The chemical coloring method has the advantages of simple process, easy control, high efficiency, low cost, low equipment investment, wide color gamut, and bright color. However, large-area products are prone to color unevenness, and are easily discolored after washing after coloration, improper sealing, or mechanical damage. The light resistance of the colored film is relatively poor. Therefore, it is often used only for interior decoration and daily coloring of aluminum products. . The chemical coloring of the aluminum anodized film is based on the ability of the porous film layer to have the same dye adsorbing ability as textile fibers. Generally, the pore diameter of the anodized film is 0.01-0.03 μm, and the dye is separated into a single molecule in water with a diameter of 0.0015-0.0030 μm. When dyeing, the dye is adsorbed on the pore surface and diffuses and accumulates in the pore, and is also associated with alumina. The ionic bond and hydrogen bonding are combined to color the film layer. After the sealing treatment, the dye is fixed in the pores.
2 Co(NO3)2+ H2O2+4NH4OH→Co(OH)3+4 NH4 NO3
(I) Organic dyeing
1, the choice of dye
A wide variety of organic dyes, according to different uses and product grade selection of dyes. For example, soluble vat dyes are expensive and have excellent color fastness. Therefore, they are mostly used for the dyeing of high-grade aluminum products, gold pens, lighters, and hearing aids; alcohol-soluble dyes are used for aluminum foil dyeing; oil-soluble dyes are used for the printing of aluminum foil and are dissolved in nitrocellulose before use. In lacquer such as enamel, vinyl resin or polyamide resin, or in melamine resin and epoxy resin that are dissolved in baking paint, a resin film with dye is formed on the surface of the cleaned aluminum foil after printing. The dyes used for the dyeing of aluminum products include acid dyes, acid complex dyes, acid mordant dyes, direct dyes, weak acid dyes, disperse dyes, soluble vat dyes, reactive dyes, basic dyes, alcohol-soluble dyes, oil-soluble dyes, etc. .
2, organic dye coloring process and control
(1) Monochrome dyeing: The anodized aluminum products washed with clean water are immersed in the dye bath of the specified temperature. The dyeing time depends on the color depth, and the dyeing bath volume can be controlled at a ratio to the product volume of 10: 1.
(2) Multi-color dyeing: If two or more different colors, such as landscapes, flowers, birds, tasks, words, etc., are dyed on the aluminum parts, the printing process is mostly used to complete the printing. The printing plate can be used in the type (zinc plate, paper Version) and screen version, available direct printing method, coating anti-dyeing method, foam plastic dyeing method and so on. The general practice is to dye the first color, apply a protective film on the part to be left in color with a floral print, remove the remaining color, second, third, and more colors and so on. See Table 9 for dyeing concentrations and process conditions for various organic dyes.
colour
Dye name
Concentration g/L
Temperature 0C
