JP2003293362A - Corrosion-proof method for joint section for steel sheet pile covered with polyethylene, method for repairing covering damage section of steel material covered with polyethylene and corrosion-proof structure covered with polyethylene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion-proof method for a joint section for a steel sheet pile covered with polyethylene, in which a polyethylene sheet for a corrosion-proofness or a repair is stuck continuously on a polyethylene covering on the steel sheet pile side uniformly and firmly, and a method for repairing the covering damage section of a steel material covered with polyethylene. <P>SOLUTION: Receiving nuts 10a are installed on the surface of the steel material for the joint section 2 for the steel sheet piles 1 at regular intervals by a welding or the like. Bolts 11 having the same diameter as the nuts 10a are screwed and mounted on the nuts 10a. The polyethylene sheet 5, to which a heating wire 6 is secured previously, is fitted, the joint section 2 and the edge section of the polyethylene covering 3c are covered, a cushioning material 8 is set up on the sheet 5, and wood 9 in which a hole 9a is bored in conformity with the bolt 11 is attached as a holddown material for the sheet 5 on the cushioning material 8. A washer 12 having the same diameter as the bolt 11 is installed to the bolt 11, a locknut 10b having the same diameter as the bolt 11 is clamped to the bolt 11, and the sheet 5 is fixed. Electricity is conducted through the heating wire 6 to generate heat, and the sheet 5 and the polyethylene covering 3c are welded continuously and firmly. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile, a method for repairing a damaged coating portion of a polyethylene-coated steel material, and a polyethylene-coated anticorrosion structure, and a steel sheet pile having a polyethylene coating belonging to an organic lining. It is also used to prevent corrosion of joints of steel pipe piles and repair damaged polyethylene coatings.

[0002]

2. Description of the Related Art Conventionally, corrosion protection methods for harbor steel structures have mainly been applied to cathodic protection methods mainly for seawater and subsoil, and mainly for sea atmosphere, splash zones, tidal zones, and seawater. There is a coating covering for. The coating method includes coating, organic lining, inorganic lining, petrolatum lining and the like.

An invention relating to a steel sheet pile or a steel pipe pile having a polyethylene coating as an organic lining is described in, for example, Japanese Patent Application Laid-Open No. 61-72127.

FIG. 5 shows a general structure of a polyethylene-coated steel sheet pile, which has a surface treatment layer 3a, an adhesive layer 3b, and a polyethylene coating layer 3c on the surface of the steel sheet pile 1 having joints 1a at both ends. The layers are layered together to form an anticorrosion structure.

Anticorrosion with a polyethylene coating is excellent in terms of anticorrosion properties and usage results, but is not suitable for coating with a complicated shape. Therefore, normally, the joint 1a of the steel sheet pile 1 is avoided and each steel sheet pile is used. Is applied to.

Therefore, after the polyethylene-coated steel sheet pile is cast on site, the polyethylene coating does not become a completely continuous surface, and the uncoated portion remains in the joint portion 2 between the steel sheet piles 1. A method of attaching a polyethylene coating to such an uncoated joint portion 2 in seawater is disclosed in, for example, Japanese Unexamined Patent Application Publication No.
No. 1-131957.

FIGS. 6 and 7 show a method of preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile according to the method, in which a joint 1 of a steel sheet pile 1 protected by a polyethylene coating 3 is used.
Filling the recess 2a of the joint portion 2 with the filler 4 in a state where they are fitted together, covering the polyethylene sheet 5 with the filler 4 and attaching the end of the polyethylene sheet 5 to the surface of the polyethylene coating 3. Thus, a continuous polyethylene anticorrosion layer is formed on the surfaces of the steel sheet pile 1 and the joint portion 2.

As a method of attaching the polyethylene sheet to the polyethylene coating, there are a heat welding method of energizing the heating wire 6 shown in FIG. 6 and an ultrasonic method using an ultrasonic welder 7 shown in FIG. is there.

[0009] In addition, assuming that the steel sheet pile or the steel pipe pile is to be installed at sea (construction by impact, construction by vibration), during construction, scratches due to wire rope, scratches due to guide frames, scratches due to driving, gas cutting and welding are performed. It is conceivable that the polyethylene-coated surface may be damaged by the heat of the above, or after the construction, such as by the collision of floating substances. A method for repairing such a polyethylene-coated surface is disclosed in, for example, Japanese Patent Laid-Open No. 2001-1.
It is described in Japanese Patent No. 29892.

