JPH11115099A - Polyester-coated steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistance to shock, scratch, and corrosion by applying chromate-treatment to a steel material surface of a specified degree of roughness, and then coating its top layer with a protective corrosion-resistant layer, which is composed of polyester hardening resin containing glass fiber and pigment and having specified thickness and composition. SOLUTION: The surface of steel material 1 is adjusted through surface treatment such as blasting or the like so that 10 average roughness Rz is 45 μm or higher. A chromate-treated layer 2, and a protective corrosion-resistant layer 3 having 2-10 mm thickness composed of polyester hardening resin, which contains 5-40 vol.% glass fiber having length of at least 5 mm, and pigment, where the total combined loaded amount is 43 vol.% or lower, are coated thereon. In the case of marine structure such as steel pipe posts or the like, it is preferable that the entire outer periphery of a part of the longer direction, where violent corrosion is generated by splashes from a tide, is primer treated, and that the heavy corrosion-resistant coating composed of polyethylene or polyurethane is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable when burying steel pipes requiring an anticorrosion coating on the outer surface, or when protecting outer surfaces such as piers and seawalls of ports and rivers such as steel pipe piles, steel pipe sheet piles, steel sheet piles and the like. Polyester-coated steel material that has excellent impact resistance to the impacts generated by throwing stones and other floating materials including ships when casting or after the casting of steel structures, and enables external corrosion protection at low cost Is provided.

[0002]

2. Description of the Related Art Steel pipes, steel pipe piles,
When long-term durability of several decades is required for steel pipe sheet piles, steel sheet piles, etc., a resin such as polyethylene or polyurethane, which is an inexpensive resin that is excellent in various anticorrosion properties such as electrical insulation and chemical resistance, is used. Heavy corrosion protection coated steel materials used as coating materials are manufactured. In particular, in order to secure long-term corrosion resistance and impact resistance for several decades, a coating having a thickness of about several mm is generally used. Heavy corrosion protection coated steel using these coating materials such as polyethylene or polyurethane is extremely excellent in the anticorrosion of the coating, but the strength of the resin itself is low, so it is not enough to give the resin a thickness to improve the impact resistance. There is naturally a limit, and the occurrence of scratches on the coating due to collisions and friction during transportation, storage, and construction has become a problem. For this reason,
In steel pipe piles used in the ocean, anti-corrosion coating is applied only to the splash zone and tidal zone on the highly corrosive sea surface, and the anti-corrosion coating is applied to the underwater part to prevent the occurrence of scratches by omitting the coating . However, for cathodic protection of underwater bare pipes, Al
And the like, there is a problem such as periodic electrode replacement after construction.

As a method of imparting impact resistance to a heavy corrosion-resistant coated steel material, there is a method of improving abrasion resistance and impact resistance by providing a metal layer on a surface layer as disclosed in JP-A-8-300599. In addition, as proposed in Japanese Patent Publication No. 7-006595, in heavy corrosion protection coating on propulsion steel pipes, glass fiber or metal fiber mixed polyester or glass fiber or metal fiber mixed epoxy is used while the corrosion protection coating made of polyethylene or polyurethane resin is kept as it is. Methods have been proposed in which an acrylate layer is used as its protective coating.

[0004]

There is a method for imparting impact resistance to a heavy-duty anticorrosion coating by forming a scratch-resistant coating layer having excellent strength and hardness on its surface layer.
The method of applying a metal coating layer to the surface layer as shown at 59 is effective. However, the metal coating is vulnerable to corrosion, and in the coating process, a mechanical fixing method such as caulking and a working or bending process such as welding are required, and the production efficiency is poor.

[0005] Furthermore, there is a method of selecting an alloy such as titanium as a metal coating material resistant to corrosion, but there is a problem that not only the material cost is high but also processing is more difficult.

