JP6230474B2 - Anticorrosion method for steel and anticorrosive treated steel structure - Google Patents

Description

  The present invention relates to a steel material corrosion prevention method for preventing corrosion by covering the surface of a steel material used for forming a steel structure, and a corrosion-proof steel structure.

Conventionally, many steel structures such as bridges, steel towers, tanks, sluices, dust removal devices, construction equipment, and plant equipment are known as steel structures installed outdoors.
A problem in manufacturing steel structures that are installed outdoors using steel materials is corrosion of the steel materials used to form the steel structures.
In particular, steel materials used as structural members such as bridges are exposed to the natural environment over a long period of time and exposed to rain and wind, etc., thus causing corrosion, reducing the strength of the steel structure, and shortening the service life. .

Therefore, in order to maintain the strength of the steel structure over a long period of time and to extend the life, it is essential to take measures for preventing corrosion of the steel material. As a method for preventing corrosion of steel materials used as members of steel structures, for example, a method of coating a steel material with a rust preventive paint (so-called rust preventive coating) is well known. Generally used in steel structures.
In addition, as a method of applying the anticorrosive paint, for example, a method of applying the paint using a roller or a brush, a method of applying the paint by spraying (sometimes referred to as application in the bridge industry), etc. Numerous methods are known.

However, even when steel materials with anti-corrosion coating are used outdoors for a long time, deterioration of the coating due to exposure to ultraviolet rays or wind and rain in the natural environment is inevitable. The effect will be reduced. For this reason, steel materials that are used outdoors for a long period of time need to be repainted at regular intervals to restore the painted surface or regenerate the painted surface.
In addition, as an anticorrosion method other than the rust-proof coating, for example, a method of using a steel material that is difficult to corrode by adjusting the components of the steel material itself (so-called weather resistant steel material, or steel material called corrosion resistant steel material), or An anticorrosion method is known in which a metal foil made of a metal having a high anticorrosion property is bonded to the surface of a steel material to perform metal coating.

  As another anticorrosion method, for example, an anticorrosion method using a paste tape as disclosed in Patent Document 1 is known.

JP-A-6-328040

By the way, it is partial corrosion of steel materials that is likely to be a problem particularly in steel materials used as structural members in forming steel structures such as bridges.
For example, as shown in FIG. 6, assuming a case where rust-proof coating is applied on the steel material 1 as shown in FIG. 6, the film thickness is less likely to adhere to the corners of the steel material 1 as shown in FIG. 7. However, the portion where the film thickness of the coating film is partially thinned as described above is likely to be a starting point of corrosion because the rust prevention effect is quickly reduced.

  In addition to the corners, the shape tends to deteriorate, for example, in parts that are easily exposed to ultraviolet rays and rain winds, and the deterioration of the coating tends to be faster than in other parts. The coating film was likely to deteriorate partially due to accumulation of rainwater.

  For this reason, for example, the above-mentioned corners and the like have been taken with a gentle curved surface finish so that the paint film can be attached as easily as possible, or measures such as increasing the coating during painting are sufficient, but they are not always sufficient as a corrosion prevention measure. However, there has been a demand for rust prevention means that can extend the period until repainting.

  On the other hand, it is also useful as one means of the anticorrosion method to use a weathering steel material that is made difficult to corrode by adjusting the components of the steel material itself. However, even when using weather-resistant steel, in steel structures such as bridges that are installed near the coast, dust that contains salt on uneven parts of the steel structure, such as recesses and rests, etc. In some cases, it may become a starting point of corrosion due to accumulation of rain or accumulation of rainwater. For this reason, it has been demanded to take some rust prevention method for such a portion that tends to be a starting point of corrosion.

  In addition, although the rust prevention method using metal foil mentioned above is one of the effective rust prevention means, since metal foil is generally not necessarily easy to cut and process on site, depending on the situation Problems such as “displacement”, “floating”, “distortion”, etc. may occur at the construction site (for example, on-site connection part, repaired part of existing structure, etc.). It was.

