Coated metal article

Abstract

To provide a coated metal article capable of exhibiting excellent durability and corrosion resistance.SOLUTION: There is provided a coated metal article 10, comprising: on a surface of a metal article 1, a first topcoat layer 2a mainly composed of an epoxy resin; and a second topcoat layer 2ba mainly composed of a zinc-aluminum composite coating, and has, on a surface of the first topcoat layer 2a, a most-upper layer 3 made of an organic-inorganic composite material mainly composed of silicon obtained by a sol-gel method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated metal article, and more particularly to a coated metal article used for bridge bolts and the like. [Background technology]

[0002] In recent years, bridge technology has made remarkable progress, and there is a growing need for high durability and miniaturization in order to reduce the life cycle cost (LCC) of metal fittings such as bridge bolts. For this reason, anti-rust treatments are being carried out on metal fittings. For example, in Patent Document 1, durability and the like are achieved by forming a zinc coating on the surface of a metal molded product by plating or the like, and then laminating a top layer mainly composed of a silicone compound on that surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4947823 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the top layer is mainly composed of a silicone compound, which means that it has low hardness and is easily scratched, and there is room for improvement in terms of durability and corrosion resistance.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a coated metal article that can exhibit excellent performance in terms of durability and corrosion resistance. [Means for solving the problem]

[0006] The present inventors attempted to form a first topcoat layer mainly composed of an epoxy resin on the surface of a metal article and then cover that surface with a silica coating layer (top layer) that has excellent corrosion resistance, but found that the adhesion of the first topcoat layer to the epoxy resin was poor. As a result of further research into the top layer, they found that forming the top layer using an organic-inorganic composite material mainly composed of silicon prepared by the sol-gel method results in excellent adhesion between the first topcoat layer and the top layer, and the desired object can be achieved, thereby completing the present invention.

[0007] That is, in order to achieve the above object, the present invention is summarized as follows [1] to [7]. [1] A coated metal article having, on the surface of the metal article, a first topcoat layer whose main component is an epoxy resin and a second topcoat layer whose main component is a zinc-aluminum composite coating, and a top layer on the surface of the first topcoat layer, which is made of an organic-inorganic composite material whose main component is silicon by the sol-gel method. [2] The coated metal article according to [1], wherein the second topcoat layer contains an acrylic resin and / or an epoxy resin. [3] The coated metal article according to [1] or [2], which has an undercoat layer between the metal article and the second overcoat layer. [4] The coated metal article according to [3], wherein the undercoat layer is formed by dry galvanization. [5] The coated metal article according to any one of [1] to [4], wherein the first topcoat layer has an arithmetic mean roughness (Ra) of 1 to 4 μm. [6] The coated metal article according to any one of [1] to [5], wherein the first topcoat layer has an Rz (maximum height) of 10 to 30 μm. [7] The coated metal article according to any one of [1] to [6], wherein the thickness of the uppermost layer is 3 to 30 μm. [Effects of the Invention]

[0008] From the above, the coated metal article of the present invention has a top layer on the surface of the first top coat layer, which is made of an organic-inorganic composite material mainly composed of silicon by the sol-gel method, and therefore can exhibit excellent durability and corrosion resistance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a coated metal article according to one embodiment of the present invention. [Figure 2] 3 is a cross-sectional view of a coated metal article according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0011] In this specification, the term "major component" refers to the component that is most abundant in the target substance, and typically accounts for preferably 50% by mass or more of the target substance, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, especially preferably 90% by mass or more, and most preferably 100% by mass.

[0012] Furthermore, in this specification, when the expression "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it means "X or more and Y or less," as well as "preferably larger than X" or "preferably smaller than Y." Furthermore, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." Furthermore, "X and / or Y (X and Y are any configuration)" means at least one of X and Y, and can mean three possibilities: X only, Y only, or X and Y. In the case of numerical ranges described in stages, the upper or lower limit of a numerical range in one stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0013] A coated metal article according to one embodiment of the present invention (hereinafter, sometimes referred to as "the coated metal article") will be described below with reference to FIG.

[0014] As shown in Figure 1, the coated metal article 10 has, on the surface of the metal article 1, a second topcoat layer 2b mainly composed of a zinc-aluminum composite coating and a first topcoat layer 2a mainly composed of an epoxy resin, and has, on the surface of the first topcoat layer 2a, a top layer 3 made of an organic-inorganic composite material mainly composed of silicon by the sol-gel method.

