JP2000303188A - Heavy corrosion protection coated steel for offshore structures - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In the case where conventional products have excellent corrosion protection at low cost and equivalent, and when used together with cathodic protection without repair for construction flaws etc. in the middle of the sea However, an object of the present invention is to provide a heavy corrosion protection coated steel material for marine steel structures which exhibits excellent corrosion protection performance and economic efficiency with little consumption of the anode. SOLUTION: In a steel material for an offshore steel structure, a conventional heavy-corrosion-coated portion 2 having a film thickness of 1 mm or more is provided in the vicinity of a corrosion area from the sea atmosphere to the lowest sea level below -1 m. The thickness is 0.3-1.
An anticorrosion coating portion 3 having a thickness of 0 mm is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a marine steel structure requiring external corrosion protection due to a severely corrosive environment such as a steel pipe pile, a steel pipe sheet pile, a steel sheet pile, a harbor or a river pier, or a seawall. The present invention relates to a heavy corrosion protection coated steel material for ensuring the corrosion resistance of marine structures, and more particularly, to a heavy corrosion protection coated steel material for marine structures that can secure corrosion protection for a long time at a lower cost even when there is no electrolytic protection in the sea part or in combination with the electrolytic protection. .

[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., resins such as polyolefin or polyurethane, which are inexpensive resins that are excellent in various corrosion protection properties such as electrical insulation and chemical resistance, are used. Heavy corrosion protection coated steel materials used as coating materials are manufactured. In particular, in order to ensure long-term corrosion resistance and impact resistance for several decades, the thickness is several mm
Coated layers are generally used. It is preferable from the viewpoint of anticorrosion technology to apply heavy corrosion protection over the entire outer surface, but due to problems such as flaws during construction, heavy corrosion protection is carried out only within a few meters around the tidal zone where corrosion is severe. May be. It is effective from an economic point of view to apply heavy anticorrosion coating only to severe parts of the corrosive environment,
The corrosive environment of marine structures depends on the environment in which steel is installed (temperature,
(Corresponding to water quality, water depth, soil, waves, etc.), and due to an environmental change from the time of the anticorrosion design, the unsealed underwater portion may be more likely to corrode than designed. Therefore, in order to prevent corrosion of the undersea part, which is a bare steel material, a method using electrolytic protection is also used. However, the general sacrificial anode method has a problem that replacement due to exhaustion of electrodes requires maintenance costs. To solve this problem, an electric method using a solar cell is proposed as in Japanese Patent Application Laid-Open No. 4-346683, but there are many problems such as stability of the solar cell device, securing of a place, and cost. Further, in the external power supply method, it is necessary to monitor the electrochemical potential, and there is a problem that it is difficult to completely perform long-term maintenance.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a marine steel structure having a high corrosion resistance equivalent to a heavy corrosion protection coating even in the sea, in contrast to the cost and flaw resistance which were problems of the conventional heavy corrosion protection coating. By applying a coating on the entire surface, the initial investment cost, which was a problem when the entire steel material was coated with a heavy corrosion protection coating, was suppressed, and there was almost no consumption of the sacrificial anode when combined with cathodic protection. Therefore, a special anticorrosion method and monitoring are not required, and long-term anticorrosion can be realized at low cost.

As a means for solving the above-mentioned problem, the present inventors provide a highly durable thin film coating equivalent to the heavy duty anticorrosion coating in the sea where corrosion is relatively mild in addition to the conventional heavy duty anticorrosion coating. We perform anticorrosion by doing. It is another object of the present invention to provide an anticorrosion system which can be used in combination with the entire surface coating and the cathodic protection, which have not been performed conventionally.

[0005]

