Desmutting agent for silicon-containing aluminum alloys and method for desmutting silicon-containing aluminum alloys

Abstract

The purpose of the present invention is to newly provide a desmutting agent. This silicon-containing aluminum alloy desmutting agent contains an alkaline compound and a silicate.

Description

[Technical Field]

[0001] The present invention relates to a desmutting agent for silicon-containing aluminum alloys and a method for desmutting silicon-containing aluminum alloys. [Background technology]

[0002] Patent Document 1 discloses a method for anodizing and plating silicon-containing aluminum alloys, in which a desmutting treatment is carried out using a desmutting agent consisting of an inorganic acid and a fluoride. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2016-125100 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a novel desmutting agent. [Means for solving the problem]

[0005] As a result of extensive research, the present inventors have developed a technology that enables effective removal of smut from silicon-containing aluminum alloys by immersing the alloys in a fluoride-free desmutting agent that contains an alkaline compound and a silicate.

[0006] That is, the present invention includes the following desmutting agent for silicon-containing aluminum alloys and method for desmutting silicon-containing aluminum alloys.

[0007] Section 1. A desmutting agent for silicon-containing aluminum alloys, A desmutting agent containing an alkaline compound and a silicate.

[0008] Section 2. Item 2. The desmutting agent according to Item 1, wherein the alkaline compound is at least one alkaline compound selected from the group consisting of hydroxides of alkaline metals selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; and ammonium compounds selected from the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediaminepyrocatechol (EDP), ammonium hydroxide (NH4OH), and hydrazine.

[0009] Section 3. 3. The desmutting agent according to claim 1, wherein the silicate is at least one silicate selected from the group consisting of lithium silicate, sodium silicate, and potassium silicate.

[0010] Section 4. 4. The desmutting agent according to any one of items 1 to 3, further comprising a persulfate.

[0011] Section 5. 5. The desmutting agent according to Item 4, wherein the persulfate is at least one persulfate selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and a double salt of potassium hydrogen persulfate, potassium hydrogen sulfate, and potassium sulfate.

[0012] Section 6. 6. The desmutting agent according to any one of items 1 to 5, wherein the desmutting agent contains the alkaline compound in an amount of 1.0% by mass to 20.0% by mass.

[0013] Section 7. 7. The desmutting agent according to any one of items 1 to 6, wherein when sodium silicate and / or potassium silicate is used as the silicate, the desmutting agent contains 20.0 mass % to 38.0 mass % of SiO and 6.5 mass % to 19.0 mass % of NaO and / or KO.

[0014] Section 8. 7. The desmutting agent according to any one of items 1 to 6, wherein when lithium silicate is used as the silicate, the desmutting agent contains 20.0 mass % to 22.0 mass % of SiO2 and 1.3 mass % to 3.1 mass % of Li2O.

[0015] Section 9. 9. The desmutting agent according to any one of items 4 to 8, wherein the desmutting agent contains 0.1% by mass to 10.0% by mass of the persulfate.

[0016] Section 10. A method for desmutting a silicon-containing aluminum alloy, comprising: (1) a step of immersing a silicon-containing aluminum alloy in a desmutting agent containing an alkali compound and a silicate; A smut removal method comprising:

[0017] Section 11. Item 11. The desmutting method according to Item 10, wherein the desmutting agent further contains a persulfate. [Effects of the Invention]

[0018] The present invention can provide a novel desmutting agent. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing an embodiment of the use of the desmutting agent of the present invention. Criteria 1 to 5 are used as the evaluation criteria for smut removal in Tables 1 to 7, and are listed in the tables. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below.

[0021] The embodiments of the present invention are intended to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the content of the invention.

[0022] In this specification, the terms "comprise" and "contain" are concepts that encompass all of "comprise," "consist essentially of," and "consist only of."

[0023] In this specification, when a numerical range is expressed as "A to B," it means A or more and B or less.

[0024] [1] Smut remover Aluminum alloys are used in (1) the production of castings by melting the aluminum alloy, pouring it into a sand mold, and then cooling and solidifying it to form a mold, and (2) the production of die-cast products by melting the aluminum alloy, pouring it into a metal mold, and then cooling and solidifying it under pressure to form a mold. In particular, die-casting production has excellent moldability.

[0025] Aluminum alloys have excellent electrical and thermal conductivity, as well as corrosion resistance. Cast and die-cast aluminum alloy products can be molded into complex shapes with high dimensional accuracy, making them popular for use in automobile parts.