[0015] 《Metal articles》 The material of the metal article 1 is not particularly limited, and examples thereof include carbon steel, alloy steel, stainless steel, and special steel. Furthermore, metal articles 1 made of such materials may be processed into desired shapes such as plates or rods by methods such as rolling, casting, drawing, etc., or may be components and parts for building materials, construction machinery, ships, bridges, automobiles, containers, etc. Specific examples of the metal article 1 include staples, nails, bolts, nuts, screws, washers, clamps, pins, dowels, coils, and the like.

[0016] First top coat The first topcoat layer 2a is formed using a first topcoat layer material whose main component is epoxy resin.

[0017] [Epoxy resin] The epoxy resin basically means a resin containing an epoxy group in the molecule. Examples of the resin containing an epoxy group include bisphenol-type epoxy resins and novolac-type epoxy resins. These can be used alone or in combination of two or more.

[0018] Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, bisphenol A propylene oxide adduct type epoxy resin, bisphenol F propylene oxide adduct type epoxy resin, etc. Among these, bisphenol A type epoxy resin is preferred.

[0019] [Curing agent] A polyamine or the like may be used as a curing agent for the epoxy resin. The polyamine is a compound having two or more amino groups in one molecule.

[0020] Examples of the polyamine include aliphatic polyamines such as ethylenediamine, N-hydroxyethylethylenediamine, tetramethylenediamine, hexamethylenediamine, and diethylenetriamine, alicyclic polyamines such as 4,4'-diaminodicyclohexylmethane, 1,4-diaminocyclohexane, and isophoronediamine, aromatic polyamines such as 4,4'-diaminodiphenylmethane, tolylenediamine, benzidine, and phenylenediamine, aliphatic polyamines having an aromatic ring such as xylylenediamine and tetramethylxylylenediamine, and polyamidoamines obtained by reacting these polyamines with polymerized fatty acids. These may be used alone or in combination of two or more.

[0021] The content of the polyamine is preferably in the range of 0.5 to 2 equivalents of active hydrogen in the polyamine relative to the sum of the equivalents of epoxy groups and double bonds in the epoxy resin.

[0022] The first topcoat layer material may contain components other than the epoxy resin and curing agent (such as polyamine) as long as the effects of the present invention are not impaired. These components may be used alone or in combination of two or more.

[0023] There are no particular limitations on the method for forming the first topcoat layer 2a, and it is possible to use coating means such as a dipping method, a spraying method, a roller method, or the like.

[0024] The surface roughness of the first topcoat layer 2a is typically 0.5 to 6 μm, preferably 1 to 4 μm, in terms of Ra (arithmetic mean roughness). The surface roughness of the topcoat layer 2 is typically 5 to 40 μm, preferably 10 to 30 μm, in terms of Rz (maximum height). If Ra (arithmetic mean roughness) or Rz (maximum height) is too small, adhesion between the topcoat layer 2 and the uppermost layer 3 tends to be poor, resulting in poor scratch resistance (durability). If Ra (arithmetic mean roughness) or Rz (maximum height) is too large, corrosion resistance tends to be poor. The surface roughness can be measured using the method described in the Examples below.

[0025] The thickness of the first topcoat layer 2a is usually 10 to 100 μm, and preferably 20 to 70 μm.

[0026] Second top coat The second topcoat layer 2b is formed using a second topcoat layer material whose main component is a zinc-aluminum composite coating.

[0027] 〔binder〕 The second topcoat layer 2b may contain an acrylic resin, an epoxy resin, or the like as a binder.

[0028] [Metal particles] The metal particles forming the zinc-aluminum composite coating may contain, in addition to zinc and aluminum, metal particles such as magnesium, which is preferable in terms of adhesion between the second topcoat layer 2b and the first topcoat layer 2a. That is, the metal particles can create roughness on the surface of the second topcoat layer 2b, and the anchor effect improves adhesion between the second topcoat layer 2b and the first topcoat layer 2a. In addition, the metal particles can prevent moisture and oxygen from reaching the metal article, improving corrosion resistance and self-repairing properties.

[0029] The particle size of the metal particles is usually 10 to 100 μm, and preferably 20 to 80 μm.

[0030] The amount of the metal particles used is usually 10 to 500 parts by mass, and preferably 50 to 300 parts by mass, per 100 parts by mass of the binder (acrylic resin or the like).

[0031] The second topcoat layer material may contain other components besides the metal particles and binder (acrylic resin, etc.) as long as the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0032] There are no particular limitations on the method for forming the second topcoat layer 2b, and it is possible to use coating means such as a dipping method, a spraying method, a roller method, or the like.