Moreover, in the anticorrosion technique using the paste tape described in Patent Document 1, a step is generated between a portion where the paste tape is bonded and a portion where the paste tape is not bonded, and a corrosive factor such as dust or moisture is generated in the step. There was a possibility that this could become a starting point of corrosion.
Furthermore, if the linear expansion coefficient of the material used for the paste tape differs from that of the steel material, the adhered paste tape may be peeled off from the steel material due to a change in the external temperature.
In addition, about the problem that dust or moisture accumulates on the step and becomes the starting point of corrosion, the problem that the adhesive peels off due to the difference in linear expansion coefficient, depending on the conditions, even by the method of anti-corrosion by bonding the metal foil described above Problems can arise as well.

  The present invention has been made in view of the problems as described above, and exhibits a rust-preventing effect in any part of the steel material. Moreover, even if the starting point of corrosion occurs, the corrosion prevention method of the steel material is difficult to spread. And it aims at providing the steel structure by which anticorrosion processing was carried out.

  In order to achieve the above object, a first aspect of the present invention is a steel material comprising a step of forming a polyimide layer on the surface of a steel material or a surface-treated steel material, and a step of coating the surface of the polyimide layer with a resin paint. The anticorrosion method is provided.

In the corrosion prevention method for a steel material according to the first aspect of the present invention configured as described above, the step of coating with the resin paint is performed by coating the surface of the polyimide layer with an epoxy resin paint, and then applying with a fluorine resin paint Can be made up of.
In the above corrosion prevention method for steel materials, the linear expansion coefficient of the polyimide forming the polyimide layer can be in the range of 5.0 × 10 ⁻⁶ / K to 35.0 × 10 ⁻⁶ / K.

In the above corrosion prevention method for steel materials, the step of forming the polyimide layer can be performed by sticking a polyimide film to the surface of the steel material.
Or the process of forming the said polyimide layer can be performed by apply | coating a polyimide varnish to the surface of the said steel material, baking and baking.
In the above-described steel material corrosion prevention method, the base treatment is performed by applying an inorganic zinc rich paint on the surface of the steel material, and then applying an epoxy resin paint to fill the voids in the inorganic zinc rich paint coating film. be able to.

A second aspect of the present invention is a steel structure characterized in that the surface of the steel material constituting the steel structure or the steel material subjected to the ground treatment is subjected to anticorrosion treatment by coating with a resin paint via a polyimide layer. I will provide a.
In the steel structure according to the second aspect of the present invention configured as described above, the steel structure can be a bridge.

  According to the present invention, the corrosion resistance of a steel material can be improved by a simple method, in particular, it is difficult to ensure the layer thickness of a rust-proof coating, and the corrosion resistance of an end portion or a corner portion of a member that tends to start corrosion. There is provided a method for preventing corrosion of a steel material, which is highly effective in improving the resistance, and a steel structure obtained thereby.

It is a flowchart which shows the corrosion prevention method of the steel materials which concern on the 1st Embodiment of this invention in process order. It is sectional drawing which shows the structure of the rust prevention layer formed by the corrosion prevention method of the steel materials which concern on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the rust prevention layer formed only in the corner part of steel materials with the corrosion prevention method of the steel materials which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the corrosion prevention method of the steel materials which concern on the 2nd Embodiment of this invention in process order. It is a figure explaining the shape of the test piece used for the corrosion test of the steel materials anticorrosion-treated by embodiment of this invention. It is sectional drawing which shows the structure of the rust prevention layer on the steel material which concerns on a prior art. It is sectional drawing which shows the structure of the antirust layer formed only in the corner | angular part of the steel material which concerns on a prior art.

Various embodiments of the present invention will be described in detail with reference to the drawings.
Note that the present invention is not limited to the following embodiments, and various other embodiments are possible without departing from the technical idea of the present invention.
FIG. 1 to FIG. 4 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a flow chart showing a steel material corrosion prevention method according to the first embodiment in order of steps, and FIG. It is a figure which shows the structure of the rust prevention layer formed in FIG. 3, FIG. 3 is a figure which shows the structure of the rust prevention layer formed in the corner part of steel materials. Moreover, FIG. 4 is a flowchart which shows the corrosion prevention method of the steel materials which concern on 2nd Embodiment in process order. In addition, FIG. 5 is a figure which shows the test piece used for the corrosion test.

