Aluminum alloy parts contain a lot of silicon inside, so the oxidation process cannot be used, which will cause the silicon to oxidize, blacken, and be uneven.
The surface treatment methods of aluminum alloy parts are:
1. Anodizing treatment;
2. Spraying;
3. Plastic spraying treatment;
4. Wire drawing treatment;
5. Dyeing treatment.
During various heat treatment, mechanical processing, transportation and storage, the metal surface will inevitably be oxidized, resulting in an oxide layer with uneven thickness. At the same time, it is also easily polluted by various oils or adsorbed by some other impurities. Oil stains and certain adsorbents, and the thinner oxide layer can be cleaned with solvents, chemically treated and mechanically treated, or directly chemically treated. For the heavily oxidized metal surface, the oxide layer is thicker, so it cannot be directly cleaned with solvents and chemically treated, but it is better to perform mechanical treatment first. Usually treated metal surfaces are highly reactive and more susceptible to re-contamination by dust, moisture, etc. For this purpose, the treated metal surfaces should be glued as quickly as possible.
The metal storage period after different treatments is roughly as follows:
(1) Aluminum alloy parts treated by wet sandblasting, 72 hours;
(2) Aluminum alloy parts treated with chromic acid-sulfuric acid, 6 hours;
(3) Anodized aluminum alloy parts, 30 days;
(4) Stainless steel parts treated with sulfuric acid, 20 days;
(5) Sand blasted steel parts, 4 hours;
(6) Wet blasted brass parts, 8 hours.
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Aluminum and aluminum alloy surface treatment method:
1. Degreasing treatment: wipe with absorbent cotton moistened with solvent, after removing the oil, wipe it several times with a clean cotton cloth.
Commonly used solvents are: trichloroethylene, ethyl acetate, acetone, butanone and gasoline.
There are roughly seven types of chemical treatment methods:
2. Chemical treatment method one: Concentrated sulfuric acid 27.3 Potassium dichromate 7.5 Water 65.2 Immerse at 60-65°C for 10-30min, take out and rinse with water, dry in the air or dry below 80°C; or wash in the following solution Then dry: Phosphoric acid 10 positive 3 water 20 This method is suitable for phenolic, nylon glue, etc., and the effect is good.
3 Chemical treatment method two: 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 Immerse at 25-40°C for 4.5-6min, then wash with water and dry. This method has high bonding strength, and it can be bonded within 4 hours after treatment. It is suitable for bonding epoxy glue and epoxy-nitrile glue.
4. Chemical treatment method three: Phosphoric acid 7.5 chromium oxide 7.5 alcohol 5.0 formaldehyde (36-38%) 80 Immerse at 15-30°C for 10-15min, then wash and dry at 60-80°C.
5. Chemical treatment four: Potassium dichromate 66 sulfuric acid (96%) 666 water 1000 immersion at 70°C for 10 minutes, then washed with water and dried.
6. Chemical treatment five: nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 soaked at 20°C for 3s, rinsed with cold water, then washed with hot water at 65°C, rinsed with distilled water, and dried . This method is suitable for cast aluminum alloys with higher copper content.
7. Chemical treatment method six: Sodium silicate 10 non-ionic detergent 0.1 soak at 65°C for 5min, then wash with water below 65°C, then wash with distilled water and dry. Suitable for bonding aluminum foil.
8. Chemical treatment method seven: soak sodium fluoride 1 concentrated nitric acid 15 water 84 at room temperature for 1 min, wash with water and then treat in the following solution: concentrated sulfuric acid 30 sodium dichromate 7.5 water 62.5 soak for 1 min at room temperature, wash with water, and dry .
9. After sandblasting or grinding, anodize in the following solution: chromium oxide 100 sulfuric acid 0.2 sodium chloride 0.2 At 40°C, increase the voltage from 0V to 10V within 10 minutes, keep it for 20 minutes, and then increase from 10V to 10V within 5 minutes 50V, keep for 5min, then wash with water and dry at 700C. Note: The free chromium oxide concentration must not exceed 30-35g/l.
10. Anodizing treatment: immerse concentrated sulfuric acid 22g/l at a DC strength of 1-1.5A/dm2 for 10-15min, then in a saturated potassium dichromate solution at 95-100°C for 5-20min, then Wash and dry.