Mechanical polishing-degreasing-water washing-chemical polishing-water washing-anodic oxidation-water washing-sealing-mechanical polishing.
Chemical polishing products: aluminum anodizing alkaline polishing solution products: aluminum anodizing sealing solution products: aluminum coloring sealing solution aluminum anodizing and dyeing process.
The aluminum products treated by dyeing method have beautiful color, bright color, corrosion resistance, wear resistance and higher insulation than ordinary aluminum products. The aluminum workpiece is suspended in an appropriate electrolyte solution and used as an anode for electrolysis. In the process of electrolysis, hydroxyl ions in water release electrons at the anode to become water and new ecological oxygen, which oxidizes aluminum into a thick alumina film. This process is called anodic oxidation because the metal products are used as anodes for oxidation. After anodic oxidation, aluminum products are colored, sealed and treated to form dyed products.
I. Dyeing process
1. Pretreatment:
In many machining processes, aluminum parts will be contaminated with a lot of grease, a little abrasive, dust and defective oxide film. These substances have poor conductivity and cannot be anodized, so they need to be pretreated. The method is to use carbon tetrachloride, trichloroethylene, gasoline or toluene as cleaning agent, immerse aluminum parts in water, brush them with a brush, then air dry them, and then immerse them in water for cleaning many times. Rinse with hot water as soon as the oil is gone. If a black film is formed on the surface, it should be soaked in 32% nitric acid solution for 20 seconds to remove the black film, and finally washed with cold water. Immersing in distilled water to prepare oxide film. ?
2. Anodizing:
Preparation of (1) sulfuric acid electrolyte: it is made by mixing 18-20kg sulfuric acid and 80-82kg deionized water. At this time, the specific gravity of the solution is about1.125-1.140. Sometimes a small amount of oxalic acid is usually added to sulfuric acid electrolyte to obtain an oxygen oxide film with good protective performance.
⑵ Oxidation process: install the circuit instrument, use the aluminum piece to be dyed as the anode, immerse it in the electrolyte, then turn on the power supply, and control it according to the following process conditions.
The electrolyte temperature is controlled at 12-25℃, the anode current density is 1-2 A/dm2, and the voltage in the cell is between 13-23 volts. The time is about 30-40 minutes.
After the above process is completed, take the aluminum parts out of the electrolyte at any time, and rinse the acid solution with clear water, especially the concave part, otherwise white spots will appear. After cleaning the acid solution, immerse it in clear water for later use.
3. Dyeing:
After anodic oxidation of aluminum parts, colored complexes are formed on the surface, which can be adsorbed and combined by valence bonds or hydrogen bonds, and colors appear.
⑴ Dye selection: There are two kinds of dyes: inorganic dyes and organic dyes. Inorganic dyes are mostly composed of inorganic salts. When dyeing, aluminum parts are respectively soaked in the solution of compound A and compound B to generate colored compounds, so as to achieve the purpose of dyeing.
Inorganic dyeing solution.
Dye color solution A solution B dye compound name name concentration name concentration:
Blue or light blue potassium ferrocyanide 10-50 ferric chloride 10- 100 prussian blue-brown potassium ferrocyanide 10-50 copper sulfate 10- 100 copper ferrocyanide black cobalt acetate 50-/kloc-. 100-200 lead dichromate gold baking soda 10-50 lead permanganate 10-50 lead manganate 10-50 sodium sulfate 10-50 lead sulfate orange aluminum lead acid 5-/kloc-
There are many kinds of organic dyes. The commonly used dyes, dye concentrations and colors are listed below for your reference.
Dye Color Dye Name Dye Solution Concentration Remarks
Yellow acid medium RH directly yellow brown D3G alcohol soluble yellow GR directly frozen yellow G0.7-11-50.5-11-2.
All acid dyes should be added with glacial acetic acid 1-2 ml to adjust pH, and alcohol is used as solvent: yellow alizarin yellow indirubin orange, acid orange H1-21-2.
When dyeing this dye, add 10g sodium nitrite, and use a heated water to prepare the dye solution. The dyeing time should be 30 minutes, and then develop color in 25 ml warm sulfuric acid water for one minute.
Red direct sunlight-fast pink G acid red GR alizarin red S 2-55- 105- 10 Red alkaline rose essence acid orange II 0.753 is dissolved and merged into one liter of grass green direct sunlight-fast emerald green B 3-52-5.
Blue direct fast turquoise blue GL active brilliant blue acid lake blue V acid lake blue A 2-5522-5
Black acid wool ATT acid leather NBC10-1510-15?
Second, the dyeing operation:
(1) Monochrome dyeing method: the aluminum products washed with clean water after anodic oxidation are immediately immersed in the coloring solution at 40-60℃. Soaking time: light color for 30 seconds to 3 minutes; Diablo 3- 10 minutes. Take it out after dyeing and wash it with water.
(2) Multicolor dyeing method: If two or more different colors are dyed on the same piece of aluminum, or landscapes, flowers, birds, figures and characters are printed, the procedures are very complicated, including coating masking method, direct printing and dyeing method, and foam impregnation method. The above methods are different in operation, but the principle is the same. Now let's introduce the coating masking method: this method mainly covers the quick-drying and easy-to-clean varnish thinly and evenly on the really needed yellow for masking. After the paint film is dried, all aluminum parts are immersed in dilute chromic acid solution to remove the yellow color of the unpainted parts, taken out, washed with clear water, dried at low temperature, and then dyed red. If you want to dye the third and fourth colors, you can follow the above method. 4. Sealing: After the dyed aluminum parts are washed with water, they are immediately boiled in distilled water at 90- 100℃ for 30 minutes. After this treatment, the surface becomes uniform and nonporous, forming a dense oxide film. The dye coated with coloring is deposited in the oxide film and can't be wiped off any more. The closed oxide film is no longer absorbent, and its wear resistance, temperature resistance and insulation are strengthened.
The sealed aluminum surface is dried, and then polished with soft cloth to obtain beautiful and bright aluminum, such as multi-color. After sealing treatment, the protective agent coated on aluminum should be removed, and a small area should be wiped off with cotton dipped in acetone, and a large area can be dipped in acetone to wash off the paint. ?
? Third, matters needing attention
1. After oil washing, aluminum parts should be oxidized immediately and should not be left for too long. When making oxide film on aluminum parts, all of them should be immersed in electrolyte, the cell voltage should be stable and consistent from beginning to end, and the same batch of products must be completely consistent, even if they are dyed.
2. In the process of anodic oxidation, the aluminum, copper and iron in the electrolyte increase continuously, which affects the luster of aluminum. When the aluminum content is more than 24 g/L, the copper content is more than 0.02 g/L, and the iron content is more than 2.5 g/L, the electrolyte should be replaced.
3. Buy high-purity raw materials and dyes, because there are more impurities or sodium sulfate and dextrin, the dyeing effect is not good.
4. When a large number of dyes are used, the dye solution will be concentrated first and then diluted, and the dyed colors will have different shades. Therefore, attention should be paid to stirring the slightly concentrated dye solution in time to keep the consistency of dye solution concentration as much as possible.
5. When dyeing multicolor, you should dye light color first, then dark color, and then yellow, red, blue, brown and black. Before dyeing the second color, the paint should be dried to make it close to the aluminum surface, otherwise the dye will penetrate and the edge of the raw edge will be unclear.
Related terms: anodized aluminum plate, alumina, aluminum, aluminum products, aluminum plate, color anodizing.