FIGS. 8 and 9 show a method for repairing a damaged portion of a polyethylene-coated steel sheet pile by this method, and a damaged portion 3d of the polyethylene coating 3 covering the surface of the steel sheet pile 1 is shown.
To the surface of the polyethylene coating 3, and the polyethylene sheet 5 is covered so as to cover the same, and the polyethylene coating 3 is damaged. An anticorrosion layer is formed to completely cover the portion 3d.

As a method for attaching the polyethylene sheet to the polyethylene coating, there are a heat welding method of energizing the heating wire 6 shown in FIG. 8 and an ultrasonic method using an ultrasonic welder 7 shown in FIG. is there.

[0012]

As a method of attaching the polyethylene sheet to the above-mentioned polyethylene coating, there are a method using ultrasonic waves and a method using heat welding.

In the method using ultrasonic waves, as shown in FIGS. 7 and 9, a polyethylene sheet 5 is superposed on the polyethylene coating 3 and directly welded using an ultrasonic welder 7. However, since the welded portion is circular with a diameter of about 5 mm and is not continuous, there is a problem that seawater enters from the unwelded portion.

On the other hand, the method using heat welding is performed by polyethylene coating 3 and polyethylene sheet 5 as shown in FIGS.
A heating wire 6 in the form of a film called a heat tape is sandwiched between the two and the heating tape is energized to generate heat, and the polyethylene coating 3 and the polyethylene sheet 5 are melted and bonded to each other.

However, there has been a problem that the welded portion becomes non-uniform because a method of pressing the polyethylene sheet 5 to the polyethylene coating 3 as a whole uniformly and with sufficient force has not been established.

The object of the present invention is to solve the above-mentioned problems, and to adhere a polyethylene sheet for corrosion protection or repair to the polyethylene coating on the side of the steel sheet pile continuously, uniformly and firmly. Provided are a method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile, a method for repairing a damaged portion of a polyethylene-coated steel material, and a polyethylene-coated anticorrosion structure.

[0017]

A method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile according to a first aspect of the present invention is a receiving nut (anchor nut) attached to a steel material surface of a joint portion between steel sheet piles having a polyethylene coating on the surface. Attach the bolt to the heating element, cover the joint and the polyethylene coating with polyethylene to which the heating wire is attached, attach the pressing material on it, and tighten the tightening nut on the bolt to fix the polyethylene, then energize the heating wire. Then, the polyethylene and the polyethylene coating are welded together.

As the pressing material in this case, for example, wood or FRP can be used, and by interposing a rubber pad or the like as a cushioning material between the polyethylene and the pressing material, polyethylene can be evenly coated on the polyethylene coating. It can be fixed by pressure.

After the polyethylene and the polyethylene coating are welded together, the pressing material, bolts and tightening nuts can all be removed.
When P or the like is used, these members may remain attached. Further, the receiving nut may be attached in the vicinity of the joint portion of each steel sheet pile in advance before driving the steel sheet pile.

According to a second aspect of the present invention, there is provided a method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile, wherein a bolt is attached to a steel material surface of the joint portion of the steel sheet pile having a polyethylene coating on the surface, and a heating wire is attached to the joint portion of polyethylene. The polyethylene coating is covered, a pressing material is attached on the polyethylene coating, and the polyethylene is fixed by tightening a tightening nut on the bolt to fix the polyethylene, and then the heating wire is energized to weld the polyethylene and the polyethylene coating. .
In this case, the bolt may be attached in the vicinity of the joint portion of each steel sheet pile in advance before driving the steel sheet pile.

Further, in the case of the anticorrosion method according to the first and second aspects, the polyethylene can be more surely adhered by reducing the installation interval of the bolts. The installation interval in this case may be determined in consideration of the magnitude of water pressure acting on the joint.

According to a third aspect of the present invention, there is provided a method for repairing a coating damaged portion of a polyethylene-coated steel material, wherein a bolt is attached to the steel material surface of the coating-damaged portion of the steel material having a polyethylene coating on the surface thereof, and the heating-wire-attached polyethylene is applied to the coating damaged portion. And covering the polyethylene coating, attaching a pressing member on it, and tightening the tightening nut to the bolt to fix the polyethylene, and then energizing the heating wire to weld the polyethylene coating and the polyethylene. To do.

