventh embodiment, an inverted right conical recess that reaches the base steel plate is formed in the evaluation site. When the recess is observed under magnification from the bird's-eye direction z shown in FIG. 19(A), the base steel plate, alloy layer, zinc layer, paint film, and red rust can be visually recognized as different areas, as shown in FIG. 19(B). can. That is, the base steel sheet/alloy layer boundary, the alloy layer/zinc layer boundary, the zinc layer/paint film boundary, and the paint film/red rust boundary can be specified. Therefore, although red rust is observed in the surface appearance investigation, magnified observation of the recesses reveals that both the alloy layer and the zinc layer remain on the base steel plate in the area being evaluated, and the soundness is good. It can be evaluated as follows. Further, similarly to the sixth embodiment, the thicknesses of the zinc layer, alloy layer, and corrosion product (red rust) can be determined individually. In this manner, in this embodiment, the thickness of each layer can be determined after separating and identifying the zinc layer, alloy layer, and corrosion product (red rust). This embodiment is preferable in that it can eliminate the possibility of performing unnecessary repairs.

Referring to FIGS. 20(A) and 20(B), in the eighth embodiment, a concave portion having an inverted right circular cone shape reaching the base steel plate is formed in the evaluation site. When the concave portion is magnified and observed from the bird's-eye direction z shown in FIG. 3(A), the base steel plate, alloy layer, zinc layer, white rust, and paint film are each visible as different areas, as shown in FIG. 20(B). Can be done. That is, the base steel plate/alloy layer boundary, the alloy layer/zinc layer boundary, the zinc layer/white rust boundary, and the white rust/paint film boundary can be specified. Therefore, by magnifying observation of the recessed portion, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate at the evaluation site, and it can be evaluated that the soundness is good. Further, similarly to the first embodiment, the thicknesses of the zinc layer, alloy layer, and corrosion product (white rust) can be determined individually. In this manner, in this embodiment, the thickness of each layer can be determined after separating and identifying the zinc layer, alloy layer, and corrosion product (white rust).

Although not shown, the fourth embodiment (Fig. 4 (A ), (B)), the soundness can be evaluated as poor, and the condition where the base steel plate is exposed under the coating and red rust (corrosion products of the base steel plate) is present is also evaluated as poor. Similar to the fifth embodiment (FIGS. 5A and 5B) in which there is no membrane, the health can be evaluated as particularly poor.

That is, the evaluation of the soundness based on the presence or absence of the alloy layer and the presence or absence of the zinc layer can be performed by the steps (i) and (ii) described above, regardless of the presence or absence of the coating film.

In addition, in the enlarged observation of the recessed portion, the coating film and other layers can be distinguished based on one or both of the difference in color and the difference in brightness. Since the coating film has an appearance without metallic luster, it can be easily distinguished from the zinc layer beneath the coating film based on the presence or absence of metallic luster. Since corrosion products have an appearance without metallic luster, it is difficult to distinguish between a paint film and a corrosion product based only on the presence or absence of metallic luster, but they can be distinguished because they differ in color tone and brightness.

In the examples shown below, in the "method of the present invention", a drill-cut type film thickness meter (Paint Boreer 518PC, manufactured by Erichsen) was used. An inverted right cone-shaped recess that reached the base steel plate was formed at the evaluation site using an electric drill with a right cone-shaped tip made of tungsten carbide steel that was attached to the film thickness gauge. At that time, the rotational speed (torque setting value) of the electric drill was set to 120 rpm, and the pressing load was set to 55 N, and then an enlarged image of the recess was obtained using a CCD camera attached to the film thickness meter. LED lights were installed around the CCD camera from eight directions, and an enlarged image of the recess was obtained under light irradiation. Thereafter, the operator identified each layer and the boundaries between adjacent layers in each enlarged image. Based on the results, specialized software performed an analysis and calculated the thickness of each layer.

(Example 1)
As shown in FIG. 7(A), a sample was prepared in which a 100×200×10 mm base steel plate (SS400 material) was hot-dip galvanized. The plating thickness was measured using an electromagnetic film thickness meter, and the concave portion was observed under magnification using the method of the present invention, on an arbitrarily determined portion of the sample to be evaluated. In addition, a part of the vicinity of the evaluation site was cut out and cross-sectional observation was performed using an optical microscope.

FIG. 7(B) is an enlarged image of the concave portion of the sample taken with a commercially available digital camera (without light irradiation). In this enlarged image, a white ring-shaped area and a gray area inside it could be seen.

