JPS6014839B2 - Method of forming opaque colored film on aluminum surface - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming an opaque colored film on the surface of aluminum or aluminum alloy (hereinafter referred to as aluminum). BACKGROUND ART Conventionally, as a method for coloring aluminum coated with an anodized film, an alternating current electrolytic coloring method (Asada method) is known in which aluminum is electrolyzed with alternating current in an inorganic coloring bath containing a metal salt. However, the colored anodic oxide film obtained by the alternating current electrolytic coloring method has a transparent metallic luster and gives a cold feeling peculiar to metal, and furthermore, the state of light reflection on the aluminum surface differs depending on the viewing direction. A uniform sense of color cannot be obtained. By the way, the applicant has already proposed Hakama Sosho 55-55150 as a method for finishing the surface of aluminum to an opaque white color. The present invention applies the technology of the above-mentioned patent application No. 55-55150 to the Asada method, thereby producing a color that is uniform in appearance and does not have metallic luster, which cannot be obtained with the conventional AC electrolytic coloring method.
The present invention provides a method for forming an opaque colored film having a soft color tone. The first aspect of the present invention is to add a fluorine compound to an aqueous solution containing at least one type of 'a' inorganic acid, organic acid, or salt thereof to aluminum that has been anodized by a conventional method, so that the fluorine content is 1. 5) After AC electrolysis or DC electrolysis with the aluminum connected to the anode in a secondary electrolyte with a polysaturated, pH of ~3, ``b} containing one or more inorganic acids, organic acids, or salts thereof. AC electrolysis is carried out in a tertiary electrolytic coloring solution in which a metal salt is added to an aqueous solution, followed by 'c}
This is a method of forming an opaque colored film on an aluminum surface, which is characterized by painting with a transparent resin paint. Furthermore, the second invention of the present invention is to reverse the order of the above steps (b) on aluminum coated with an anodized film.
') and (a') steps are carried out. The third invention is the above 'a},

[b] This is a method in which steps are performed simultaneously. To explain these in detail below, in the method of the present invention, aluminum is degreased in a conventional manner, etched as necessary, and smut removed, and then the aluminum is anodized by a conventional method in a sulfuric acid bath or in a sulfuric acid bath using the aluminum as an anode. Obtained by processing (primary electrolysis). The first invention uses aluminum having an anodized film on its surface as a starting material, and in the {a} step, the material is subjected to secondary electrolysis. As the secondary electrolyte, sulfuric acid,
Examples include one or more inorganic acids such as boric acid, phosphoric acid, nitric acid, sulfurous acid, pyrophosphoric acid, persulfuric acid, one or more salts thereof, or a mixed aqueous solution of an inorganic acid and an inorganic acid salt. In addition, oxalic acid, acetic acid, sulfosalicylic acid, sulfophthalic acid, phthalic acid, malonic acid, maleic acid, tartaric acid, citric acid, carbolic acid, malic acid, sulfamic acid, succinic acid,
One or more organic acids such as glycolic acid, one or more salts thereof, or a mixed aqueous solution of an organic acid and an organic acid salt are used. Furthermore, a mixed aqueous solution of an inorganic acid and an organic acid, a mixed aqueous solution of an inorganic acid and an organic acid salt, an organic acid and an inorganic acid salt, and a mixed aqueous solution of an inorganic acid salt and an organic acid salt are also used. In the method of the present invention, a fluorine compound is added to any of the above aqueous solutions to form a secondary electrolyte. Examples of fluorine compounds include fluorides, silicofluorides, fluoroborates, and phosphorus fluorides that contain fluorine in their molecules.Specific examples include: ohydrofluoric acid, lithium fluoride, sodium fluoride, and potassium fluoride. , allyl fluoride,
Methyl fluoride, ammonium fluoride, aluminum fluoride, sodium fluoroaluminate o hexafluorosilicic acid, lithium hexafluorosilicate, sodium hexafluorosilicate, potassium hexafluorosilicate, ammonium hexafluorosilicate, hexafluorosilicic acid These include calcium tetrafluoroborate sodium, potassium tetrafluoroborate, ammonium tetrafluoroborate, magnesium tetrafluoroborate, lithium tetrafluoroborate, calcium tetrafluoroborate sodium phosphate, ammonium phosphate, and the like. These fluorine compounds are added to the aqueous solution for secondary electrolysis as a fluorine amount of 1.5 or more until saturation, preferably 2.0
A secondary electrolytic solution is prepared by melting the mixture for 40 minutes to finally have a pH of 1 to 3. In this case, if the fluorine content is 2.0%, it is not preferable because a satisfactory opacity cannot be obtained. A satisfactory opaque colored film can be obtained when the amount is 40 t/d or more, but the opaque coloring effect does not change even if a large amount is added, so from economical considerations, it is preferable to use 40 t/d or less.
