JPH10226860A - Coated article and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated article capable of suppressing the generation of blisters even if a coating film is formed on a galvanizing film by heating and capable of maintaining high corrosion resistance and durability. SOLUTION: A coating film is formed on an iron base substrate via a primary galvanizing layer contg. at least 0.5 to 15wt.% aluminum. Furthermore, the primary galvanizing layer may contain 0.1 to 3wt.% magnesium. Moreover, an intermediate galvanizing or zinc alloy layer may be interposed between the iron base substrate and zinc alloy layer, and the intermediate zinc alloy layer may contain nickel. As for the coating film, a thermosetting coating material is used, and it can be formed by heating such as baking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated product in which a zinc alloy plated coating which is stable for a long time is coated with a paint, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, steel products are hot-dip galvanized to prevent corrosion. However, zinc-based plating is sacrificial corrosion-resistant plating, and corrosion products called so-called white rust and black rust are generated due to corrosion of the plating film itself. Also, if the zinc-based plating coating is left in the air, it will be discolored and reduce its commercial value.

Further, zinc-based plating films and oxides thereof are relatively easily dissolved in acids. Therefore, when a zinc-based plating coating is used outdoors or the like, it is eroded early due to acid rain or the like. Therefore, it is difficult to say that zinc-based plating is a corrosion-resistant means having excellent weather resistance.

[0004] In order to solve these problems, it has been proposed to apply a coating material on a zinc-based plating film and heat it to form a coating film. In particular, high-temperature baking is preferred in order to use zinc-based plating as a corrosion-resistant means having excellent weather resistance. However, when baking is applied to the hot-dip galvanized film, bubbles (blisters) are generated. Although air baking is performed to suppress the generation of air bubbles, the generation of air bubbles cannot be sufficiently suppressed. Further, the zinc-based plating film has a low chemical conversion treatment property as a coating base and poor adhesion between the zinc-based plating film and the coating film, so that high corrosion resistance cannot be maintained for a long period of time. In addition, due to the poor corrosion resistance of the zinc-based plating film, the coating film is damaged or defective, and the adhesion is deteriorated. Further, the deterioration of the coating film is caused by the deterioration.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a coated article which suppresses the generation of air bubbles (blisters) even when the coating film is heated, and a method for producing the same.

Another object of the present invention is to provide a zinc-based plating film having a high chemical conversion treatment property, excellent adhesion to a zinc alloy layer, and, even if there is a defect in the coating film, deterioration of adhesion and deterioration. It is an object of the present invention to provide a coated article capable of extremely suppressing the expansion of the range and maintaining high corrosion resistance and durability, and a method for producing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a coating film can be formed on an iron-based substrate through a zinc alloy layer having a specific composition. ,
Good chemical conversion property, excellent adhesion to zinc alloy layer, extremely reduced degradation of adhesion and expansion of degradation range, and suppression of air bubble (blister) even when heated coating film And completed the present invention.

That is, the coated article of the present invention is obtained by forming a coating film on an iron-based substrate via a first zinc alloy layer containing at least 0.5 to 15% by weight of aluminum. Further, the first zinc alloy layer is 0.1 to 3% by weight.
Of magnesium. An intermediate zinc or zinc alloy layer may be present between the iron-based substrate and the zinc alloy layer. The intermediate zinc alloy layer may include nickel. The coating film may be formed of a thermosetting paint.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The coated article of the present invention is
A coating film is formed via a first zinc alloy layer containing at least 0.5 to 15% by weight of aluminum (hereinafter, may be referred to as a first plating layer). A zinc or zinc alloy layer (hereinafter, sometimes referred to as an intermediate plating layer) may be interposed between the iron-based substrate and the first plating layer. The plating bath for forming the first plating layer may be referred to as a first plating bath, and the plating bath for forming the intermediate plating layer may be referred to as an intermediate plating bath.

[Iron-based substrate] The iron-based substrate applicable to the present invention is not particularly limited as long as it contains an iron component and can be subjected to hot-dip galvanizing. As a preferable iron-based substrate, a corrosive steel material is used, and the composition, composition ratio and shape of the steel material are not particularly limited. Examples of the iron-based substrate include a steel plate, a steel wire, a steel strip, a casting, and the like; products required to form a uniform and thin plating coating, for example,
Steel products with uneven surfaces such as expansion joints, bolts and nuts; high rails, main poles, bridge protective fences, road signs, road guard fences that require acid resistance, salt resistance, weather resistance, scratch resistance, etc. Examples include steel products such as river fences, rock fall prevention nets, and power transmission fittings.

