Detergents for silicon-containing aluminum alloys and methods for cleaning silicon-containing aluminum alloys

Abstract

The purpose of this invention is to provide a new detergent. This detergent is for silicon-aluminum alloys and contains an alkaline compound and silicates.

Description

Technical Field

[0001] This invention relates to a detergent for silicon-containing aluminum alloys and a method for cleaning silicon-containing aluminum alloys. Prior Technology

[0002] Patent document 1 discloses that in the anodizing treatment method and plating method of silicon-containing aluminum alloy, a decontamination agent composed of inorganic acid and fluoride is used for decontamination treatment.

[0003] [Preliminary Technology Documents] [Patent Literature] [Patent Document 1] Japanese Patent Application Publication No. 2016-125100 Summary of the Invention

[0004] [Invention Summary] [The problem the invention aims to solve] The purpose of this invention is to provide a new detergent.

[0005] [Methods used to solve problems] As a result of in-depth research, the inventors of this case developed the following technology: by immersing silicon-containing aluminum alloys in a detergent containing alkaline compounds and silicates, but without fluorides, stains on silicon-containing aluminum alloys can be effectively removed.

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

[0007] Item 1. A detergent, which is a detergent for aluminum-silicon alloys, and contains an alkaline compound and silicates.

[0008] Item 2. As in the detergent described in item 1 above, the aforementioned alkaline compound is selected from at least one alkaline compound of the group consisting of: Hydroxides selected from alkali metals in 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), ethylenediamine catechol (EDP), ammonium hydroxide (NH4OH), and hydrazine.

[0009] Item 3. The detergent described in item 1 or 2 above, wherein the silicate is selected from at least one silicate in the group consisting of lithium silicate, sodium silicate, and potassium silicate.

[0010] Item 4. The detergents mentioned in any of items 1 to 3 above contain persulfates.

[0011] Item 5. As in the detergent described in item 4 above, the aforementioned persulfate is selected from at least one persulfate from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and potassium peroxymonosulfate, which together with potassium persulfate and potassium sulfate form a complex salt.

[0012] Item 6. The detergent described in any of items 1 to 5 above contains 1.0% to 20.0% by mass of the aforementioned alkaline compound.

[0013] Item 7. When sodium silicate and / or potassium silicate are used as the silicates in any of the detergents described in items 1 to 6 above, the detergent contains 20.0% to 38.0% by mass of SiO2 and 6.5% to 19.0% by mass of Na2O and / or K2O.

[0014] Item 8. When lithium silicate is used as the silicate in any of the detergents described in items 1 to 6 above, the detergent contains 20.0% to 22.0% by mass of SiO2 and 1.3% to 3.1% by mass of Li2O.

[0015] Item 9. The detergent described in any of items 4 to 8 above contains 0.1% to 10.0% by mass of the aforementioned persulfate.

[0016] Item 10. A decontamination method, specifically a decontamination method using silicon-aluminum alloys, comprising: (1) The step of immersing silicon-containing aluminum alloy in a detergent containing an alkaline compound and silicates.

[0017] Item 11. The cleaning method described in item 10 above contains a cleaning agent that contains persulfate.

[0018] This invention provides a new type of detergent. Simple Explanation of the Diagram

[0019] Figure 1 is a diagram showing the usage of the detergent of the present invention. Criteria 1 to 5 are listed in the tables as evaluation criteria for detergency in Tables 1 to 7. Implementation

[0020] [The form in which the invention is implemented] The present invention will be described in detail below.

[0021] The description of the embodiments of the present invention is provided to enable a better understanding of the purpose of the invention. Unless otherwise specified, the invention is not limited thereto.

[0022] In this specification, "comprise" and "contain" include any of the following concepts: "comprise", "consist essentially of", and "consist of".

[0023] In this specification, when the numerical range is represented as "A~B", it means above A and below B.

[0024] [1] Stain remover Aluminum alloys are used to: (1) melt aluminum alloys and pour them into a sand mold to cool and harden them, thereby producing castings; or (2) melt aluminum alloys and pour them into a mold to cool and harden them while applying pressure, thereby producing die castings. In particular, when using die casting, the formability of the products is excellent.