[0026] Aluminum alloys easily form a dense and strong oxide film (Al2O3) due to oxygen in the atmosphere. Therefore, before forming a plating film on an aluminum alloy (article) or before dyeing it, pretreatments such as degreasing, etching, chemical polishing, smut removal, and anodizing are performed in this order. Then, a sealing treatment may be performed as a processing process to add high added value to the aluminum alloy (article) with the anodized film. Then, the aluminum alloy (article) with the anodized film may be subjected to an electrolytic coloring treatment, dyeing treatment, or the like, followed by a sealing treatment solution.

[0027] In the die-casting of aluminum alloys, etching is performed to remove the oxide film on the surface. Aluminum alloys contain a high content of silicon (approximately 10% by mass) to lower their melting point and improve their formability (castability). In the die-casting of aluminum alloys, silicon remains on the surface as an alloy component or impurity.

[0028] In anodizing of aluminum alloys, impurities remaining on the surface after acid treatment, etching, etc. are called "smut," and the process of removing smut is called "smut removal."

[0029] Smut is a black deposit that adheres to the aluminum surface during etching, chemical polishing, etc. Smut is primarily composed of metal oxides and hydroxides derived from copper (Cu), silicon (Si), etc. contained in the aluminum alloy. If anodizing is performed with smut remaining on the surface of the aluminum alloy, problems such as poor appearance of the aluminum alloy surface, contamination of the electrolyte used in the anodizing process, and powdering of the aluminum alloy surface can occur.

[0030] Smut is generally removed from aluminum alloys (articles) using nitric acid, but because aluminum alloy castings and die-cast products have a high silicon content (about 10% by mass) and the smut also contains a lot of silicon, it is difficult to effectively remove smut from aluminum alloy castings and die-cast products using nitric acid alone.

[0031] Therefore, there is a conventional technique for removing smut from aluminum alloy castings and die-cast products that uses hydrofluoric acid in addition to nitric acid. However, fluorine compounds are considered environmentally regulated substances (environmentally burdensome substances), and their use is restricted.

[0032] The desmutting agent of the present invention is characterized by containing an alkali compound and a silicate. By immersing a silicon-containing aluminum alloy in the desmutting agent of the present invention, smut from the silicon-containing aluminum alloy can be effectively removed. The desmutting agent of the present invention is particularly capable of removing smut from cast and die-cast products made of aluminum alloys with a high silicon content, and has excellent smut removal properties.

[0033] The desmutting agent of the present invention does not require the use of hydrofluoric acid, is highly safe to work with, places little burden on the environment, and is useful for aluminum materials such as aluminum alloy castings, die-cast products, and wrought materials.

[0034] [1-1] Alkaline compounds The desmutting agent for silicon-containing aluminum alloys of the present invention contains an alkali compound, which allows the desmutting agent of the present invention to effectively dissolve silicon contained in aluminum alloys and remove smut.

[0035] The alkali compound is preferably at least one alkali compound selected from the group consisting of hydroxides of alkali metals selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; and ammonium compounds selected from the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediaminepyrocatechol (EDP), ammonium hydroxide (NH4OH), and hydrazine. The alkali compound is more preferably potassium hydroxide or tetramethylammonium hydroxide (TMAH), which can effectively dissolve silicon contained in aluminum alloys (at a high dissolution rate).

[0036] The alkaline compounds may be used alone or in the form of a mixture (blend) of two or more kinds.

[0037] In the desmutting agent of the present invention, the mass percent (wt%) of the alkali compound is not particularly limited, and is preferably 1.0 wt% to 20.0 wt% (content in 1 L of the desmutting agent), more preferably 3.0 wt% to 15.0 wt%, and even more preferably 6.0 wt% to 10.0 wt%. By adjusting the concentration of the alkali compound within the above range, the desmutting agent of the present invention can effectively dissolve silicon contained in aluminum alloys.

[0038] [1-2] Silicate The desmutting agent for silicon-containing aluminum alloys of the present invention contains a silicate, which makes it possible to effectively inhibit dissolution of aluminum contained in the aluminum alloy.

[0039] The silicate is preferably at least one selected from the group consisting of lithium silicate, sodium silicate, and potassium silicate. The silicate is more preferably sodium silicate or potassium silicate, which provides good liquid stability of the desmutting agent.

[0040] The silicate may be used alone or in the form of a mixture (blend) of two or more kinds.