6 and 7 show the prior art, FIG. 6 is a view showing the structure of a rust prevention layer formed on a steel material by a conventional anticorrosion method, and FIG. 7 is a rust prevention layer formed on the corner of the steel material. FIG.
Hereinafter, a steel material corrosion prevention method according to the first embodiment of the present invention will be described with reference to FIG.
In FIG. 1, step (1) is a base material adjusting step, and a steel material for constituting a bridge is blasted (in accordance with ISO Sa2 1/2 in the present embodiment), so that the mill scale adhered to the surface of the steel material. Remove rust, foreign matter and oil. For the substrate adjustment, a power tool or the like can be used in addition to the blasting process.

Step (2) is an anticorrosion base step, and an anticorrosion base layer made of inorganic zinc rich paint is formed by applying the inorganic zinc rich paint to the steel material prepared in step (1). The thickness of the anticorrosion base layer made of an inorganic zinc rich paint is not particularly limited, but is about 75 μm in the present embodiment. The anticorrosion base layer made of an inorganic zinc rich paint is porous and has voids in the layer.
In addition to inorganic zinc rich paint, organic zinc rich paint or the like can be applied to the anticorrosion base.

Step (3) is a mist coating step. The surface of the anticorrosion base layer made of the inorganic zinc rich paint formed in step (2) is sprayed with a sufficiently diluted and thinned epoxy resin paint to mist coat and prevent corrosion. An epoxy resin is filled in the void portion of the base layer and solidified to fill the void portion.
In addition, when the surface of the anticorrosion base layer made of inorganic zinc rich paint is directly coated with another resin paint, the air in the above-mentioned voids affects the painted surface of the paint, pinholes or bubbles, etc. Can cause problems.

  Therefore, in the first embodiment of the present invention, unlike the prior art, mist coating is performed on the surface of the anticorrosion foundation layer made of inorganic zinc rich paint. However, the mist coating is not necessarily essential in the present invention. However, when mist coating is not performed, the voids in the anticorrosion undercoat layer may affect the adhesion of the polyimide film described later or the baking of the polyimide varnish performed in the second embodiment described later. Therefore, in the present embodiment, as a particularly preferable structure, the epoxy resin paint is mist coated on the anticorrosion base layer to fill the voids in the anticorrosion base layer.

The mist coating with the epoxy resin paint is performed to fill the voids in the anticorrosion underlayer, and the thickness of the anticorrosion underlayer made of an inorganic zinc rich paint is not particularly increased.
As described above, in the first embodiment, mist coating with an epoxy resin coating is performed as a preferable configuration in order to suppress the influence of voids and the like present in the anticorrosion base layer made of inorganic zinc rich paint.

However, the base treatment method is not limited to the one with mist coating as described above, and may only form the anticorrosion base layer made of an inorganic zinc rich paint, and other methods may be used without departing from the technical idea of the present invention. The known ground surface treatment method can be employed.
Next, a process (4) is a polyimide sticking process and forms a polyimide layer by sticking a polyimide film on the steel material which carried out the ground treatment. Although the layer thickness of a polyimide layer is not specifically limited, Usually, it is 5-25 micrometers, and it was about 12.5 micrometers in this embodiment.

In the first embodiment, a thin double-sided pressure-sensitive adhesive sheet is used as a polyimide sticking method, and a polyimide film is stuck with an adhesive.
As described above, in this embodiment, as a simple method, a double-sided pressure-sensitive adhesive sheet is used, and a polyimide film is attached to a steel material or the like that has been subjected to a ground treatment. It is not limited, and other sticking methods such as using a single-sided adhesive sheet may be used.

Step (5), step (6), and step (7) are painting steps using a resin paint. That is, after the polyimide sticking step, the surface of the polyimide layer is sequentially coated with, for example, an undercoat with an epoxy resin paint (step (5)), an intermediate coat with a fluororesin paint (step (6)), and an overcoat with a fluororesin paint ( Step (7)) is performed. However, the resin paint is not limited to these combinations.
In this way, a rust prevention layer is formed on the steel material surface.