pH value
Time min
Aludye Black Black HBK 8-10
50-60
5.5-6
15-30
Black MBK 8-10
50-55
5.0-5.5
5-10
Black MRL 10-12
50-60
5.0-6.0
5-30
Black BBK 10-12
50-60
5.0-6.0
15-30
Black DG 10
55-60
6.0-7.0
10-30
Black WAL 10-12
50-55
6.0-7.0
15-30
Black MLW 8-12
50-60
4.2-4.8
5-30
Aludye Red Red A 2-5
50-60
5-5.5
5-10
Red D4BS <25
55-60
6.0-7.0
5-10
Brilliant Red MB 0.5-5
50-55
5.5-6.0
5-15
Red B 2-5
55-60
5.5-6.0
5-15
Red D4B 2
55-60
5.5-6.0
5-10
Red SBR <3
50-55
5.0-6.0
5-10
Red FRB 0.5-5
50-55
5.0-5.5
5-10
Brilliant Red 3B 1-2
50-55
5.5-6.0
5-15
Red MBES 1-2
55-60
5.0-5.5
5-10
Red MBES 1-2
55-60
5.0-5.5
5-10
Red RBL 2
55-60
4.5-5.0
5-15
Red PBL 2
55-60
5.0-6.0
5-10
Red CFB 0.5-5
50-55
6.0-7.0
5-15
Red FPR high concentration 0.5-5
50-55
5.0-6.0
5-15
Red FAR high concentration 0.5-5
50-55
6.0-7.0
5-10
Pink BN 0.5-5
50-55
6.0-7.0
5-15
Aludye Purple Purple VB <2
50-55
5.5-6.0
5-10
Purple MFBL <5
50-55
5.5-6.0
5-10
Purple RVB <5
50-55
5.0-6.0
5-15
Purple MBB <5
50-55
5.0-6.0
5-15
Burgundy BL 50-55
5.0-5.5
5-15
Aludye Brown Brown BRL <2
50-60
4.5-5.0
5-15
Brown CFA 0.5-2
55-60
4.5-5.5
5-15
Brown THM 0.5-5
55-60
5.0-6.0
5-10
Brown BM 0.5-5
55-60
5.5-6.0
5-15
Brown GL 0.5-5
55-60
5.5-6.0
5-15
Brown KBL 1-5
55-60
5.5-6.5
5-15
Red Brown AG 0.1-2
50-55
6.0-7.0
5-10
Yellow Brown ASG 0.2-2
56-60
4.5-5.0
5-10
Aludye Green Green BGLN <2
50-55
5.0-5.5
5-15
Green RGS 1-9
55-60
5.0-5.5
5-15
Green 5GM <2
50-55
5.0-6.0
5-15
Green M6B <2
50-60
5.5-6.0
5-15
Green ABGL <2
50-55
5.5-6.0
5-10
Green DB 0.5-2
55-60
5.0-6.0
5-10
Green A3GM 2-5
55-60
6.0-7.0
5-15
Aludye Yellow Yellow FD 0.5-5
50-55
5.0-5.5
5-10
Yellow FLY 0.2-5
50-60
5.0-5.5
5-10
Yellow DRL 0.5-2
55-60
6.0-6.5
5-10
Yellow GR 0.2-2
50-55
5.5-6.0
5-10
Yellow DGL 0.2-2
50-55
6.0-7.0
5-10
Yellow 3RF 0.5-5
55-60
4.5-5.5
5-10
Yellow YBL 0.2-2
50-55
5.0 -5.5
5-15
Golden MBES 0.5-2
55-60
5.5-6.5
5-10
Yellow 2GL 1-2
50-55
5.5-6.0
5-15
Yellow GLL <2
50-55
5.5-6.0
5-10
Yellow Yellow ALNW 1-2
50-55
6.0-7.0
5-10
Aludye Orange Gold D2GL 0.1-2
55-60
6.0-7.0
5-15
Orange GR 0.1-2
50-55
5.5-6.5
5-10
Gold G 2
27-60
5.5-6.5
1-10
Orange SRL 2-5
50-55
5.5-6.5
1-10
Orange MBES <2
50-55
4.5-5.5
5-10
Orange GNS 0.5-5
50-55
5.5-6.0
5-10
Aludye Blue Lake Blue AB 1-2
50-55
4.5-5.0
5-15
Blue 2LW 0.5-2
55
5.5-6.0
5-15
Blue GBL 1-2
50-55
4.5-5.5
5-15
Blue 2AL 1-2
50-55
4.5
5-15
Navy Blue NBL 1-2
55
5.8
5-15
Green Blue GB 0.5-2
55-60
5.0-6.0
5-15
Aludye Grey Grey MBL 0.5-2
55-60
6.0-7.0
5-10
Grey BRL 0.5-1
50-55
6.0-7.0
5-10
Gray 2BL 0.1-1
55-60
5.0-6.0
5-10
Grey ABL 0.5-10
55-60
6.0-6.5
5-20
Grey GBL 0.5-2
55-60
5.5-6.0
5-10
Grey VA 0.5-1
50-55
5.0-5.5
5-10
Grey G2RC 1-10
55-60
5.0-6.0
5-15
Grey GR 1-10
50-55
5.0-5.5
5-15
Grey GL 2-5
55-60
6.0-6.5
5-10
Aludye Bronze Bronze 2LW 2-5
55-60
4.0-5.0
5-10
3, coloring technology measures
(1) The higher the purity of the dye used for dyeing, the better, and the dyeing effect of the dyes that are mixed with a large amount of filler (such as Yuan Mingfen, dextrin) is poor. Batch dyeing should pay attention to the change of dye concentration in the first cylinder, and correct supplement to ensure the consistency of color depth.