The repairing method of the present invention is particularly used for driving steel sheet piles and steel pipe piles at the time of sea construction, or for repairing scratches on the polyethylene coating due to heat of gas cutting or welding.

A polyethylene-coated anticorrosion structure according to a fourth aspect of the present invention is an attachment comprising a polyethylene-coated anticorrosion layer attached to a steel surface, a bolt attached to the steel surface, and a tightening nut screwed to the bolt. A device, a corrosion protection layer made of polyethylene attached on the polyethylene coating, and a heating device sandwiched between the polyethylene coating and polyethylene, and a fixing device. is there. In this case, a receiving nut may be attached to the surface of the steel material and a bolt may be attached to the receiving nut.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the invention according to claim 1, a steel having a polyethylene coating 3c and fitting joints 1a at both ends to each other is fitted. In the case of the joint portion 2 of the sheet pile 1, as shown in FIG. 1, after the receiving nuts 10a are attached to the surface of the steel sheet pile 1 of the joint portion 2 at regular intervals by welding or the like, the receiving nut 10
A bolt 11 having the same diameter as this is screwed and attached to a.

Next, the polyethylene sheet 5 to which the heating wire 6 is previously attached is attached to cover the joint portion 2 and the edge portion of the polyethylene coating 3c, the cushioning material 8 is attached thereon, and further the polyethylene sheet 5 is attached thereon. As a pressing member, a timber 9 having a hole 9a formed therein is attached to the bolt 11.

A washer 12 having the same diameter as that of the bolt 11 is attached to the bolt 11, and then a tightening nut 10b having the same diameter as the bolt 11 is tightened to fix the polyethylene sheet 5. Then, the polyethylene wire 5 and the polyethylene coating 3c are generated by energizing the heating wire 6 to generate heat.
And are continuously and strongly welded together to form a structure that does not allow seawater to enter through the gaps.

After the polyethylene sheet 5 and the polyethylene coating 3c are welded, the cushion material 8, the timber 9 and the bolt 11 are removed as shown in FIG. Further, the bolt hole after removing the bolt 11 is closed with an underwater curing type epoxy resin.

In the invention of claim 2, in the case of the joint portion 2 of the steel sheet pile 1 having the polyethylene coating 3c and the joints 1a at both ends fitted together, as shown in FIG. After the bolts 11 are attached to the surface of the sheet pile 1 at regular intervals by welding or the like, the heating wire 6 is attached in advance and the polyethylene sheet 5 in which holes are formed in accordance with the bolts 11 is attached to the joint portion 2 and the edge of the polyethylene coating 3c. The portion is covered, and the FRP 13 having holes formed according to the intervals of the bolts 11 is attached thereon as a pressing member.

A washer 12 having the same diameter as that of the bolt 11 is attached, and a tightening nut 10b having the same diameter as that of the bolt 11 is tightened to fix the polyethylene sheet 5.

Then, the heating wire 6 is energized to generate heat to continuously and firmly weld the polyethylene coating 3c and the polyethylene sheet 5, thereby integrating the polyethylene coating 3c and the polyethylene sheet 5 into a gap. The structure is designed to prevent seawater from entering the steel surface.

In the third aspect of the present invention, in the case of the damaged coating portion of the steel material 1 having the polyethylene coating 3c, as shown in FIG. 4, a bolt 11 is attached to the surface of the steel material of the coated damage portion 3d of the steel material 1 by welding or the like. After that, the heating wire 6 is attached in advance, and the polyethylene sheet 5 having holes formed in accordance with the bolts 11 is attached to cover the covering damaged portion 3d and the edge portion of the polyethylene coating 3c, and as a pressing member for the polyethylene sheet 5 thereon. An FRP 13 having a hole 13a formed in accordance with the bolt 11 is attached, a washer 12 having the same diameter as the bolt 11 is attached, and a fastening nut 10b having the same diameter as the bolt 11 is tightened to fix the polyethylene sheet 5.

Then, the heating wire 6 is energized to generate heat and the polyethylene coating 3c and the polyethylene sheet 5 are continuously and firmly welded to each other, whereby the polyethylene coating 3 is formed.
c and the polyethylene sheet 5 are integrated so that seawater does not enter through the gap.

[0034]

EXAMPLES The present invention will be described in more detail below based on examples.