[0041] Silicates are mixtures of SiO2 and Na2O (and / or K2O) (and / or Li2O) in specific ratios, and are expressed by the chemical formula Na2O (and / or K2O) (and / or Li2O)·nSiO2·XH2O in aqueous solution, and by the chemical formula Na2O (and / or K2O) (and / or Li2O)·nSiO2 in powder form.

[0042] When sodium silicate and / or potassium silicate is used as the silicate in the desmutting agent of the present invention, the mass percentage (wt%) of SiO2 is preferably 20.0 wt% to 38.0 wt% (content in 1 L of the desmutting agent), more preferably 25.0 wt% to 30.0 wt%. The mass percentage (wt%) of Na2O (and / or KO) is preferably 6.5 wt% to 19.0 wt% (content in 1 L of the desmutting agent), more preferably 9.0 wt% to 16.0 wt%.

[0043] When lithium silicate is used as the silicate in the desmutting agent of the present invention, the mass percentage (wt%) of SiO2 is preferably 20.0 wt% to 22.0 wt% (content in 1 L of the desmutting agent), although there are no particular limitations. Also, the mass percentage (wt%) of Li2O is preferably 1.3 wt% to 3.1 wt% (content in 1 L of the desmutting agent), and particularly preferably 2.1 wt% to 2.7 wt%.

[0044] [1-3] Persulfate The desmutting agent for silicon-containing aluminum alloys of the present invention preferably further contains a persulfate (oxidizing agent). By containing the persulfate, the desmutting agent of the present invention can effectively suppress the dissolution of aluminum contained in the aluminum alloy.

[0045] The persulfate is preferably at least one persulfate selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and a double salt of potassium hydrogen persulfate, potassium hydrogen sulfate, and potassium sulfate (2KHSO5·KHSO4·K2SO4).

[0046] The persulfates may be used singly or in the form of a mixture (blend) of two or more kinds.

[0047] In the desmutting agent of the present invention, the mass percent (wt%) of the persulfate is not particularly limited, and is preferably 0.1 wt% to 10.0 wt% (content in 1 L of the desmutting agent), more preferably 0.3 wt% to 5.0 wt%, and even more preferably 0.5 wt% to 2.0 wt%. By adjusting the concentration of the persulfate within the above range, the desmutting agent of the present invention can effectively suppress dissolution of aluminum contained in an aluminum alloy.

[0048] [1-4] Anti-clinker agents, etc. The desmutting agent for silicon-containing aluminum alloys of the present invention may contain other components such as an anti-clinker agent, as needed, such as organic acids such as tartaric acid and gluconic acid, or salts thereof, and sorbitol.

[0049] [2] Smut removal method The method for desmutting a silicon-containing aluminum alloy of the present invention comprises the steps of (1) immersing the silicon-containing aluminum alloy in a desmutting agent containing an alkali compound and a silicate, the desmutting agent preferably further containing a persulfate.

[0050] The desmutting agent containing the alkali compound, the silicate, and the persulfate is the desmutting agent for silicon-containing aluminum alloys of the present invention.

[0051] The alkali compound, silicate, and persulfate contained in the desmutting agent, as well as the clinker inhibitor that may further be contained, are as described above in [1] Desmutting Agent.

[0052] When the surface of a silicon-containing aluminum alloy is treated before anodizing using the method for removing smut from a silicon-containing aluminum alloy of the present invention, it has excellent smut removal properties, high operational safety, and a low environmental impact, and can be applied to aluminum alloy castings, die-cast products, wrought materials, and other aluminum materials.

[0053] When an aluminum alloy (article) is subjected to anodizing, pretreatments include degreasing, etching, or chemical polishing, desmutting, and anodizing, and if necessary, dyeing and sealing are performed.

[0054] On the other hand, when applying a plating film to an aluminum alloy (article), degreasing treatment, etching treatment, chemical polishing treatment, desmutting treatment, zinc substitution, and plating treatment such as electroless nickel are carried out.

[0055] The surface treatment of aluminum alloys will be described in detail below.

[0056] [2-1] Degreasing This is a process to remove oil that has adhered to the aluminum alloy. The degreasing process uses an alkaline degreasing agent based on phosphate and surfactant, which can remove the oil that has adhered to the aluminum alloy surface by the emulsifying action of the surfactant.

[0057] The degreasing agent may be acidic or alkaline, and there are no restrictions on the treatment conditions (concentration, temperature, time, etc.) as long as it is a chemical that can remove oil from the aluminum surface.