On the other hand, as proposed in Japanese Patent Publication No. 7-006595, a glass fiber or metal fiber mixed polyester, or a glass fiber or metal fiber mixed epoxy acrylate is provided on the upper layer of a conventional anticorrosion coating layer made of polyethylene or polyurethane resin. There is a method of forming a high hardness organic resin protective coating having excellent impact resistance, such as using the layer as its protective coating. However, since different kinds of resins are laminated on the anticorrosion coating, the adhesion becomes a problem,
Various methods have been proposed. For example,
When a polyethylene coating is used for the anticorrosion coating, there is a method as described in JP-A-6-146271, in which the protective layer can be coated by embossing the polyethylene surface layer to give physical irregularities. As shown in Japanese Patent Application Laid-Open No. 6-122173, there has been proposed a method of securing impact resistance by interposing a flocked material at the interface, as shown in JP-A-6-122173. However, in each case, a new process is required for strengthening the physical adhesion, and problems in quality control and cost remain.

As described above, various methods for imparting impact resistance to heavy corrosion protection coatings have been proposed, while heavy corrosion protection coatings are required for offshore structures such as piles as described above. In the case of a coating structure combining a conventional anticorrosive coating and a protective coating, it is rare to cover even a submarine part with less corrosion due to the high cost of a complicated production process. In the undersea area, it is sufficient that the coating film has barrier properties, and even simple coating can prevent corrosion, but coating with general tar epoxy etc. does not have impact resistance, so it can not withstand discarded stones etc. Defects occur. Also,
Even in a buried steel pipe, in an environment that is moderate to corrosion of steel materials, an inexpensive anticorrosion coating having impact strength is required.

According to the present invention, in a steel pipe coating having no end peeling problem, anticorrosion in an area with little corrosion is performed at a low cost, and a surface treatment for imparting shear adhesive force is performed even in combination with a conventional anticorrosion layer. The present invention provides an unnecessary polyester anticorrosion coated steel material having impact resistance.

[0009]

Means for Solving the Problems As a means for solving the above-mentioned problem, the present inventors have proposed a method of forming a steel sheet having an average roughness R of 10 points.
After imparting a roughness of 45 μm or more in z and performing a chromate treatment, the upper layer contains a glass fiber having a length of 5 mm or more in a range of 5 to 40 vol%, and the combined total amount of the glass fibers is 43 vol%. It has been found that a polyester-coated steel material excellent in impact resistance, scratch resistance and corrosion resistance can be obtained by coating a protective anticorrosion layer having a thickness of 2 to 10 mm with a polyester cured resin containing a pigment in the following range. Reached.

That is, as shown in the sectional view of FIG. 1, the present invention provides a chromate-treated layer 2 on the surface of a steel material 1 adjusted to have a 10-point average roughness Rz of 45 μm or more by a base treatment such as a blast treatment. A thickness of 5 to 40 vol% of glass fiber having a length of 5 mm or more, and a total thickness of 2 to 2 of a polyester cured resin containing a pigment containing a pigment in a total addition amount of 43 vol% or less.
A polyester-coated steel material characterized by being coated with a protective anticorrosion layer 3 of 10 mm.

Further, as shown in the sectional view of FIG. 2, the surface of the steel pipe 4 is adjusted to have a 10-point average roughness Rz of 45 μm or more by a base treatment such as blast treatment, as shown in the cross-sectional view of FIG. A thickness of 5% by a polyester cured resin containing a pigment containing 5 mm or more of glass fibers in a range of 5 to 40 vol%, and a combined total amount of the pigment in a range of 43 vol% or less.
A protective and anticorrosive layer 3 of 〜１０10 mm is coated.

One of the uses in an offshore structure such as a steel pipe pile is as shown in the axial sectional view of the coated steel pipe in FIG. Both surfaces of a portion 6 coated with a primer 5 and a heavy corrosion protection coating of polyethylene or polyurethane on the entire circumference, and a portion provided with a chromate treatment layer 2 on a steel portion having an average surface roughness Rz of 45 μm or more on the outer surface. A thickness of 2 to 5% by a polyester cured resin containing a glass fiber having a length of 5 mm or more in a range of 5 to 40% by volume, and a combined total amount of the pigment in a range of 43% by volume or less.
What laminated | stacked 10 mm of protective anticorrosion layers 3 in order can be used.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The steel material used in the present invention is a steel pipe for piping,
Alternatively, it is a steel structure used in the ocean or river, such as a steel pipe pile, a steel pipe sheet pile, a steel sheet pile, or the like, and uses carbon steel, alloy steel such as stainless steel, titanium alloy steel, or its clad steel. Plating of zinc, aluminum, nickel, copper, etc. on its surface, alloy plating of zinc-iron, zinc-aluminum, zinc-nickel, zinc-nickel-cobalt,
Alternatively, a steel material obtained by performing dispersion plating in which fine particles of an inorganic substance such as silica or titanium oxide are dispersed in the plating or alloy plating may be used.

