JP2008229998A - Heavy corrosion-proof coated steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy corrosion-proof coated steel material capable of improving durability without using chromating processing. <P>SOLUTION: The heavy corrosion-proof coated steel material has a first primer layer 2, a clay film layer 3, a second primer layer 4 and a resin layer 5 composed of a polyurethane or an olefinic resin layer which are successively laminated on a steel material 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heavy anticorrosion coated steel material suitable for long-term corrosion protection of steel structures in the ocean, harbors and rivers.

  For steel materials used in offshore structures and the like, heavy anticorrosion coatings covering polyurethane resins or polyolefin resins are often used as anticorrosion methods. These steel materials are called heavy anticorrosion coated steel materials, and main types include steel pipe piles, steel pipe sheet piles, steel sheet piles and the like. Many of these are also used in combination with cathodic protection. Although this anticorrosion suppresses corrosion of the steel material from the scratched part and the end part, it causes cathode peeling that reduces the covering adhesive force around the steel part. This cathodic stripping is facilitated by oxygen penetrating the heavy anticorrosion coating. This resistance to cathodic peeling becomes important when the heavy-duty anticorrosion coated steel material is used for a long period of time. In order to improve the cathode peeling resistance, conventionally, chromate treatment is generally performed as a base treatment. In recent years, development of alternative treatments for chromate treatment has been demanded from the viewpoint of environmental measures.

As a technique to improve durability without using chromate treatment, oxygen barrier coating with a thickness of 50 to 1000 μm and oxygen permeability adjusted to 100 cm ³ / m ² · day · atm (20 ° C.) or less on a heavy anticorrosion resin layer. A method for improving the cathode peel resistance by laminating a film has been proposed (see, for example, Patent Document 1). Further, a method is disclosed in which a 0.2 to 2 μm inorganic coating layer formed by applying a polysilazane solution on the surface of the heavy anticorrosion coating layer is used to improve the durability (see, for example, Patent Document 2).

  However, the method of Patent Document 1 does not reach the chromate treatment in terms of improving the cathode peel resistance. Further, in the method of Patent Document 2, since the inorganic coating layer having low strength is in the outermost layer, the impact resistance is inferior. As described above, at present, no effective technique has been found to improve the durability of the heavy anticorrosion coated steel material without using the chromate treatment.

Patent Document 3 will be described in the section “Best Mode for Carrying Out the Invention”.
JP 2004-332010 A JP 2006-43934 A JP 2006-77237 A

  This invention solves the said subject and makes it a subject to provide the heavy-duty anticorrosion coating steel material which can improve durability, without using a chromate process.

Means of the present invention for solving the above problems are as follows.
(1) A heavy anticorrosion-coated steel material, wherein a first primer layer, a clay film layer, a second primer layer, and a resin layer made of a polyurethane resin layer or a polyolefin resin layer are sequentially laminated on the steel material. .
(2) The heavy anticorrosion-coated steel material according to (1), wherein the clay film layer has a thickness of 30 to 100 μm.
(3) The heavy corrosion-resistant coated steel material according to (1), wherein the clay film layer has an oxygen permeability of 15 cm ³ / (m ² · day · atm) or less.

  The present invention makes it possible to significantly suppress oxygen from the surface by including a clay film layer in the heavy anticorrosion coating layer, and cathodic peeling from scratches and edges of the heavy anticorrosion coated steel material. Compared to coated steel, it can be greatly suppressed. This prolongs the life of heavy anticorrosion-coated steel materials and enables use in harsher environments. The heavy anticorrosion coated steel material of the present invention is also effective in omitting the chromate treatment.

  It is disclosed that a protective film made of a clay film mainly composed of clay has excellent gas barrier properties and mechanical strength that can be used as a self-supporting film (see Patent Document 3). However, Patent Document 3 merely discloses a material having a high gas barrier property. The present inventors have arranged a clay film layer as one of the coating layers of the heavy anticorrosion coated steel material, so that even when the chromate treatment is omitted, the chromate treatment is performed in terms of cathode separation resistance and impact resistance. It has been found that equivalent characteristics can be obtained, and the present invention has been achieved.

  The present invention will be described in detail below.

  One structural example of the coating layer of the heavy anticorrosion coated steel material of the present invention is shown in FIG. As shown in FIG. 1, the heavy anticorrosion coated steel material is obtained by sequentially laminating a primer layer 2 (first primer layer), a clay film layer 3, a primer layer 4 (second primer layer), and an anticorrosion resin layer 5 on the surface of the steel material 1. It is.