Furthermore, the reason for limiting the number of secondary electrolytes to 1 to 3 is that the PH
If the pH value is 3 or more, the opacity of the final product will be insufficient, and if the pH is less than 1, the anodic oxide film will be so dissolved that it will not be possible to obtain a film that is sufficiently durable for practical use. The higher the temperature of the secondary electrolyte, the faster the reaction and the shorter the processing time, but in consideration of management, film performance, economic efficiency, etc., it is preferably 15 to 35q0. In step (a'), the starting material is subjected to alternating current electrolysis in the electrolytic solution described above, or direct current electrolysis is carried out by connecting this material to the anode, but the point is that there is only enough time for aluminum to be applied to the brass. In this case, The electrolytic conditions are not limited to specific ones, but considering economic efficiency, productivity, etc., AC: 10 to 40
V, 0.1-1.5A/d〆 3-8 minutes DC: 15-6
It is desirable to set the voltage to 0V, 0.1 to 1.0 A/d, and 3 to 8 minutes. Next, in step 'b}, a tertiary electrolytic coloring treatment is performed, and the tertiary electrolytic coloring solution is an aqueous solution containing one or more of the same inorganic or organic acids or salts thereof as in the case of the secondary electrolytic solution. Metal salts (nickel, tin, cobalt,
Inorganic acids or organic acid salts of iron, manganese, copper, zinc, selenium, antimony, lead, cadmium, silver, bismuth, molybdenum, etc.) are used. When AC electrolysis is carried out in this colored liquid, the aluminum surface becomes
A so-called electrolytic coloring reaction occurs and the surface is colored. Needless to say, the conditions for AC electrolysis are not constant because the degree of coloration required changes depending on the purpose and use.
Processed material colored in step 'b} is washed with water 'c}
transferred to the process. 'c} process is a painting finish using transparent resin paint,
The transparent resin coating may be any resin known in the art, such as acrylic, urethane, alkyd, melamine, acrylic alkyd, urea, vinyl, etc.
It is made by dissolving paint resin such as epoxy in water or organic solvent. Further, the coating method may be any of the conventionally known box coating methods, immersion coating methods, electrostatic coating methods, spraying methods, roll coating methods, brush coating methods, and the like. Only by carrying out this [c-step] does an opaque appearance appear on the surface of the aluminum, and an opaque colored film is completed. The second invention provides the electrolytic coloring treatment in the first invention (b
This is a method in which the step 'a) is carried out first, and then the step 'a' is carried out as the step (a') of tertiary electrolysis, but its effects are the same as in the first invention. The third invention is to carry out the above {a-step and [b' step] simultaneously in the same state, and the following three methods are adopted for the electrolytic treatment. Step A' and Step B' are performed simultaneously using AC electrolysis. (b) After step [a} and step [b' are performed simultaneously by alternating current electrolysis, the treated material is connected to an anode and subjected to direct current electrolysis. C. After connecting the treated material to the anode and performing DC electrolysis, [step a' and step 'b' are performed. The method of the third invention performs the steps [a} and 'b} in the same bath, so it is economical and most suitable for practical use because the number of electrolytic baths and washing baths is small. According to the method of the present invention, it is possible to uniformly form an elegant opaque colored film with no strong metallic appearance on the aluminum surface, and the electrolytic conditions are relatively low voltage, low current density, room temperature, and short time, making it suitable for industrial use. It can be recommended. The present invention will be explained below with reference to Examples and Comparative Examples. Example 1 (Third Invention) After degreasing, etching, and removing smut from aluminum (A.606$-T5) by a conventional method, it was electrolytically treated under the following conditions to form an anodic oxide film. Electrode ratio 1:1 (counter electrode aluminum) electrolyte
