JP6081876B2 - Life evaluation method for plated parts - Google Patents

Description

  The present invention relates to a plating member life evaluation method for evaluating the life of a member plated with metal.

  Metal is often used in outdoor environments as a structural material for outdoors and plants. In order to evaluate the life of a member or structure made of such a metal material, it is made of the same material as the member or structure that is actually used, or the member or structure that is actually used. In many cases, the corrosion rate obtained by exposing the test specimen to the environment in which it is actually used and measuring the amount of decrease in the metal of interest over time is used as an index.

  For example, a metal structure made of a plated member obtained by performing metal plating on a metal substrate is configured as follows. First, the thickness of the formed metal plating film is measured in advance, and a test body made of the same material as the metal structure is exposed to the target environment for a certain period. After this exposure, the film thickness of the remaining metal plating film is measured, and the difference in film thickness, that is, the corrosion weight loss (film thickness notation) is divided by the period to obtain the corrosion rate. If the unit of film thickness is μm and the period is given in years, the unit of corrosion rate is μm / year. If the value of corrosion weight loss (film thickness notation) is determined every year based on the initial plating film thickness, and the corrosion weight loss (film thickness notation) or corrosion rate is followed over time, the film thickness of the remaining metal plating film will be It is possible to estimate a period during which the value is below a certain value. With this estimated period, it can be evaluated as the lifetime of a part or the whole of the metal structure. For example, a period in which the remaining plating film thickness is 1/10 or less of the initial plating film thickness may be defined as the lifetime.

The life evaluation method for a metal structure made of a plated member as described above needs to use a test body having the same metal plating film as the metal structure. However, it is impossible to measure the film thickness of the metal plating film in the early stage of construction in the existing structure that has been constructed in the past and is currently used. In such a state, whether or not a test body having the same metal plating film as an existing metal structure can be prepared is important in evaluating the life. For this reason, generally, a test body is prepared based on the product standard adopted with the existing metal structure. In this case, it is considered that the initial plating film thickness of the existing metal structure can be calculated from the corresponding product standard. For example, in Type 55 55 defined in “JIS H8641” which is a standard for hot dip galvanizing, 550 g / m ³ is defined as the amount of zinc adhered, and according to this, the average film thickness is 76 μm.

http://www.aen-mekki.or.jp/faq/014.html, Japan Association of Hot Dip Galvanizing. Miyata Keimori and Handa Takao, “Aging Characteristics of Atmospheric Corrosion of Galvanized Steel Sheet”, Proc. 53rd Materials and Environmental Discussion, C-203, 2006. http://www.horiba.com/jp/scientific/products-jp/x-ray-fluorescence-analysis/details/mesa-portable-8946/, HORIBA, Ltd. Yasuhiro Higashi, Hoichi Nakae, Jun Kawai, Isao Shinozuka, Takao Handa, Takashi Sawada, "Evaluation of Communication Line Structure Materials Using Handheld X-ray Fluorescence Analyzer", Proceedings of the 46th X-ray Analysis Discussion Meeting, Japan Analytical Chemistry Meeting, 2010.

However, the actual initial plating film thickness is generally thicker than the film thickness calculated by the product standard. For example, when the plating film thickness of a member adopting the above-described type 2 55 is measured with an electromagnetic film thickness meter, the average film thickness often exceeds 100 μm, which is estimated from the regulation of the adhesion amount. Thicker than the film thickness. This is simply due to the fact that, in terms of manufacturing design, plating with an adhesion amount exceeding a specified amount is applied for safety. For example, for Type 55, if it is 550 g / m ³ or more, the regulation is satisfied. The plating film thickness varies depending on the manufacturer as long as it satisfies the regulations. Moreover, even if the same manufacturer has the same plating bath and plating tank, the plating film thickness varies depending on the heat capacity and shape of the member to be plated. Therefore, calculating the initial plating film thickness of the metal structure from the definition alone is extremely inaccurate. Although the film thickness of the test body can be measured with an electromagnetic film thickness meter, there is no guarantee that it is the same as the initial plating film thickness of the metal structure.

  In addition, it is naturally useful to be able to perform the life evaluation using the metal structure itself as a test object, not the test body imitating the metal structure. In this case, however, life evaluation based on the initial plating film thickness is desired.