In this embodiment, the structure of the antirust layer formed on a steel material is shown in FIG.
As shown in FIG. 2, the rust-preventing layer formed on the surface of the steel material 1 is composed of, in order from the surface of the steel material 1, an anticorrosion base layer 2, a polyimide layer 3, an undercoat layer 4 made of an epoxy resin coating, and a fluorine resin. It is comprised from the intermediate coating layer 5 and the topcoat layer 6 which consists of a fluorine resin.
The process names and process outlines of the first embodiment described above are shown in Table 1 below.

According to the first embodiment, a strong three-layer rust-preventing layer is formed on the steel material surface by taking three stages of rust-preventing means: base treatment, polyimide film sticking, and resin coating.
As a result, according to the first embodiment, on the anticorrosive underlayer, a polyimide layer is formed by pasting a polyimide film, and the anticorrosive layer does not exist in the conventional anticorrosive layer, and has excellent corrosion resistance. By adding a polyimide layer that hardly permeates corrosion factors such as water and oxygen, it is possible to dramatically improve the rust prevention effect on steel.

FIG. 3 shows an example in which the polyimide layer 3 is attached only at the end portion and the corner portion where it is difficult to ensure the layer thickness of the rust prevention layer.
In the first embodiment described above, since the polyimide layer is formed by pasting a polyimide film, it is easy to ensure the desired thickness of the polyimide layer even at the corners, etc., and effectively prevent rust. It is possible to increase.
In particular, the polyimide film can be easily processed on site, and can be reliably applied in accordance with the shape of the steel material on site, so that it can be efficiently applied.

Moreover, when it says about the linear expansion coefficient (50-200 degreeC) of a polyimide, the thing of the range of 5.0 * 10 < ^-6 > / K or more and 50.0 * 10 < ^-6 > / K or less can be used preferably, By approximating the linear expansion coefficient to the linear expansion coefficient of the steel material, it is possible to suppress strain due to the difference in thermal expansion that occurs between the polyimide and the steel material.
More preferably, the linear expansion coefficient of polyimide is in the range of 8.0 × 10 ⁻⁶ / K or more and 20.0 × 10 ⁻⁶ / K or less, and particularly preferably 11.4 × 2 × 10 ⁻⁶ / K or more. 12.6 × 10 ⁻⁶ / K or less, the strain between the steel material and the polyimide layer can be suppressed as much as possible. In addition, by making the linear expansion coefficient of polyimide the same as the steel material to stick, it is also possible to completely suppress the strain between the steel material and the polyimide caused by the difference in the linear expansion coefficient.

Therefore, according to the above-described configuration of the present embodiment, the anticorrosion treatment can be easily performed even on a steel material in an environment where the temperature change is extremely severe.
Moreover, in the anticorrosion technique using the tape illustrated by patent document 1 demonstrated as a prior art, when sticking a tape on steel materials and forming a rust prevention layer, air between steel materials and a tape does not remain. It was necessary to construct with care.

The reason is that if air remains between the steel material and the tape, there is a possibility that the tape will be poorly bonded and may cause partial peeling, etc. This is because it becomes a major factor of corrosion.
In this way, with the conventional technique of sticking tape to steel material, if construction is insufficient and air remains, it is difficult to solve the problem because it is not possible to confirm the part where air remains later. is there.

On the other hand, in this embodiment, since a translucent or transparent polyimide film can be used, when a polyimide film is stuck on a steel material in the field, air remains between the steel material and the polyimide film. It can be confirmed by visual inspection.
Therefore, in this embodiment, it is possible to work while confirming that air does not remain between the steel material and the polyimide layer at the time of construction, greatly increasing the risk of air remaining between the steel material and the polyimide layer. Can be reduced.

  In particular, bridges, sluices, dust removal devices, etc. that may come into direct contact with seawater etc. are large steel structures, and there are many cases in which partial rust prevention layer repair is required during use. In many cases, on-site rust prevention is required. The method according to the present embodiment using a polyimide film is suitable for repairing a partial rust prevention layer, is relatively easy to perform rust prevention on site, and has a high anticorrosion effect.