[0025] Aluminum alloys have excellent electrical and thermal conductivity, as well as excellent corrosion resistance. Castings and die-cast products made of aluminum alloys can be formed into complex shapes, and are characterized by high dimensional accuracy of shaped products, making them widely used in vehicle parts.

[0026] Aluminum alloys readily form a dense and robust oxide film (Al₂O₃) due to atmospheric oxygen. Therefore, before forming the coating film or before coloring, aluminum alloys (articles) undergo pretreatment processes such as degreasing, etching, chemical polishing, cleaning, and anodizing. Afterward, a sealing process can be performed to impart high added value to aluminum alloys (articles) with anodized coatings. Alternatively, an electrolytic coloring or dyeing process can be applied to aluminum alloys (articles) with anodized coatings followed by a sealing solution.

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

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

[0029] Stains are black deposits that adhere to the aluminum surface during etching, chemical polishing, and other processes. The main components of these stains are metal oxides and hydroxides formed from copper (Cu) and silicon (Si) contained in the aluminum alloy. If anodizing is performed on the aluminum alloy surface with residual stains, problems such as poor surface appearance of the aluminum alloy, contamination of the electrolyte used for anodizing, and the generation of scattered dust on the aluminum alloy surface may occur.

[0030] For aluminum alloys, nitric acid is generally used to remove stains. However, aluminum alloy castings and die-cast products have a high silicon content (around 10% by mass), and the stains also contain a lot of silicon. Therefore, nitric acid alone is not sufficient to effectively remove stains from aluminum alloy castings and die-cast products.

[0031] Therefore, in the past, in addition to nitric acid, hydrofluoric acid was used to remove stains from aluminum alloy castings and die-cast products. However, fluorinated compounds are environmentally regulated substances (substances that burden the environment), and their use is restricted.

[0032] The detergent of this invention is characterized by containing an alkaline compound and silicates. Immersing silicon-containing aluminum alloys in the detergent of this invention effectively removes stains from the silicon-containing aluminum alloys. The detergent of this invention is particularly effective in removing stains from aluminum alloy castings and die-cast products with high silicon content, demonstrating excellent cleaning power.

[0033] Moreover, the detergent of this invention does not require the use of hydrofluoric acid, has high operational safety, causes less environmental burden, and is suitable for use in aluminum alloy castings, die-cast products, extended materials and other aluminum materials.

[0034] [1-1] Alkali compounds The detergent for silicon-containing aluminum alloys of this invention contains an alkaline compound. By containing an alkaline compound, the detergent of this invention can effectively dissolve the silicon contained in the aluminum alloy and remove stains.

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

[0036] The aforementioned alkali compounds can be used alone or in combination with two or more.

[0037] In the detergent of the present invention, the mass percentage (wt%) of the aforementioned alkaline compound is not particularly limited, but is preferably 1.0wt% to 20.0wt% (content in 1L of detergent), more preferably 3.0wt% to 15.0wt%, and even more preferably 6.0wt% to 10.0wt%. In the detergent of the present invention, by adjusting the aforementioned alkaline compound to the aforementioned concentration range, silicon contained in aluminum alloys can be effectively dissolved.

[0038] [1-2]Silica The detergent for silicon-containing aluminum alloys of the present invention contains silicates. By containing silicates, the detergent of the present invention can effectively inhibit the dissolution of aluminum contained in aluminum alloys.

[0039] The aforementioned silicate is preferably selected from at least one silicate in the group consisting of lithium silicate, sodium silicate, and potassium silicate. Sodium silicate and potassium silicate are more preferably selected as silicates, as they provide good liquid stability for the detergent.

[0040] The aforementioned silicates can be used alone or in combination with two or more.

[0041] A silicate is a mixture of SiO2 and Na2O (and / or K2O) (and / or Li2O) in a specific ratio. When it is an aqueous solution, it is represented by the chemical formula Na2O (and / or K2O) (and / or Li2O)·nSiO2·XH2O; when it is a powder, it is represented by the chemical formula Na2O (and / or K2O) (and / or Li2O)·nSiO2.

[0042] In the detergent of the present invention, when sodium silicate and / or potassium silicate are used as silicates, the mass percentage (wt%) of SiO2 is not particularly limited, but is preferably 20.0wt% to 38.0wt% (content in 1L of detergent), more preferably 25.0wt% to 30.0wt%. Furthermore, the mass percentage (wt%) of Na2O (and / or K2O) is preferably 6.5wt% to 19.0wt% (content in 1L of detergent), more preferably 9.0wt% to 16.0wt%.