That is, the gist of the present invention is as follows. (1) After the surface treatment of steel for offshore structures, it is mainly 1 mm or more in the area from the atmospheric part of the sea to the lowest sea level -1 m or more, and 0.3 in the underwater area.
A heavy corrosion-resistant coated steel material for marine structures, characterized in that the entire outer surface to be corroded is coated by applying a coating or an organic resin coating having a thickness of up to 1.0 mm. (2) After a ground treatment is carried out on a steel material for an offshore structure, a primer layer and a urethane resin anticorrosion layer are mainly formed on the steel material in an area from the sea air portion to a minimum of -1 m below the sea level, at least 1 mm in the sea. A heavy corrosion-resistant coated steel material for marine structures, characterized in that a primer layer and a urethane resin anticorrosion layer are entirely coated on a steel material so as to have a thickness of 0.3 to 1.0 mm. (3) After a base treatment is performed on a steel material for an offshore structure, a primer layer, a modified polyolefin adhesive, and a polyolefin layer are sequentially formed on the steel material in the region from the sea surface atmosphere to the lowest sea level below -1 m or more. 1 mm or more, in the submarine region part, on a steel material, a primer layer, a modified polyolefin adhesive layer as a single anticorrosive layer, or in addition to the modified polyolefin adhesive layer to perform polyolefin coating, and a film thickness of 0.3 to 1.0 mm Heavy corrosion-resistant coated steel for offshore structures, characterized by being coated on the entire surface.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the construction sectional view of FIG. 1, the present invention is applied to a marine steel structure 1 in the vicinity of an area where concentrated corrosion occurs from the sea atmosphere to a minimum of -1 m below sea level. Is a conventional anticorrosion coating 2 having a film thickness of 1 mm or more, and a thickness of 0.3 to 1.
A heavy corrosion protection coated steel material for offshore structures having a corrosion protection coating portion 3 having a thickness of 0 mm is provided.

The heavy duty anticorrosion coating used herein is a steel material which has been subjected to a base treatment and is mainly coated with conventional polyolefin or polyurethane which is excellent in anticorrosion properties and cost, but is suitable for the corrosive environment which is the essence of the present invention. Any resin having excellent anticorrosion properties may be used as long as the thickness of the heavy anticorrosion film can be arranged inclining in the depth direction of the ocean. In addition, as for the conventional coating length of heavy corrosion protection coating of 1 mm or more, in the case of bare steel material, concentrated corrosion may occur up to a depth of about -2 m. It is desirable to do. In addition, regarding the upper covering range, since there is no effect of the electrolytic protection in the atmosphere, it is desirable to cover a portion overlapping with the upper covering structure such as concrete.

On the other hand, a 0.3-1.0 mm thick thin film coating in the underwater area means that, if the same resin as the conventional anticorrosion coating is used, it is possible to use a common base treatment, primer treatment, etc. Therefore, since there is no problem of adhesion of different resins at the boundary between portions having different thicknesses, a coating having stable quality can be formed. As the thickness of the coating,
Secure a thickness of 0.3 to 1.0 mm. In the underwater part, a coating thickness of 0.
A film thickness of 3 mm or more is required. The thickness of the film is preferably 1 mm or less from an economic viewpoint. Further, by applying the coating to the underwater portion, the reliability of the thick-film coated portion from the sea air portion to the lowest sea level -1 m or more is also improved. When the corrosive environment is severe, the thickness may be changed on the taper in the depth direction as shown in FIG. In addition, it is desirable to coat the coating tip up to the soil so as not to be a starting point of corrosion and peeling.

Any type of steel material may be used for corrosion protection, but insufficient base treatment may cause blistering.
Sufficient undercoating is performed on the entire coating area. Processing is dirt,
Any method may be used as long as the oxide film is sufficiently removed. Specifically, a degreasing / pickling treatment and a blast treatment are performed for a sufficient time. Further, a chemical conversion treatment such as a chromate treatment is performed as necessary to improve the adhesion to the organic resin and the water-peeling resistance. Thereafter, a primer layer in which an organic resin and a pigment are mixed is applied within a range of 30 to 500 μm. The area from the sea atmosphere to the lowest sea level -1 m is coated with anticorrosion to form a total film thickness of 1 mm or more.
Coating is performed in the range of mm. For example, in the case of polyolefin coating, a heated steel material is coated with a polyolefin anticorrosion coating layer via a modified polyolefin adhesive layer, and in the case of polyurethane, a polyurethane anticorrosion coating layer is directly applied. When using a polyolefin anticorrosion coating layer, since the modified polyolefin adhesive layer also functions as an anticorrosion coating, 0.3 to 1.0 mm
If the thickness of the modified polyolefin adhesive layer can be secured, the modified polyolefin adhesive layer can be used as an anticorrosion coating. FIG. 3 is a cross-sectional view showing an example of the coating structure of a typical polyolefin anticorrosion coated steel material of the present invention, and FIG. 4 is a cross-sectional view showing an example of a polyurethane anticorrosion coating.