[0033] The thickness of the second topcoat layer 2b is usually 10 to 100 μm, and preferably 20 to 70 μm.

[0034] 《Apex》 The top layer 3 is made of an organic-inorganic composite material containing silicon as a main component by the sol-gel method. An organic-inorganic composite material is formed from an organic material (raw material for the organic component) and an inorganic material (raw material for the inorganic component), and the organic material and the inorganic material are composited at the nano-level or molecular level. Organic-inorganic composite materials are formed by, for example, a polymerization reaction or other reaction between an inorganic material dispersed in an organic material and an organic material, resulting in a network-like crosslinked structure in which the inorganic component is highly dispersed in the organic component via chemical bonds. They can also be obtained by polycondensation of trifunctional alkoxysilane oligomers. Organic-inorganic composite materials can be formed by the sol-gel method.

[0035] The top layer 3 contains inorganic components, making it a dense layer and providing excellent corrosion resistance. Because it is a dense layer, the thickness required for corrosion protection can be reduced. The reduced thickness has little effect on the dimensions of the component, allowing for satisfactory dimensional accuracy. Furthermore, the top layer 3 contains silicon as an inorganic component, which provides excellent adhesion to the first topcoat layer 2a. Furthermore, if the top layer 3 further contains chromium as an inorganic component, the top layer 3 provides even better adhesion to the first topcoat layer 2a.

[0036] Examples of raw materials for the organic components that form the organic-inorganic composite material include curable resins. Examples of curable resins include acrylic resins, epoxy resins, and urethane resins. These may be used alone or in combination of two or more. Among these, acrylic resins and / or epoxy resins are more preferred, and a combination of acrylic resin and epoxy resin is particularly preferred. Using an acrylic resin and an epoxy resin in combination can increase the content of the organic components in the organic-inorganic composite material compared to using an acrylic resin or an epoxy resin alone. This results in particularly excellent alkali resistance. In addition, the content of the organic components can be adjusted over a wide range.

[0037] The inorganic component raw material forming the organic-inorganic composite material is a compound containing Si as the inorganic component, which can be composited by reacting with the organic component raw material, such as by polymerization. More specifically, the inorganic component raw material includes organometallic compounds. Examples of organometallic compounds include silane coupling agents, silane alkoxides, silane acylates, silane chelates, and silazanes. These can be used alone or in combination of two or more.

[0038] The silicon content in the top layer 3 is preferably within a range of 20 to 60 mass %, more preferably within a range of 30 to 50 mass %, based on the total amount of the top layer 3. If the silicon content is too low, corrosion resistance and adhesion to the first top coat layer 2a tend to deteriorate, while if the silicon content is too high, the organic component content becomes too low, and alkali resistance tends to deteriorate. The silicon content in the top layer 3 can be measured, for example, using X-ray photoelectron spectroscopy (XPS) or the like.

[0039] The uppermost layer material may contain components other than the organic-inorganic composite material containing silicon as a main component by the sol-gel method, as long as the effects of the present invention are not impaired. Examples of other components include chromium.

[0040] The method for forming the top layer 3 is not particularly limited, and for example, coating means such as a dipping method, a spraying method, a roller method, or the like can be used.

[0041] The thickness of the top layer 3 is usually 3 to 30 μm, and preferably 5 to 25 μm. If the thickness of the top layer 3 is too small, corrosion resistance tends to deteriorate, whereas if the thickness of the top layer 3 is too large, dimensional stability and adhesion tend to deteriorate.

[0042] The coated metal article 10 shown in FIG. 1 can be fabricated, for example, as follows. Specifically, a first topcoat layer material primarily composed of an epoxy resin and a second topcoat layer material primarily composed of a zinc-aluminum composite coating are prepared. An organic-inorganic composite material (top layer material) primarily composed of silicon is also prepared by a sol-gel process. Next, the second topcoat layer material is coated on the surface of the metal article 1, followed by drying or other treatments to form a second topcoat layer 2b of a predetermined thickness. Similarly, the first topcoat layer material is coated on the surface of the second topcoat layer 2b, followed by drying or other treatments to form a first topcoat layer 2a of a predetermined thickness. The top layer material is then coated on the surface of the first topcoat layer 2a by immersion, followed by drying, curing, and crosslinking to form a top layer 3 of a predetermined thickness. In this manner, the coated metal article 10 shown in FIG. 1 can be fabricated.

