JP4355251B2 - Rust prevention method for steel and painted steel - Google Patents

Description

  The present invention relates to primary and secondary rust prevention methods and coated steel materials that have greatly improved rust prevention performance for ships, civil engineering, architecture, plants, industrial machinery, etc., and more specifically, specific alloy elements as steel materials TECHNICAL FIELD The present invention relates to a rust prevention method and a rust prevention steel material that can economically improve the coating durability of the surface of a steel material by applying an inorganic zinc rich primer containing a Zn-Mg alloy powder to a low alloy steel containing bismuth. .

  Inorganic systems using zinc powder as a pigment, organic solvents, and inorganic materials as vehicles (liquid binder components) as a corrosion countermeasure for steel materials used in steel structures such as ships, civil engineering, architecture, plants, and industrial machinery Zinc rich paint is mainly used. Inorganic zinc-rich paints are used for primary rust prevention and undercoating for heavy anticorrosion coating. As a primary rust preventive application, for example, a rust preventive method in which zinc rich paint is applied after a suitable substrate preparation at a steel mill or a steel processing factory as a shop primer is common.

The anticorrosive action of zinc rich paint is the sacrificial anticorrosive action of zinc powder on the steel. However, even in primary rust prevention applications, the disappearance rate of zinc was high depending on the environment, and sufficient rust prevention effects could not be obtained. In response to these problems, high-performance zinc chloride rich paints that exhibit sacrificial anticorrosive action for a longer period have been proposed. For example, in Patent Document 1 and Patent Document 2, a zinc-rich paint of a high rust prevention type using Mg alloy powder is used, or in Patent Document 3, a zinc-rich paint containing Zn-Mg alloy powder and Mg powder in addition to zinc powder. Paint was proposed. Furthermore, Patent Document 4 shows the long-life anticorrosion performance of Zn— (5 to 15% by mass) Mg alloy powder in paint. Further, Patent Document 5 shows the long-life anticorrosion performance of Zn—Mg alloy powder whose metal structure is composed of Zn and MgZn ₂ . In Patent Document 6, it has been proposed that when a Zn—Mg alloy powder is mainly composed of a Zn phase and a solid solution phase of Zn and Mg, high antirust performance can be obtained.

  However, the prior art Zn-Mg alloy powder has improved rust prevention performance compared to Zn powder, but it cannot be said that it is sufficient for primary and secondary rust prevention applications, and further improvement is required. It was. For example, when using zinc rich paint for primary anti-corrosion applications, the steel material may be stored outdoors for a long period of time. Depending on the storage conditions and environmental conditions, deep pits may form in the gaps between the steel plates that have been stored, and the steel material must be maintained. There was also a problem that disposal may still be necessary. When used as an undercoat for heavy corrosion protection as a secondary rust prevention application, it could not be said that the performance was satisfactory in application environments involving seawater such as ships, and further improvements were required.

JP 59-52645 JP 59-167249 A JP 59-198142 A Japanese Unexamined Patent Publication No. 1-311178 Japanese Patent Laid-Open No. 2-73932 JP 2000-80309 A

  The present invention aims to provide a technique for overcoming the above-mentioned problems, and has primary and secondary rust prevention methods with greatly improved rust prevention capability for ships, civil engineering, construction, and plants. In particular, the coating durability of the steel surface is improved by applying an inorganic zinc rich primer containing Zn-Mg alloy powder to a low alloy steel containing a specific alloy element as a steel material. The present invention relates to a rust prevention method and painted steel that can be economically improved.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research on the anticorrosion performance of an inorganic zinc rich primer containing an alloy powder of Zn—Mg, and as a result, the surface of a steel material containing a specific alloy element. It was found that when an inorganic zinc rich primer containing Zn-Mg was applied to the rust preventive performance, the rust prevention performance was more remarkably exhibited. As a result of further investigation of the mechanism, (i) Zn and / or Mg corrosion products formed by sacrificial anticorrosive action of Zn-Mg alloy powder itself have anticorrosive action. (Ii) Zn-Mg alloy The consumption rate of the powder greatly depends on the characteristics of the corrosion product. (Iii) When the corrosion product of the Zn-Mg alloy coexists with Cu ions in the generation atmosphere, the effect of improving the anticorrosive action of (i) above. It was also found that the effect of reducing the consumption rate of (ii) is enhanced. As a result of further investigation, (iv) by containing a specific amount of Cu in the base iron, the functions (i) to (iii) can be stably expressed without adding Cu ions to the coating film. I found out. The present invention is configured based on the above findings, and the gist thereof is as follows.

