JPH10286909A - Steel pipe and steel-pipe pile with heavy-duty anti-corrosion coating, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a shearing adhesive strength of a poyethylene layer and a protective layer or mortar layer and coated film release preventing effect by laminating a primer layer, polyethylene adhesive layer and polyethylene layer having a spiral recess of specific size on an outer surface of a substitute- treated steel tube. SOLUTION: A surface of a steel pipe or steel pipe pile 1 made of alloy steel such as carbon steel or stainless steel is rust-removed by degreasing or pickling, and anti-corrosiveness is enhanced by chromate treatment agent. To obtain large adhesive strength and anti-corrosiveness by this surface, an epoxy primer layer 2 made of reactive curing epoxy is formed, and a polyethylene adhesive layer 3 and low, intermediate or high density polyethylene layer 4 are laminated thereon. And, to improve a shearing adhesive force of further laminating fiber-reinforced plastic and mortar, a spiral recess 6 having a depth of 0.1 to 3 mm and a width of 3 to 100 mm is formed on a surface of the layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy corrosion-resistant coated steel pipe, a heavy corrosion-resistant coated steel pipe pile, and a method for producing the same. More specifically, the present invention relates to a shear adhesion between a polyethylene layer which is a corrosion protection layer and a fiber reinforced plastic layer or a mortar layer. TECHNICAL FIELD The present invention relates to a heavy corrosion-resistant coated steel pipe, a heavy corrosion-resistant coated steel pipe pile, and a method for producing the same.

[0002]

2. Description of the Related Art Polyethylene-coated steel pipes in which the outer surface of a steel pipe is coated with polyethylene are frequently used in various buried pipes such as gas, oil, water and sewage, and electric cables and civil engineering building materials such as steel pipe piles. Since polyethylene is chemically stable, polyethylene-coated steel has excellent corrosion resistance over a long period of time. However, through contact with pebbles or the like during burial or casting, collision or abrasion between the coated steel materials, penetration flaws may occur in the polyethylene coating, and the corrosion resistance may be impaired. Also, when polyethylene-coated steel pipes are laid across roads, etc., when used in a direct push propulsion method in which steel pipes are propelled and laid in the soil under the road, only polyethylene coating is used. While the polyethylene-coated steel pipe is propelled in the ground, the coating may be scratched by rocks and the like in the soil to cause penetration flaws and peeling of the coating, thereby impairing the corrosion resistance.

[0003] Therefore, a coated steel pipe and a coated steel pipe pile having improved impact resistance, scratch resistance, wear resistance and the like of the polyethylene coated steel pipe and the polyethylene coated steel pipe pile have been developed. For example, heavy corrosion-resistant coated steel materials in which a polyethylene-coated surface is coated with a fiber-reinforced plastic as a protective layer are disclosed in Japanese Patent Publication No. 7-6595 and Japanese Patent Publication No. 6-78606. In addition, polyethylene-coated steel pipes are often used in pipelines laid on the sea floor and rivers.However, when used, the weight of the steel pipes is increased in order to increase the stability of the steel pipes against the flow of water on the sea floor and river bottoms. Mortar coating such as concrete is often applied to the outer surface of the polyethylene-coated steel pipe in order to increase the water content.

[0004] When the outer surface of a polyethylene coating is coated with a fiber-reinforced plastic or mortar as described above, the polyethylene layer is bonded to the fiber-reinforced plastic coating or a mortar coating in order to prevent peeling of the outer coating. Force, especially shear adhesion, is required.
However, polyethylene is chemically stable, and it is difficult to obtain chemical adhesion to fiber-reinforced plastics and mortar. Therefore, in order to obtain a shearing adhesive force, it is necessary to make the surface of the polyethylene layer uneven, and to mechanically join the polyethylene layer and the outer surface coating.

For example, in Japanese Patent Application Laid-Open No. 58-89974, immediately after coating with polyethylene, polyethylene pellets are sprayed on the surface and fused to form irregularities on the surface of the polyethylene layer, thereby forming an adhesive force between the polyethylene layer and the mortar. Has been improved. In Japanese Patent Publication No. 7-6595, immediately after coating with polyethylene, a metal roll having embossed irregularities is pressed against the polyethylene layer, and the irregularities on the roll surface are transferred to the polyethylene layer surface. Irregularities are formed.