As a base treatment of the steel material, a blast treatment is performed by using a sand, a grid, a shot, or the like to remove surface deposits and impart a surface roughness. Since the polyester resin has low adhesion to steel, if the surface roughness is low, the anchor effect is insufficient and the anticorrosion performance is reduced. Therefore, as an index of the surface roughness, the ten-point average roughness Rz indicating the correlation of the adhesion is set to 45 μm or more. When Rz is less than 45 μm, the adhesion between the coating film after immersion and the steel material tends to decrease.

After the blast treatment, a chromate treatment is performed to secure the adhesion between the polyester and the steel material surface. Since polyester has the property of being weak against alkali, peeling is likely to proceed due to corrosion or alkali generated by cathodic protection. Therefore, a chromate-treated layer having a neutralizing and anticorrosive action is essential as a base treatment for the polyester anticorrosive coating. As the chromate treatment agent, one obtained by reducing chromic acid with a reducing agent in a range of 30 to 60% and adding dry silica fine particles at a ratio of 1 to 3 with respect to the total amount of chromium added is used. Silica produced by a wet method generally used for a thin plate or the like is not preferable because of poor adhesion.
Further, phosphoric acid and its compound are added to the main component in a range of 0.5 to 2.5 with respect to the total chromium addition amount, and a silane coupling agent is added in a range of 0.3 to 3 with respect to the total chromium addition amount. When used, the film has excellent peel resistance. The application amount is such that the total chromium adhesion amount is in the range of 100 to 1000 mg / m ² . If the amount of chromium adhered is less than 100 mg / m ² , the anticorrosion properties such as the cathodic peeling resistance decrease, and
If it exceeds 0 mg / m ² , the chromate film itself is brittle, so that the adhesion decreases.

On the surface of the steel material subjected to the above-mentioned undercoating treatment, a glass fiber having a length of 5 mm or more was contained in a range of 5 to 40 vol%, and a pigment was contained in a total added amount of 43 vol% or less. A polyester cured resin layer is formed with a thickness of 2 to 10 mm. For coating the polyester resin layer, a method such as a hand lay-up method, a spray-up method, a cold press method, a filament winding method, or an injection molding using a mold is used. The polyester cured resin used in the present invention may be any resin having an ester bond and a double bond in the molecule, and ortho-, iso-, and bisphenol-based unsaturated polyester resins can be used. Although there is a problem of material cost, a vinyl ester which is chemically stable and has a terminal double bond can also be used. A solution of these polyester resins dissolved in a polymerizable monomer such as a styrene monomer is treated with a peroxide catalyst such as ketone peroxide or hydroperoxide and a promoter such as cobalt, vanadium, manganese or amine. Use a thermosetting resin that cures.