    (1) As a base steel material, using corrosion resistant steel for welded structure containing Cu: 0.1 to 0.7% by mass with the balance being Fe and unavoidable impurities, as an inorganic zinc rich primer on the surface of the steel material, 5 to 80% by mass of Zn—Mg alloy powder having a Mg content of 0.3 to 10% by mass, the balance being Zn as a main component and a particle size in the range of 1 to 15 μm, and the balance being a silicate solution A method for preventing rusting of steel, characterized by applying a primer comprising a vehicle, a solvent, and a paint additive as main components.

(2) The method for rust prevention of steel according to (1), wherein an epoxy resin coating is applied in an amount of 200 to 400 μm on a primer coating film formed by applying a primer.
(3) The method for preventing rust of a steel material according to (1) or (2), wherein a part or all of an inner surface of a steel oil tank is rust-prevented.

    (4) The steel ball rust prevention method according to (2), wherein part or all of the inner surface of the ship ballast tank is rust proof.

    (5) As the base steel material, Cu is contained in the surface of the corrosion-resistant steel for welded structure containing 0.1 to 0.7% by mass of Cu and the balance is Fe and inevitable impurities, and the Mg content is 0.3 to 10% by mass. %, And the balance is formed of an inorganic zinc rich primer layer containing Zn-Mg alloy powder whose main component is Zn and the grain system is in the range of 1 to 15 μm, with a thickness of 5 to 30 μm. Painted steel material.

    (6) The painted steel material according to (5), wherein an epoxy resin coating film is formed on the surface of the inorganic zinc rich primer layer with a thickness of 200 to 400 μm.

    (7) The painted steel material according to (5) or (6), which is a steel oil tank inner surface material.

    (8) The painted steel material according to (6), which is a material for the inner surface of a ship ballast tank.

  As described above, the present invention provides an antirust performance superior to that of the prior art by providing an inorganic zinc rich primer layer containing Zn-Mg alloy powder to a low alloy steel containing a specific alloy element. It is provided economically. The coated steel material of the present invention is suitable as a rust-preventing method for a ship, civil engineering, building, plant, industrial machine, etc., a structure of an industrial machine, or a corrosion-resistant steel material for corrosion countermeasures. In particular, a steel oil tank (crude oil tanker cargo, which has not been sufficiently durable with conventional rust prevention methods, by combining a steel material satisfying a specific alloy composition and an inorganic zinc rich primer to which Zn-Mg powder is added. It shows extremely excellent rust prevention performance on the inner surface of tanks, etc.) and on the inner surface of ship ballast tanks. Therefore, the industrial value of the present invention is extremely high.

  The limiting requirements of the present invention will be described in detail.

  First, the steel material was made of steel containing 0.1 to 0.7% by mass of Cu. The reason for this is that the Cu ions necessary for improving the anticorrosion performance of the corrosion product of the Zn-Mg alloy powder described above are derived from the ground iron. For natural supply, addition of less than 0.1% by mass is ineffective, and addition of over 0.7% by mass is effective, but reduces the rolling property of the steel material, so 0.1 to 0.7% by mass %.

  Next, the composition of the inorganic zinc rich primer will be described.

  Mg content in metal powder: If the Mg content is less than 0.3% by mass, the effect of improving the rust-preventing effect is reduced, and if it exceeds 10% by mass, the rust-preventing effect is adversely reduced. Was limited to 0.3 to 10% by mass. Since Mg has a higher raw material cost than Zn, 0.3 to 2% by mass is more preferable in consideration of economy.

  Average particle diameter of metal powder: When the average particle diameter exceeds a general film thickness (15 μm) as a primer, thin coating becomes difficult. Moreover, since the handling and manufacturability of powder become difficult when it is less than 1 μm, the range is limited to 1 to 15 μm.

  As the vehicle of the inorganic zinc rich primer, a silicate solution as a main component can be used, and examples thereof include ethyl silicate, lithium silicate, sodium silicate, potassium silicate, ammonium silicate, and the like. Preferred vehicles are ethyl silicate, potassium silicate, and lithium silicate. In addition, other additives can be added as long as they do not impair the rust prevention performance. However, when used as an undercoat, a third component such as boron is added to improve adhesion to the top coat. Also good.