  As described above, it is difficult to estimate the initial plating film thickness of the existing metal structure only from the regulations. In addition, in the case of an existing metal structure where it is impossible to measure the initial plating film thickness, the residual plating film thickness is a constant value with the initial film thickness using a test body made of the same material as the existing metal structure. A method for evaluating the life of a metal structure using the following period is not applicable. Thus, at present, there is a problem that it is not easy to evaluate the lifetime of an existing metal structure using a plating member.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to more easily evaluate the life of an existing metal structure using a plated member.

The plating member life evaluation method according to the present invention measures the thickness of the plating film at a time point t ₁ after a set time has elapsed since the construction of the plating member made of the metal structure on which the plating film is formed. A first film thickness measuring step for obtaining a thickness d ₁ ; and a second film thickness measuring step for obtaining a second film thickness d ₂ by measuring the thickness of the plating film of the plating member at time t ₂ after time t _1. The constant b determined by the material of the plating film is used, and d ₀ = (d ₁ t ₂ ^b −d ₂ t ₁ ^b ) / (t ₂ ^b −t ₁ ^b ) The initial film thickness estimation step for estimating the initial film thickness d ₀ , which is the thickness, and a = (d ₁ −d ₂ ) / (t ₂ ^b −t ₁ ^b ) The first-year film thickness reduction estimation step for estimating the film thickness reduction a after the year, and t _L = {(0.9d ₀ ) / a} ^{1 / b} A life estimation step for estimating the life t _L of the plated member from the time of construction.

  In the plating member life evaluation method, in the plating film thickness measurement in the first film thickness measurement step and the second film thickness measurement step, a removal step of removing the corrosion layer formed on the plating film, and corrosion A confirmation step for confirming the state of removal of the layer using a fluorescent X-ray analyzer, and a measurement step for measuring the thickness of the plating film using the fluorescent X-ray analyzer after the removal of the corrosion layer is confirmed. What is necessary is just to prepare. When the plating film is made of galvanizing, the constant b is 0.7.

  As described above, according to the present invention, it is possible to obtain an excellent effect that the lifetime of an existing metal structure using a plated member can be more easily evaluated.

FIG. 1 is a flowchart illustrating a method for evaluating the life of a plated member according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the state of the surface of a metal structure used in a building. FIG. 3 is an explanatory diagram for explaining the removal of corrosion products (corrosion layer) performed prior to the measurement of the thickness of the plating film. FIG. 4 is a flowchart for explaining the life evaluation method in the embodiment including the removal of the corrosion layer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating a method for evaluating the life of a plated member according to an embodiment of the present invention.

In this evaluation method, first, in step S101, the thickness of the plating film is measured at a time point t ₁ after a set time has elapsed since the construction of the plating member made of the metal structure on which the plating film is formed. obtain d ₁ (first film thickness measuring step). Next, in step S102, by measuring the thickness of the plated film of the plated member at time t ₂ after the time t ₁ to obtain a second thickness d ₂ (second film thickness measuring step).

  A metal structure is a structure comprised from steel, for example, and plating is galvanization. Moreover, the film thickness measurement of a plating film may be performed with a well-known electromagnetic induction type film thickness meter, for example. According to the electromagnetic induction type film thickness meter, for example, the thickness of a non-magnetic galvanized film on steel having magnetism can be measured. If it is electrogalvanizing, an almost accurate film thickness can be obtained. The film thickness of the plating film may be measured with a fluorescent X-ray film thickness meter. It is desirable to measure the plating film thickness a plurality of times and use the average value of these results.

Further, the interval between the time point t ₁ and the time point t ₂ may be, for example, one year. The amount of reduction (change) in the plating film varies depending on the environment in which the plating member is used. Therefore, the interval between the time point t ₁ and the time point t ₂ may be set to such an extent that the reduction amount of the plating film can be determined from the measurement result of the film thickness. It should be noted that a long interval comparable to the lifetime is not preferable for the purpose of the original lifetime evaluation, and the interval between the time point t ₁ and the time point t ₂ is preferably as short as possible.