10% sulfuric acid current density
1.25A/d electrolysis time
39 minutes liquid temperature
After washing at 20° C. and water, secondary electrolytic treatment was performed under the following conditions. Makoto Aranan Sulfuric acid 22 evenings/Yuhekibufluoroke 7 evenings/Ammonium sorate (F=4.48 evenings/so) Ammonium sulfate
20 pm/y silver nitrate 0.05 pm/so pHI. 9. Liquid temperature: 25 pm Voltage, time: AC 16 V x 5 minutes (against magnetic force) The total amount of coulombs was 171 coulombs/d. As a result, the aluminum surface exhibited a yellowish transparent metallic luster. After successively washing with water and hot water, electrocoat paint Yamaichi 7500 manufactured by Honey Kasei Co., Ltd., which is used for the purpose of forming a transparent resin coating film mainly composed of acrylic-melamine, was applied at 170 V for 3 minutes at a liquid temperature of 220. After box electrophoresis coating treatment (hereinafter referred to as ED treatment) under the conditions described above, this was subjected to leech treatment, and an opaque dark beige composite film was obtained. The hue was the same regardless of the viewing angle. Comparative Example 1 The same process as in Example 1 was carried out except that the pH of the secondary electrolyte in Example 1 was adjusted to 3.8 with ammonium water. The result was a slightly translucent film with a pale yellow tinge, but it was far from being called an opaque film. Example 2 (Third invention) The same treatment as in Example 1 was performed except that secondary electrolysis was performed under the following conditions. Electrolyte composition: Permanganic acid: 0.5% sulfuric acid: 13%/acetic acid: 15%
evening/evening ammonium fluoride 4.52/sohexafluorosilicic acid 2.0 evening/tanium pH 2. Inlet liquid temperature 25qo, voltage AC 17V, time 5 minutes,
The total amount of coulombs was 120 coulombs/d〆. As a result, the finish of the aluminum surface exhibited an opaque mustard color after the coating was applied. Comparative Example 2 When the secondary electrolyte in Example 2 was treated under the same conditions except that the fluorides ammonium fluoride and sodium hexafluorosilicate were removed, the aluminum surface became a mustard color with a transparent metallic feel. It showed. On the surface, the color was uniform, but when viewed from a different angle, the shading appeared different due to the reflection of light. Example 3 (Third invention) In the same machine as in Example 1, anodized aluminum was subjected to secondary electrolysis under the following conditions, and then painted in the same manner as in Example 1. Electrolyte solution Ammonium sulfate 25 minutes / Hexafluorosilicic acid 30 days / Ammonium silver sulfate 0.25 days / Softness was set to 2.7 with sulfuric acid, liquid temperature 2 was ○, voltage 15V, time 5 minutes. 3 Treated with inkstone sand. The amount of coulombs was 78 coulombs/d〆. the result,
An opaque pale yellow film was obtained on the aluminum surface after the paint was baked. Comparative Example 3 An anodized film obtained under the same conditions as in Example 1 was subjected to secondary electrolysis under the following conditions with a reduced fluorine content, and was further subjected to the same coating treatment as in Example 1. Denkai flea composition: stannous fluoride 42/sokuF=0.9
7) Sulfuric acid 5 evenings/Tartaric acid 12 evenings/So When the pH was 2.1 with sulfuric acid, the liquid temperature was 20 oo, and the alternating current was 15 V x 2 minutes and 23 x 5 minutes, the amount of coulombs was 24.