<Steel>
The steel material 1 used in the present invention is ordinary steel or alloy steel to which elements such as Ni, Cu, Cr, Mo, Mg, Al, and Ti are added. Generally, steel structures such as marine, harbor, and river structures are used. Steel used in the field of application can be used. The steel material shape is not limited. Steel pipes, shaped steels, etc. can be used as appropriate. Before the steel material is coated with a primer layer, a surface treatment is performed to remove scale, contaminants and the like on the surface. As the base treatment, blasting such as sand blasting, steel shot blasting, steel grit blasting, alkali degreasing and pickling are performed.

<First primer layer>
The first primer layer 2 is formed by coating in order to improve the adhesion between the clay film layer and the steel material and the cathode peeling resistance of the heavy anticorrosion coating. For the first primer layer 2, a material mainly composed of a thermosetting resin may be used, and a known inorganic pigment such as calcium phosphate or aluminum tripolyphosphate may be added as needed to impart corrosion resistance. Examples of the thermosetting resin include an epoxy resin and a polyurethane resin. Epoxy resins include bisphenol A type and bisphenol F type as main components. The polyurethane resin is a two-part curing type with a main agent and a curing agent that utilizes the reaction between polyol and isocyanate, a moisture-curing one-part curing type that uses a prepolymer, and a thermosetting powder type that can be made thicker. Etc. In the case of liquid type, paint using brush, roll or air spray painting method. The powder type is coated using the electrostatic powder coating method.

  As a material containing a thermosetting resin suitable for the first primer layer and an inorganic pigment, a commercially available product can be used. Examples of those containing a commercially available thermosetting resin and an inorganic pigment include “Permaguard 331 (main agent and curing agent, registered trademark)” manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

  The film thickness is desirably in the range of 30 to 600 μm. When the film thickness is less than 30 μm, pinholes are generated. On the other hand, when the film thickness exceeds 600 μm, the impact resistance decreases.

<Clay film layer>
The clay film layer 3 is provided in order to improve the gas barrier property of the heavy anticorrosion coating and to improve the resistance to cathode peeling. The clay film layer 3 is mainly composed of clay minerals such as montmorillonite, beidellite, saponite, mica and smectite. These clay minerals are desirably artificially purified from the viewpoint of not containing impurities. Commercially available clay minerals can be used. Examples of commercially available artificially refined clay minerals include “Kunipia F” (registered trademark) manufactured by Kunimine Kogyo Co., Ltd.

  A method for coating the clay film layer 3 will be described. First, the clay mineral alone or a mixture thereof is added to water to prepare a uniform dispersion. As for the density | concentration of the clay mineral in a dispersion liquid, 1-10 mass% is desirable. When the clay mineral concentration is less than 1 mass%, it takes too much time to form a film. On the other hand, when the concentration is higher than 10 mass%, it is difficult to form a uniform dispersion. Next, this dispersion is allowed to stand horizontally on the primer layer. At this time, the end of the steel material is covered and covered so that the dispersion does not flow out. Then, the clay mineral is deposited by allowing to stand for 5 to 24 hours at room temperature, and then drying in an electric furnace at 50 ° C. for 5 to 24 hours to evaporate the liquid, and the clay film layer 3 is placed on the first primer layer 2. Generate. The film thickness is adjusted by the amount of the dispersion, but is preferably in the range of 30 to 100 μm. When the film thickness is less than 30 μm, pinholes and see-through occur. When it exceeds 100 μm, the impact resistance decreases.

<Second primer layer>
The second primer layer 4 is a primer layer on the clay film layer 3 and is formed to improve the adhesion between the clay film layer 3 and the anticorrosion resin layer 5. The components and film thickness of the second primer layer 4 can be the same as those of the first primer layer 2. The method for forming the second primer layer 4 is the same as the method for forming the first primer layer 2 described above.

<Anti-corrosion resin layer>
A polyurethane resin or a polyolefin resin is used for the anticorrosion resin layer 5.