(2) The multicolor dyeing using the printing process should be shallow, deep, yellow, red, blue, brown and black. When the second color is printed, the paint should be dried so that the paint adheres to the aluminum surface, otherwise the dye will be immersed and the boundary of the hair is not clear.
(3) In order to ensure uniform coloring and consistent color, the anodizing conditions of aluminum parts must be the same and the dyeing conditions should be the same.
(4) The dyeing solution is prepared with pure water. If hard water is used, hexametaphosphate (with a concentration of less than 5%) should be added to avoid precipitation. The dye should be completely dissolved, otherwise it will be unevenly colored and prone to dark spots.
(5) The coloring tank is made of non-active materials such as enamel, ceramics, stainless steel, glass, etc. so as not to cause deterioration of the dye liquor due to chemical reaction.
(6) Do not allow oil stains to enter the dye bath, otherwise the colored surface may be prone to streaks or stain defects.
(7) Colouring can be done with mixed dyes, but attention must be paid to the possible selective adsorption of the film in the dye liquor, so that the color is not harmonized or the color is changed, so that the color of the treated film is not as fast as a single dye. Color-staining dyes should be dissolved separately and then placed in the dye bath. Where acid dyes must be adjusted with acetic acid pH, the amount of acetic acid added depends on the concentration of the dye, the dye solution pH value of 4.5-6 by adding 98% acetic acid about 0.5-1ml/L.
(8) The alcohol-soluble dye is dissolved with ethanol as a solvent. After the soluble vat dye is dyed, it must be developed for 1 minute in a coloring solution containing sodium nitrite 10g/L, 1.84g/cm3 sulfuric acid 25ml/L, and a temperature of 50~60C. The disperse dyestuff dyeing solution in aqueous solution must be agitated constantly. Disperse the orange GR and disperse the blue FFR in the disperse dye to obtain very satisfactory dyeing effect. The other anodized aluminum before disperse dyeing must be treated with maleic acid, lactic acid, tartaric acid, 5-sulfonic acid salicylic acid and other treatments.
(9) Metallic aluminum contains impurities that affect dyeing. Silicon containing more than 25% of the underlying film is gray, and only dark colors should be dyed; magnesium containing more than 1% of the dyed tape with dark ash; manganese containing light and not bright; pure copper-containing color, Iron, nickel, and chromium are too much dull in color.
(10) Sulfuric acid is present in some dye baths, rendering the film less colored. Even if the sulfuric acid has no effect on the dye, the pH of the dye will be reduced, resulting in a change in hue. Therefore, the cleaning of pre-colored products is particularly important. When coloring with a basic dye, the oxide film must be treated with a 2%-3% tannic acid solution, otherwise it will not be colored. The oxide film to be colored should not have fingerprints and water droplets that are liable to generate stains. Otherwise, the adsorption capacity of these parts will be reduced.
(11) In order to improve the adsorption capacity of the oxide film, especially for dark products, they may be soaked in a 50 ml/L sulfuric acid solution at 80 degrees for 1 minute or soaked at 40 degrees for 15 minutes before being colored.
(12) Products that are not ideally colored can fade in 50% nitric acid or 5 ml/L sulfuric acid solution. Some of the hard-to-remove dyes may be bleached in more concentrated sulfuric acid or 1% sodium hypochlorite solution and then recolored after washing.
