JP2000241340A - Method and apparatus for measuring corrosion rate of weatherable steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the corrosive reduction in wt. of a steel material of a structure as simply as possible. SOLUTION: In a method for measuring the corrosion rate of a weatherable steel material, a wedge-shaped test body 1 having the same steel material component and constitution as a structure comprising the steel material is prepared to be arranged to at least one place of the structure and the length change of the leading end portion exposed to the open air of the wedge-shaped test body 1 arranged to the structure is measured to measure the advance degree of the corrosion of the structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring the degree of corrosion of a weather-resistant steel which can easily measure the weight loss of a structure using the weather-resistant steel in an atmospheric corrosion environment.

[0002]

2. Description of the Related Art In general, corrosion resistance in the atmosphere can be improved by adding elements such as P, Cu, Cr, and Ni to steel. Low-alloy steels to which these specific elements are added are called weatherable steels. Rust that protects against corrosion when exposed to the atmosphere outdoors for several years to several decades (hereinafter referred to as “stable rust”) Is formed, and after stable rust is formed, it is a so-called maintenance-free steel that does not require anticorrosion treatment such as painting.

However, in weather-resistant steel, it takes a long time to form stable rust, and the time required to stabilize rust varies greatly depending on environmental conditions. Further, stable rust may not be formed depending on environmental conditions. That is, when weathering steel is used for a structure or the like, the time required for stable rust to be formed on the structure differs depending on the individual use environment. However, grasping the time required until stable rust is formed is important from the viewpoint of appropriately performing the anticorrosion treatment, but involves significant difficulty.

By the way, during the period until the rust layer formed by atmospheric corrosion is stabilized and becomes stable rust, floating rust such as red rust and yellow rust and flowing rust are generated, which is not only externally undesirable. In addition, it may cause pollution of the surrounding environment, so it is necessary to accurately grasp the degree of stabilization of the rust layer in order to take countermeasures.

On the other hand, as a conventional evaluation method for evaluating the degree of stabilization of the rust layer, there is disclosed a method of measuring the overall change in the amount of corrosion from the weight reduction of the base steel material and evaluating the degree of stabilization of the rust layer. (Nippon Steel Pipe Technical Report, No. 46, 250 (1969))
(Hereinafter, referred to as “prior art 1”).

[0006] Further, as a method for evaluating the formed rust layer,
Appraisal by appearance in "Research Report on Application of Weathering Steel to Bridges (11)" (March 1984) by Public Works Research Institute, Ministry of Construction, Steel Club, Japan Bridge Construction Association, etc. A method is disclosed (hereinafter, referred to as “prior art 2”). That is, this method is a method of evaluating a rust layer using a blue spot generated by a reaction with the ground iron through a pinhole of the rust layer using a ferroxil test. However, this method has a drawback that the evaluation is subjective and it is difficult to perform quantitative evaluation.

As a method for non-destructively and relatively quantitatively evaluating the protection performance of a steel material having a rust layer on the spot, “Corr
osion, Vol. 45, p. 347 (1989) discloses a method using a rust steel protection tester (RST) (hereinafter referred to as “prior art 3”). This evaluation method is an evaluation method based on the principle of measuring the ion permeation resistance in the rust layer, and is an evaluation method excellent in quickness.

Further, Japanese Patent Application Laid-Open No. 6-241982 discloses that a very small amount of rust of about 100 mg is directly collected from a structure, the ratio of a specific crystal component of the rust is measured by an X-ray diffraction method, and a transmission type rust is measured. A method for measuring the average crystal grain size of rust particles using an electron microscope is disclosed (hereinafter, referred to as “prior art 4”).

Further, Japanese Patent Application Laid-Open No. 8-278245 discloses that a scribe line is formed on a weather-resistant steel structure having a rust formed on its surface by a sharp blade, an organic film is adhered to a flaw portion, and peeled off. There has been disclosed a method of measuring the particle size of the rust with an electron microscope or the like to evaluate the stability of the rust (hereinafter referred to as “prior art 5”).

As described above, if there is a method for appropriately evaluating stable rust, the maintenance and management cost of a structure using weather-resistant steel can be optimized and reduced. Realization of a stability evaluation method is strongly demanded.

[0011]

SUMMARY OF THE INVENTION Prior art 1, ie, Nippon Kokan Technical Report, No. 46, 250 (1969), the change over time in the amount of corrosion is measured and evaluated from the weight loss of the base steel material. However, in the case of a once-constructed structure in which a test piece for measurement is not prepared, there is a problem that it is practically impossible to actually measure the weight loss.