FIGS. 1, 2 and 3 show an example of anticorrosion of a joint portion of a heavy anticorrosion coated steel sheet pile, and FIG. 4 shows an example of repair of a coating damage portion of a heavy anticorrosion coated steel sheet pile.

In FIG. 1, a steel sheet pile SP-II type 1 is a specimen having a length of 100 cm, which is provided with a polyethylene coating 3c having a thickness of 2.5 mm, and joints 1a at both ends are fitted together. Joint part 2 of steel sheet pile 1 using hand tools and power tools
The marine organisms and other deposits that had adhered to the surface of the steel material were removed.

M12 receiving nuts 10a are attached to the joint surface 2 by welding at 90 cm intervals on the surface of the steel material, and bolts 11 having the same diameter as the receiving nuts 10a are screwed onto the respective receiving nuts 10a. Underwater curing type epoxy resin 4 was filled in 2a.

A polyethylene sheet 5 having a thickness of 2.5 mm, to which a film-shaped heating wire 6 made by sandwiching five heating wires with a polyolefin film is attached in advance, is provided with a recess 2a of the joint portion 2 and an edge portion of the polyethylene coating 3c. Covered.

Further, the rubber cushion material 8 is attached on the polyethylene sheet 5, and the square timber 9 with holes at 90 cm intervals according to the bolts 11 is attached.
Further, a washer 12 having the same diameter as this was attached to the bolt 11, and a tightening nut 10b of the same type as the bolt 11 was tightened to fix the polyethylene sheet 5.

Then, the heating wire 6 is energized to generate heat,
The polyethylene sheet 5 and the polyethylene coating 3c are welded together. After welding the polyethylene sheet 5 and the polyethylene coating 3c, as shown in FIG. 2, the rubber cushion material 8, the timber 9 and the bolt 11 are removed, and the bolt hole after the bolt 11 is removed is set in water. Blocked with epoxy resin.

As a result, the polyethylene sheet 5 and the polyethylene coating 3c are continuously and firmly integrated, and the joint portion 2 has a structure that does not allow seawater to enter.

In FIG. 3, a steel sheet pile SP-II type 1 is a specimen having a length of 100 cm, which is provided with a polyethylene coating 3c having a thickness of 2.5 mm and in which the joints 1a at both ends are fitted. The surface of the steel material of the joint portion 2 is cleaned with a hand tool and a power tool to remove deposits such as marine life. In the joint part 2,
M12 bolts 11 were attached to the surface of the steel material at 90 cm intervals by welding, and the recess 2a of the joint portion 2 was filled with the underwater curing type epoxy resin 4.

Further, a film-shaped heating wire 6 in which five heating wires are sandwiched by a polyolefin film is previously attached, and a joint portion 2 and a polyethylene coating 3c are formed by a polyethylene sheet 5 having holes formed at 90 cm intervals in accordance with the bolts 11. Covered.

Then, an FRP 13 having holes formed at 90 cm intervals according to the intervals of the bolts 11 was attached to the bolts 11, a washer 12 having the same diameter as the bolts 11 was attached, and a tightening nut 10b having the same diameter as the bolts 11 was tightened. Then, the polyethylene sheet 5 was fixed.

Then, the heating wire 6 is energized to generate heat,
The polyethylene coating 3c and the polyethylene sheet 5 were welded together. As a result, the polyethylene coating 3c and the polyethylene sheet 5 are continuously and firmly integrated, and the joint 2
Has a structure that does not allow seawater to enter.

In FIG. 4, 210 mm × 29 from the steel sheet pile SP-II type flange portion provided with the polyethylene coating 3c.
Specimen cut into a size of 0 mm, 100
An artificial damaged part 3d of mm × 100 mm was made.

On the surface of the steel material of the damaged coating portion 3d, a hand tool and a power tool are used to remove deposits such as marine life.
The surface of the steel material was attached with M12 bolts 11 by welding and filled with underwater curing type epoxy resin 4.

Further, a film-shaped heating wire 6 in which five heating wires are sandwiched between polyolefin films is attached in advance, and the polyethylene sheet 5 having holes formed in accordance with the bolts 11 covers the damaged portion 3d and the edge of the polyethylene coating 3c. Covered the edges.