[0006]

However, when the surface of the polyethylene layer is subjected to unevenness processing by these methods, sufficient unevenness cannot be formed unless the operation speed is reduced, and the polyethylene layer and the outer surface coating layer cannot be formed. High shear adhesion cannot be obtained. For example, in the method of spraying and fusing polyethylene pellets, the surface of the pellet is partially melted and adhered by heat transfer from the polyethylene layer to the pellets. And the shear adhesion to the outer coating does not improve much because of the reduction of the melting and the insufficient fusion. In order to obtain a sufficient shear adhesive strength, it is necessary to reduce the conveying speed of the steel pipe. Also, when embossing is performed, if the conveying speed of the steel pipe is high, the contact time between the metal roll with irregularities and the polyethylene layer is short, and it is not possible to form a sufficient emboss, so like the former,
It is necessary to reduce the transfer speed of the steel pipe. That is, it is difficult for the conventional method to achieve both of the two problems, that is, the improvement in the shearing adhesive strength between the polyethylene layer and the outer surface coating layer and the improvement in the production efficiency.

[0007]

Means for Solving the Problems The present inventors have intensively studied to solve the above problems. As a result, as shown in FIG. 3, a primer layer (2), a polyethylene adhesive layer (3), a depth of 0.1 to 3 mm, A fiber reinforced plastic layer (7) or a mortar layer (7) on the surface of a heavy corrosion resistant coated steel pipe and a heavy corrosion resistant coated steel pipe pile in which a polyethylene layer (4) having a spiral depression (6) having a width of 3 to 100 mm is sequentially laminated. When a strong shearing adhesion force is obtained by laminating and a polyethylene layer (4) having a spiral depression (6) is formed, as shown in FIG.
Polyethylene is melted, extruded into a sheet, and coated with a T-die that coats a steel pipe (11) that is transported in the pipe axis direction while rotating. A tape-like material having properties is applied to the surface of the polyethylene coating that has not been solidified yet.
If the tape is removed after the polyethylene is solidified after being wound in a spiral shape so as to bite in 1 to 3 mm, and the tape-shaped object is removed, the irregularities for obtaining a sufficient shearing adhesive force without depending on the conveying speed of the steel pipe. Can be formed, which has led to the present invention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A steel pipe (1) and a steel pipe pile (1) used in the present invention are a steel pipe and a steel pipe pile made of alloy steel such as carbon steel or stainless steel. Also, a clad steel pipe or a clad steel pipe pile in which a metal such as titanium, aluminum, nickel, copper, stainless steel or an alloy steel thereof is laminated on the inner surface, outer surface or both surfaces of the steel pipe and the steel pipe pile can be used. Also, a plated steel pipe or a plated steel pipe pile in which the inner surface, the outer surface, or both surfaces of the steel pipe and the steel pipe pile are plated can be used. The surfaces of these steel pipes and steel pipe piles are subjected to a derusting / pickling treatment or a rust removal treatment such as grid blasting.

It is desirable that the surfaces of the steel pipe (1) and the steel pipe pile (1) that have been subjected to the rust removal treatment be subjected to a surface treatment with a chromate treatment agent in order to obtain better corrosion protection. The chromate film is formed by applying a chromate treatment agent to the surface of the rust-removed metal with a roll, brush, etc.
It is formed by baking. Good results are obtained when the chromate film has a thickness of 1000 mg / m ² or less in terms of the total amount of chromium deposited after heating and baking. 1000mg
/ M ² , the adhesion between the primer layer and the metal decreases.