[0043] In the detergent of this invention, when lithium silicate is used as the silicate, the mass percentage (wt%) of SiO2 is not particularly limited, but is preferably 20.0wt% to 22.0wt% (content in 1L of detergent). Furthermore, the mass percentage (wt%) of Li2O is preferably 1.3wt% to 3.1wt% (content in 1L of detergent), and particularly preferably 2.1wt% to 2.7wt%.

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

[0045] The aforementioned persulfate is preferably selected from at least one persulfate from the group consisting of the following complex salts: sodium persulfate, potassium persulfate, ammonium persulfate, and potassium peroxymonosulfate, which together with potassium persulfate and potassium sulfate form a complex salt (2KHSO₅·KHSO₄·K₂SO₄).

[0046] The aforementioned persulfates can be used alone or in combination with two or more.

[0047] In the detergent of the present invention, the mass percentage (wt%) of the aforementioned persulfate is not particularly limited, but is preferably 0.1wt% to 10.0wt% (content in 1L of detergent), more preferably 0.3wt% to 5.0wt%, and even more preferably 0.5wt% to 2.0wt%. By adjusting the aforementioned persulfate to the aforementioned concentration range, the detergent of the present invention can effectively inhibit the dissolution of aluminum contained in aluminum alloys.

[0048] [1-4] Anti-caking agents, etc. The silicon-aluminum alloy detergent of this invention may also include other components such as anti-clinker agents, depending on the requirements. Examples of other components include, for instance, organic acids such as tartaric acid and gluconic acid or their salts, and sorbitol.

[0049] [2] Stain removal methods The present invention provides a method for cleaning silicon-containing aluminum alloys, comprising (1) immersing the silicon-containing aluminum alloy in a cleaning agent containing an alkaline compound and a silicate. The cleaning agent preferably further contains persulfate.

[0050] The detergent containing the aforementioned alkaline compound, the aforementioned silicate, and the aforementioned persulfate is the detergent for silicon-containing aluminum alloys of the present invention.

[0051] The aforementioned detergent contains alkaline compounds, silicates, persulfates, and may also contain anti-caking agents, as described in the description of the aforementioned [1] detergent.

[0052] The method for cleaning silicon-containing aluminum alloys according to the present invention provides excellent cleaning performance, high operational safety, and low environmental impact for surface treatment of silicon-containing aluminum alloys before anodizing. It is also applicable to aluminum alloy castings, die-cast products, extended materials, and other aluminum materials.

[0053] When anodizing aluminum alloys (articles), degreasing, etching, chemical polishing, cleaning, and anodizing are performed as pretreatments, and dyeing and sealing are performed as needed.

[0054] On the other hand, when applying a coating to aluminum alloys (articles), degreasing, etching, chemical polishing, cleaning, zinc substitution, and electroless nickel plating are performed.

[0055] The following details the surface treatment of aluminum alloys.

[0056] [2-1] Degreasing treatment This is a step to remove oil adhering to aluminum alloys. The degreasing treatment uses an alkaline degreasing agent based on phosphates and surfactants. Through the emulsifying effect of the surfactants, the oil adhering to the surface of the aluminum alloy can be removed.

[0057] Degreasing agents, whether acidic or alkaline, are not limited by treatment conditions (concentration, temperature, time, etc.) if they are chemicals that can remove oil from aluminum surfaces.

[0058] [2-2] Etching or chemical polishing Etching is a step to remove the oxide film (Al₂O₃) formed on the surface of aluminum alloys. A high-temperature, strong alkaline solution based on sodium hydroxide can be used to dissolve and remove the oxide film formed on the aluminum alloy surface.

[0059] Etching processes can roughen the surface of aluminum alloys, causing them to lose their luster. The silicon dioxide (silicon oxide) and copper alloy components generated during etching can remain on the aluminum alloy surface as stains.

[0060] Chemical polishing is a process that smooths the surface of aluminum alloys and imparts a glossy finish. A high-temperature solution based on phosphoric acid is used to smooth the surface of aluminum alloys and impart a glossy finish.