  The blending ratio of the metal powder containing the Zn—Mg alloy is limited to a range of 5 to 80% by mass in order to achieve both the rust preventive action of the metal powder and the sound physical properties of the coating film. In order to maximize the rust prevention performance, 60 to 90% by mass of metal powder, preferably 70 to 80% by mass, and 10 to 40% by mass of vehicle, more preferably 20 to 30% by mass are uniformly mixed. It is preferable to do this.

  Next, the details of the rust-proof coating method of the present invention will be described. In the case of primary rust prevention, the shop primer is first applied by spraying or brushing to the steel surface that has been sufficiently rusted by sandblasting or shot blasting. In the rust prevention method of the present invention, the thickness of the dry paint film of the shop primer is 5 to 30 μm, preferably 10 to 20 μm. When the film thickness is less than 5 μm, it is difficult to obtain the desired anticorrosive property. Conversely, when the film thickness exceeds 30 μm, it tends to cause cohesive failure inside the dry paint layer of the shop primer. This is not preferable because the coating layer is easily peeled off by slight impact, mechanical stress, and heat shock.

  In the case of secondary rust prevention, dry coating is performed on the coating film obtained by drying the above shop primer at room temperature for the purpose of obtaining long-term durability that cannot be obtained with a single primer layer using a spray coating machine, a roller, or the like. The tar epoxy resin paint JIS type 2 or 1 type is applied so that the thickness of the film is 200 to 400 μm, preferably 250 to 300 μm, and dried at room temperature to finish.

  In the case of rust prevention of a part or all of the inner surface of a steel oil tank, such as a crude oil tanker or a ground or underground crude oil tank, it is excellent by combining the primary rust prevention of the present invention, that is, a steel material of a specific component and the primer. Durability. In addition, when tar-epoxy paint is overcoated, even greater durability is obtained. The oil tank includes all kinds of oil tanks, such as light oil, heavy oil, and tar, in addition to the above-described oil tanks.

  When rust-proofing part or all of the inner surface of a ballast tank equipped on a ship, it is excellent if the secondary rust prevention of the present invention, that is, combining a steel material of the specific component and the primer, and further applying a tar epoxy paint. Durability.

  The effect of the rust prevention method of the present invention does not depend on the tank work method. For rust prevention of steel oil tanks or ship ballast tanks, rust prevention treatment may be performed after the tank is built, or after the tank is assembled using a rust-proof steel material, the rust prevention of welded parts, etc. The effect of the rust-preventing method of the present invention can be obtained even by using a work method for performing the treatment.

  Hereinafter, the present invention will be specifically described based on examples.

First, an inorganic zinc rich primer shown in Table 2 was prepared according to the following formulation 1 using the metal powder shown in Table 1.
[Formulation 1]
Alloy powder 43% by mass
Anti-rust pigment 5% by mass
Anti-precipitation agent 3% by mass
Isobutanol 13% by mass
Isopropanol 13% by mass
Toluene 13% by mass
Ethyl silicate solution 10% by mass
Next, after removing the scale completely from the test pieces (plate thickness 6 mm, size 500 mm × 500 mm) of the Cu-containing steel and the ordinary steel related to the present invention shown in Table 3, the primers shown in Table 2 Is coated with air spray to a dry film thickness of 15 ± 5μm, and dried for 7 days at 20 ° C and 75% relative humidity (hereinafter sometimes referred to as RH) to obtain a shop primer coating specimen. It was.

Next, tar epoxy paint (Nippon Steel Chemical Co., Ltd., NB coating 20FV-R) was applied on the primer coating by air spray so that the dry film thickness was 250 to 300 μm, and 20 ° C., 75% by mass. It was dried with RH for 7 days to obtain a sample material for heavy anticorrosion coating.
[Exposure test 1]
The two sets of shop primer-coated test steel sheets shown in Table 4 were stacked as shown in Fig. 1 and exposed to the product quay vacant space of Kimitsu Steel Works, Chiba Prefecture for one year. After the test, the shop primer was removed, and the area where the corrosion of the base iron occurred in the overlapped area and the maximum corrosion depth were determined by three-dimensional measurement of surface irregularities. The results are also shown in Table 4.
[Exposure test 2]
The shop primer coating specimens shown in Table 5 were welded to the deck plate (ceiling) and bottom plate inside the new crude oil tanker tank, and the corrosion status was evaluated 2.5 years after service. The evaluation results are also shown in Table 5.
[Exposure test 3]
After putting a cross-cut reaching the base iron into the coating film of heavy anticorrosion coating material shown in Table 6, a cyclic corrosion test was conducted for 3 months under the following conditions to evaluate the corrosion situation.