[0010] A primer layer (2) is formed on the surface of the surface-treated steel pipe in order to obtain greater adhesive strength and better corrosion resistance. As the primer layer, an epoxy primer layer made of a reaction-curable epoxy is most suitable. The epoxy primer layer is formed by applying a liquid or powdery reaction-curable epoxy made of a mixture of an epoxy, a curing agent and a pigment by a method such as ironing or spraying, and then applying a high-frequency induction heating device to the steel pipe for 120 to 25 times.
Heat to 0 ° C. to cure and form. Good results are obtained when the thickness of the epoxy primer layer is 5 to 200 μm or less. If it is less than 5 μm, the adhesion to the steel material is insufficient, and if it exceeds 200 μm, the low-temperature impact resistance decreases.

As the polyethylene adhesive layer (3), any material can be used as long as it has excellent adhesiveness with the primer layer (2) and fusion property with the polyethylene layer (4).
The use of maleic anhydride-modified polyethylene obtained by graft-polymerizing maleic anhydride to polyethylene is preferable because of excellent adhesion to the primer layer. Good results are obtained when the thickness of the polyethylene adhesive layer (3) is 0.02 to 1.0 mm. If it is less than 0.02 mm, the adhesive strength with the primer layer is insufficient. Further, if it exceeds 1.0 mm, it is not preferable from the viewpoint of economy. As a method for forming the polyethylene adhesive layer, a T-die method of extruding and coating a molten modified polyethylene from a T-die is preferable. In this case, the polyethylene adhesive is the lower layer using a two-layer T-die,
It is also possible to simultaneously extrude the polyethylene adhesive layer (3) and the polyethylene layer (4) by extruding the two layers integrally so that the polyethylene is the upper layer.

For the polyethylene layer (4), low density, medium density and high density commercially available polyethylene can be used. Further, a color pigment, an antioxidant, an ultraviolet absorber, a lubricant, a flame retardant, an antistatic agent, and the like can be mixed and used according to the application. As shown in FIG. 6, a method for forming a polyethylene layer (4) is a preheated steel pipe on which a primer layer and a polyethylene adhesive layer are transported in the tube axis direction while rotating on a skew-turning type transport device (14). (1
In 1), melted polyethylene was coated with a T-die (1
It is extruded into a sheet shape using 2), covered, and pressed by a rubber roll (15) to form. If the thickness of the polyethylene layer (4) is 0.3 mm or more, sufficient corrosion resistance can be obtained. Further, in order to prevent poor molding and oxidative deterioration of polyethylene during coating, it is desirable that the temperature of the extruded molten polyethylene be in the range of 160 ° C to 260 ° C.

The surface of the polyethylene layer (4) has a depth of 0.1 to 3 mm in order to further improve the shearing adhesion with the fiber reinforced plastic or mortar to be laminated.
A spiral depression (6) having a width of 3 to 100 mm is formed. As shown in FIG. 5, the tapered material (5) in the spiral depression (6) on the surface of the polyethylene layer (4) is still solidified immediately after the polyethylene coating by the T-die. It is formed by spirally winding 0.1-3 mm into the surface of the unexposed polyethylene layer, cooling it, and removing the tape-like material (5) after the polyethylene layer has solidified. In order to make the tape-shaped object (5) bite into the polyethylene layer surface, the tape-shaped object (5) is wound and then pressed with a rubber roll, or an appropriate tension is applied when the tape-shaped object (5) is wound. You can also wrap it.

The material and the shape of the tape-shaped material that can be used are those which do not adhere to or fuse with the molten polyethylene and have heat resistance. After removal from the polyethylene surface, the surface has a depth of 0.1 to 3 mm and a width of 3 mm. Any material may be used as long as it has a cross-sectional shape capable of forming a spiral depression of about 100 mm. For example, a silicone rubber tape, a Teflon tape, a polyester tape, an aluminum wire, a hemp string and the like can be used.
The shape of the spiral depression (6) is determined by the shape of the tape-shaped object (5) used and the degree of biting into the polyethylene layer. The effect of improving the shear adhesion is insufficient.