The polyester resin anticorrosion layer is filled with a glass fiber having a length of 5 mm or more. When the length is 5 mm or less, the effect of improving the impact strength by the glass fiber cannot be obtained. There is no particular upper limit on the length when using the filament winding method or glass cloth, but when using short glass fibers in the spray-up method, if the glass fibers are long, the defoaming property of the paint film is reduced. It is desirable to use around the range of ５０50 mm. Further, the addition amount is in the range of 5 to 40 vol%. The addition amount is 5vo
If the amount is less than 1%, the adhesive strength to steel and the impact resistance are reduced. On the other hand, if the added amount exceeds 40% by volume, the anticorrosion property decreases. As the fiber to be added, glass fiber is used because it is excellent in price, resin reinforcing effect, and anticorrosion performance.
In carbon fiber and metal fiber as inorganic fibers other than glass,
The corrosion resistance of the film is reduced due to the conductivity. On the other hand, organic fibers have high shrinkability, and when added alone, the physical properties of the film are reduced, but since the effect of lowering the corrosion resistance due to conductivity is small, the organic fibers may be added in combination with the glass fibers of the present invention. . In addition, an inorganic filler pigment is used in combination with the fiber. The inorganic filler pigment may be any inorganic fine powder that is insoluble in neutral water and has no conductivity, and may be silicon oxide, alumina, titanium oxide, magnesium silicate, calcium carbonate, a chromate compound,
Phosphoric acid compounds, boric acid compounds, or mixtures thereof can be used. When design and weather resistance are required, the polyester resin layer is colored by adding a coloring pigment.
Examples of the coloring pigment used include, for example, cadmium yellow, iron oxide, polyazo yellow, quinophthalone yellow, isoindolinone yellow, quinacridone yellow, vengara red, polyazo brown, azo lake yellow, perylene red, phthalocyanine blue, and phthalocyanine green. , Bengala yellow, cobalt aluminate, aniline black, carbon black, titanium oxide, ultramarine blue, aluminum fine powder and the like. When used outdoors such as in steel piles, the surface layer of the unsaturated polyester is deteriorated by ultraviolet rays. Therefore, a coloring pigment is added in an amount of 0.5% or more to improve the weather resistance and corrosion resistance. In addition, when the surface gel coat coating is performed, adding a coloring pigment only to that portion is economical.
These pigments have a total added amount of 43 in combination with the fiber.
When the content exceeds vol%, the anticorrosion property is reduced.
% (Not including 0%). In addition, 12-4
3 vol% is preferred. In order to provide the polyester resin layer having the above composition with anticorrosion properties and a function as a protective layer, the polyester resin layer has a thickness of 2-1.
A 0 mm film is formed. If the thickness is less than 2mm,
Impact resistance, corrosion resistance, durability, etc. are reduced. On the other hand, if the thickness exceeds 10 mm, not only is it not economical, but also the adhesive strength is reduced.

By successively laminating the above polyester coatings as shown in the sectional view of FIG. 1, a polyester coated steel material having excellent impact resistance, scratch resistance and corrosion resistance can be obtained.

Further, when used as an offshore structure in steel piles, steel sheet piles, etc., as shown in the axial sectional view of the steel pipe pile in FIG. Is provided with a heavy corrosion protection coating 6 of polyethylene or polyurethane. Heavy corrosion protection coating 6 is blast treatment, chromate treatment 2,
The outer surface of the steel material subjected to the primer treatment 5 is laminated with a polyethylene anticorrosion layer extruded and coated via a modified polyethylene adhesive, or the same base treatment and primer treatment are performed, followed by spray coating of polyurethane to form. I do. Thereafter, the 10-point average roughness of the outer surface is 4 in Rz.
A protective and anticorrosive coating layer 3 made of a polyester cured resin containing glass fibers and pigments is sequentially laminated on both the surface of the steel material portion having a thickness of 5 μm or more where the chromate treatment layer 2 is applied and the heavy anticorrosion coating portion 6. With this, even in the case of the heavy-duty anticorrosion coating that does not adhere to the polyester protective coating, the surface between the coating and the bare pipe, and the shearing force generated by driving in due to the adhesion of the polyester layer and the steel material in the bare pipe, can be used. It is possible to manufacture without processing.

[0021]