On the other hand, when a test piece for measurement is prepared, Conventional Technique 1 is considered to be a direct evaluation method for monitoring the corrosion state of a structure. However, in order to accurately measure the weight change, it is necessary to consider the installation method of the measurement test piece that can accurately measure the weight, the influence on the weight change due to flying or attached substances, etc. There are many problems that must be solved in order to measure changes with high accuracy.

Further, the method of the prior art 2 has a disadvantage that, as described above, the evaluation is subjective and the quantitative evaluation is difficult.

Further, the prior art 3, that is, the method using the steel material protection tester (RST) has a problem that sufficient accuracy cannot be obtained in a severe environment. In order to accurately evaluate the characteristics of weathering steel, which has begun to be used even in severer environments in recent years, it is necessary to use an evaluation method with a further improved viewpoint from a different viewpoint.

Prior art 4, that is, JP-A-6-24198
According to the method disclosed in Japanese Patent Publication No. 2 (1993), regarding the point that a particular crystal in rust is advantageous for stability, the 136th Autumn Meeting of the Iron and Steel Institute of Japan (Materials and Processes Volume 11, No. 6, P.2).
63, Fig. As described in 3), there is no clear correlation between the crystal component ratio and the rust stability, and there is a problem that it is difficult to say that the method for evaluating stability is very excellent.

Further, the prior art 4 for measuring the rust crystal grain size using an electron microscope, that is, JP-A-6-24198.
According to the method disclosed in Japanese Patent Publication No. 2 and the prior art 5, that is, the method disclosed in Japanese Patent Application Laid-Open No. 8-278245, it is difficult to accurately measure the crystal grain size.
The reason is that the rust generated on weathering steel in an atmosphere exposed to air contains a considerable proportion of amorphous material, and the size of the grains changes depending on the sampling method, and the relatively large size of 1μm or more This is because the particles are difficult to measure with a normal transmission electron microscope, and there is a high possibility that large particles are missed.

As described above, in order to accurately evaluate the characteristics of weather-resistant steel, which has begun to be applied even in severer environments in recent years, it is necessary to consider an evaluation method with a further improved viewpoint from a different viewpoint. .

That is, whatever the environment,
Also, no matter what kind of rust was generated, it was considered that measuring the amount of corrosion of the steel material of the structure was the most important for the stability evaluation and maintenance inspection of the weathering steel structure. Accordingly, an object of the present invention is to provide a method and an apparatus for measuring weight loss of corrosion, which can measure the weight loss of steel of a structure as simply as possible.

[0019]

Means for Solving the Problems The inventors have conducted intensive studies to solve the above-mentioned problems of the prior art. That is,
The present inventors have studied in detail the relationship between the rust structure analysis result and the corrosion loss of steel materials. As a result, the composition of αFeOOH, γFeOOH, etc., is an exceptional case where corrosion progresses due to the existence of defects in the rust itself, regardless of the electrical resistance or the rust crystal particle size. I found it. This means that the corrosion weight loss of the steel material changes greatly depending on the corrosive environment, and the stability of the steel material in which rust has formed cannot be determined from the rust structure alone.

It is generally difficult to directly measure the rust structure to evaluate the stability of a low-alloy corrosion-resistant steel of a structure, and no reliable method has been found in rust stability evaluation. It is considered that the reason is that the form of corrosion changes variously depending on the environment to which the steel is exposed. Therefore, the present inventors have found it important to investigate the structure of rust. However, the inventors of the present invention have considered that it is first to investigate corrosion loss of steel materials as simply as possible, and have reached the present invention.

The first aspect of the method for measuring the degree of corrosion of weathering steel according to the present invention is to prepare and prepare a wedge-shaped specimen of a known shape having the same steel composition and structure as a steel structure. The wedge-shaped test body is installed at one or more locations of the structure, and a change in the length of the tip of the wedge-shaped test body installed in the structure that is exposed to the atmosphere is measured. And measuring the degree of progress of corrosion of the structure.

A first aspect of the apparatus for measuring the degree of corrosion of a weather-resistant steel material according to the present invention is the same steel material as a structure made of steel for mounting on the structure and measuring the degree of progress of corrosion of the structure. A wedge-shaped test body having a known shape having components and a structure, and a substrate fixed to the wedge-shaped test body and having a scale capable of measuring the length of the wedge-shaped test body It is characterized by the following.