Next, in step S103, a constant b determined by the material of the plated film is used, and “d ₀ = (d ₁ t ₂ ^b −d ₂ t ₁ ^b ) / (t ₂ ^b −t ₁ ^b ). The initial film thickness d ₀ which is the thickness of the plating film of the plating member at the time of construction is estimated by (1) ”(initial film thickness estimation step). When the plating film is made of galvanizing, the constant b is 0.7. Next, in step S104, the film thickness after one year from the time of construction of the plating film of the plating member by “a = (d ₁ −d ₂ ) / (t ₂ ^b −t ₁ ^b ) (2)”. The weight loss a is estimated (first year film thickness reduction step). The film thickness reduction a is the film thickness of the plating film decreased in the first year of construction of the plating member.

Finally, in step S105, the lifetime t _L of the plated member from the time of construction is estimated by “t _L = {(0.9d ₀ ) / a} ^{1 / b} (3)” (life estimation step) ).

  What is necessary is just to implement estimation (calculation of each formula) using each formula mentioned above using a computer. The computer includes a central processing unit (CPU), a main storage device, an external storage device, a network connection device, and the like. The CPU is operated by a program developed in the main storage device and is stored in the external storage device. The above-described calculation for estimation is realized based on the measured values and constants.

  Next, the life estimation by the equations (1), (2), and (3) will be described in more detail.

The plating film formed on steel or the like decreases due to corrosion or the like. The amount of reduction of the plating film (thickness reduction) is Δd, the reduction of the plating film in the first year from the construction of the plating member is a, and the time (unit is year) elapsed from the start of use of the plating member is t. Then, it is empirically known that “Δd = at ^b (4)” is established (see Non-Patent Document 2). In Formula (4), b is a constant. In the case of galvanization, b takes a value of about 0.7. By using a plurality of equations (4) obtained from a plurality of measurement results, the value of b in the target plating material is obtained.

The construction time of the plating member and 0, the time has elapsed from this and t _1, the time of the elapse of a predetermined period of time from time t ₁ to t _2. Further, the thickness of the plating film measured at time t ₁ is d _1, and the thickness of the plating film measured at time t ₂ is d ₂ . When these are applied to the equation (4), the above-described equations (1) and (2) are obtained.

Next, according to the idea of evaluating the period when the plating film thickness remaining after aging is a certain value of the initial film thickness at the time of construction as the lifetime of the plating member, the remaining plating film thickness is the estimated initial film thickness. The point in time at which d ₀ reaches a certain value can be the life of the plated member. When this constant value is 0.1, the life t _L can be calculated from “Δd = 0.9d ₀ = at _L ^b (5)” from the equation (4). From this equation (5), the above-described equation (3) is obtained.

  As described above, according to the embodiment, in the plated member that is a metal structure used in an existing building or the like, the initial plated film thickness is estimated even when the initial plated film thickness is unknown. The lifetime of the metal structure can be easily evaluated using this estimated value. Further, according to the embodiment, it is possible to use the existing plated member itself as the test body without using the test body.

  Hereinafter, it demonstrates in detail using an Example.

[Example]
As shown in FIG. 2A, metal structures such as steel materials used for buildings are often used as plating members by forming a metal plating film 202 on the surface of a metal substrate 201. As is well known, by forming the metal plating film 202, the metal substrate 201 can be protected from corrosion factors in this use environment.

However, the metal plating film 202 having a film thickness d ₀ is initially corroded as time passes by being used in the use environment, and as shown in FIG. 2B, the surface side of the metal plating film 202 is corroded. Thus, the corrosion layer 203 is formed. As a result, the metal plating film 202 is thinned to a film thickness d ₁ (<d ₀ ). In an environment where corrosion proceeds, such as outdoors, the corrosion layer 203 increases and the metal plating film 202 decreases, and eventually the metal plating film 202 disappears. If the metal plating film 202 is thinned, the function of protecting the metal substrate 201 is impaired, and the metal substrate 201 is corroded. Therefore, the period until the film thickness of the metal plating film 202 reaches a certain value can be the life of the plating member.