[0061] There are no restrictions on the etchant or chemical abrasive, whether it is acidic or alkaline, or on the processing conditions (concentration, temperature, time, etc.).

[0062] [2-3] Decontamination treatment This process involves removing impurities (stains) composed of silicon dioxide (silicon oxide), copper, and other alloying components that remain after etching and chemical polishing. The detergent of this invention contains alkaline compounds that effectively dissolve the silicon in aluminum alloys, thus effectively removing silicon dioxide (silicon oxide). Acidic solutions containing inorganic acids such as nitric acid effectively remove copper and other alloying components.

[0063] Before treatment with the detergent of this invention, it is necessary to treat with nitric acid or the like. Alternatively, treatment with the detergent of this invention followed by treatment with nitric acid or the like is also possible. The detergent containing copper or other alloy components is not limited in terms of acidity or alkalinity, nor in terms of treatment conditions (concentration, temperature, time, etc.).

[0064] Silicon-containing cleaning treatment includes the step of immersing a silicon-containing aluminum alloy in the cleaning agent of the present invention. Methods for immersing the silicon-containing aluminum alloy in the cleaning agent of the present invention include, for example: mixing the cleaning agent with the silicon-containing aluminum alloy, dripping the cleaning agent onto the silicon-containing aluminum alloy, and immersing the silicon-containing aluminum alloy in the cleaning agent.

[0065] In the stain removal method of this invention, when using the stain remover of this invention, heat treatment can also be performed as needed. The stain removal treatment temperature (immersion temperature) is preferably around 40℃~100℃, and more preferably around 60℃~95℃. By adjusting the stain removal treatment temperature within the aforementioned temperature range, stains can be effectively removed.

[0066] The stain removal treatment time (immersion time) can be set appropriately according to the condition of the stain removal. The stain removal treatment time should be around 1 minute to 60 minutes, preferably around 5 minutes to 45 minutes. By adjusting the stain removal treatment time within the aforementioned range, stains can be removed effectively.

[0067] [2-4] Anodizing treatment, or plating Anodizing involves immersing an aluminum alloy in an electrolytic solution such as sulfuric acid, oxalic acid, or phosphoric acid, which serves as the anode (positive electrode) to conduct electricity. This current forms a dense, porous, positively charged oxide film on the aluminum alloy surface. This oxide film imparts functional properties such as corrosion resistance and wear resistance. Furthermore, negatively charged organic and inorganic dyes can be adsorbed onto the oxide film to color it, adding decorative value. After the oxide film is formed, a high-temperature sealing solution containing nickel acetate is used to seal the micropores.

[0068] Regarding plating, aluminum alloys tend to naturally form an oxide film, which reduces plating adhesion. Therefore, zinc substitution (zincate treatment) is performed to improve plating adhesion. Typically, to further enhance adhesion, a second zincate treatment (secondary zincate treatment) is conducted. After the secondary zincate treatment, electroless plating such as nickel-phosphorus plating or copper sulfate plating is performed to impart functional properties such as corrosion resistance and wear resistance.

[0069] [Example] The following examples illustrate the present invention in detail.

[0070] This invention is not limited to the following specific embodiments.

[0071] The silicon-aluminum alloy (ADC12, manufactured by Testpanel, Nippon Chemi-Conductor Co., Ltd.) used in the following examples and comparative examples was prepared under the following conditions. Since the prepared test pieces were to be evaluated for their decontamination properties, anodizing and sealing treatments were not performed after the decontamination treatment. Even if anodizing and sealing treatments were performed after the decontamination treatment, it would not adversely affect the performance. Furthermore, water washing was performed between the following preparation steps.

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

[0073] Test pieces that have undergone degreasing, etching, chemical polishing, or cleaning of copper and other alloy components using the methods described above are immersed in a cleaning agent containing alkaline compounds, silicates, and persulfates to remove the silica content. Furthermore, the cleaning process is carried out at a bath temperature of 90°C and the sample is left to stand for 30 minutes.

[0074] The detergency was evaluated by visually assessing the appearance after treatment and confirming any stain residue. The composition of the detergent and the detergency results 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 detergent of the present invention contains an alkaline compound and a silicate. When a silicon-containing aluminum alloy is immersed in the detergent of the present invention, the dissolution of aluminum contained in the aluminum alloy can be effectively inhibited, and silicon can be dissolved, thereby removing stains (Examples 1-3, 13-15, 22-24, 31-33, 40-42, 52-54).