[0010]

<Example 1> Outer diameter 200A x length 8000mm
× Grid blasting was performed on the outer surface of the steel pipe having a wall thickness of 5.8 mm to remove scales and the like, and then a chromate treatment of silica chromate was applied to the entire surface to be coated and dried to perform a base treatment. Thereafter, the steel pipe is heated to 200 ° C. by induction heating, and the liquid epoxy resin-based primer is heated to 30 to 70 μm.
Was spray-coated so that the film thickness range was as follows. Thereafter, the modified polyethylene adhesive layer was extruded using a T die,
The entire surface was covered in a gaiter shape so as to have a thickness of 400 μm. At the same time, a 2.1 mm polyethylene coating was coated on the adhesive layer at the same time as the adhesive using another T-die from a position 5.0 m from the pipe end. Thereby, the anticorrosion layer of 0.4 mm or more from 0 to 5.0 m was coated with the anticorrosion layer of 2.5 mm or more from 5.0 m after the pipe tip. After coating, 0.5 m of the rear end was removed for welding with a fixed base.

<Comparative Examples 1-2> In the same manner as in Example 1, chromate treatment and plummer treatment were carried out from 4.5 m from the end of the pipe, and a modified polyethylene adhesive layer (thickness: 0. 1) was obtained.
4 mm), a polyethylene layer (thickness: 2.1 mm) was coated thereon to prepare a comparative example 1 of a conventionally known heavy anticorrosion coating.
After the coating, the coating was removed so that the coating remained only in the 5.0 to 7.5 m portion. Further, Comparative Example 2 of a conventionally well-known heavy anticorrosion coating in which the same thick film was coated on the entire surface was prepared.
2.5 mm coating was performed on the 5 m portion.

<Examples 2 to 6> Outer diameter 200A x length 80
Grid blasting was performed on the outer surface of the steel pipe having a thickness of 00 mm and a thickness of 5.8 mm to remove scales and the like, and then a liquid urethane primer was spray-coated so as to have a thickness of 30 to 70 µm. After that, a two-component curing type polyurethane resin is mixed and spray-painted, and the
A 1 mm thick coating was formed. Further, after the position of 5.0 m from the end of the tube as a reference, coating was repeated and a polyurethane coating having a thickness of 1 to 4 mm was applied. Thus, a thin film coating of 0.3 to 1.0 mm from 0 to 5.0 m and a thick film coating of 1 mm or more after 5.0 m are performed based on the tip of the pipe. Heavy corrosion protection coated steel for offshore structures was manufactured.

<Comparative Examples 3 to 7> After blasting was performed in the same manner as in Examples 2 to 6, plummer processing was performed, and
Up to 5.0 position, polyurethane coating of 0 to 2 mm, after 5.0 m, coating of 0.3 to 2.5 mm thick polyurethane coating to produce anticorrosion coated steel materials of Comparative Examples 3 to 7. did. After coating, the last 0.5 m was stripped for welding to the fixture.

<Comparative Example 8> A blast treatment was performed 4.5 m or more in the same manner as in Examples 2 to 6, followed by a plummer treatment, and a 2.5 mm-thick polyurethane coating was applied. Removing the coating, leaving a position of 5.0-7.5 m,
After 0 to 5.0 m, a tar-epoxy paint was applied aiming at 200 μm after the treatment with kelenium to produce a heavy corrosion-resistant coated steel material of Comparative Example 8.

A sacrificial aluminum alloy anode of 5.0 kg was attached to each of the heavy corrosion-resistant coated steel materials of Examples 2 to 6 and Comparative Examples 2 to 8 at a position 3 m from the lower end of the tube, and was installed on the opposite surface of the tube. A 10 x 50 mm coating removal portion was prepared in parallel with the pipe length direction assuming a flaw, and an ocean exposure test was performed on a seawall with a water depth of about 6 m. After simple driving, the upper 0.5m
The fixed base was welded to the part, and on-site repair painting was performed. After exposing for 5 years, it was removed and the surface appearance and the consumption of the sacrificial anode were examined. Table 1 shows the results.

[0016]

[Table 1]

As is evident from the results in Table 1, when a conventionally known thick film of polyethylene of Comparative Example 1 and polyurethane of Comparative Example 2 was coated near the tidal zone, the anticorrosion performance at that portion was extremely excellent. However, when the cathodic protection is not applied as in Comparative Example 1, corrosion occurs in the exposed portion of the steel material in the sea. Further, when the cathodic protection was performed as in Comparative Example 3, the amount of wear of the anode was large. On the other hand, in the embodiment of the present invention, since most of the undersea part is covered with the anticorrosion coating, the anode hardly dissolves, and the stability of long-term anticorrosion and the cost of inspection, repair, replacement, etc. are greatly increased. It is possible to lower it. Even when the entire surface is coated with a thick film (2.5 mm) having a thickness of 1 mm or more as in Comparative Example 2, it is very effective in preventing corrosion in the sea and preventing dissolution of the anode, but the initial cost is a problem. . Furthermore, as is clear from comparison with the examples, there is no problem even if the film thickness is small in the underwater part if the coating thickness is 0.3 mm or more. On the other hand, when compared with a state in which nothing is painted in the underwater part, even in a thin film coating having a film thickness of less than 0.3 mm as in Comparative Examples 4 to 7 or a tar epoxy coating for on-site coating as in Comparative Example 8, The effect of preventing consumption of the anode used for cathodic protection is expected to be great for several years. However, since the coating is violently blistered, the coating is peeled off with time, and an excellent effect cannot be expected for a long time. In addition, there is a problem that when the tar epoxy is applied locally, the coating cost is high.