It was 67 coulombs/d. The aluminum surface after coloring and ED treatment had a bronze color in the former case and a dark bronze color in the latter case, which was not much different from the usual so-called Asada method color tone. Comparative Example 4 An anodic oxide film obtained under the same conditions as in Example 1 was subjected to secondary electrolysis under the following conditions, and was further subjected to the same coating treatment as in Example 1. The pH was 5.3, the liquid temperature was 21°C, and the voltage was 12V for 2 minutes, and the amount of coulombs was 17 coulombs/d.As a result, the coloring was a pale yellow bronze with a metallic feel. When subjected to ED treatment, the color was considerably bleached and became pale, but an opaque colored film was not obtained. Comparative Example 5 The anodic oxide film obtained under the same conditions as in Example 1 was subjected to secondary electrolysis under the following conditions, and then subjected to the same coating treatment as in Example 1. Electrolyte system side formation Fui supply 6 evenings/soku F = 2.
25) Kobuta Soanmo 24/So PH 3 with ammonia water
．． 4, the liquid temperature was 20 pm, the voltage was AC 16 V, and the time was 2 minutes and 5 minutes. After coloring, the finish after coloring was pale gray red for 2 minutes, and light wine red for 5 minutes, with no opacity. Furthermore, after the ED treatment, it was decolored and a transparent silver color was obtained. Example 4 (Third invention) The same treatment as in Example 1 was carried out except that secondary electrolysis was performed under the following conditions. Electrolyte composition Bismuth sulfate 2.0 m/sulfuric acid 23 m/s ammonium fluoride
7.0 evening/SophI. 15 evening/SophI. 9. Processed at 14V x 5 minutes at a liquid temperature of 19qo. The amount of coulombs was 85 coulombs/d. the result,
A good bronze-based opaque film was obtained on the aluminum surface after painting. Example 5 (Third invention) The same process as in Example 4 was performed except that only the energization conditions for secondary electrolysis in Example 4 were changed as described below. 'a} Connect the anodized aluminum to the anode, energize with DC (0.4 I/d〆) for 5 minutes, and then energize with AC for IW x 1.8 minutes. [b} Anodized aluminum at 15V AC
Power was applied for ×1.5 minutes, and then the aluminum was connected to the anode and current was applied with direct current (0.4 pine/d〆) for 5 minutes. After secondary electrolysis, painting was performed by ED treatment, and a pale bronze film was obtained which was opaque on the surface, and an opaque white film was obtained on 'b'. Example 6 (First invention) An anodic oxide film obtained in the same manner as in Example 1 was subjected to secondary electrolysis under the following conditions. Electrolyte composition: phosphoric acid 50%/oxalic acid
5〃Hexafluo. Silicic acid 8 Ammonium sulfate 15 pHI. 7. Liquid temperature: 25°C, AC 15V x 5 minutes After this treatment, the film became slightly opaque. After washing with water, this was further subjected to tertiary electrolysis in a bath of the Asada method having the following composition to color it. Electrolyte composition Nickel sulfate 25/boric acid
20 Magnesium sulfate
20 Ammonium sulfate
25 Ammonium thiosulfate 0
．． 6〃PH5.4 Liquid temperature 24:00, Voltage AC8.5V, Time 2 Current sand, 40 seconds, 6 sand. As a result, the coloration progressed with the passage of time, and the colors became light bronze, bronze, and dark bronze, respectively. The painted surface treated with ED is 2■ Sand: light gray,
Sand No. 4: Gray, Current sand No. 6: A dark gray opaque film was obtained. Example 7 (First invention) The anodic oxide film obtained in Example 1 was subjected to secondary electrolysis under the following conditions. Electrolyte composition: Sulfuric acid 18%/Boric acid 5% Hexafluorosilicic acid 13% Ammonium sulfate 10% pHI. 5. Liquid overflow 25q○, DC 0.45A'd 5
Electrolyte composition: stannous sulfate, 4 ta' sulfuric acid, 30 ammonium sulfate
20 formalin
10 Sodium thiosulfate