The iron-based substrate is usually subjected to a conventional pretreatment, such as a degreasing treatment and an acid cleaning treatment, prior to hot-dip plating.

[Zinc alloy plating] The first zinc alloy layer comprises:
It is composed of a high-purity zinc alloy containing a relatively large amount of aluminum. This zinc alloy layer preferably further contains magnesium. By coating the iron-based substrate with such a first zinc alloy layer, not only can the iron-based substrate be provided with high corrosion resistance, but also the foaming of the coating film can be significantly suppressed. Aluminum content is normal aluminum-
More than the aluminum content of zinc alloy plating,
Usually 0.5 to 15% by weight, preferably 1 to 13% by weight,
More preferably, it is about 3 to 10% by weight (for example, about 3 to 7% by weight).

[0013] The content of magnesium can be appropriately selected within a range that further enhances the corrosion resistance.
It is about 3% by weight, preferably about 0.2 to 2% by weight.

When the coating is applied on the zinc alloy layer containing a large amount of aluminum as described above, even when the coating is formed by heating, not only the generation of bubbles (blisters) can be suppressed, but also a stable Due to the chemical conversion property, a coating film having strong adhesion can be obtained. Also, this zinc alloy layer
Due to its excellent corrosion resistance, the adhesion can be maintained for a long time, and the spread of deterioration from scratches or defects in the coating film can be extremely reduced.

The iron-based substrate may be plated with the first zinc alloy, but it is preferable to further form the first zinc alloy layer via an intermediate plating layer. By interposing the intermediate plating layer, it is possible to prevent generation of an unplated portion due to a decrease in wettability of the first zinc alloy having a high aluminum content with respect to the iron-based substrate.

The intermediate plating layer may be a high-purity zinc layer, but is preferably a zinc alloy layer from the viewpoint of corrosion resistance. The type of zinc alloy is not particularly limited, and examples thereof include various conventional zinc alloys, for example, a zinc alloy containing at least one component of tin, aluminum, magnesium, nickel, copper, titanium, zirconium and sodium. Preferable zinc alloys include zinc-aluminum alloys in view of affinity with the first zinc alloy layer.

The aluminum content of the intermediate plating layer is as follows:
It can be appropriately selected within a range that does not cause an unplated portion without reducing the wettability with the iron-based substrate, and is usually 0 to less than 0.5% by weight (eg, 0.001 to 0.4% by weight). , Preferably 0.001 to 0.1% by weight, more preferably 0.001% by weight.
It is about 1 to 0.05% by weight.

[0018] The intermediate plating layer made of zinc or a zinc-aluminum alloy may further contain nickel. By containing nickel, the first zinc alloy layer can be prevented from falling off. This nickel may be derived from nickel in the nickel plating layer or the intermediate plating bath. The content of nickel can be appropriately selected within a range that does not increase the hot-dip plating temperature and the like.
It is about 1.0% by weight, preferably about 0.01 to 0.5% by weight, and more preferably about 0.01 to 0.3% by weight. In the present specification, the first plating layer, the intermediate plating layer and the first plating bath, the intermediate plating bath, unless otherwise specified, unavoidable impurities, for example, lead, iron, cadmium and the like. May be included.

The first plating layer and the intermediate plating layer can be formed by a conventional method, for example, by immersing an iron-based substrate in a plating bath and hot-dip plating. When an intermediate plating layer is interposed between the iron-based substrate and the first plating layer, the intermediate plating layer can be immersed in the intermediate plating bath and then immersed in the first plating bath.
The nickel-containing intermediate plating layer is formed by (1) immersing the iron-based substrate in an intermediate plating bath after electroless nickel plating, and (2) immersing the iron-based substrate in a nickel-containing intermediate plating bath. Among them, it can be formed by at least one of the methods. For example, after the electroless nickel plating treatment, it may be immersed in an intermediate plating bath containing nickel. As the first plating bath and the nickel-containing intermediate bath, a molten zinc bath having a composition corresponding to the first plating layer and the intermediate plating layer can be used. In the method (1), the thickness of the nickel plating layer is, for example, 0.01
To 5 μm, preferably 0.05 to 2.5 μm, and more preferably 0.1 to 1 μm. The temperature and immersion time of the first plating bath and the intermediate plating bath can be appropriately selected according to the desired thickness of the plating layer and workability.

The temperature of the bath can be selected according to the composition of the bath,
Usually, it is higher than the melting temperature of the alloy by 20 ° C. or more, for example, 3
The temperature is about 50 to 500C, preferably about 400 to 500C, and more preferably about 420 to 480C. The temperature of the first plating bath is preferably lower than the temperature of the intermediate plating bath in order to prevent the elution of the intermediate plating layer.