The corrosive layer 203 is partially damaged by dry and wet weather or wind and rain, but accumulates over time. In general, the progress of corrosion is assumed to be delayed as time elapses due to the deposition of the corrosion layer 203. This is said to be the reason why b in Formula (4) is smaller than 1. In order to measure the plating film thickness d ₁ of the metal plating film 202, it is necessary to remove the corrosion layer 203 by a predetermined method. Considering the slowing of the progress of corrosion due to the deposition of the corrosive layer 203, the part for measuring the first film thickness d ₁ and the part for measuring the second film thickness d ₂ must be different parts. When considered, it is desirable that these are adjacent parts.

  In addition, not only for the life evaluation of the plating member where the film thickness is measured, but also for the purpose of life evaluation of the entire metal structure composed of the plating member, of course, it is assumed that corrosion is likely to proceed. It should be selected as one of the parts to be measured. Specifically, a part that is always placed in a moist environment, for example, a part where water can exist but is shadowed and difficult to dry should be selected as one of the measurement target parts.

  Next, the removal of the corrosion product (corrosion layer) performed prior to the measurement of the thickness of the plating film will be described with reference to FIG. FIG. 3 schematically shows a cross section.

  As shown in FIG. 3A, a plating film 302 is formed on the surface of the metal substrate 301, and a corrosion layer 303 is formed on the plating film 302. As a method of removing the corrosive layer 303, chemicals such as acids corresponding to the components of the corrosive layer 303 may be used. However, the corrosive layer 303 is often more fragile than the plating layer 302, and a brush or the like is used. In many cases, it can be removed sufficiently by polishing. In any removal method, when measuring the thickness of the plating layer 302, it is necessary to determine the end point of the removal of the corrosion layer 303 so that the thickness of the corrosion layer 303 is not added.

  As a method for determining the end point of removal of the corrosive layer 303, there is a method of checking the metallic luster on the surface of the plating layer 302. In addition, when there is a difference in density between the corrosion layer 303 and the plating layer 302, it may be possible to confirm the presence or absence of the corrosion layer 303 by an ultrasonic method or the like. Here, the removal state of the corrosive layer 303 is confirmed using a portable fluorescent X-ray analyzer 311 in the case where the plating layer 302 under the corrosive layer 303 is sufficiently thick. For example, a handheld X-ray fluorescence analyzer sold by HORIBA, Ltd. may be used (see Non-Patent Document 3).

  First, as shown in FIG. 3A, incident X-rays 312 are irradiated from the X-ray fluorescence analyzer 311 onto the plating film 302 and the corrosive layer 303, the X-ray fluorescence 313 is detected, and the X-ray fluorescence intensity of zinc is detected. Get. In the measurement using a specific model of HORIBA, Ltd. handheld fluorescent X-ray analyzer, if the plating film thickness is 32.5μm or more, the zinc film is zinc compared to the very thick zinc plating film. The fluorescent X-ray intensity is 90% or more.

  Therefore, first, as shown in FIG. 3B, a reference plating member in which a very thick reference plating film 306 is formed on the surface of the metal substrate 305 is prepared, and zinc in the reference plating film 306 is prepared. Measure fluorescence X-ray intensity. Next, after removing the corrosive layer 303 by a predetermined method, the fluorescent X-ray intensity of zinc in the plating film 302 is measured as shown in FIG. If, for example, a fluorescent X-ray intensity of 90% or more is obtained with respect to the measurement result of the reference plating film 306, it is determined that the corrosive layer has been sufficiently removed (see Non-Patent Document 4). Thereafter, the thickness of the plating film 302 may be measured using a fluorescent X-ray analyzer 311.

  The life evaluation method in the embodiment including the removal of the corrosion layer described above will be described with reference to the flowchart of FIG.

First, in step S401, the removal process of the corrosion layer formed on the plating film surface of the target plating member is performed by a predetermined method. Next, in step S402, the state of removal due to the removal process is confirmed by the method described above. If it is determined by this confirmation that the removal is sufficient (y in step S403), the process proceeds to step S404, and the thickness of the plating film at the time point t ₁ after the set time has elapsed since the construction of the plating member is measured. A first film thickness d ₁ is obtained. On the other hand, when it is determined that the removal is not sufficient (step S403: n), the process returns to step S401 and the removal process is performed again. Needless to say, the removal process of the corrosive layer and the confirmation of the removal state are performed immediately before the measurement of the first film thickness d ₁ .

