ã€China Aluminum Network】 Metal surfaces are inevitably oxidized during heat treatment, mechanical processing, transportation and storage, resulting in an uneven thickness of the oxide layer. At the same time, it is also vulnerable to various oil pollution and adsorption of some other impurities. For oil and certain adsorbents, the thinner oxide layer may be washed with solvents, chemically and mechanically, or chemically treated directly.
For heavily oxidized metal surfaces, the oxide layer is thick and cannot be directly cleaned with solvents and chemically treated, but mechanical treatment is preferred. The treated metal surface is highly active and is easily re-contaminated with dust, moisture, and the like. For this purpose, the treated metal surface should be glued as fast as possible. The period of storage of the metal after different treatments is as follows:
(1) wet blasted aluminum alloy, 72h;
(2) chromic acid-sulfuric acid treated aluminum alloy, 6h;
(3) Anodized aluminum alloy for 30 days;
(4) Sulfuric acid treated stainless steel, 20 days;
(5) blasted steel, 4h;
(6) Wet blasted brass, 8h.
First, aluminum and aluminum alloy surface treatment methods 1. Degreasing treatment. Wipe the solvent with cotton wool to wipe it off. After removing the oil, wipe it several times with a clean cotton cloth. Commonly used solvents are: trichloroethylene, ethyl acetate, acetone, butanone, and gasoline.
2. After degreasing, chemical treatment in the following solution: Concentrated sulfuric acid 27.3 Potassium dichromate 7.5 Water 65.2 After immersed in 60-65°C for 10-30min, remove and rinse with water, dry or dry below 80°C; or After the solution is washed and then dried: Phosphoric acid 10 3 water 20 This method is suitable for phenolic, nylon rubber, etc., with good results.
3. After degreasing, chemical treatment in the following solution: ammonium bifluoride 3-3.5 chromium oxide 20-26 sodium phosphate 2-2.5 concentrated sulfuric acid 50-60 boric acid 0.4-0.6 water 1000 impregnated at 25-40 °C 4.5-6min, ie Wash and dry. The method has higher bonding strength and is glued within 4 hours after treatment, and is suitable for bonding epoxy adhesive and epoxy-nitrile rubber.
4. After degreasing, chemically treat in the following solution: phosphoric acid 7.5 chromium oxide 7.5 alcohol 5.0 formaldehyde (36-38%) 80 is impregnated at 15-30°C for 10-15 minutes, then washed and dried at 60-80°C.
5. After degreasing, perform anodization in the following solution: Concentrated sulfuric acid 22g/l is immersed for 10-15min at a DC strength of 1-1.5A/dm2 and then in a saturated potassium dichromate solution at 95-100°. C immersed for 5-20 min, then washed with water and dried.
6. After degreasing, chemical treatment in the following solution: potassium dichromate 66 sulfuric acid (96%) 666 water 1000 was dipped at 70°C for 10 minutes, then washed and dried.
7. After degreasing, chemical treatment in the following solution: nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 is impregnated at 20°C for 3s, i.e., rinsed with cold water, and then heated at 65°C with hot water. Wash, rinse with distilled water, dry. This method is suitable for casting aluminum alloys with high copper content.
8. After sandblasting or grinding, anodize in the following solution: chromium oxide 100 sulfuric acid 0.2 sodium chloride 0.2 raise the voltage from 0V to 10V at 40°C for 10 minutes, hold for 20 minutes, and then increase from 10V within 5 minutes To 50V, hold for 5min, then wash with water and dry at 700C. Note: The free chromium oxide concentration must not exceed 30-35 g/l.
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