The immersion time can be appropriately selected according to the desired thickness of the plating layer, and is, for example, 1 second to 5 minutes, preferably 1 second.
It is about 5 seconds to 3 minutes.

The thickness of the first plating layer and the intermediate plating layer containing no nickel is usually about 5 to 60 μm, preferably about 10 to 50 μm. The thickness of the intermediate plating layer containing nickel is usually 5 to 40 μm,
Preferably it is about 10 to 30 μm.

[Coating] In the present invention, as a coating capable of forming a coating, a coating containing a resin capable of forming a coating by heating is used.

Prior to coating, it is desirable to treat the surface of the plating layer in order to improve the adhesion of the coating film. The surface treatment can be performed by a conventional method, for example, a chemical conversion treatment for forming a chemical conversion film using a phosphate or the like.

The resin capable of forming a coating film includes a thermoplastic resin and a thermosetting resin. Examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene; acrylic resins; styrene resins; chlorine-containing resins such as polyvinyl chloride; and fluororesins such as polyhexafluoropropylene and perfluoro (propyl vinyl ether). Polyvinyl acetate; ethylene-
Vinyl acetate; saturated polyester; polyvinyl acetal; polyamide; polycarbonate and the like.
Examples of the thermosetting resin include a thermosetting acrylic resin; an epoxy resin; an epoxy ester resin; an unsaturated polyester; an alkyd resin; a phenol resin; a furan resin; an amino resin (such as a urea resin, a melamine resin, or a guanamine resin); Diallyl phthalate resin; polyurethane;
Polyimide; silicone resin; Also,
The resin may be a light curable resin such as an ultraviolet curable resin or an electron curable resin. These resins can be used alone or in combination of two or more.

Preferred resins include, for example, resins which form a film by heating (including polyamides, unsaturated polyesters, epoxy resins, etc., powder immersion, powder coatings used for electrostatic coating, fluororesins, etc.), and crosslinking by heating. Resins that form coating films (thermosetting acrylic resins, epoxy resins, epoxy ester resins, alkyd resins, amino resins, silicone resins, and the like) are exemplified. More preferably, a thermosetting resin used for baking coating, in particular, for example, a thermosetting acrylic resin, a melamine resin, an epoxy resin, an alkyd resin, a silicone resin, and the like are exemplified. When two or more resins are mixed, usually, a thermosetting acrylic polymer and a melamine resin, an epoxy resin and a melamine resin, an unsaturated polyester and a melamine resin,
It often contains a melamine resin such as an alkyd resin and a melamine resin.

The type of paint is not particularly limited.
It may be any of a water-based paint, a solvent-based paint, a powder paint, a photocurable paint, an emulsion paint, a sol paint and the like. The paint may be either a clear paint or an enamel paint.

[0028] In addition to the above-mentioned resins, paints include, for example, plasticizers, desiccants, curing agents, leveling agents, coating surface smoothness improvers, pigments, pigment dispersants, pigment sedimentation inhibitors, stabilizers (antioxidants , UV absorbers, heat stabilizers, etc.), antistatic agents, rust inhibitors, mold inhibitors, fillers, reinforcing agents, defoamers, viscosity modifiers, surfactants, anti-skinning agents, anti-sagging agents, preservatives An additive such as an agent may be included.

Water-based or solvent-based paints include water; alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as toluene; ethyl acetate, butyl acetate and the like. Esters; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ethers such as diethyl ether and dibutyl ether; halogenated hydrocarbons such as chloroform; and solvents such as cellosolves.

The thickness of the coating film can be appropriately selected within a range that can provide high corrosion resistance, and is usually about 5 to 150 μm, preferably about 10 to 120 μm, and more preferably about 15 to 90 μm.

The coating film may be formed of a plurality of the same or different coating films. For example, the undercoating (primer) may be applied to the plating surface and then the overcoating may be applied, or an intermediate coating (surfacer) layer may be formed between the undercoating layer and the overcoating layer.
For example, as a paint used for the undercoat, a paint having adhesion to a plating surface and rust prevention (for example, an unsaturated polyester paint that may contain a melamine resin or an epoxy that may contain a melamine resin) Resin-based paint). As the paint used for the top coat, a paint having a desired color and gloss and having weather resistance (for example, a thermosetting acrylic paint that may contain a melamine resin, a ceramic paint containing a silicone resin, and the like) ).

