Metal surfaces are inevitably oxidized during heat treatment, mechanical processing, transportation, and storage, resulting in a thick and uneven 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 severely oxidized metal surfaces, the oxide layer is thick and cannot be directly cleaned with solvents and chemically treated. It is best to perform mechanical treatment first.
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 metal storage period 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, 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 method [Method 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.
[Method 2]
After degreasing, chemical treatment in the following solution:
Concentrated sulphuric acid 27.3 Potassium dichromate 7.5 Water 65.2 After immersing for 10-30 min at 60-65°C, rinse with water, dry or dry below 80°C; or wash in the following solution and then dry:
Phosphoric acid 10 n-butanol 3 water 20 This method is suitable for phenolic-nylon adhesives, etc., with good results.
[Method 3]
After degreasing, chemical treatment in the following solution:
Ammonium Hydrogen Fluoride 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 for 4.5-6 minutes, ie, washed and dried. 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.
[Method 4]
After degreasing, chemical treatment in the following solution:
Phosphoric acid 7.5 Chromium oxide 7.5 Alcohol 5.0 Formaldehyde (36-38%) 80 Impregnated at 15-30°C for 10-15 min, then washed and dried at 60-80°C.
[Method 5]
After degreasing, anodizing in the following solution:
Concentrated sulfuric acid 22g/l is immersed for 10-15min at a DC intensity of 1-1.5A/dm2, and then saturated potassium dichromate solution is impregnated at 95-100C for 5-20min, then washed with water and dried.
[Method 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 with water and dried.
[Method 7]
After degreasing, chemical treatment in the following solution:
Nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 is dipped at 20° C. for 3 seconds, ie, rinsed with cold water, washed with hot water at 65° C., rinsed with distilled water, and dried. This method is suitable for casting aluminum alloys with high copper content.
[Method 8]
After sandblasting or grinding, anodize in the following solution:
Chromium oxide 100 Sulfuric acid 0.2 Sodium chloride 0.2 The voltage is increased from 0 V to 10 V at 40° C. within 10 min, held for 20 min, then raised from 10 V to 50 V within 5 min, held for 5 min, then washed with water, and dried at 700° C. Note: The free chromium oxide concentration must not exceed 30-35 g/l.
[Method 9]
After degreasing, chemical treatment in the following solution:
Sodium silicate 10 Nonionic detergent 0.1 was immersed for 5 min at 65°C, then washed below 65°C, washed with distilled water and dried. Suitable for adhesive bonding of aluminum foil.
[Method 10]
After degreasing, chemical treatment in the following solution:
Sodium fluoride 1 Concentrated nitric acid 15 Water 84 Dipped at room temperature for 1 min, washed with water and treated in the following solution:
Concentrated sulfuric acid 30 sodium dichromate 7.5 water 62.5 immersed for 1 min at room temperature, washed and dried.
For oil and certain adsorbents, the thinner oxide layer may be washed with solvents, chemically and mechanically, or chemically treated directly. For severely oxidized metal surfaces, the oxide layer is thick and cannot be directly cleaned with solvents and chemically treated. It is best to perform mechanical treatment first.
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 metal storage period 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, 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 method [Method 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.
[Method 2]
After degreasing, chemical treatment in the following solution:
Concentrated sulphuric acid 27.3 Potassium dichromate 7.5 Water 65.2 After immersing for 10-30 min at 60-65°C, rinse with water, dry or dry below 80°C; or wash in the following solution and then dry:
Phosphoric acid 10 n-butanol 3 water 20 This method is suitable for phenolic-nylon adhesives, etc., with good results.
[Method 3]
After degreasing, chemical treatment in the following solution:
Ammonium Hydrogen Fluoride 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 for 4.5-6 minutes, ie, washed and dried. 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.
[Method 4]
After degreasing, chemical treatment in the following solution:
Phosphoric acid 7.5 Chromium oxide 7.5 Alcohol 5.0 Formaldehyde (36-38%) 80 Impregnated at 15-30°C for 10-15 min, then washed and dried at 60-80°C.
[Method 5]
After degreasing, anodizing in the following solution:
Concentrated sulfuric acid 22g/l is immersed for 10-15min at a DC intensity of 1-1.5A/dm2, and then saturated potassium dichromate solution is impregnated at 95-100C for 5-20min, then washed with water and dried.
[Method 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 with water and dried.
[Method 7]
After degreasing, chemical treatment in the following solution:
Nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 is dipped at 20° C. for 3 seconds, ie, rinsed with cold water, washed with hot water at 65° C., rinsed with distilled water, and dried. This method is suitable for casting aluminum alloys with high copper content.
[Method 8]
After sandblasting or grinding, anodize in the following solution:
Chromium oxide 100 Sulfuric acid 0.2 Sodium chloride 0.2 The voltage is increased from 0 V to 10 V at 40° C. within 10 min, held for 20 min, then raised from 10 V to 50 V within 5 min, held for 5 min, then washed with water, and dried at 700° C. Note: The free chromium oxide concentration must not exceed 30-35 g/l.
[Method 9]
After degreasing, chemical treatment in the following solution:
Sodium silicate 10 Nonionic detergent 0.1 was immersed for 5 min at 65°C, then washed below 65°C, washed with distilled water and dried. Suitable for adhesive bonding of aluminum foil.
[Method 10]
After degreasing, chemical treatment in the following solution:
Sodium fluoride 1 Concentrated nitric acid 15 Water 84 Dipped at room temperature for 1 min, washed with water and treated in the following solution:
Concentrated sulfuric acid 30 sodium dichromate 7.5 water 62.5 immersed for 1 min at room temperature, washed and dried.