[0058] [2-2] Etching or chemical polishing Etching is a process to remove the oxide film (Al2O3) formed on the surface of aluminum alloys. The oxide film formed on the surface of aluminum alloys can be dissolved and removed using a high-temperature strong alkaline solution based on sodium hydroxide.

[0059] Etching roughens the surface of aluminum alloys and makes them lose their luster. The alloy components, such as silica (silicon oxide) and copper, produced by the etching process remain on the surface of the aluminum alloy as smut.

[0060] Chemical polishing is a process that smooths and polishes the surface of aluminum alloys using a high-temperature phosphoric acid-based solution.

[0061] The etching agent and chemical polishing agent may be either acidic or alkaline, and there are no limitations on the treatment conditions (concentration, temperature, time, etc.).

[0062] [2-3] Smut removal treatment This process removes impurities (smut) consisting of alloy components such as silica (silicon oxide) and copper that remain after the etching and chemical polishing processes. The alkaline compound contained in the smut remover of the present invention is effective in removing silica (silicon oxide) because it can effectively dissolve the silicon contained in aluminum alloys. An acidic solution containing an inorganic acid such as nitric acid is effective in removing alloy components such as copper.

[0063] Before treatment with the desmutting agent of the present invention, it is necessary to treat with nitric acid or the like. Alternatively, treatment with the desmutting agent of the present invention may be followed by treatment with nitric acid or the like. The desmutting agent for alloy components such as copper may be either acidic or alkaline, and there are no limitations on the treatment conditions (concentration, temperature, time, etc.).

[0064] The silicon-containing smut removal treatment includes a step of immersing a silicon-containing aluminum alloy in the desmutting agent of the present invention. Methods for immersing a silicon-containing aluminum alloy in the desmutting agent of the present invention include, for example, mixing the desmutting agent with the silicon-containing aluminum alloy, dropping the desmutting agent onto the silicon-containing aluminum alloy, or immersing the silicon-containing aluminum alloy in the desmutting agent.

[0065] In the desmutting method of the present invention, a heat treatment may be carried out, if necessary, using the desmutting agent of the present invention. The temperature (immersion temperature) for the desmutting treatment is preferably about 40°C to 100°C, more preferably about 60°C to 95°C. By adjusting the temperature for the desmutting treatment within the above temperature range, smut can be effectively removed.

[0066] The time for the smut removal treatment (immersion time) can be set appropriately depending on the conditions for smut removal. The time for the smut removal treatment is preferably about 1 to 60 minutes, and more preferably about 5 to 45 minutes. By adjusting the time for the smut removal treatment within the above time range, smut can be removed effectively.

[0067] [2-4] Anodizing or plating Anodizing involves immersing an aluminum alloy in an electrolytic solution such as sulfuric acid, oxalic acid, or phosphoric acid, and passing an electric current through it as an anode (positive electrode). This creates a dense, positively charged, porous oxide film on the surface of the aluminum alloy. The formation of this oxide film on the surface of the aluminum alloy provides functionality such as corrosion resistance and abrasion resistance, and if necessary, negatively charged organic or inorganic dyes can be adsorbed onto the oxide film to dye it, adding decorative value. After the oxide film is formed, it is treated with a high-temperature sealing solution such as nickel acetate to close the micropores.

[0068] Regarding plating, aluminum alloys easily form natural oxide films, which deteriorate the adhesion of plating, so zinc substitution (zincate treatment) is performed to improve the adhesion of the plating. Normally, zincate treatment is performed twice (double zincate treatment) to further improve adhesion. After double zincate treatment, electroless plating such as nickel-phosphorus plating or electroplating such as copper sulfate plating is performed to impart functionality such as corrosion resistance and abrasion resistance. [Example]

[0069] The present invention will be specifically described below with reference to examples.

[0070] The present invention is not limited to the following specific examples.

[0071] A silicon-containing aluminum alloy (ADC12 manufactured by Nippon Test Panel Co., Ltd.) used in the following Examples and Comparative Examples was prepared according to the following conditions. The prepared test pieces were used to evaluate smut removal, so no anodizing or sealing treatment was performed after the smut removal treatment. Performing anodizing and sealing treatment after the smut removal treatment does not adversely affect performance. Water washing was performed between the following preparation steps.