FIG. 7(C) is an enlarged image of the concave portion of the sample taken with a CCD camera included in the cut-type film thickness meter. In this enlarged image, halation caused by LED lights from eight directions was seen radially inside the white ring-shaped area. However, the halation pattern was unclear in the center, and the halation pattern was clear in the area near the white ring-shaped area, and the halation pattern was divided into two areas with different patterns. Therefore, analysis was performed by specifying three boundaries as shown in FIG. The analysis results showed that the thickness corresponding to the distance from the innermost circle to the outermost circle was 80 μm, and the thickness corresponding to the white ring-shaped area was 50 μm.

The measured value of the electromagnetic film thickness meter was 77.8 μm. Therefore, it was found that the reinner circle (where the halation pattern changes) in the enlarged image (FIG. 9) is the boundary between the base steel plate and the alloy layer.

The results of cross-sectional observation using an optical microscope are shown in FIGS. 8(A) and 8(B). In cross-sectional observation, the thickness of the galvanized layer was 83.7 μm, which was equivalent to the value measured by the electromagnetic film thickness meter (77.8 μm) and the thickness of the galvanized layer obtained by the method of the present invention (80 μm). . In addition, since the thickness of the zinc layer (η layer) was approximately 50 μm from the cross section after etching, the white ring-shaped area observed in the enlarged image of the recess by the method of the present invention corresponds to the η layer. I found out that

From the above, it was found that by using the method of the present invention, the thicknesses of the zinc layer (η layer) and the alloy layer can be measured.

(Example 2)
The soundness of bridge A, which has been in service for 18 years, was evaluated using the method of the present invention. We selected locations where no corrosion products were visually observed and where soundness was considered to be maintained (assessed locations 1 to 3 in Figure 10), and measured the plating thickness using an electromagnetic film thickness meter and using the method of the present invention. We evaluated the soundness. The results are shown in Table 2. The results of measuring plating thickness using both methods were equivalent. Furthermore, with the method of the present invention, it was possible to measure the thicknesses of the η layer and the alloy layer.

FIG. 11 shows an enlarged image of the concave portion of the evaluation site 1. In this enlarged image, three areas are identified in order from the outer periphery: a white ring-shaped area, a black ring-shaped area, and a slightly white circular area, and these three areas all have metallic luster. Therefore, these three regions were identified as the zinc layer (η layer), the alloy layer, and the base steel sheet, respectively. The same was true for evaluation sites 2 and 3. In these evaluated parts 1 to 3, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate, and it can be evaluated that the soundness is good.

(Example 3)
The soundness of bridge A, which has been in service for 18 years, was evaluated using the method of the present invention. Sites where the surface appeared red when visually observed (evaluation sites 4 to 6 in FIG. 12) were selected, and the plating thickness was measured using an electromagnetic film thickness meter and the soundness was evaluated using the method of the present invention. The results are shown in Table 3. With the method of the present invention, the thicknesses of the rust layer, η layer, and alloy layer could be measured.

FIG. 13 shows an enlarged image of the recess of the evaluated site 4. This enlarged image shows, in order from the outside, an area with no metallic luster and no halation pattern, a white ring-shaped region with metallic luster, a black ring-shaped region with metallic luster, and a white circular region with metallic luster. Four regions are identified. Therefore, these four regions were respectively identified as a rust layer, a zinc layer (η layer), an alloy layer, and a base steel sheet. Since the η layer was observed and the alloy layer was not exposed, it was found that the parts that appeared red in appearance were red rust from other parts. Upon careful observation of the surrounding situation at the site, it was discovered that there was water leaking from the expansion and contraction equipment, and that water was being blown onto the area being evaluated by wind blowing from the vents at the end of the girder. In these evaluated parts 4 to 6, red rust is observed in the surface appearance investigation, but enlarged observation of the recesses reveals that both the alloy layer and the zinc layer remain on the base steel plate, and the soundness is confirmed. It can be evaluated as good.

(Example 4)
The soundness of bridge B, which has been in service for 29 years, was evaluated using the method of the present invention. Locations where corrosion seemed to be progressing rapidly (assessed locations 7 and 8 in FIG. 14) were selected, and the plating thickness was measured using an electromagnetic film thickness meter and the soundness was evaluated using the method of the present invention. The results are shown in Table 4 and Figures 15 and 16.

FIG. 15 shows an enlarged image of the concave portion of the evaluation site 7. In this enlarged image, two areas are identified: a ring-shaped area that has no metallic luster and no black halation pattern, and a circular area that has metallic luster and has a halation pattern inside it. . Therefore, these two regions were identified as the alloy layer and the base steel plate, respectively. The thickness of the alloy layer was calculated to be 309 μm. In the evaluation site 7, although the alloy layer remains, it can be seen that the zinc layer has disappeared, and the soundness can be evaluated as poor. Furthermore, it can be seen that the red rust visible on the surface other than the recessed portions is a corrosion product of the alloy layer.