Further, the effect of improving the shearing adhesive force increases as the depth of the recessed portion is increased, but when the polyethylene layer (4), which is an anticorrosive layer, is penetrated, the anticorrosive property is reduced. Therefore, the maximum depth is desirably not more than half of the thickness of the polyethylene layer (4) and not more than 3 mm. When the width of the spiral depression is 3 mm or more, a sufficient effect of improving the shear adhesion can be obtained. If the width is 3 mm or less, when the outer surface coating is applied, the flow of the coating material into the depressed portion is insufficient, so that the shear adhesive strength is not significantly improved. Note that the maximum width is smaller than the helical pitch width. Further, if the width of the depression is increased, a large number of tape-shaped objects (5) are required. Therefore, the width is desirably 100 mm or less from an economic viewpoint. The pitch width of the helical depression is determined by the outer diameter of the steel pipe and the skew turning roll type transfer device (13).

On the surface of the polyethylene layer (4) having the spiral depression (6), a glass fiber reinforced polyester layer (7) or a glass fiber reinforced polyester layer (7) as a protective layer for the purpose of preventing damage to the coating during transportation, construction and construction. The glass fiber reinforced urethane elastomer layer (7) is laminated. When the coated steel pipe is used submerged in the bottom of the sea or river, a mortar layer (7) is laminated to increase the weight. The glass fiber reinforced polyester layer (7) and the glass fiber reinforced urethane elastomer layer (7), which are protective layers, are formed on the surface of the polyethylene layer having a spiral depression by hand lay-up, spray-up, or the like. For example, a glass chop strand mat, a glass roving cloth, or the like is wound around a polyethylene-coated steel pipe having a spiral depression, and after being impregnated with a polyester resin or a urethane elastomer using a brush and a roller, curing and curing are performed.

In the case of the spray-up method, a glass roving cut into an appropriate length and a polyester or urethane elastomer are simultaneously sprayed onto the surface of polyethylene having a spiral depression to be cured. The thickness of the protective layer can be set arbitrarily according to the required impact resistance and wear resistance. When the mortar layer (7) is laminated, mortar made of Portland cement, sand, water, an admixture, or the like is coated on the surface of the polyethylene layer having a spiral depression by a centrifugal lining method, and cured and cured. The thickness of the mortar layer can be arbitrarily set according to the required weight increase.

If it is necessary to color the coating in order to harmonize the heavy duty anticorrosion coated steel pipes and heavy duty anticorrosion coated steel pipe piles with the surrounding scenery, a fiber reinforced plastic layer (7)
Alternatively, the mortar layer (7) may be preliminarily blended with an organic or inorganic coloring pigment, colored and laminated. In order to further improve the smoothness and gloss of the appearance, as shown in FIG. 4, a colored layer (8) of the same color as the protective layer is laminated on the surface of the protective layer (7) colored in an arbitrary color. I do. Coloring layer (8)
As the coating material used, a commercially available acrylic resin or fluororesin is suitable from the viewpoint of performance and cost. in this case,
It is sufficient that the thickness of the colored layer (8) is about 10 to 200 μm.

When a long-term weather resistance is required for the protective layer (7), the outer surface of the protective layer (7) is colored with a white acrylic resin layer (9) and an arbitrary color as shown in FIG. When the colored layer (10) made of a fluororesin layer is laminated, the deterioration of the protective layer (7) due to ultraviolet rays or moisture can be suppressed, so that the durability can be improved. In this case, a white acrylic resin layer (9) and a colored layer (10) made of fluororesin
If the total film thickness is about 10 to 200 μm, excellent weather resistance can be obtained. Hereinafter, the present invention will be described in detail by way of examples in which a polyethylene-coated steel pipe is coated with glass fiber reinforced polyester as a protective layer.

[0020]

【Example】

(A) Manufacture of polyethylene-coated steel pipe The outer surface of a steel pipe (SGP250A x 5500 mm length x 6.6 m thickness) was rust-removed by blast treatment, and a chromate treatment agent (the weight ratio of trivalent chromium to all chromium in the aqueous solution was 0. 4, a weight ratio of silica of 2.0 and a weight ratio of phosphoric acid of 1.0) were applied with a brush and dried. The total chromium deposition amount of the chromate film was 550 mg / m ² . The chromate-treated steel pipe is placed on a skew-turning transfer device,
While rotating, it was conveyed at a speed of 0.5 m / min in the tube axis direction. On the outer surface of this steel pipe, an epoxy primer (Eicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd .: 100 parts by weight,
A mixture of 50 parts by weight of Epomate B-002 manufactured by Yuka Shell Epoxy Co., Ltd. and 3 parts by weight of fine particle silica) was spray-coated. The steel pipe was heated by high frequency induction heating so that the surface temperature became 200 ° C., and the epoxy primer was cured. The thickness of the epoxy primer layer was 0.05 mm.