[0043] Next, a coated metal article according to another embodiment of the present invention will be described with reference to FIG.

[0044] As shown in FIG. 2, coated metal article 20 has the same configuration as coated metal article 10 shown in FIG. 1, except that a primer layer 4 is formed between metal article 1 and second top coat layer 2b.

[0045] << Undercoat layer >> The undercoat layer 4 is not particularly limited, and can be formed by methods such as metal plating, metal spraying, and metal powder coating. Of these, metal plating is particularly preferred in terms of adhesion to the metal article 1, corrosion resistance, and the like. Examples of metal plating include dry metal plating and hot-dip metal plating. Of these, dry metal plating, with dry zinc plating being particularly preferred. Dry metal plating can be performed using, for example, plasma. Dry metal plating is preferred because it does not involve pickling or hydrogen absorption during plating treatment, as is the case with wet metal plating, and therefore can suppress rusting of the underlying metal article 1.

[0046] The thickness of the undercoat layer 4 is usually 1 to 100 μm, and preferably 1 to 10 μm. If the thickness of the undercoat layer 4 is too small, the corrosion resistance tends to deteriorate, whereas if the thickness of the undercoat layer 4 is too large, the dimensional stability tends to deteriorate. [Example]

[0047] Next, examples will be described together with comparative examples, but the present invention is not limited to these examples.

[0048] First, prior to the Examples and Comparative Examples, the following materials were prepared.

[0049] [First topcoat layer material] (1) Resin-based coating agent with epoxy resin as the main component (content 50-80% by mass)

[0050] [Second topcoat layer material] (1) A coating solution containing a zinc-aluminum composite film as the main component (content 40 to 70% by mass)

[0051] [Top layer material] (1) Organic-inorganic composite materials based on silicon produced by the sol-gel method Product name: Protector HB-LTC2 (silica content 30-50% by mass), manufactured by Okuno Pharmaceutical Industries Co., Ltd.

[0052] (2) Inorganic silica by sol-gel method Product name: Protector S-6140 (silica content 20-50% by mass), manufactured by Okuno Pharmaceutical Industries Co., Ltd.

[0053] (3) Acrylic resin-inorganic silica particle dispersion paint A coating material was prepared by dispersing 70 parts by mass of acrylic resin in 30 parts by mass of inorganic silica.

[0054] [Examples 1 to 7] A steel material (material: SPCC, size: 70 × 150 mm, thickness: 0.8 mm) was dry-galvanized to form an undercoat layer (thickness: 3 μm). Next, the surface of the undercoat layer was coated with the second topcoat layer material and dried to form a second topcoat layer (thickness: 30 μm). Similarly, the surface of the second topcoat layer was coated with the first topcoat layer material and dried to form a first topcoat layer (thickness: 30 μm). Next, the surface of the first topcoat layer was coated with the top layer material (1) by a dipping method, and then dried, cured, and crosslinked to form a top layer of a predetermined thickness, thereby obtaining a coated metal article.

[0055] [Comparative Example 1] A coated metal article was obtained in the same manner as in Example 1, except that the top layer was not formed.

[0056] Comparative Example 2 A coated metal article was obtained in the same manner as in Example 1, except that the top layer was formed using the top layer material (2) instead of the top layer material (1).

[0057] Comparative Example 3 A coated metal article was obtained in the same manner as in Example 1, except that the top layer was formed using the top layer material (3) instead of the top layer material (1).

[0058] Comparative Example 4 The surface of a steel material (material: SPCC, size 70 × 150 mm, thickness 0.8 mm) was dipped in hot dip galvanizing to a predetermined thickness, followed by alkali cleaning, pure water cleaning, and drying to obtain a coated metal article having only a primer layer, but no first top coat layer, second top coat layer, or top layer.

[0059] Comparative Example 5 A coated metal article was obtained having only a primer layer of aluminum-magnesium alloy sprayed onto the surface of a steel material (material: SPCC, size 70 x 150 mm, thickness 0.8 mm), and no first top coat layer, second top coat layer, or top layer.

[0060] The coated metal articles of the examples and comparative examples thus obtained were evaluated for their properties according to the following criteria, and the results are shown in Tables 1 and 2 below.

[0061] <Scratch resistance (durability)> The scratch resistance of the obtained coated metal articles (number of samples: 3) was evaluated by a pencil hardness test. Those with 3H or more were evaluated as "◯", those with H or more but less than 3H were evaluated as "△", and those with less than H were evaluated as "X".