[0018]

As is clear from the examples, the heavy corrosion protection coated steel material for offshore structures of the present invention is obtained by subjecting the steel material for offshore structures to undercoat treatment and then reducing the minimum sea level below the sea atmosphere. By coating or organic resin coating having a thickness of 1 mm or more mainly in the area up to 1 m and 0.3 to 1.0 mm in the underwater area, the entire outer surface to be corroded is coated.
As a result, if there is a film thickness of 0.3 mm in the underwater part with little corrosion, even if the thickness is changed, the corrosion protection performance is excellent, so it is necessary to reduce the initial corrosion protection cost and use it together with the sacrificial anode assuming construction flaws. Even if it is carried out, it is possible to provide a product which is less worn out of the electrode and which is excellent in long term anticorrosion reliability and economic efficiency.

[Brief description of the drawings]

FIG. 1 shows an example of a cross-sectional view after construction of a heavy corrosion protection coated steel material for offshore structures of the present invention.

FIG. 2 shows an example of a cross-sectional view after construction of a heavy corrosion protection coated steel material for an offshore structure according to the present invention.

FIG. 3 is an example of a cross-sectional view of a coating structure when a polyolefin coating is used in the heavy corrosion protection coated steel material for marine structures of the present invention.

FIG. 4 is an example of a cross-sectional view of a coating structure when a polyurethane coating is used as the heavy corrosion protection coated steel material for marine structures of the present invention.

[Explanation of symbols]

Reference Signs List 1 steel material 2 coating or organic resin coating having a thickness of 1 mm or more 3 coating or organic resin coating having a thickness of 0.3 to 1.0 mm 4 sea surface 5 sea bottom 6 steel base treatment 7 primer layer for polyolefin coating 8 0.3 to Modified polyolefin adhesive layer having a thickness of 1.0 mm 9 Polyolefin anticorrosive layer having a thickness of 1.0 mm or more 10 Primer layer for urethane coating 11 Polyurethane anticorrosive layer having a thickness of 0.3 to 1.0 mm 12 Having a thickness of 1.0 mm or more Polyurethane anticorrosion layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) E02D 31/06 E02D 31/06 F-term (Reference) 4D075 AA01 AA82 AC56 AC92 BB04X BB24X BB35X BB74X CA33 DA15 DB02 DC06 EA41 EB13 EB38 4F100 AA22A AB03A AK01B AK03B AK03G AK04 AK51B AK51G AL06G BA02 BA25 CB03 EJ65B EJ69A GB04 JB02 4K044 AA02 AB03 BA15 BA21 BB02 CA07 CA16 CA53

Claims (3)

[Claims] 1. After a ground treatment is performed on a steel material for an offshore structure, 1 mm or more is mainly used in a region from the atmospheric portion of the sea to -1 m or more below the minimum sea level, and 0.3 to 1.0 mm is used in an underwater region. A heavy corrosion-resistant coated steel material for marine structures, characterized in that the entire outer surface to be corroded is coated by applying a coating or an organic resin coating having a thickness of 3 mm. 2. After a base treatment is performed on a steel material for an offshore structure, a primer layer and a urethane resin anticorrosion layer are mainly formed on the steel material in an area from the sea atmosphere to a minimum of -1 m below the sea level. A heavy corrosion-resistant coated steel material for marine structures, characterized in that a primer layer and a urethane resin anticorrosion layer are entirely coated on a steel material in an undersea region so as to have a thickness of 0.3 to 1.0 mm. 3. After performing a base treatment on a steel material for an offshore structure, a primer layer, a modified polyolefin adhesive, and a polyolefin layer are formed on the steel material in a region from the sea air portion to at least -1 m below the sea level. In order, the primer layer and the modified polyolefin adhesive layer are used as a single anticorrosive layer or in addition to the modified polyolefin adhesive layer on the steel material in the submarine region, and a polyolefin coating is performed. Heavy corrosion-resistant coated steel for offshore structures, characterized in that the entire surface is coated so as to be thick.