The surface was extrusion-coated with a T-die with a modified polyethylene (a modified polyethylene obtained by modifying a homopolymer of ethylene with maleic anhydride, and the amount of maleic anhydride added to 1 g of the modified polyethylene was 1 × 10 −5 mol). .
The thickness of the modified polyethylene layer was 0.15 mm. Subsequently, low-density polyethylene (density 0.92, compounded with 2.5% by weight of carbon black) was extruded at 220 ° C. and covered with a T-die having a die lip width of 180 mm. At this time, the pitch was adjusted so that the steel pipe surface was double-coated with the sheet-like polyethylene. Immediately after the coating, a roll made of silicone rubber was pressed and pressed. Immediately after this, a silicone rubber tape having a cross section of 5.0 mm and a thickness of 2.0 mm was wound around the surface of the polyethylene layer while applying a tension of 100N. Air-cooling and water-cooling were performed to obtain a polyethylene-coated steel pipe wound with a silicone rubber tape spirally biting. The tape was removed to obtain a polyethylene-coated steel pipe having a spiral depression. The thickness of the polyethylene layer was 2.5 mm. The maximum depth of the spiral depression was 1.0 mm, the width was 5.0 mm, and the spiral pitch was 50 mm. For comparison, a coated steel pipe having a spiral depression with the same shape was manufactured by changing the conveying speed of the steel pipe to 0.1 to 2.0 m / min. Also,
Without changing the conveying speed of the steel pipe, the shape of the silicone rubber tape used was changed, and a coated steel pipe was formed in which the depth and width of the spiral depression on polyethylene were changed.

(B) Coating of Glass Fiber Reinforced Polyester Layer A glass chop strand mat was wound around the polyethylene-coated steel pipe manufactured in (a), and a polyester resin was impregnated thereon using a brush and a roller. Further, a glass roving cloth was wound thereon, and the polyester resin was again impregnated from above using a brush and a roller to flatten the surface, and then the polyester resin was cured. This operation was repeated to form a glass fiber reinforced polyester layer having a thickness of 30 mm on the outer surface of the polyethylene layer, to obtain a target heavy-corrosion-coated steel pipe.

(C) Measurement of shear adhesive strength In order to evaluate the shear adhesive strength between the polyethylene layer and the fiber-reinforced polyester layer of the heavy-corrosion-coated steel pipe obtained in (b), as shown in FIG. The polyester layer portion (17) is supported by a cradle (19), a metal plate (18) is applied to the inner steel pipe and the polyethylene layer (16), and a load is gradually applied to the metal plate (18). The load when the glass fiber reinforced polyester layer peeled was measured. Then, the obtained load was divided by the surface area of the polyethylene layer to determine the shear adhesive strength per unit area.

Comparative Example 1 The outer surface of a steel pipe having the same size as that of the example was rust-removed by blast treatment, and chromate treatment was performed in the same manner as in the example. It was placed on a skew-turning type transport device, transported at a speed of 0.5 m / min in the tube axis direction while rotating, and subjected to epoxy primer coating, steel tube heating, and modified polyethylene coating. Subsequently, the same polyethylene as in the example was covered with a T-die having a die lip width of 180 mm. Immediately after the coating, a roll made of silicone rubber was pressed and pressed. further,
Spraying the same polyethylene pellets as the polyethylene used for coating at a rate of 100 per 100 cm2 of coating,
After compression bonding with a roll made of silicone rubber, the mixture was cooled to obtain a polyethylene-coated steel pipe to which polyethylene pellets had been fused. The adhesion density of the pellet is 100cm2
Approximately 60 pieces. 0.1 ~
Perform the same operation as above, changing to 2.0 m / min,
Polyethylene coated steel pipes with different degrees of pellet attachment were obtained. The polyethylene-coated steel pipe was coated with glass fiber reinforced polyester in the same manner as in Example (b), and the shear adhesion was measured in the same manner as in Example (c).