Then, the FRP 13 having a hole corresponding to the bolt 11 is attached thereon, the washer 12 having the same diameter as the bolt 11 is attached to the bolt 11, and the tightening nut 10b having the same diameter as the bolt 11 is tightened to secure the polyethylene sheet 5 to the polyethylene sheet 5. After fixing, the heating wire 6 was energized to generate heat, and the polyethylene coating 3c and the polyethylene sheet 5 were welded. As a result, the polyethylene coating 3c and the polyethylene sheet 5 were continuously and firmly integrated, and seawater did not enter the coating damaged portion 3d.

The test piece prepared as described above is used for 2 days a day.
Each time, it was installed at the exposure test site where the seawater was regularly showered for 3.5 hours. When the polyethylene sheet was peeled off after 396 days, it was confirmed that the steel surfaces of the joint portion 2 and the coating damage portion 3d were kept in a healthy state.

[0051]

According to the first aspect of the present invention, there is provided a method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile, in which a bolt is attached to a receiving nut attached to a steel material surface of a joint portion of steel sheet piles having a polyethylene coating on the surface to heat the heating wire. After covering the joint portion and the polyethylene coating with the attached polyethylene and attaching a pressing member on the polyethylene, and fixing the polyethylene by tightening the tightening nut on the bolt, the heating wire is energized to form the polyethylene and the polyethylene coating. Since it is welded, especially by tightening the tightening nuts screwed on each bolt evenly, it is possible to adhere the anticorrosion polyethylene to the polyethylene coating on the steel sheet pile side with an even pressure. Compared with the anticorrosion method of the steel sheet pile joint part, the polyethylene coating on the steel sheet pile side and There is an effect that it is possible to continuously and firmly integrated and Len.

Further, since each bolt is screwed and attached to the receiving nut attached to the surface of the steel material of the joint portion, not only recovery of the steel sheet pile in the future is easy, but also the bolt, the pressing material and the tightening nut are removed and repeated. It is very economical to use.

According to a second aspect of the present invention, there is provided a corrosion preventing method for a joint portion of a polyethylene-coated steel sheet pile, wherein a bolt is attached to a steel material surface of the joint portion of a steel sheet pile having a polyethylene coating on the surface, and the joint portion is made of polyethylene with a heating wire attached. The polyethylene coating is covered, a pressing member is attached on the polyethylene coating, and the fastening nut is fastened to the bolt to fix the polyethylene, and then the heating wire is energized to weld the polyethylene and the polyethylene coating. Similar to the anticorrosion method described above, compared with the conventional anticorrosion method for the steel sheet pile joint portion, there is an effect that the polyethylene coating on the steel sheet pile side and the polyethylene for anticorrosion can be continuously and firmly integrated.

Since each bolt is directly attached to the joint portion of the steel sheet pile without the receiving nut, the cost can be reduced by omitting the receiving nut and the receiving nut is obstructed when filling the joint portion. Careful filling can be carried out without being carried out.

According to a third aspect of the present invention, there is provided a method for preventing corrosion of a coating-damaged portion of a polyethylene-coated steel material, wherein a bolt is attached to the steel material surface of the coating-damaged portion of the steel material having a polyethylene coating on the surface, and the coating-damaged portion is made of polyethylene to which a heating wire is attached. And covering the polyethylene coating, attaching a pressing member on it, and tightening the tightening nut to the bolt to fix the polyethylene, and then energizing the heating wire to weld the polyethylene coating and the polyethylene. By evenly tightening the tightening nuts that are screwed onto the bolts, it is possible to bring the anticorrosion polyethylene into close contact with the polyethylene coating on the steel sheet pile side with even pressure, thereby repairing damaged areas of conventional steel coating. Compared with the construction method, the polyethylene coating on the steel material side and the polyethylene sheet for repair are more continuous. One can be firmly integrated.

A polyethylene-coated anticorrosion structure according to a fourth aspect of the present invention is an attachment comprising a polyethylene-coated anticorrosion layer attached to the surface of a steel material, a bolt attached to the surface of the steel material, and a tightening nut screwed to the bolt. Since it is composed of a device, an anticorrosive layer made of polyethylene attached on the polyethylene coating, and a heating wire sandwiched between the polyethylene coating and polyethylene, the structure is extremely simple. In spite of this, the polyethylene coating and the polyethylene sheet can be continuously and firmly integrated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for corrosion protection of a joint portion of a steel sheet pile having a polyethylene coating according to claim 1 of the present invention.

FIG. 2 is a sectional view in which a joint portion of a steel sheet pile having a polyethylene coating according to claim 1 of the present invention is corrosion-protected.