A first aspect of the apparatus for measuring the degree of corrosion of a weather-resistant steel material according to the present invention is the same steel material as a structure made of steel for mounting on the structure and measuring the degree of progress of corrosion of the structure. A wedge-type specimen having a known shape having components and tissues, and a scale fixed to the wedge-type specimen and capable of measuring the length of the wedge-type specimen,
And a substrate that does not generate a contact potential difference with the wedge-shaped test body.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method and apparatus for measuring the degree of corrosion of the present invention will be described below. The method for measuring the degree of corrosion of a weather-resistant steel material according to the present invention comprises preparing a wedge-shaped test body of a known shape having the same steel composition and structure as a steel-made structure, and preparing the wedge-shaped test body having the structure described above. It is installed at one or more places on the structure, and the change in the length of the tip of the wedge-type test body installed on the structure exposed to the atmosphere is measured to determine the corrosion progress of the structure. Measure the degree.

[0025] The wedge-shaped steel material as a test specimen prepared in a known shape is exposed to the atmosphere and corrodes, thereby reducing the thickness of the wedge-shaped steel material. The point is shorter because it is sharp. In a normal plate-like steel material, rust generated on the surface of the steel material has a lower specific gravity than metal iron and expands. Therefore, it is difficult to measure the thickness of the steel material without removing rust.

In measuring the corrosion loss, as factors affecting the corrosion amount, both a mass increasing factor to which oxygen, water or flying objects adhere to the steel surface and a mass decreasing factor such as flowing rust and rust peeling are considered. Therefore, in order to accurately measure the decrease in the thickness of the steel material, rust must be removed. However, if the rust is peeled off, it becomes impossible to continuously measure the corrosion weight loss of the steel material by the test specimen, and it is necessary to install the test specimen as many times as the measurement.

According to the present invention, the above-mentioned problem is solved. That is, the method of the present invention, as described above,
By installing it in one or more locations on the structure and measuring the change in the length of the wedge-shaped specimen exposed to the atmosphere, it is possible to determine what It is possible to measure the thickness reduction of steel material
This is a very simple measurement method.

The apparatus for measuring the degree of corrosion of a weather-resistant steel according to the present invention has the same steel composition and structure as a steel-based structure for mounting on the structure and measuring the degree of progress of corrosion of the structure. A wedge-shaped specimen of known shape, and
A substrate fixed to the wedge-shaped specimen and having a scale capable of measuring the length of the wedge-shaped specimen.

Further, the apparatus for measuring the degree of corrosion of a weather-resistant steel material according to the present invention has the same steel composition and structure as a steel-based structure for measuring the degree of progress of corrosion of the structure by being mounted on the structure. A wedge-type specimen having a known shape, and a scale fixed to the wedge-type specimen and capable of measuring the length of the wedge-type specimen, between the wedge-type specimen. And a substrate that does not generate a contact potential difference.

In order to more easily know the amount of corrosion reduction of the steel material, it is more convenient to fix a wedge-shaped steel material of a known shape to a substrate having a scale as described above. That is,
With the initial tip set to zero, the length of the tip reduced by the corrosion may be measured by reading the scale on the substrate with the wedge fixed. However, it is not desirable that the material of the substrate having the scale be electrically noble or noble than the test material.

The reason is that when an electrically noble substrate is used, the corrosion of the test body proceeds, and when a noble substrate is used, the corrosion of the test body is suppressed by the sacrificial corrosion protection of the substrate. For this reason, it is desirable that the material suitable for the substrate is a material that does not cause potential difference corrosion due to contact with steel such as resin.

These methods and devices of the present invention,
By installing a wedge-shaped steel specimen of known shape on the weathered steel being applied and applying the present invention, the rust stability can be evaluated multiple times with one specimen without destroying the structure can do. Even if the onset of deterioration is found, it is possible to prevent a catastrophic damage as a building by taking measures such as partial coating immediately.

[0033]

FIG. 1 is a view showing one example of the preparation of a test body according to the present invention. As shown in FIG. 1, a wedge-shaped specimen 1 having the same treatment surface 10 as the steel material used was
And cut diagonally along the cut surface 6 to prepare. That is,
As a specimen of the present invention, using a steel material subjected to the same rolling and shot blasting as possible with the structure,
As shown in FIG. 1, cutting is performed with the surface held.