Comparative Example 2 The outer surface of a steel pipe having the same size as that of the example was rust-removed by blasting, and was subjected to a chromate treatment in the same manner as in the example. It was placed on a skew-turning type transport device, transported at a speed of 0.5 m / min in the tube axis direction while rotating, and subjected to epoxy primer coating, steel tube heating, and modified polyethylene coating. Subsequently, the same polyethylene as in the example was covered with a T-die having a die lip width of 180 mm. Immediately after the coating, a roll made of silicone rubber was pressed and pressed. further,
A steel roll having a large number of protrusions with a height of 5 mm and a square of 5 mm on a side is pressed against the surface of the polyethylene layer, and the unevenness of the roll surface is transferred to the surface of the polyethylene layer, and a number of recesses are formed on the surface by cooling. The obtained polyethylene coated steel pipe was obtained. The density of the concave portions on the surface of the polyethylene layer was 100 per 100 cm 2, and the maximum depth of the concave portions was about 0.2 mm. 0.1 ~
Perform the same operation as above, changing to 2.0 m / min,
Polyethylene-coated steel pipes having different degrees of formation of concave portions were obtained.
The polyethylene-coated steel pipe was coated with glass fiber reinforced polyester in the same manner as in Example (b), and the shear adhesion was measured in the same manner as in Example (c).

The results of the obtained shear adhesion are summarized in Tables 1 and 2. Table 1 shows the dependence of the shearing adhesive force on the shape of the irregularities on the surface of the polyethylene layer when the conveying speed of the steel pipe is constant. Table 2 shows the dependence of the shear adhesion on the conveying speed of the steel pipe. From Table 1, a heavy-corrosion-coated steel pipe and a heavy-corrosion coating in which a primer layer was provided on the surface of a steel pipe subjected to rust removal treatment, and a polyethylene adhesive layer, a polyethylene layer and a fiber-reinforced plastic layer or a mortar layer were sequentially laminated thereon. In the steel pipe pile, by forming a spiral depression having a depth of 0.1 to 3 mm and a width of 3 to 100 mm on the surface of the polyethylene layer, a heavy corrosion-resistant coated steel pipe and a heavy corrosion-resistant coated steel pipe pile having excellent shear adhesive strength can be obtained. Can be obtained.

[0027]

[Table 1]

From Table 2, it can be seen that the polyethylene was melted and extruded into a sheet, and the polyethylene was coated with a polyethylene die by means of a T-die for coating the steel pipe conveyed in the axial direction while rotating. A tape-shaped material that does not adhere and adhere and has heat resistance is spirally wound so as to bite into the surface of the polyethylene coating that has not yet been solidified to 0.1 to 3 mm, and then cooled, and the tape is formed after the polyethylene is solidified. By removing the material, irregularities can be formed on the surface of the polyethylene layer without depending on the conveying speed of the steel pipe, and a heavy corrosion resistant coated steel pipe and a heavy corrosion resistant coated steel pipe pile having excellent shear adhesion can be obtained.

[0029]

[Table 2]

[0030]

According to the present invention, a heavy-corrosion-coated steel pipe and a heavy-corrosion-coated steel pipe pile, a method for producing the same, and a production apparatus for the same are provided.
Compared with the conventional heavy duty anti-corrosion coated steel pipe and heavy duty anti-corrosion coated steel pipe pile, the shear adhesion between the polyethylene layer and the protective layer or the mortar layer is higher, and it has an excellent effect of preventing peeling of the coating film. In addition, the method for forming unevenness on the surface of the polyethylene layer required for improving the shear adhesive force is easy, there is no need to lower the operation speed for forming the unevenness, and furthermore, the colored layer is laminated to harmonize with the scenery. Because you can
INDUSTRIAL APPLICABILITY The present invention is useful as a polyethylene-coated steel pipe with a protective layer, a polyethylene-coated steel pipe pile with a protective layer, a polyethylene-coated steel pipe with a mortar coating, and a method and apparatus for producing the same.