  The polyurethane resin is not particularly limited as long as it is a general-purpose product that is usually used for corrosion prevention. Specifically, it only has to contain a polyol and an isocyanate compound. It is more desirable if it contains a filled inorganic pigment in order to prevent shrinkage due to heat, and still more desirable if it contains a colored pigment in order to impart weather resistance. Examples of commercially available polyurethane resins include “Permguard 137 (main agent: A black (Z), curing agent: B, registered trademark)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., or “Nippe” manufactured by Nippon Paint Co., Ltd. Urethane elastomer U1001-S "and the like. These polyurethane resins are coated with an airless spray to form the anticorrosion resin layer 5. The film thickness at this time is preferably 1 to 6 mm. If it is thinner than 1 mm, impact resistance, cathode peel resistance and the like are lowered, and if it exceeds 6 mm, the performance is not improved, which is not economical.

  As the polyol, polyester polyol, polybutadiene polyol, castor oil-based polyol, or the like is used. As the filled inorganic pigment, calcium carbonate, silica, titanium oxide or the like is used. Carbon black is used as the color pigment. Moreover, in order to provide other characteristics, you may contain a plasticizer, an adjuvant, a thickener, antioxidant, a light stabilizer, etc.

  As the isocyanate, polyisocyanate such as diphenylmethane diisocyanate (MDI) or tolylene diisocyanate (TDI) is used.

  When a polyolefin resin is used for the anticorrosion resin layer 5, the anticorrosion resin layer 5 is composed of a polyolefin resin layer and a modified polyolefin adhesive layer, and is coated in a molten state by heating with a die or the like. The polyolefin resin layer contains a polyolefin resin, and low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, or the like is used as the polyolefin resin. Moreover, you may contain a coloring pigment (for example, carbon black etc.) in order to provide a weather resistance as needed. Furthermore, an additive such as an antioxidant or a light stabilizer may be contained in order to impart other characteristics. Further, the modified polyolefin adhesive layer is obtained by modifying the above polyolefin resin with an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid or its acid anhydride, or by appropriately diluting the modified product with a polyolefin resin, etc. Is used.

  The film thickness is desirably 0.3 to 1 mm for the modified polyolefin adhesive layer and 1 to 6 mm for the polyolefin resin layer. If the modified polyolefin adhesive layer is thinner than 0.3 mm, it may cause see-through during heat coating. Moreover, even if it exceeds 1 mm, adhesiveness etc. are not improved and it is not economical. When the polyolefin resin layer is thinner than 1 mm, impact resistance, cathode peel resistance and the like are lowered, and when it exceeds 6 mm, improvement in performance is not seen and it is not economical.

1. Preparation of test heavy anti-corrosion coated steel material <Preparation of heavy anti-corrosion coated steel material of the present invention example>
Steel grit blasting was performed as a base treatment on a hot rolled steel sheet having dimensions of 3 mm × 100 mm × 100 mm. Next, a polyurethane resin two-component curing type primer (“Permguard 331” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to 30 to 40 μm. The primer was cured for 24 hours at room temperature after painting. Next, a clay mineral dispersion was prepared. As the clay mineral, purified montmorillonite (“Kunipia F” manufactured by Kunimine Industries Co., Ltd.) was used. The purified montmorillonite was added to distilled water and stirred well to uniformly disperse the montmorillonite, thereby preparing a dispersion having a montmorillonite concentration of 1.0 to 3.3 mass%. The dispersion 60 cm ³ was poured from above onto a steel plate coated with 30 to 40 μm of the above primer so that the dispersion did not flow out, poured from above, placed in an electric furnace together with the steel plate and left to stand horizontally. This was slowly deposited at room temperature for 24 hours, and then the water was forcibly evaporated at 50 ° C. for 24 hours to produce clay film layers having different film thicknesses in the range of 30 to 100 μm. The thickness of the clay film layer was prepared by using dispersions having different concentrations. The primer was then painted again and cured for 24 hours. After that, 3.0 to 3.5 mm of polyurethane resin was applied as an anticorrosion resin layer. Here, as the polyurethane resin, “Permaguard 137 (main agent: A black (Z), curing agent: B, main agent: curing agent ratio = 2.7: 1)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a commercial product, is used. Then, after coating, it was cured at room temperature (20 ° C. or higher) for 7 days (Invention Examples 1 to 5).