【Example】

Example and Comparative Example 1 The outer surface of a steel pipe having an outer diameter of 200 A × length 5500 mm × wall thickness 5.8 mm was subjected to grid blasting treatment, scales and the like were removed, and the surface was given a roughness of Rz of 45 μm or more. Thereafter, a chromate treatment agent of chromium-phosphoric acid-silica system adjusted to a chromate reduction rate of 55%, a silica / total chromium ratio of 2.0, and a phosphoric acid / total chromium ratio of 0.5 was added to the total chromium deposition amount. Coating and drying were performed to 150 mg / m ^2, and a base treatment was performed. After this, by spray-up method,
A silane-based 2.3 kg / km glass roving cut with a different fiber length and an unsaturated polyester resin mixed and added in advance with a calcium carbonate-filled pigment in a different amount are peroxide-oxidized. The mixture was spray-mixed while the curing agent containing the catalyst was added, and spray coating was performed at the same time. Thereby, Comparative Example 1-1 which does not add glass fiber, Examples 1-1 to 1-5 and Comparative Examples 1-2 to 3 in which the fiber length was cut to 3 to 70 mm with the glass fiber addition amount being 12 vol%, and The glass fiber length was cut to 12.5 mm to make the addition amount 12 vol%, and the filled pigment was 17 to 4%.
Examples 1-2 and 1-6 to 1 added in a range of 2 vol%
7 and polyester coated steel pipes of Comparative Examples 1-4 to 5 were produced. The coated steel pipe was cut and the penetration energy of the coating was measured by a falling weight impact test specified in ASTM G14. In addition, as an evaluation method of anticorrosion properties, an adhesion evaluation test after immersion in warm water and a cathode peel test were performed. In the hot water immersion test, after immersion in hot water at 60 ° C. for 800 hours, a cut is made in the polyester anticorrosion layer up to the steel surface, a jig for measuring vertical adhesion is adhered via an adhesive, and vertical adhesion is measured by pull-off measurement. Power was evaluated. Cathode peel test is 3% in electrolyte
Using -NaCl, a voltage of 1.5 V was applied by a copper sulfate standard electrode, and a test was performed at a temperature of 60 ° C for 30 days. Thereafter, the average peel distance at four points from the initial through-hole (diameter: 9 mm) of the coating was measured and evaluated.

Table 1 shows the results of evaluating the effect of the glass fiber length in the spray-up method and the effect of the total amount of glass fiber and pigment added. The glass fiber length shows excellent performance only at the fiber length of 5 mm or more, which is the range of the present invention. Further, in the spray-up method, when the cut length exceeds 50 mm, the anticorrosion property tends to gradually decrease due to the decrease in the defoaming property described above. If the total amount of the fiber and the filler exceeds 43 vol% with respect to the polyester resin, the anticorrosion property decreases.

[0023]

[Table 1] Example and Comparative Example 2 Grid blasting is applied to the outer surface of a steel pipe having an outer diameter of 200 A x length 5500 mm x wall thickness 5.8 mm to remove scales and the like, so that the surface has a roughness with a 10-point average roughness Rz of 45 m or more. Chromate treatment agent adjusted to a chromate reduction ratio of 30%, a silica / total chromium ratio of 1.5, and a silane coupling agent / total chromium ratio of 0.5, with a total chromium adhesion of 1000 mg / m2. ^A base treatment was performed so as to be ² . Thereafter, a 2.3 kg / km glass roving having a silane-based surface treatment cut by a spray-up method and cut to a length of 5 mm was added, and the amount of addition was changed.
An iso-unsaturated polyester resin to which 0.7 vol% of a coloring pigment is added and a curing agent containing a peroxide catalyst are spray-mixed simultaneously while spray-mixing, and the thickness is 3 mm.
An anticorrosive layer of an iso-based unsaturated polyester was formed. Thus, polyester-coated steel pipes of Examples 2-1 to 5 and Comparative examples 2-1 to 3 in which the glass fiber addition amount was added in the range of 0 to 50.6 vol% were produced. This coated steel pipe was cut and subjected to a falling weight impact test, a cathode peeling test, and an adhesion evaluation test after immersion in hot water under the same conditions as in Example 1.

Table 2 shows the results of evaluating the effect of the amount of glass fiber added. The amount of glass fiber added is within the scope of the present invention.
Excellent performance is shown at ４０40 vol%. When the amount of the fiber is less than 5 vol% with respect to the polyester resin, the adhesive strength and the strength of the resin are reduced, so that various properties are reduced. On the other hand, if the added amount exceeds 40% by volume, the anticorrosion property decreases.