[Brief description of the drawings]

FIG. 1 shows a primer layer on the surface of a steel pipe subjected to a rust removal treatment.
Polyethylene adhesive layer and polyethylene layer are sequentially laminated,
Further, a diagram showing a partial cross-section of a heavy-corrosion-coated steel pipe and a heavy-corrosion-coated steel pipe pile wound partially wound with a tape-like object in a spiral shape on the polyethylene layer surface,

FIG. 2 is a view showing a partial cross section of the heavy-corrosion-coated steel pipe and heavy-corrosion-coated steel pipe pile according to claim 1.

FIG. 3 is a view showing a partial cross section of the heavy-corrosion-coated steel pipe and heavy-corrosion-coated steel pipe pile according to claim 2,

FIG. 4 is a diagram showing a partial cross section of the heavy-corrosion-coated steel pipe and heavy-corrosion-coated steel pipe pile according to claim 3;

FIG. 5 is a view showing a partial cross section of the heavy-corrosion-coated steel pipe and heavy-corrosion-coated steel pipe pile according to claim 4;

FIG. 6 is a schematic view showing a method for producing a heavy-corrosion-coated steel pipe and a heavy-corrosion-coated steel pipe pile according to claim 5.

FIG. 7 is a schematic view showing a method for measuring a shear adhesive force.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel pipe or steel pipe pile 2 Primer layer 3 Polyethylene adhesive layer 4 Polyethylene layer 5 Tape-like thing 6 Spiral depression 7 Fiber reinforced plastic layer or mortar layer 8 Colored layer 9 White acrylic resin layer 10 Colored fluororesin layer 11 Primer layer Preheated steel pipe having a polyethylene adhesive layer laminated thereon 12 T-die for coating steel pipe 13 Partition line or partition plate for dividing die lip into right and left 14 Skew turning roll type transfer device 15 Rubber roll 16 Polyethylene coated steel pipe 17 Fiber reinforced Plastic layer or mortar layer 18 pad 19 cradle

Claims (5)

[Claims] 1. A heavy duty corrosion resistant coated steel pipe and a heavy duty corrosion resistant coated steel pipe pile in which a primer layer is provided on the surface of a steel pipe subjected to rust removal treatment, and a polyethylene adhesive layer and a polyethylene layer are sequentially laminated thereon. A heavy corrosion resistant coated steel pipe and a heavy corrosion resistant coated steel pipe pile, wherein a spiral depression having a depth of 0.1 to 3 mm and a width of 3 to 100 mm is formed on the surface. 2. The heavy corrosion resistant coated steel pipe and the heavy corrosion resistant coated steel pipe pile according to claim 1,
A heavy-duty coated steel pipe and a heavy-duty coated steel pipe pile characterized by laminating glass fiber reinforced urethane elastomer or mortar. 3. A heavy-corrosion-coated steel pipe and a heavy-corrosion-coated steel pipe pile, characterized in that a colored layer is laminated on the surface layer of the heavy-corrosion-coated steel pipe and heavy-corrosion-coated steel pipe pile according to claim 2. 4. The heavy corrosion protection coated steel pipe according to claim 3, wherein the colored layer of the heavy corrosion protection coated steel pipe pile is a laminate of a white acrylic urethane resin layer and a colored fluorine resin layer. Coated steel pipe and heavy duty anticorrosion coated steel pipe pile. 5. An outer surface of a steel pipe which is conveyed in the pipe axis direction while rotating is coated while extruding molten polyethylene in a sheet shape, and a tape-like material which is not adhered to or fused with polyethylene is solidified on the surface. A spiral depression is formed on the surface of the polyethylene layer by spirally wrapping around the unexposed polyethylene layer, and after cooling, the polyethylene is solidified and the tape-like material is removed. 5. The method for producing a heavy-corrosion-coated steel pipe and a heavy-corrosion-coated steel pipe pile according to 2, 3, or 4.