[0062] <Corrosion resistance (Corrosion resistance evaluation by CCT test)> The obtained coated metal article was subjected to an SST test based on JIS Z2371 (temperature: 35°C, salt spray with a concentration of 5% by weight) for 4 hours, followed by dry treatment at 60°C for 2 hours, and wet treatment at 50°C with 95% Rh for 2 hours, for a total of 8 hours as one cycle.This cycle was repeated up to 60 times, and the number of cycles until red rust appeared was measured. The number of cycles required to generate red rust was evaluated as "Good" if it was 50 or more, "Good" if it was 20 or more but less than 50, and "Poor" if it was less than 20.

[0063] <Adhesion> The resulting coated metal articles were evaluated for adhesion between the first topcoat layer and the top layer by a cross-cut tape peel test (2 mm intervals) based on JIS D0202. Peeling classification 0-1 was evaluated as "○", peeling classification 2-3 as "△", and peeling classification 4-5 as "×".

[0064] <Dimensional stability> The dimensional stability of the resulting coated metal article was evaluated based on the thread engagement depending on whether or not the female thread needed to be over-tapped. Then, those for which female thread over-tapping was not required were evaluated as "◯", and those for which female thread over-tapping was required were evaluated as "×".

[0065] <Surface roughness of the first topcoat layer> The Ra (arithmetic mean roughness) and Rz (maximum height) were measured using a stylus roughness tester based on JIS B0671.

[0066] <Top layer thickness> The thickness (film thickness) of the cross section of the uppermost layer of the obtained coated metal article was measured.

[0067] [Table 1]

[0068] [Table 2]

[0069] The results in Table 1 above show that the coated metal articles of Examples 1 to 7 are excellent in scratch resistance (durability), corrosion resistance, dimensional stability, and adhesion.

[0070] In contrast, the results in Table 2 show that the coated metal article of Comparative Example 1, which does not have a top layer, exhibits inferior corrosion resistance compared to the Examples, and the corrosion resistance was comparable to or inferior to that of the Examples. The coated metal article of Comparative Example 2 has a top layer formed using a material containing inorganic silica produced by the sol-gel method, and therefore exhibits corrosion resistance and adhesion comparable to or inferior to that of the Examples. The coated metal article of Comparative Example 3 has a top layer formed using a material in which an acrylic resin is dispersed in inorganic silica, and therefore exhibits significantly inferior scratch resistance (durability) compared to the Examples, and exhibits corrosion resistance and adhesion comparable to or inferior to that of the Examples. The coated metal article of Comparative Example 4 has only a hot-dip galvanized undercoat layer, and does not have a first topcoat layer, a second topcoat layer, or a top layer, and therefore exhibits significantly inferior dimensional stability compared to the Examples, and exhibits corrosion resistance comparable to or inferior to that of the Examples. The coated metal article of Comparative Example 5 only had a primer layer sprayed with an aluminum-magnesium alloy, and did not have a first topcoat layer, a second topcoat layer, or a top layer, so its dimensional stability was significantly inferior to that of the Examples, and its scratch resistance (durability) was equal to or inferior to that of the Examples. [Industrial Applicability]

[0071] The coated metal article of the present invention is preferably used for bridge bolts and the like, but can also be used for steel girders and the like. [Explanation of symbols]

[0072] 1 Metal articles 2a First top coat 2b Second top coat 3. Top layer 10 Coated metal articles

Claims

1. A coated metal article having, on the surface of the metal article, a first topcoat layer mainly composed of an epoxy resin and a second topcoat layer mainly composed of a zinc-aluminum composite coating, and a top layer on the surface of the first topcoat layer, the top layer being made of an organic-inorganic composite material mainly composed of silicon by a sol-gel method.

2. The coated metal article of claim 1 , wherein the second topcoat layer comprises an acrylic resin and / or an epoxy resin.

3. 3. The coated metal article of claim 1, further comprising a primer layer between the metal article and the second overcoat layer.

4. 4. The coated metal article of claim 3, wherein said primer layer is dry galvanized.

5. 3. The coated metal article according to claim 1, wherein the first topcoat layer has an arithmetic mean roughness (Ra) of 1 to 4 μm.

6. 3. The coated metal article according to claim 1, wherein the first topcoat layer has a maximum height Rz of 10 to 30 μm.

7. 3. The coated metal article according to claim 1, wherein the thickness of the top layer is 3 to 30 μm.

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