The ceramic coating is typically a hydrolyzable silyl group (hydroxy silyl group, C _1-2 alkoxy silyl group) includes an oligomer or polymer having a (silicone resin), oligomer or polymer, an acrylic resin And a modified silicone resin obtained by co-condensation with a co-condensation resin such as an oil-free alkyd resin (saturated polyester) or an alkyd resin. In particular, when a ceramic paint is used as the top coating, the properties of organic paints such as aesthetic protection, workability, workability, and storage stability, and hardness, stain resistance, weather resistance, chemical resistance, etc. The properties of the inorganic paint can be exhibited.

The coating film can be formed by applying a coating material to the plating and heating it. For paints containing solvents,
The heating of the coating film may be performed after the drying of the coating film.

In the coating step, a conventional method such as brush coating, dipping, roll coating, spray coating, flow coating and the like can be employed. In the case of powder coating, any of thermal spraying, electrostatic coating (electrostatic spray coating, electrostatic powder coating, etc.), fluid immersion, and the like may be used.

When long-term weather resistance is required, heating,
In particular, it is preferable to form a crosslinked or cured coating film by baking. By heating the coating film in this way, a highly durable coating layer can be formed on the plating layer.

The heating or baking temperature can be appropriately selected depending on the kind of the coating material and the thickness of the coating film.
° C, preferably from 120 to 200 ° C, more preferably from 1 to 200 ° C.
It is about 40 to 180 ° C.

The heating or baking time can be appropriately selected depending on the kind of the coating material, the thickness of the coating film, and the baking temperature, but is usually about 10 to 60 minutes, preferably about 15 to 50 minutes, and more preferably about 20 to 40 minutes. It is. When heating to form a coating film on the zinc alloy plating layer, in order to suppress the generation of air bubbles, generally, after forming the plating layer, baking is performed to form the coating film. I have. However, in the present invention, without baking, even when heating and forming a coating film on the first zinc alloy layer, the generation of bubbles can be significantly suppressed, and a coated article with almost no bubbles can be obtained. .

When the thus obtained coated product of the present invention is used for steel plates, guard ropes, power transmission fittings, protective fences for bridges, etc., it is more resistant to weathering and corrosion than the zinc alloy layer itself. Because of its excellent properties, it can be used for a long time without maintenance. In addition, since no air bubbles are generated in the coating film, the spread of adhesion deterioration from the air bubbles is extremely small. In particular, high corrosion resistance can be maintained even when used in a coastal area, a road using a snow melting agent, or a heavy industrial area.

[0039]

The coated article of the present invention can be obtained by forming a coating film on a ferrous base material through a zinc alloy layer having a specific composition.
Even if the coating film is heated, the generation of bubbles (blisters) can be suppressed. Further, the zinc alloy layer has good chemical conversion treatment properties, has excellent adhesion to the zinc alloy layer, and can extremely suppress the spread of the adhesion deterioration.

[0040]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following examples and comparative examples, a gas pipe material (SGP 50A) was used as the iron-based substrate.
-300L) and hot-rolled material (SPHC 75x1)
50 3.0 t) was used.

Example 1 A gas pipe material (hereinafter, simply referred to as SGP) was plated under the following conditions, and then coated under coating conditions -A to D to obtain a coated product.

[Plating Conditions] The SGP was subjected to a degreasing treatment and an acid washing treatment with hydrochloric acid, and then immersed in an aqueous flux containing 30 g / L of zinc chloride and 100 g / L of ammonium chloride for flux immersion treatment. Then, nickel was added to 0.1.
A molten nickel-aluminum-zinc alloy bath containing 2 wt. Units and 0.005 wt.
(60 ° C.) for 180 seconds to form a nickel-aluminum-zinc alloy layer. After the SGP after the formation of the nickel-aluminum-zinc alloy layer is cooled with water, a molten aluminum-magnesium-zinc alloy bath (bath temperature 440) containing 5 weight units of aluminum and 1 weight unit of magnesium is used.
° C) for 60 seconds, aluminum-magnesium-
A zinc alloy layer was formed. Next, the SGP after plating is
After degreasing and surface conditioning with a titanium colloid solution having a pH of about 8, it was immersed in a phosphoric acid aqueous solution containing ferrous phosphate and zinc phosphate, subjected to a chemical conversion treatment, washed with water, and dried.

[Coating conditions] Coating conditions-A A polyester-based electrostatic powder coating (Konak No. 1760, manufactured by NOF Corporation) was electrostatically coated on a plating surface with a thickness of 80 μm, and baked at 170 ° C. for 30 minutes. Was.