In addition, the corrosion test using the test piece 10 of the shape shown in FIG. 5 was done as each test piece for verification of the rust prevention effect by sticking a polyimide layer. Although an outline of the test will be described later, in the test piece 1 for verifying the effect of the first embodiment, a film A (trade name / Upilex SN, thickness: 12.5 μm, manufactured by Ube Industries, Ltd.) (“ “UPILEX” was a registered trademark of Ube Industries, Ltd., and for test piece 2, film B (trade name / UPILEX CA, manufactured by Ube Industries, Inc., thickness: 12.5 μm) was used as a polyimide film.
In the following, the second embodiment of the present invention will be described with a focus on differences from the first embodiment.

FIG. 4 shows a process outline of the second embodiment.
The second embodiment is only different from the first embodiment described above in the step of forming the polyimide layer. That is, in the first embodiment, the polyimide layer is formed by pasting a polyimide film, but in the second embodiment, the polyimide layer is baked and the polyimide film is baked to form the polyimide layer on the steel material. Forming.
The linear expansion coefficient of the baked polyimide is as described above.
The layer thickness of the baked polyimide layer is not particularly limited, but is usually 1 to 10 μm, and in the present embodiment, it is about several μm.
Each process name and process outline of the second embodiment are shown in Table 2 below.

In addition, in order to verify the rust prevention effect by baking of the polyimide layer, a corrosion test using the test piece 10 having the shape shown in FIG. 5 was performed as each test piece as in the first embodiment described above.
Hereinafter, the outline of the polymerization method and the baking method to the test piece 10 are shown about the varnish A of the polyimide used for the test piece 3 manufactured by the method according to the second embodiment and the varnish B used for the test piece 4.

(A) Polyimide varnish A
To a glass reaction vessel having an internal volume of 500 mL equipped with a stirrer and a nitrogen gas introduction / discharge pipe, 406 g of water was added as a solvent, and 12.97 g (0.12 mol) of PPD and 28 of 1,2-DMZ were added thereto. .84 g (0.30 mol, 2.5 times equivalent of tetracarboxylic acid component) was added and stirred at 25 ° C. for 1 hour to dissolve. To this solution, 35.31 g (0.12 mol) of s-BPDA was added and stirred at 70 ° C. for 4 hours to obtain a polyimide precursor having a solid content concentration of 9.1% by mass, a solution viscosity of 63 Pa · s, and a logarithmic viscosity of 1.86. Varnish A, a body composition, was prepared.

  The obtained varnish A was coated on the test piece 10 with the base prepared by a bar coater, and the coating film was defoamed and pre-dried at 25 ° C. under reduced pressure for 30 minutes, and then heated under normal pressure under a hot air drier. And dried at 80 ° C. for 30 minutes, followed by heat treatment at 350 ° C. for 30 minutes, and a polyimide film having a thickness of about 1 μm to 10 μm was baked onto the test piece 10. Thus, the characteristic was evaluated about the test piece 10 (test piece 3) by which the polyimide film was baked.

(B) Polyimide varnish B
Varnish B was prepared in the same manner as Varnish A except that the composition was changed. That is, varnish B, which is a polyimide precursor composition having a solid content concentration of 9.2 mass%, a solution viscosity of 52 Pa · s, and a logarithmic viscosity of 0.46, was prepared.
The obtained varnish B was coated on the test piece 10 with the base adjusted by a bar coater, and the coating film was defoamed and pre-dried at 25 ° C. under reduced pressure for 30 minutes, and then placed in a hot air dryer under normal pressure. The polyimide film having a thickness of several μm (about 1 μm to 10 μm) was baked on the test piece 10 by heat treatment at 80 ° C. for 30 minutes and then at 200 ° C. for 30 minutes. Thus, the characteristic was evaluated about the test piece 10 (test piece 4) by which the polyimide film was baked.

The abbreviations of the compounds used in the above steps are as follows.
s-BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride PPD: p-phenylenediamine 1,2-DMZ: 1,2-dimethylimidazole

Each test piece is a test piece 10 having the shape shown in FIG. 5, that is, the test piece 1 and the test piece 2 according to the first embodiment, and the test piece 3 and the test piece 4 according to the second embodiment. Similarly, a test piece (Comparative Example 1) according to a conventional product having an anticorrosion layer having the configuration shown in FIG. 6 was prepared for comparison.
And about the test piece 1 thru | or the test piece 4 and the comparative example 1, the X-shaped scratch 12 was formed in the depth of the grade which reaches | attains steel materials with a cutter knife.