[0072] The degreasing treatment involved immersion in Top ADD-100 (manufactured by Okuno Chemical Industries Co., Ltd.) at 55°C for 2 minutes. The etching treatment involved 5% sodium hydroxide solution at 55°C for 30 seconds. The chemical polishing treatment involved using a mixed solution of 700 mL / L of 85% phosphoric acid and 300 mL / L of 98% sulfuric acid at 95°C for 30 seconds. The desmutting treatment involved using 20% ​​nitric acid at 25°C for 1 minute to remove alloy components such as copper.

[0073] The test pieces were degreased, etched, or chemically polished, and desmutted using the methods described above, and then immersed in a desmutting agent containing an alkali compound, silicate, and persulfate to remove silicon-containing smut. The bath temperature for the desmutting treatment was 90°C, and the treatment was left stationary for 30 minutes.

[0074] The smut removal ability was evaluated by visually inspecting the appearance after treatment to confirm the presence of smut residue. The compositions of the desmutting agents and the results of smut removal are shown in Tables 1 to 7.

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3]

[0078] [Table 4]

[0079] [Table 5]

[0080] [Table 6]

[0081] [Table 7]

[0082] The desmutting agent of the present invention contains an alkaline compound and a silicate, and by immersing a silicon-containing aluminum alloy in the agent, it was possible to effectively suppress the dissolution of aluminum contained in the aluminum alloy, dissolve the silicon, and remove smut (Examples 1 to 3, 13 to 15, 22 to 24, 31 to 33, 40 to 42, 52 to 54).

[0083] The desmutting agent of the present invention further contains a persulfate, which allows it to more effectively inhibit the dissolution of aluminum contained in aluminum alloys, dissolve silicon, and remove smut (Examples 4 to 12, 16 to 21, 25 to 30, 34 to 39, 43 to 51, and 55 to 60).

[0084] Smut could not be removed by treatment with an alkaline compound, silicate, or oxidizing agent alone (Comparative Examples 1, 2, and 5). Smut could not be removed by a combination of silicate and persulfate, or a combination of an alkaline compound and persulfate (Comparative Examples 3 and 4).

[0085] [3] Industrial Applicability By immersing a silicon-containing aluminum alloy in the desmutting agent of the present invention, smut from the silicon-containing aluminum alloy can be effectively removed. The desmutting agent of the present invention is particularly capable of removing smut from cast and die-cast products made of aluminum alloys with a high silicon content, and has excellent smut removal properties. The desmutting agent of the present invention also does not require the use of hydrofluoric acid, has high work safety, has a low environmental impact, and is useful for aluminum materials such as aluminum alloy casts, die-cast products, and wrought materials.

Claims

1. A desmutting agent for silicon-containing aluminum alloys, Contains an alkali compound, a silicate, and a persulfate, The alkali compound is at least one alkali compound selected from the group consisting of hydroxides of alkali metals selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; and ammonium compounds selected from the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediaminepyrocatechol (EDP), ammonium hydroxide (NH 4 OH), and hydrazine; The silicate is at least one silicate selected from the group consisting of lithium silicate, sodium silicate, and potassium silicate. Smut remover.

2. 2. The desmutting agent according to claim 1, wherein the persulfate is at least one persulfate selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and a double salt of potassium hydrogen persulfate, potassium hydrogen sulfate, and potassium sulfate.

3. 2. The desmutting agent according to claim 1, wherein the alkali compound is contained in the desmutting agent in an amount of 1.0% by mass to 20.0% by mass.

4. When sodium silicate and / or potassium silicate is used as the silicate, the SiO 2 Contains 20.0 mass% to 38.0 mass% of Na 2 O and / or K 2 2. The desmutting agent according to claim 1, comprising 6.5% by mass to 19.0% by mass of O.

5. When lithium silicate is used as the silicate, the SiO 2 Contains 20.0 mass% to 22.0 mass% of Li 2 2. The desmutting agent according to claim 1, comprising 1.3% by mass to 3.1% by mass of O.

6. 2. The desmutting agent according to claim 1, wherein the persulfate is contained in the desmutting agent in an amount of 0.1% by mass to 10.0% by mass.

7. A method for desmutting a silicon-containing aluminum alloy, comprising: (1) A method for removing silicon from an aluminum alloy by immersing the aluminum alloy in a desmutting agent containing an alkali compound, a silicate, and a persulfate, The alkali compound is at least one alkali compound selected from the group consisting of hydroxides of alkali metals selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; and ammonium compounds selected from the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediaminepyrocatechol (EDP), ammonium hydroxide (NH 4 OH), and hydrazine; The silicate is at least one silicate selected from the group consisting of lithium silicate, sodium silicate, and potassium silicate. Smut removal method.

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