(13) After the coloring, it must be sealed. This is particularly important for copper-containing alloy products. If the pores are sealed in a 0.5% nickel acetate solution, black spots on the surface of the product can be eliminated or minimized by reducing the pH in the sealing fluid to 5.3-5.5 by adding 0.5% boric acid or acetic acid. (14) In order to improve the brightness of the surface of the product, polishing treatment may be performed prior to anodization, and polishing or dipping of melted paraffin wax or spray varnish may be performed after sealing the hole with a fine velvet cloth or the like.
(II) Inorganic dyeing
So far, there are not many weather-resistant organic dyes, and the color of the film layer changes at temperatures above 100 degrees. Inorganic dyes do not change color when the temperature exceeds the melting point of the metal. Inorganic dyes have one liquid and two liquids. The former means that the anodized film is immersed in a solution, and this metal salt is hydrated in the film pores to form a lake and the film is colored. The latter is where the anodized product is first immersed in a salt solution, cleaned enough to be immersed in another salt solution, and the two impregnated adsorbed salts are reacted to form an insoluble precipitated color, which results in the surface of the product. Color. Some inorganic dye coloring process and formula are shown in Table-10.
Table-10 Partial inorganic dye coloring process and formula colour
Coloring compound
Inorganic salt name
Dosage g/L
Temperature/degree
Time/min
Note Red brown
Ferricyanide
Copper sulphate
Potassium ferrocyanide
10-100
10-50
80-90
80-90
10-20
10-20
2CuSo4+[Fe(CN)6]K4→[Fe(CN)6] Cu2+2K2 So4 brown
Copper cyanide
Copper sulphate
Copper cyanide
10-100
10-50
80-90
80-90
10-20
10-20
3CuSo4+2[Fe(CN)6]K3→[Fe(CN)6] 2Cu3+3K2 So4 Monoethanolamine
Nickel chloride
27
32
60-70
10
Silver dichromate
Silver nitrate
Potassium dichromate
50-100
10-50
75
75
5
10
2 AgNO3+ K2Cr2O7→Ag2 Cr2O7+2 KNO3 Dark brown
Cobalt acetate
Ethylenediamine
30
20
80-90
3
Nickel sulfate
Ethylenediamine
30
20
80-90
5
Lead sulfide
Lead acetate
Ammonium sulfide
100-200
50-100
90
75
5
10
PbAc2+(NH4)2S→PbS+2 NH4Ac Cobalt hydroxide
Cobalt nitrate
Hydrogen peroxide
ammonia
2 Co(NO3)2+ H2O2+4NH4OH→Co(OH)3+4 NH4 NO3
yellow
Lead dichromate
Lead acetate
Potassium dichromate
100-200
50-100
90
90
5
10
PbAc2+ K2Cr2O7→Pb Cr2O7+2 KAc Lead chromate
Lead acetate
Potassium chromate
100-200
50-100
90
75
5
10
PbAc2+ K2CrO4→Pb CrO4+2 KAc Cadmium sulfide
Cadmium Acetate
Ammonium sulfide
50-100
50-100
75
75
5
10
Cd Ac2+(NH4)2S→Cd S+2 NH4Ac white
Lead sulfate
Lead acetate
Sodium sulfate
10-50
10-50
50
60
15
30
PbAc2+ Na2SO4→Pb SO4+2 NaAc Barium sulfate
Barium nitrate
Sodium sulfate
10-50
10-50
60
60
15
30
Ba(NO3)2+ Na2SO4→Ba SO4+2 Na NO3 black
Cobalt sulfide
Cobalt acetate
Sodium sulfide
50-100
50-100
90-100
90-100
10-15
20-30
Co Ac2+Na2S→CoS+2 NaAc Cobalt oxide
manganese dioxide
Cobalt acetate
potassium permanganate
50-100
15-25
90-100
90-100
10-15
20-30
CoAc2+2KMnO4→2 KAc+ CoO+Mn2 O3+2O2 blue
Prussian blue
Potassium ferrocyanide
Iron sulfate
10-50
10-100
90-100
90-100
5-10
10-20
Fe2(SO4)3+3[Fe(CN)6]K4→[Fe(CN)6]3 Fe4+6K2SO4 Prussian blue
Potassium ferrocyanide
Ferric chloride
10-50
10-100
90-100