FIG. 16 shows an enlarged image of the recess of the evaluation site 8. In this enlarged image, only one approximately circular region having metallic luster and in which a halation pattern is present is visible. Therefore, this area was identified as the base steel plate. In the evaluation site 8, it can be seen that the entire galvanized layer has disappeared and the base steel sheet is exposed, and the soundness can be evaluated as being particularly poor. It is also clear that red rust is a corrosion product of the base steel plate.

(Example 5)
Sample C was prepared by hot-dip galvanizing a 100 x 200 x 10 mm base steel plate (SS400 material) and exposed for 15 years in a real environment, and its soundness was evaluated using the method of the present invention. A portion whose surface appeared white to the naked eye was selected as evaluation portion 9, and the plating thickness was measured using an electromagnetic film thickness meter and the soundness was evaluated using the method of the present invention. The results are shown in Table 5. With the method of the present invention, the thicknesses of the rust layer, η layer, and alloy layer could be measured.

FIG. 17 shows an enlarged image of the concave portion of the evaluation site 9. This enlarged image shows, in order from the outside, a dull white first region with no metallic luster, a second white region with metallic luster, a black ring-shaped region with metallic luster, and a white circular region with metallic luster. Four regions are identified, the combination of the first region and the second region forming a ring-shaped region. Therefore, these four regions were respectively identified as a rust layer, a zinc layer (η layer), an alloy layer, and a base steel sheet. In this evaluation part 9, a region (rust layer) separated from the η layer was observed, and considering that the combination of this region and the η layer forms a ring-shaped region, this rust layer is due to the corrosion of the η layer. It can be seen that it is a product (white rust). In this case, by magnifying observation of the recess, it can be seen that both the alloy layer and the zinc layer remain on the base steel sheet, and the soundness can be evaluated as good. However, since the minimum thickness of a healthy η layer is close to zero, corrosion has progressed considerably and the alloy layer is almost exposed.

(Example 6)
Sample D was prepared by hot-dip galvanizing and painting a 100 x 200 x 10 mm base steel plate (SS400 material) and exposed for 15 years in a real environment, and its soundness was evaluated using the method of the present invention. A location where some unevenness was observed on the coating film surface and where coating corrosion was thought to have progressed slightly was selected as evaluation site 10, and the plating thickness was measured using an electromagnetic coating thickness meter and the soundness was determined using the method of the present invention. We conducted an evaluation. The results are shown in Table 6. With the method of the present invention, the thicknesses of the rust layer, η layer, and alloy layer could be measured.

FIG. 21 shows an enlarged image of the concave portion of the evaluated site 10. This enlarged image shows, from the outside, a dull white ring-shaped area with no metallic luster that has the same tone and brightness as the surrounding area (paint film) of the recess, and a dull white ring-shaped area with no metallic luster that is different in tone from the ring-shaped area. Five regions are identified: a first white region, a second white region with metallic luster, a black ring-shaped region with metallic luster, and a slightly white circular region with metallic luster, and the outermost ring-shaped region A combination of the first region and the second region forms a ring-shaped region inside the ring. Therefore, these five regions were respectively identified as a paint film, a rust layer, a zinc layer (η layer), an alloy layer, and a base steel sheet. In this evaluation site 10, a region (rust layer) separated from the η layer is observed, and considering that the combination of this region and the η layer forms a ring-shaped region, this rust layer is caused by the corrosion of the η layer. It can be seen that it is a product (white rust). By observing the recesses under magnification, it can be seen that both the alloy layer and the zinc layer remain on the base steel plate, and it can be evaluated that the soundness is good. However, since the minimum thickness of a healthy η layer is close to zero, corrosion has progressed considerably.

According to the method for evaluating the health of a hot-dip galvanized structure of the present invention, the health of a hot-dip galvanized structure can be evaluated more accurately. By knowing the accurate remaining thickness of the zinc layer and alloy layer, it becomes possible to efficiently plan future maintenance timing, priorities, and maintenance.

Furthermore, the corrosion rate of the zinc layer can be considered as the corrosion rate of pure zinc. The corrosion rate of pure zinc can be measured using an exposure test or an electrical resistance sensor. Based on the thickness of the zinc layer and the corrosion rate of pure zinc, which have been made measurable by the present invention, it is possible to obtain a more detailed estimate of the period until the zinc layer disappears, that is, the period until the alloy layer is exposed. can. This guideline provides useful information when considering when to perform maintenance.