[0083] The detergent of the present invention, by containing more persulfate, can more effectively inhibit the dissolution of aluminum contained in aluminum alloys and dissolve silicon, thereby removing stains (Examples 4-12, 16-21, 25-30, 34-39, 43-51, 55-60).

[0084] Treatment with alkali compounds, silicates, or oxidants alone failed to remove stains (Comparative Examples 1, 2, and 5). Combinations of silicates and persulfates, or combinations of alkali compounds and persulfates, did not remove stains (Comparative Examples 3 and 4).

[0085] [3] Industrial availability By immersing silicon-containing aluminum alloys in the detergent of this invention, stains on silicon-containing aluminum alloys can be effectively removed. The detergent of this invention is particularly effective at removing stains from aluminum alloy castings and die-cast products with high silicon content, demonstrating excellent cleaning power. Furthermore, the detergent of this invention does not require the use of hydrofluoric acid, resulting in high operational safety, minimal environmental impact, and suitability for use on aluminum alloy castings, die-cast products, extended materials, and other aluminum materials.

[0086] (none)

Claims

1. A detergent for use with aluminum-silicon alloys, comprising an alkaline compound, a silicate, and a persulfate; wherein the alkaline compound is selected from at least one alkaline compound of the group consisting of: hydroxides of alkali metals of the group consisting of lithium, sodium, potassium, rubidium, and cesium, and ammonium compounds of the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediamine catechol (EDP), ammonium hydroxide (NH4OH), and hydrazine; wherein the silicate is selected from at least one silicate of the group consisting of lithium silicate, sodium silicate, and potassium silicate; When sodium silicate and / or potassium silicate are used as the aforementioned silicate, the aforementioned detergent contains 20.0% to 38.0% by mass of SiO2 and 6.5% to 19.0% by mass of Na2O and / or K2O; when lithium silicate is used as the aforementioned silicate, the aforementioned detergent contains 20.0% to 22.0% by mass of SiO2 and 1.3% to 3.1% by mass of Li2O.

2. The detergent of claim 1, wherein the aforementioned persulfate is selected from at least one persulfate in the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and a complex salt formed by potassium peroxymonosulfate, potassium bisulfate, and potassium sulfate.

3. The detergent as claimed in claim 1, wherein the aforementioned detergent contains 1.0% to 20.0% by mass of the aforementioned alkaline compound.

4. The detergent as claimed in claim 1, wherein the detergent contains 0.1% to 10.0% by mass of the aforementioned persulfate.

5. A cleaning method for silicon-aluminum alloys, comprising: (1) immersing the silicon-aluminum alloy in a cleaning agent containing an alkaline compound, a silicate, and a persulfate; wherein the alkaline compound is selected from at least one alkaline compound of the group consisting of: hydroxides of alkali metals of the group consisting of lithium, sodium, potassium, rubidium, and cesium, and ammonium compounds of the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAOH), tetrabutylammonium hydroxide (TBAOH), ethylenediamine catechol (EDP), ammonium hydroxide (NH4OH), and hydrazine; wherein the silicate is selected from at least one silicate of the group consisting of lithium silicate, sodium silicate, and potassium silicate; When sodium silicate and / or potassium silicate are used as the aforementioned silicate, the aforementioned detergent contains 20.0% to 38.0% by mass of SiO2 and 6.5% to 19.0% by mass of Na2O and / or K2O; when lithium silicate is used as the aforementioned silicate, the aforementioned detergent contains 20.0% to 22.0% by mass of SiO2 and 1.3% to 3.1% by mass of Li2O.

6. The cleaning method of claim 5, wherein the aforementioned persulfate is selected from at least one persulfate in the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, and a complex salt formed by potassium peroxymonosulfate, potassium bisulfate, and potassium sulfate.

7. The cleaning method of claim 5, wherein the aforementioned cleaning agent contains 1.0% to 20.0% by mass of the aforementioned alkaline compound.

8. As in the cleaning method of claim 5, the aforementioned cleaning agent contains 0.1% to 10.0% by mass of the aforementioned persulfate.

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