90-100
5-10
10-20
4 FeCl3+3[Fe(CN)6]K4→[Fe(CN)6]3 Fe4+12KCl golden
Manganese trioxide
Sodium thiosulfate
potassium permanganate
10-50
10-50
90-100
90-100
5-10
5-10
Orange yellow
Silver chromate
Potassium chromate
Silver nitrate
5-10
50-100
75
75
10
5
K2CrO4+2AgNO3→2KNO3+Ag2 CrO4 Copper acetate
1,3-diaminopropane
30
15
70-80
5
Copper acetate
Ethylenediamine
30
15
70-80
5
golden
Zinc chromate
Zinc fluoride
Nitric acid
4
1.5
3.5
60
10
Iron oxalate
Ammonium
15-25
Proper amount
40
1-5
pH 5.5-6.5 Yellow tea
Ferrous sulphate
Ethylenediamine
30
15
80-90
5
bronze
Cobalt acetate
potassium permanganate
20
twenty two
30
5-20
pH 6-7, dip soda solution 10g/L before coloring. Gold (Shallow)
Gold (dark)
Oxalic acid ferric ammonium
Oxalic acid ferric amine trihydrate
10
25
50
50
2
2
Other coloring techniques include immersion in copper salt solution followed by impregnation of the sulfide solution, or reaction between copper sulfate and sodium arsenite to obtain a green film: orange film reacts with potassium bismuth tartrate and hydrogen sulfide. Obtained; Bronze can be obtained by dipping oxalic acid solution containing ferric chloride or a mixed solution of ferrous sulfate, potassium ferrocyanide, and potassium permanganate to produce ferric hydroxide lake with gallic acid or pyrogallic acid. Blending can make it darker. With an aqueous solution of 0.4 parts of chromium trioxide, 0.35 parts of sodium dichromate, 0.08 parts of sodium fluoride, and 0.5 parts of a surfactant (C9-alkylphenol polyoxyethylene ether), the pH value of 1.8 will pass at 50 degrees Celsius. Stearic acid-treated aluminum powder (50 μm) is immersed and can be impregnated with light yellow aluminum powder. Dissolve 6 parts of gold in aqua regia and dilute it with proper amount of distilled water. Separate 30 parts of lime into 160 parts of distilled water. After 2 hours, add the gold solution to the lime solution, stand for 5-6 hours, and pour the upper layer of water. Calcium chlorate precipitation; then add 1000ml of water, add sodium thiosulfate, heat for 10 minutes, can not be boiling, immersed in aluminum after filtration can be dyed golden yellow. Cobalt acetate 10-30g/L was immersed in the aluminum product at 50°C for 2 minutes, then washed, then immersed in a solution containing potassium permanganate 5-30g/L, and treated at 30°C for 2 minutes to obtain a bronze color. The AC electrolytic sulfate membrane contains a considerable amount of free sulfur in certain dilute salt solutions that can combine with heavy metals to color the membrane, see Table -11. The film layer was washed with an ammonia solution before the coloring to remove the residual sulfuric acid in the pores, so that the resulting sulfides were less dissolved and the tone of the film was strengthened.
Table-11 AC Electrolytic Sulfuric Acid Films in Thin Salt Solutions
Salt solution
colour
Salt solution
colour
Salt solution
colour
1% silver nitrate
Olive brown
2% copper sulfate
green
1% ammonium citrate
Brown
2.5% lead acetate
Dark brown red
1% potassium bismuth tartrate
Orange
1% stannous sulfate
Yellow brown
1% cadmium acetate
yellow
1% Ferrous ammonium sulfate
Olives
1% potassium permanganate
Light yellow
1% cobalt acetate
black
1% selenium dioxide
Canary yellow
2% ferric ammonium oxalate
black