<Production of heavy duty anti-corrosion coated steel material of comparative example>
The following heavy anticorrosion coated steel materials were prepared.
(I) A steel layer coated with a primer layer and a polyurethane heavy-duty anticorrosion coating layer in the same manner as the above invention example (Comparative Example 2)
(Ii) A primer layer, a clay film layer, and a polyurethane heavy-duty anticorrosive coating layer similar to those of the above-described invention examples are formed above the surface of the steel material. The thickness of the clay film layer was less than 30 μm (Comparative Example 3) or more than 100 μm (Comparative Example 4 and Comparative Example 5).
(Iii) A steel material that has been subjected to steel grit blast treatment as a base treatment and subjected to chromate treatment, on which a primer layer and a polyurethane heavy-duty anticorrosion coating layer similar to those of the present invention example are formed (Comparative Example 1). In the chromate treatment, a chromate treatment solution was applied to the surface of the steel sheet and then heated to 100 ° C. and dried. Cr deposition amount is 200 to 400 mg / ^{m 2.}
2. Evaluation Method The anti-cathode resistance of the heavy anticorrosion coated steel material prepared above was evaluated as follows. An artificial defect reaching a steel surface with a diameter of 5 mm was prepared at the center of the heavy anticorrosion coating layer, and a vinyl chloride cylinder with an inner diameter of 75 mm was bonded to the coating layer. The inside of the cylinder was filled with a 3 mass% NaCl aqueous solution, a platinum electrode was used as a counter electrode, and a potential of −1.5 V was applied to the steel material with respect to the saturated calomel standard electrode. After applying a potential at 60 ° C. for 60 days, the peel distance (mm) from the edge of the artificial defect was measured and used as the cathode peel distance.

  The impact resistance was evaluated by a falling weight impact test at −20 ° C. using a falling weight having a tip diameter of 15.9 mm and a weight of 5 kgf in accordance with ASTM G14. The destruction of the heavy anticorrosion coating layer was confirmed by a 20 kV energization test, and the impact strength was determined from the limit height at which no destruction occurred.

  A clay film having a film thickness of 40 to 50 μm was formed on a PET film having a thickness of 100 to 110 μm × width 100 mm × length 100 mm in the same manner as the above-mentioned clay film layer preparation method. The oxygen permeability of this clay film with PET film and the oxygen permeability of only the PET film were measured. The oxygen permeability was measured at 23 ° C. and 0% RH in accordance with JIS K7126 (1987). Based on the measurement results, the oxygen permeability of only the clay film was determined from the following formula (1).

  Table 1 shows the cathode peeling distance, impact strength, and oxygen permeability of the clay film of various heavy anticorrosion coated steel materials.

  Comparative Example 2 in which only a primer layer and a polyurethane resin layer are formed on a steel material, and Comparative Example 3 in which the film thickness of the clay film is thinner than 30 μm are inferior to Comparative Example 1 in terms of cathode peel resistance. Comparative Examples 4 and 5 in which the thickness of the clay film exceeds 100 μm are inferior in impact resistance. On the other hand, Examples 1 to 5 of the present invention show excellent cathode peeling resistance and impact resistance equivalent to those of Comparative Example 1 which is a heavy anticorrosion coated steel material subjected to chromate treatment. From this, it can be seen that the heavy duty anti-corrosion coated steel material of the example of the present invention can improve the durability without using the chromate treatment.

  Since the heavy anticorrosion coated steel material of the present invention is excellent in cathode peeling resistance and impact resistance, it can be used as a heavy anticorrosion coated steel material used in a more severe environment. Moreover, the heavy anticorrosion coated steel material of the present invention is excellent in durability even if the chromate treatment is omitted, so that it is required for long-term corrosion prevention without performing chromate treatment, such as marine, harbor and river steel structures. It can be used as a heavy anticorrosion coated steel material used in

It is sectional drawing which shows one structural example of the coating layer of the heavy-duty anticorrosion coating steel material of this invention.

Explanation of symbols

1 Steel 2 Primer layer (first primer layer)
3 Clay film layer 4 Primer layer (second primer layer)
5 Anticorrosion resin layer

Claims (3)

A heavy anticorrosion-coated steel material, wherein a first primer layer, a clay film layer, a second primer layer, and a resin layer made of a polyurethane resin layer or a polyolefin resin layer are sequentially laminated on a steel material. 2. The heavy anticorrosion coated steel material according to claim 1, wherein the clay film layer has a thickness of 30 to 100 [mu] m. ^2. The heavy anticorrosion coated steel material according to claim 1, wherein the clay membrane layer has an oxygen permeability of 15 cm ³ / (m ² · day · atm) or less.

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