FIG. 3 is a cross-sectional view in which a joint portion of a steel sheet pile having a polyethylene coating according to claim 2 of the present invention is corrosion-protected.

FIG. 4 is a cross-sectional view in which a coating damaged portion of a steel material having a polyethylene coating according to claim 3 of the present invention is repaired.

FIG. 5 is a perspective view showing a layer-by-layer coating structure of a steel sheet pile having a polyethylene coating.

FIG. 6 is a cross-sectional view showing a method of integrating a joint portion of a steel sheet pile having a polyethylene coating by a conventional heat welding method in an anticorrosion method.

FIG. 7 is a cross-sectional view showing a method of integrating a joint portion of a steel sheet pile having a polyethylene coating by a conventional ultrasonic method in an anticorrosion method.

FIG. 8 is a method of repairing a coating damaged portion of a steel sheet pile having a polyethylene coating, showing a method of integrating by a conventional heat welding method, (a) is a sectional view thereof, and (b) is a plan view.

FIG. 9 shows a method of repairing a coating damaged portion of a steel sheet pile having a polyethylene coating, which is a conventional ultrasonic method and is integrated,
(A) is the sectional drawing and (b) is a top view.

[Explanation of symbols]

1 ... Steel sheet pile, steel 1a ... Joint 2 ... Joint 3 ... Polyethylene coating 3a ... Surface treatment layer 3b ... Adhesive layer 3c ... polyethylene layer 3d ... coating damage part 4 ... Filling material 5: Polyethylene sheet (polyethylene) 6 ... Heating wire 7 ... Ultrasonic welder 8 ... Cushion material 9 ... Wood (pressing member) 10a ... Receiving nut 10b ... Tightening nut 11 ... bolt 12 ... washers 13 ... FRP (pressing member)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazumasa Sato             4-53 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Sumitomo Metal Industries, Ltd. (72) Inventor, Keima Nakano             4-53 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Sumitomo Metal Industries, Ltd. (72) Inventor Norio Yoshida             2-7-17 Ikenohata, Taito-ku, Tokyo Sumiko             Corrosion Protection Co., Ltd. (72) Inventor Nobuaki Okamoto             Osaka Prefecture Osaka City Yodogawa-ku Nishinakajima 3-chome 1-12               Ocean Engineering Co., Ltd. F term (reference) 2D049 EA03 FA01 FB03 FB12 FC03                       FE02 FE03                 4K062 AA10 BC07 EA06 EA20 FA01

Claims (4)

[Claims] 1. A bolt is attached to a receiving nut attached to a steel material surface of a joint portion of a steel sheet pile having a polyethylene coating on its surface, and the joint portion and the polyethylene coating are covered with polyethylene to which a heating wire is attached, and a pressing member is provided thereon. And fixing the polyethylene by tightening a tightening nut on the bolt and fixing the polyethylene, and then energizing the heating wire to weld the polyethylene and the polyethylene coating to prevent corrosion of the joint portion of the polyethylene-coated steel sheet pile. . 2. A bolt is attached to a steel material surface of a joint portion of a steel sheet pile having a polyethylene coating on the surface, the joint portion and the polyethylene coating are covered with polyethylene to which a heating wire is attached, and a pressing member is attached thereon. A method for preventing corrosion of a joint portion of a polyethylene-coated steel sheet pile, comprising fastening a tightening nut to a bolt to fix the polyethylene, and then energizing the heating wire to weld the polyethylene and the polyethylene coating. 3. A bolt is attached to the steel material surface of the coating damage portion of the steel material having a polyethylene coating on the surface, the coating damage portion and the polyethylene coating are covered with polyethylene to which a heating wire is attached, and a pressing material is attached thereon, and A method for repairing a coating-damaged portion of a polyethylene-coated steel material, comprising fastening a tightening nut to the bolt to fix the polyethylene, and then energizing the heating wire to weld the polyethylene coating and the polyethylene. 4. An attachment device comprising a corrosion protection layer made of polyethylene coating attached to the surface of a steel material, a bolt attached to the surface of the steel material, and a tightening nut screwed to the bolt, and an attachment device on the polyethylene coating. A polyethylene-coated anticorrosion structure comprising a fixing device composed of a polyethylene anticorrosion layer attached and a heating wire sandwiched between the polyethylene coating and polyethylene.