FIG. 2 is a view showing one example of the preparation of a test piece of the present invention on which a graduated substrate is attached. Further, as shown in FIG. 2, after precisely measuring the shape of the steel material cut as a test body, the graduated substrate 3 with no potential difference between different materials with the steel material is held while the surface 10 is held. Attach it and place it at the position you want to pay attention to on the structure.

In the drawing of this embodiment, both surfaces are cut at an acute angle in order to assure accuracy, assuming that the test piece 1 is installed vertically, etc., but only one surface is installed when installed horizontally. It may be cut at an acute angle. Of course, if you place it vertically,
The four surfaces may be cut at an acute angle while holding the surfaces.

The thickness of the specimen 1 may be larger than the allowable corrosion of the structure. The reason is that when the test piece 1 is lost due to corrosion, the structure itself is in a state where a measure such as a large maintenance or a re-installation is required. Also, the depth of the specimen 1 is
It is desirable that the size of the wedge tip to be measured be as high as possible without impairing the function of the structure, since the accuracy of the length measurement of the wedge tip to be measured is increased.

When the specimen 1 prepared as shown in FIG. 2 is set on a structure and corroded, the surface 10 having the same structure as the steel material
Corrodes. FIG. 3 is a diagram showing one example of a test body of the present invention in which corrosion has progressed. In order to measure the corrosion weight loss 5, as shown in FIG. 3, it is preferable to measure the length of the wedge tip of the specimen.

In this case, if the tip is contaminated with rust juice or the like, the tip should be cleaned using a brush or the like with emphasis on measurement accuracy. Rinsing at the tip may fall off by washing, in which case the tip is considered to be in an environment different from other places where rust is generated, but at the time of measurement due to the sharp angle of the tip Since the amount of rust that can be dropped is minimized, rust is not generated by the next measurement and does not pose a major problem.

FIG. 4 is a view showing one example of a wide test specimen of the present invention. As shown in FIG. 4, it is also possible to remove the rust only in a part of the width direction using a wide steel material, and to measure the length of the test body at the rust-peeled part 8, and the rust was not peeled. The length of the test piece can be measured with the part completely in the initial state, and measurement closer to the actual environment is possible.

As described above, according to the method of the present invention,
The corrosion loss of steel can be measured most easily. These methods and devices, i.e., a test piece of a wedge-shaped steel material of known shape is installed on the weathered steel being installed, and the degree of progress of corrosion is measured by the method of the present invention, without destroying the structure. The rust stability can be evaluated any number of times with one test specimen. Even if it is found that deterioration has started as a result of the measurement, it is possible to prevent a catastrophic damage as a building by immediately taking measures such as partial coating.

[0041]

As described above, according to the present invention, it is possible to easily measure the weight loss of corrosion of a steel material of a structure.
A method and an apparatus for measuring corrosion weight loss of weathering steel are provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing one example of the preparation of a test body of the present invention.

FIG. 2 is a diagram showing one example of the preparation of a test body of the present invention fixed to a graduated substrate.

FIG. 3 is a diagram showing one example of a test specimen of the present invention in which corrosion has progressed.

FIG. 4 is a diagram showing an example of a wide test specimen of the present invention.

[Explanation of symbols]

 1. Specimen 2. Test material 3. 3. perforated substrate Mounting parts 5. 5. Corrosion weight loss Cut surface 7. 7. Surface on which rust is formed Rust peeling part 10. Same treatment surface as the constructed steel

Claims (3)

[Claims] 1. A wedge-shaped specimen of a known shape having the same steel material composition and structure as a steel-based structure is prepared, and the prepared wedge-shaped specimen is placed at one or more locations of the structure. Installing, and measuring the change in the length of the tip of the wedge-type test body installed in the structure exposed to the atmosphere, and measuring the degree of progress of corrosion of the structure. To measure the degree of corrosion of weathering steel. 2. A wedge-shaped test body of a known shape having the same steel composition and structure as a steel-based structure for mounting on the structure and measuring the degree of corrosion progress of the structure; and A substrate fixed to the wedge-shaped specimen and having a scale capable of measuring the length of the wedge-shaped specimen. 3. A wedge-type specimen of a known shape having the same steel composition and structure as a steel-based structure for mounting on the structure and measuring the degree of corrosion progress of the structure; and Having a scale fixed to the wedge-shaped specimen and capable of measuring the length of the wedge-shaped specimen,
And a substrate that does not generate a contact potential difference with the wedge-type test body.