[Cycle corrosion test conditions]
Spray: 35 ° C., 98% RH, 4 h, 5 mass% NaCl aqueous solution spray Drying: 60 ° C., 10-15% RH, 2 h
Wet: 50 ° C 95% RH or more, 2h
[Exposure test 4]
The heavy-duty anticorrosive coating material shown in Table 7 was welded to the middle part of the ship's ballast tank deck plate (ceiling) and bulkhead (partition wall), and after the cross cut reaching the ground iron was put on the coating film, it was put into service. The corrosion situation was evaluated after 5 years.
[Rust prevention performance test results for shop primer coated steel]
As shown in Table 4, in the atmospheric environment, Cu related to the present invention: 0. The test material in which the base film was formed with a primer containing Zn-Mg alloy powder using a steel material containing 1 to 0.7% by mass has a significantly lower corrosion area ratio and maximum pitting corrosion depth than the comparative example. It was recognized that

As shown in Table 5, in the environment inside the crude oil tanker, Cu related to the present invention: In the specimen material in which the base film was formed with a primer containing Zn-Mg alloy powder using a 1 to 0.7 mass% steel material, a reduction in the corrosion area ratio was recognized in the environment behind the deck as compared with the comparative example. In the tank bottom plate environment, it was found that the number of pitting points and the maximum pitting depth were reduced to 1/2 or less.
[Rust prevention performance test results of heavy anticorrosion coated steel]
As shown in Table 6, in the cyclic corrosion test, Cu according to the present invention: The test material coated with tar epoxy after forming a base film with a primer containing Zn-Mg alloy powder using a 1 to 0.7 mass% steel material was corroded from the periphery of the crosscut rather than the comparative example. The measured area was found to be significantly lower.

  As shown in Table 7, in the environment of the inner surface of the ballast tank, Cu: 0. The sample material coated with tar epoxy was corroded from the periphery of the crosscut rather than the comparative example after forming a base film with a primer containing Zn-Mg alloy powder using 1 to 0.7 mass% steel material. The area was found to be significantly lower. The effect was particularly remarkable on the back of the deck plate.

  As is clear from the above examples, when the inorganic zinc rich primer to which the Cu-added steel material and the Zn—Mg alloy powder are added is combined, a synergistic effect much stronger than the addition of the single effect is expressed. All showed excellent corrosion resistance under the coating film.

The exposure point of the test steel plate in the exposure test 1 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steel plate which applied primer 2 ... Lamination part of steel plate

Claims (8)

  As the base steel material, a corrosion-resistant steel for welded structures containing Cu: 0.1 to 0.7% by mass with the balance being Fe and inevitable impurities is used, and the Mg content as an inorganic zinc rich primer on the surface of the steel material 0.3 to 10% by mass with the balance being Zn as the main component, containing 5 to 80% by mass of Zn—Mg alloy powder having a particle size in the range of 1 to 15 μm, and the balance being mainly composed of a silicate solution. A method for preventing rust of a steel material, characterized by applying a primer comprising a vehicle, a solvent, and a paint additive.   The method for rust prevention of steel according to claim 1, wherein an epoxy resin coating is applied to a primer coating film formed by applying a primer in an amount of 200 to 400 µm.   The method for preventing rust of a steel material according to claim 1 or 2, wherein a part or all of the inner surface of the steel oil tank is rust-prevented.   The method for preventing rust of a steel material according to claim 2, wherein a part or all of the inner surface of the ship ballast tank is rust-prevented.   As a base steel material, Cu: 0.1 to 0.7% by mass with the balance being Fe and an unavoidable impurity consisting of corrosion resistant steel for welded structure, Mg content is 0.3 to 10% by mass and the balance Is characterized in that an inorganic zinc rich primer layer containing Zn-Mg alloy powder containing Zn as a main component and having a particle size in the range of 1 to 15 μm is formed with a thickness of 5 to 30 μm. Steel material.   The coated steel material according to claim 5, wherein an epoxy resin coating film is formed on the surface of the inorganic zinc rich primer layer with a thickness of 200 to 400 µm.   The coated steel material according to claim 5 or 6, wherein the material is a steel oil tank inner surface material.   The painted steel material according to claim 6, which is a material for an inner surface of a ship ballast tank.

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