When the liquid temperature 1 was set to 0, ACIOV x 1.5 minutes, and ED treatment was performed in the same manner as in Example 1, a golden yellow opaque film was obtained. Example 8 (Second Invention) The anodized film obtained in Example 1 was colored in the Asada method electrolytic bath of Example 7 to give a golden yellow film, but it had a strong metallic luster. Next, after washing this with water, "AC 16V ×
When electrolyzed for 5 minutes and subjected to the same ED treatment as in Example 1, a yellow-brown opaque film was obtained. Electrolyte composition Sulfuric acid/boric acid
5〃 Hexafluorosilicic acid 8〃 Ammonium

Claims (1)

[Claims] 1. (A) Aluminum that has been anodized by a conventional method, (B) an inorganic acid selected from sulfuric acid, boric acid, phosphoric acid, nitric acid, sulfurous acid, pyrophosphoric acid, persulfuric acid, etc., or , oxalic acid, acetic acid, sulfosalicylic acid, sulfophthalic acid, phthalic acid, malonic acid, maleic acid, tartaric acid, citric acid, carbolic acid, malic acid, sulfamic acid, succinic acid, glycolic acid, etc., or a salt thereof. (C) A fluorine compound is added to an aqueous solution containing one or more of the following, and the fluorine content is 1.5 g/l to saturated, and the aluminum is connected to the anode in a secondary electrolytic solution with a pH of 1 to 3. After direct current electrolysis, (D) a color-forming metal salt (nickel, tin, cobalt, iron, manganese, copper, zinc, selenium, antimony, lead) is added to an aqueous solution containing one or more of the above inorganic acids or organic acids or their salts. , cadmium, silver, bismuth, molybdenum, etc.) in a tertiary electrolytic coloring solution, followed by (E) coating with a transparent resin paint. A method of forming a colored film. 2 Aluminum coated with anodized film by conventional method,
Inorganic acids selected from sulfuric acid, boric acid, phosphoric acid, nitric acid, sulfite, pyrophosphoric acid, persulfuric acid, etc., or oxalic acid, acetic acid, sulfosalicylic acid, sulfophthalic acid, phthalic acid, malonic acid, maleic acid, tartaric acid, citric acid Color-forming metal salts (nickel, tin, cobalt, iron, manganese, copper, zinc, After AC electrolysis in a secondary electrolytic coloring solution to which inorganic acids or organic acid salts such as selenium, antimony, lead, cadmium, silver, bismuth, molybdenum, etc. have been added, one or more of the above inorganic acids or organic acids or salts thereof A fluorine compound is added to an aqueous solution containing fluorine, and the fluorine content is 1.
Opaque coloring on the aluminum surface, characterized by AC electrolysis in a tertiary electrolyte with a pH of 5 g/l to saturation and pH 1 to 3, or by connecting the aluminum to an anode and subjecting it to DC electrolysis treatment, followed by painting with a transparent resin paint. Method of forming a film. 3. Aluminum that has been anodized by a conventional method is treated with an inorganic acid selected from sulfuric acid, boric acid, phosphoric acid, nitric acid, sulfurous acid, pyrophosphoric acid, persulfuric acid, etc., or oxalic acid, acetic acid,
An aqueous solution containing one or more organic acids selected from sulfosalicylic acid, sulfophthalic acid, phthalic acid, malonic acid, maleic acid, tartaric acid, citric acid, carbolic acid, malic acid, sulfamic acid, succinic acid, glycolic acid, etc., or one or more of their salts. Fluorine compounds and color-forming metal salts (nickel, tin,
Inorganic acids or organic acid salts of cobalt, iron, manganese, copper, zinc, selenium, antimony, lead, cadmium, silver, bismuth, molybdenum, etc.) are added with metal salts, and the fluorine content is 1.5 g/l to saturated. , alternating current electrolysis or alternating current electrolysis in a secondary electrolytic solution with a pH of 1 to 3, followed by direct current electrolysis by connecting the aluminum to the anode in the same solution, or alternating current electrolysis in the same solution after connecting the aluminum to the anode. A method for forming an opaque colored film on an aluminum surface, which is characterized by coating the aluminum surface with a transparent resin paint.