[0025]

[Table 2] Example and Comparative Example 3 The outer surface of a steel pipe having an outer diameter of 200 A × length 5500 mm × wall thickness 5.8 mm was subjected to grid blasting treatment, scales and the like were removed, and the surface was roughened to have a 10-point average roughness Rz of 45 μm or more. After that, a chromate treatment agent adjusted to a chromate reduction ratio of 40% and a silica / total chromium ratio of 2.5 was subjected to a base treatment so that the total chromium deposition amount was 500 mg / m ² . Thereafter, a 3.5 kg / km-thick glass roving having been subjected to a silane-based surface treatment by a spray-up method and cut to a length of 25 mm was added in an amount of 12 vol.
%, A coloring pigment of 0.7 vol%, a bisphenol-based unsaturated polyester resin to which 15 vol% of talc is added as a filling pigment, and a curing agent containing a peroxide catalyst are simultaneously sprayed and sprayed. Coating was performed, and the coating thickness was changed to form an unsaturated polyester anticorrosion layer.

Thus, polyester-coated steel materials of Examples 3-1 to 4 and Comparative examples 3-1 to 3 in which the thickness of the unsaturated polyester anticorrosive layer was in the range of 0.5 to 15 mm were produced.
This coated steel pipe was cut and subjected to a falling weight impact test, a cathode peeling test, and an adhesion evaluation test after immersion in hot water under the same conditions as in Example 1.

The results of evaluating the effect of the thickness of the unsaturated polyester anticorrosion layer are shown in Table 3. From the results shown in Table 3, it can be seen that the polyester layer exhibits a function as an anticorrosion layer when the thickness exceeds 2 mm. In addition, the higher the thickness, the higher the impact resistance, but if the thickness exceeds 10 mm, the adhesion decreases.

[0028]

[Table 3] Example and Comparative Example 4 The outer surface of a steel pipe having an outer diameter of 200 A × length 5500 mm × wall thickness 5.8 mm was subjected to grid blasting. At this time, by changing the type (particle size) of the grid particles to be used, the 10-point average roughness Rz is 39.8, 46, respectively.
One steel pipe each having a roughness of 54.7 or 72.5 μm was prepared. A chromate treating agent was applied to half of the length of the steel pipe in the longitudinal direction so as to have a total chromium adhesion of 150 mg / m ^2, and was dried.

The outer surface of each of these steel pipes was subjected to a silane-based surface treatment by a spray-up method at 2.3 kg / km.
A glass roving having a count of 12.5 mm and a fiber length adjusted to 12 vol%, an ortho-unsaturated polyester resin containing 30 vol% calcium carbonate-filled pigment, and a peroxide catalyst. Is spray-coated at the same time while spray-mixing a curing agent containing a to form a 3 mm thick unsaturated polyester anticorrosion layer,
The polyester anticorrosion-coated steel materials of Examples 4-1 and 2 and Comparative examples 4-1 and 5 were produced. This coated steel pipe was cut and subjected to a falling weight impact test, a cathode peeling test, and an adhesion evaluation test after immersion in hot water under the same conditions as in Example 1.

The results are shown in Table 4.

As is clear from the results shown in Table 4, excellent adhesion and resistance were obtained only in the range of Examples of the present patent application in which the surface roughness was set to 45 μm or more in terms of the 10-point average roughness Rz and chromate treatment was performed. Cathodic peelability is obtained.

[0032]

[Table 4] Example and Comparative Example 5 After performing grid blast treatment on the outer surface of a steel pipe having an outer diameter of 200 A x length of 5500 mm x wall thickness of 5.8 mm to remove scale and the like to impart roughness to the surface, a chromate treatment agent was added to all chromium. Coating and drying were performed so that the amount of adhesion was 50 mg / m ^2, and a base treatment was performed. Next, 10% by weight of titanium oxide
An epoxy primer using the added amine-based curing agent was spray-coated so as to have a film thickness of 30 to 60 μm, and the steel material was heated to cure the primer. Next, the steel pipe was rotated and conveyed, and on its surface, a maleic anhydride-modified polyethylene adhesive and carbon black were added by 2% from a T-die.
The compounded low-density polyethylene was integrally coated in two layers, the polyethylene adhesive layer was laminated in a thickness of 200 μm and the polyethylene layer was laminated in a thickness of 2.5 mm to produce a conventionally known polyethylene heavy corrosion protection coated steel material of Comparative Example 5-1. . In addition, a 2.3 kg / km-count glass roving having a silane-based surface treatment applied to the outer surface of the steel pipe of Comparative Example 5-1 by a spray-up method was cut into a fiber length of 12.5 mm, and the added amount was 12%.
vol.% and an ortho-unsaturated polyester resin containing 30 vol% of calcium carbonate-filled pigment and a curing agent containing a peroxide catalyst are spray-mixed at the same time while spray-mixing. A polyethylene-coated steel pipe having a 3 mm unsaturated polyester anticorrosion layer and a polyester protective layer of Comparative Example 5-2 was produced.