Coating conditions-B As a primer, a polyester / melamine-based solvent-based primer (Unicorp F760, manufactured by Mitsui Kinzoku Paint Chemicals Co., Ltd.)
0) is applied on the plating surface with a thickness of 20 μm,
For 20 minutes. Next, acrylic / melamine-based solvent-based paint (Mitsui Metal Paint Co., Ltd.)
(Unicorp BAC) was applied to the coating at a thickness of 20 μm and baked at 160 ° C. for 20 minutes.

Coating Condition-C A polyester-based electrostatic powder paint (Konak No. 1760, manufactured by NOF Corporation) was electrostatically applied to the plating surface with a thickness of 80 μm as a primer, and then baked at 170 ° C. for 30 minutes. Was. Next, as a top coating agent, a ceramic silicate resin-based coating material of a composite silicate resin (Bellclean No. 1000 manufactured by NOF Corporation) was applied to the coating film at a thickness of 20 μm, and baked at 170 ° C. for 30 minutes.

Coating Condition-D An epoxy / melamine solvent-type primer coating (Nippon Oil & Fat Co., Ltd., Epico Primer BF-2) was applied as a primer to a plating surface with a thickness of 20 μm, and then was applied at 170 ° C. for 30 minutes.
Baked. Next, as a top coating agent, a ceramic silicate resin-based coating material of a composite silicate resin (Bellclean No. 1000 manufactured by NOF Corporation) was applied to the coating film at a thickness of 20 μm, and baked at 170 ° C. for 30 minutes.

[Evaluation of Bubble Generation] The number of bubbles after paint baking was counted and evaluated as the number of bubbles generated per 100 cm ² .

Example 2 Example 1 was repeated except that a hot-rolled material (hereinafter simply referred to as SPHC) was used as the iron-based substrate.

Comparative Example 1 After plating SGP under the following conditions, coating conditions -A to D
The number of air bubbles generated after coating was counted.

[Plating conditions] The degreasing treatment, the acid cleaning treatment, the flux immersion treatment, and the phosphate treatment after plating were performed in the same manner as in the above embodiment. 0.005 aluminum
A molten aluminum-zinc alloy bath (bath temperature 46
(0 ° C.) for 180 seconds to form an aluminum-zinc alloy layer.

Comparative Example 2 The same procedure as in Comparative Example 1 was carried out except that SPHC was used as the iron-based substrate.

Comparative Example 3 After plating in the same manner as in Comparative Example 1, baking was performed at 180 ° C. for 1 hour, and after coating, the number of generated bubbles was counted.

Comparative Example 4 An experiment was performed in the same manner as in Comparative Example 3 except that SPHC was used as the iron-based substrate.

Table 1 shows the results of the generation of air bubbles in the above Examples and Comparative Examples.

[0055]

[Table 1] As is clear from the above results, the coated article of the present invention can effectively suppress the generation of bubbles without using a bubble suppression means such as baking.

Claims (11)

[Claims] 1. An iron-based substrate having a first zinc alloy layer containing at least 0.5 to 15% by weight of aluminum,
A painted object on which a coating film is formed. 2. The method according to claim 1, wherein said first zinc alloy layer further comprises 0.1
2. A coated article according to claim 1, which contains -3% by weight of magnesium. 3. The coated article according to claim 1, wherein an intermediate zinc or zinc alloy layer is interposed between the iron-based substrate and the first zinc alloy layer. 4. The coated article according to claim 3, wherein the intermediate zinc alloy layer contains nickel. 5. A coated article according to claim 3, wherein said intermediate zinc alloy layer comprises 0 to less than 0.5% by weight of aluminum and 0.005 to 1% by weight of nickel. 6. The coated article according to claim 1, wherein said coating film is formed of a thermosetting paint. 7. The coating film according to claim 1, wherein said coating film is a baking coating film.
Painted material described in. 8. A method for producing a coated article in which a coating film is formed on an iron-based substrate via a zinc alloy layer containing at least 0.5 to 15% by weight of aluminum. 9. A method in which the intermediate zinc alloy layer containing nickel is hot-dip galvanized containing 0 to less than 0.5% by weight of aluminum after electroless nickel plating of an iron-based substrate, and (2) A) forming an intermediate plating layer by at least one of the methods of plating an iron-based substrate with a molten zinc alloy bath containing nickel and aluminum in an amount of 0 to less than 0.5% by weight; The method according to claim 8, wherein a coating film is formed after forming a first zinc alloy layer containing 15% by weight of aluminum. 10. The method according to claim 8, wherein the coating film is formed by heating.
The method for producing a coated article according to the above. 11. The method according to claim 8, wherein the coating is formed by baking.