After obtaining the first thickness d ₁ at time t ₁ by removing the corrosion layer in the manner described above, at time t ₂ after the time t _1, to move the measurement point in step S405, the target in step S406 The removal process of the corrosion layer formed on the plating film surface of the plating member to be performed is performed by a predetermined method. Next, in step S407, the state of removal due to the removal process is confirmed by the method described above. This check, if it is determined that the removal is sufficient (y in step S408), the process proceeds to step S409, the obtaining a second thickness d ₂ by measuring the thickness of the plated film at the time t _2. On the other hand, when it is determined that the removal is not sufficient (step S408: n), the process returns to step S406 and the removal process is performed again. Of course, removal processing of the corrosion layer described above, etc. confirm the removal state, it performed immediately before measurement of the second film thickness d _2.

When the corroded layer is removed as described above to obtain the second film thickness d ₂ at time t ₂ , d ₀ = (d ₁ t ₂ ^b) using the constant b determined by the material of the plating film in step S410. -d ₂ t ₁ ^b) / (a t ₂ ^b -t ₁ ^b) estimating an initial film thickness d ₀ is the thickness of the plated film of the plated members during construction. Next, in step S411, the film thickness reduction a after one year from the time of construction of the plating film of the plating member is estimated by a = (d ₁ −d ₂ ) / (t ₂ ^b −t ₁ ^b ). Finally, in step S412, the life t _L of the plated member from the time of construction is estimated by t _L = {(0.9d ₀ ) / a} ^{1 / b} (3).

  Although not mentioned in the present example, the present invention can also be applied when there is paint. When the paint is applied, it is necessary to remove (peel) the paint in order to measure the film thickness of the plating film under the paint. Of course, after the measurement is performed with the paint removed, the part of the painted surface that has been peeled off with the paint being used, the paint having a weather resistance higher than the weather resistance of this paint, or other coating is repaired.

  As described above, according to the present invention, in the plated member constituting the existing metal structure, the lifetime can be easily evaluated even when the initial plating film thickness is unknown. Moreover, it is also possible to use the existing metal structure itself as a test body without using the test body.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, the steel material on which galvanization is performed has been described as an example. However, the present invention is not limited to this, and the present invention can be applied to a plating member in which various plating films are formed on various metals. What is necessary is just to obtain | require previously the constant b in the plating film of the plating member used as object.

  201 ... Metal substrate, 202 ... Metal plating film, 203 ... Corrosion layer.

Claims (3)

A first film thickness measurement step for measuring the thickness of the plating film at a time t ₁ after a set time has elapsed since the construction of the plating member made of the metal structure on which the plating film is formed, and obtaining the first film thickness d ₁ ; ,
A second film thickness measuring step of measuring a thickness of the plating film of the plating member at a time t ₂ after the time t ₁ to obtain a second film thickness d ₂ ;
The constant b determined by the material of the plating film is used, and the plating film of the plating member at the time of construction according to d ₀ = (d ₁ t ₂ ^b −d ₂ t ₁ ^b ) / (t ₂ ^b −t ₁ ^b ) An initial film thickness estimation step for estimating an initial film thickness d ₀ which is a thickness of
a first-year film thickness reduction estimating step for estimating a film thickness reduction a after one year from the time of construction of the plating film of the plating member by a = (d ₁ -d ₂ ) / (t ₂ ^b -t ₁ ^b ); ,
a life estimation step of estimating a life t _{L of the} plated member from the time of construction by t _L = {(0.9d ₀ ) / a} ^{1 / b} . In the life evaluation method of the plating member according to claim 1,
In the thickness measurement of the plating film in the first film thickness measurement step and the second film thickness measurement step,
A removing step of removing a corrosive layer formed on the plating film;
A confirmation step for confirming the state in which the corrosive layer has been removed using a fluorescent X-ray analyzer;
And a measuring step of measuring the thickness of the plating film using the fluorescent X-ray analyzer after the removal of the corrosive layer is confirmed. In the lifetime evaluation method of the plating member according to claim 1 or 2,
The plated film life evaluation method, wherein the plating film is made of zinc plating, and the constant b is 0.7.

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