By forming a scratch 12 that reaches the steel material with a cutter knife, it is possible to confirm the progress of corrosion after the start of corrosion has occurred by creating a starting point of corrosion on the test piece. It is possible to reduce the time required.
The difference between Comparative Example 1 and the first and second embodiments of the present invention is the presence or absence of a polyimide layer in the rust preventive layer, and the other configurations are the same.

About the test piece 1 thru | or the test piece 4 and the comparative example 1, the salt spray cycle test (according to JISH8502) was implemented, respectively.
After completion of the salt spray cycle test (about 3900 hours in the test according to this embodiment), the corrosion state was visually confirmed. However, the corrosion state of the steel material serving as a base material such as a test piece is sufficiently hidden behind the coating. It was not visible.

Therefore, for the test piece 1 to the test piece 4 and the comparative example 1, the minimum blasting treatment is performed to remove the rust prevention layer formed on the steel material, and the resin coating, the polyimide film, and the anticorrosion foundation layer are removed. The steel material was exposed and the progress of corrosion of the steel material was confirmed.
In addition, after removing the rust preventive layer by blasting, the maximum depth, area, and volume of the defect portion were measured with a laser measuring instrument in order to quantify and compare the size of the defect portion due to corrosion of the steel material.
The measurement results are shown in Table 3 below.

As shown in Table 3, the test piece 1 to the test piece 4 are smaller in depth (shallow) than the comparative example 1 in which the polyimide layer is not included in the rust prevention layer, and both the area and the volume are small. I found it small. Thereby, the corrosion reduction effect by forming a polyimide layer was able to be confirmed.
In particular, the test piece 3 and the test piece 4 baked with polyimide varnish have a remarkable effect of suppressing the progress of corrosion in a situation having a corrosion starting point, and it has been found that this is a particularly preferable configuration.

  The present invention is applied to steel structures such as bridges, steel towers, tanks, sluices, dust removal equipment, construction equipment, plant equipment, bridges and the like installed outdoors, and is suitable for effective anticorrosion thereof. Technology.

DESCRIPTION OF SYMBOLS 1 ... Steel material 2 ... Anticorrosion base layer 3 ... Polyimide layer 4 ... Undercoat layer 5 ... Middle coat layer 6 ... Top coat layer 10 ... Test piece 12 ... Scratch

Claims (6)

A step of forming a polyimide layer on the surface of a steel material or a steel material subjected to a ground treatment, and a step of coating the surface of the polyimide layer with a resin paint ,
The step of painting with the resin paint consists of painting the surface of the polyimide layer with an epoxy resin paint and then painting with a fluororesin paint, and the base treatment comprises applying an inorganic zinc rich paint on the surface of the steel material. Then, an anticorrosion method for a steel material, characterized in that an epoxy resin paint is applied to fill the voids in the inorganic zinc rich paint coating film . The linear expansion coefficient of the polyimide which comprises the said polyimide layer exists in the range of 5.0 * 10 < ^-6 > / K or more and 50.0 * 10 < ^-6 > / K or less, The steel material of Claim 1 characterized by the above-mentioned. Anticorrosion method. 3. The method for preventing corrosion of steel according to claim 1 or 2 , wherein the step of forming the polyimide layer is performed by sticking a polyimide film to the surface of the steel. 3. The method for preventing corrosion of a steel material according to claim 1 , wherein the step of forming the polyimide layer is performed by applying a polyimide varnish to the surface of the steel material, baking it, and baking it. A steel structure characterized by being anti-corrosion-treated by coating with a resin paint through a polyimide layer on the surface of a steel material constituting the steel structure or a surface-treated steel material, and coated with the resin paint To do this, the surface of the polyimide layer is coated with an epoxy resin paint and then with a fluororesin paint, and the base treatment is performed by coating an inorganic zinc rich paint on the surface of the steel material, and then the inorganic zinc rich. A steel structure that is coated with epoxy resin paint to fill the voids in the paint film .   The steel structure subjected to anticorrosion treatment according to claim 5, wherein the steel structure is a bridge.

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