Claims (18)

Hot-dip zinc having a base steel plate and a galvanized layer on the base steel plate at the beginning of construction, and the galvanized layer having an alloy layer on the base steel plate and a zinc layer on the alloy layer. A method for evaluating the soundness of a plated structure, the method comprising:
A first step of preparing an electric drill having a right circular conical tip, the tip being rotatable around the axis of the right circular cone;
With the tip of the electric drill being rotated, the tip is pressed against the evaluation site of the hot-dip galvanized structure to scrape the evaluation site with the tip, and the evaluation site is a second step of forming an inverted right conical concave portion reaching the base steel plate;
a third step of observing the concave portion under magnification;
In the enlarged observation of the recess, (i) evaluate the soundness of the hot-dip galvanized structure based on whether or not the alloy layer is identified around the base steel plate, separated from the base steel plate; , (ii) if the alloy layer is identified, the method of determining whether or not the zinc layer is identified around the alloy layer, separate from the alloy layer, of the hot-dip galvanized structure; A fourth step of further evaluating soundness;
A method for evaluating the soundness of a hot-dip galvanized structure, comprising: In the fourth step, if the alloy layer is identified around the base steel plate in (i) and the zinc layer is identified around the alloy layer in (ii), the evaluation site The hot-dip galvanized structure according to claim 1, wherein both the alloy layer and the zinc layer remain on the base steel sheet, and the soundness of the hot-dip galvanized structure is evaluated to be good. Soundness evaluation method. In (i) of the fourth step, the base steel sheet and the alloy layer are identified based on one or both of a difference in brightness and a difference in pattern, and in (ii) of the fourth step, the brightness The method for evaluating the health of a hot-dip galvanized structure according to claim 2, wherein the alloy layer and the zinc layer are identified based on one or both of a difference in color and a difference in pattern. In the fourth step, if the alloy layer is identified around the base steel sheet in (i) and the zinc layer is identified around the alloy layer in (ii), then in (ii) Even if another area is identified around the zinc layer, separate from the zinc layer, and corrosion products are assessed to be present on the zinc layer, the integrity of the hot-dip galvanized structure is good. The method for evaluating the soundness of a hot-dip galvanized structure according to claim 2, wherein the method evaluates that the integrity of a hot-dip galvanized structure is present. The hot-dip galvanized structure according to claim 4, wherein in the fourth step (ii), the zinc layer and the other region are identified based on one or both of a difference in brightness and a difference in pattern. Health evaluation method. The hot-dip galvanized structure according to claim 2, wherein the evaluation that the soundness of the hot-dip galvanized structure is good means that the evaluated portion of the hot-dip galvanized structure can continue to be used as is. A method for evaluating the soundness of structures. In the fourth step, if the alloy layer is identified around the base steel plate in (i) and the zinc layer is not identified in (ii), the alloy layer is placed on the base steel plate at the evaluation site. The health of the hot-dip galvanized structure according to claim 1, wherein although the alloy layer remains, the zinc layer does not remain, and the health of the hot-dip galvanized structure is evaluated as poor. Evaluation method. In the hot-dip galvanized structure according to claim 7, in the fourth step (i), the base steel sheet and the alloy layer are identified based on one or both of a difference in brightness and a difference in pattern. Soundness evaluation method. The hot-dip galvanized structure according to claim 7, wherein the evaluation that the health of the hot-dip galvanized structure is poor means that the evaluated portion of the hot-dip galvanized structure requires repair. Soundness evaluation method. In the fourth step, if the alloy layer is not identified in (i), the alloy layer and the zinc layer do not remain on the base steel plate in the evaluation site, and the hot-dip galvanized structure The method for evaluating the health of a hot-dip galvanized structure according to claim 1, wherein the health of the hot-dip galvanized structure is evaluated to be particularly poor. According to claim 10, the evaluation that the health of the hot-dip galvanized structure is particularly poor means that the evaluated portion of the hot-dip galvanized structure requires repair or is unusable. A method for evaluating the soundness of hot-dip galvanized structures. The method for evaluating the health of a hot-dip galvanized structure according to any one of claims 1 to 11, wherein the third step is performed while the recess is illuminated with visible light. The method for evaluating the health of a hot-dip galvanized structure according to any one of claims 1 to 11, wherein the third step is performed using a microscope. The hot-dip galvanized structure according to any one of claims 1 to 11, wherein in the third step, an enlarged image of the recess is obtained, and the fourth step is performed using the enlarged image of the recess. Soundness evaluation method. 15. The method for evaluating the health of a hot-dip galvanized structure according to claim 14, wherein the enlarged image is acquired using a solid-state image sensor. The method for evaluating the health of a hot-dip galvanized structure according to any one of claims 1 to 11, wherein the tip of the electric drill is made of tungsten carbide steel. The method for evaluating the soundness of a hot-dip galvanized structure according to any one of claims 1 to 11, wherein the hot-dip galvanized structure is one or more selected from the group consisting of a bridge, a steel tower, and road ancillary equipment. . The method for evaluating the health of a hot-dip galvanized structure according to any one of claims 1 to 11, wherein the hot-dip galvanized structure has a coating film on the zinc layer at the time of construction.

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