Further, a blasting and chromating agent was applied to a steel pipe having several portions partially coated with polyethylene by the same method in a total chromium deposition amount of 150 mg.
/ M ² , followed by a base treatment after coating and drying, and spray-coating of a polyester protective anticorrosion layer by the spray-up method used in Comparative Example 5 to produce a polyester-coated steel pipe of Example 5. These coated steel pipes were cut and subjected to a falling weight impact test and a cathode peeling test under the same conditions as in Example 1. On the other hand, with the coated steel pipes of Comparative Example 5-2 and Example 5 holding the steel pipe portion and the polyester protective layer as shown in FIG. The maximum load was measured by a shear punching test of the high-strength layer and the steel pipe at a rate of / min.
Divide the obtained load by the outer surface covering area of the specimen,
The shear adhesion per unit area was calculated. Table 5 shows the results.

As is clear from the results in Table 5, the conventionally known polyethylene-coated steel pipe of Comparative Example 5-1 has good cathode peeling resistance, but has low impact resistance. On the other hand, the coated steel pipe of Comparative Example 5-2 in which the polyester protective layer was coated on the upper layer was excellent in impact resistance, but the shearing force between the polyester protective layer and the polyethylene anticorrosion layer was low. On the other hand, Example 5 having the coating configuration of the present invention has sufficient shear strength until partial destruction of the polyester coating occurs, and there is no problem of occurrence of coating displacement at the time of pile driving.

[0035]

[Table 5]

[0036]

As is clear from the examples, the polyester-coated steel material of the present invention is provided with anticorrosion coating by imparting adhesion to steel and anticorrosion to the polyester protective layer by imparting surface roughness and chromate treatment. As a function. Further, since it has excellent impact resistance as compared with the conventional heavy-corrosion-coated steel, it can be prevented from being damaged at the time of construction, collision of a ship or the like, and waste stones. In addition, since the number of coating steps is small and the production is easy, an inexpensive product with excellent production efficiency can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing a partial cross section of a polyester-coated steel material of the present invention.

FIG. 2 is a view showing a partial cross section of the polyester-coated steel pipe of the present invention.

FIG. 3 is a view showing an axial section of the polyester-coated heavy steel pipe of the present invention.

FIG. 4 is a cross-sectional view showing a shear test method for a polyester coating layer and a conventional anticorrosion coating layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel material 2 Chromate layer 3 Protective anticorrosion coating layer by polyester resin containing glass fiber 4 Steel pipe 5 Primer layer 6 Polyethylene or polyurethane anticorrosion layer 7 Sea surface 8 Sea bottom 9 Steel pipe pushing support 10 Polyester coating support

Claims (2)

[Claims] 1. An outer surface having a 10-point average roughness Rz of 45 μm
After the chromate treatment is applied to the steel material having the roughness as described above, the upper layer contains a glass fiber having a length of 5 mm or more in a range of 5 to 40 vol%, and the combined total amount of the glass fibers is 43 vol. %. A polyester-coated steel material coated with a protective anticorrosion layer having a thickness of 2 to 10 mm by a polyester cured resin containing a pigment in a range of not more than 10%. 2. A portion provided with a heavy-duty polyethylene or polyurethane anticorrosion coating on a part of its length, and a remaining surface having a roughness having a 10-point average roughness Rz of 45 μm or more, and then subjected to chromate treatment. The steel material contains a glass fiber having a length of 5 mm or more in a range of 5 to 40 vol%, and a total added amount of the combined fiber is 43 to 1% in a range of 43 vol% or less.
A polyester-coated steel material coated with a protective anticorrosive layer of 0 mm.