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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 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 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, chemically treat in the following solution: concentrated sulfuric acid 27.3 Potassium dichromate 7.5 Water 65.2 After immersed in 60-65°C for 10-30 min, remove and rinse with water, dry or dry below 80°C; Or in the following solution and then washed after drying: Phosphoric acid 10 n-butanol 3 water 20 This method is suitable for phenolic - nylon rubber, etc., with good results.
[Method 3] Degreasing After 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 macerated at 25-40°C for 4.5-6 min , that is, washing and drying. 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 the degreasing, chemical treatment is performed 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, and then washed at 60-80°C, dry.
[Method 5] Anodizing in the following solution after degreasing: Concentrated sulfuric acid (22 g/l) was immersed for 10-15 min at a DC strength of 1-1.5 A/dm2 and then in a saturated potassium dichromate solution at 95- Immerse at 100°C for 5-20min, then wash and dry.
[Method 6] After the degreasing, chemical treatment was performed 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] Chemically treated in the following solution after degreasing: nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 was dipped at 20°C for 3s, ie, rinsed with cold water, and then used at 65°C. Wash with hot water, rinse with distilled water, and dry. 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 Raise the voltage from 0 V to 10 V at 40° C. within 10 min, hold for 20 min, and within 5 min. 10V was raised to 50V for 5 min, then washed with water and dried at 700C. Note: The free chromium oxide concentration must not exceed 30-35 g/l.
[Method 9] Chemical treatment in the following solution after degreasing: Sodium silicate 10 Non-ionic detergent 0.1 was immersed at 65°C for 5 minutes, then washed at 65°C or less, washed with distilled water and dried. Suitable for adhesive bonding of aluminum foil.
[Method 10] Chemical treatment in the following solution after degreasing: sodium fluoride 1 concentrated nitric acid 15 water 84 dipped at room temperature for 1 min, washed with water and then treated in the following solution: concentrated sulfuric acid 30 sodium dichromate 7.5 water 62.5 at room temperature Immerse for 1 min, wash and dry.
Second, magnesium and magnesium alloy surface treatment method
[Method 1] Degreasing treatment. Commonly used solvents are: trichloroethylene, acetone, ethyl acetate and butanone.
[Method 2] After degreased, immerse in the following solution at 70-75°C for 5 minutes: Sodium hydroxide 12 water 100 is rinsed with cold water, then immersed in the following solution at 20°C for 5 minutes: chromium oxide 10 water 100 anhydrous Sodium sulfate 2.8 was rinsed with cold water, washed with distilled water, and dried at 40C.
[Method 3] After degreased, immersed in a 6.3% sodium hydroxide solution at 70°C for 10 min, washed with water, and then immersed in the following solution at 55°C for 5 min: chromium oxide 13.8 calcium sulfate 1.2 water 85 washed with distilled water, Then in the following solution was immersed for 3 minutes at 55°C: Chromium oxide 10 Sodium sulfate 0.5 Water 89.5 After washing with water, dried below 60°C.
[Method 4] Immerse for 3 minutes in the following solution at 20°C: Chromium oxide 16.6 Sodium nitrate 20 Glacial acetic acid 105 Water 100 Rinse with cold water, wash with distilled water, dry below 40°C
[Method 5] Immerse in the following solution at 60-70°C for 3 minutes: sodium dichromate 10 magnesium sulfate 5 manganese sulfate 5 water 80 Rinse with cold water, wash with distilled water, and dry below 70°C.
[Method 6] After degreased, immersed in the following boiling solution for 20 minutes: sodium dichromate 1.5 ammonium sulfate 3 ammonia (d=0.88) 0.3 water 93.7 Rinse with warm water, wash with distilled water, and dry.
[Method 7] Anodizing in a 10% solution of ammonium hydrofluoride below 30°C to a current density of less than 0.45 A/m2 (one electrode panel), alternating voltage 90-120 V, followed by washing and drying.
[Method 8] Anodizing in the following solution at 20-30°C: potassium hydroxide 12 aluminum 0.75 anhydrous potassium fluoride 3.4 sodium phosphate 3.4 potassium permanganate 1.5 water 80 AC voltage 85 V, current density 1.1-1.4 A /m2, then wash with cold distilled water and dry.
[Method 9] After degreased, wash at 5 °C for 5-15 min at 70 °C in the following lye: Sodium hydroxide 23-34 water 400 was washed with cold water for 5 min, then immersed in the following solution for 5-15 min, temperature 55 °C: Oxidation Chromium 57-68 Calcium Nitrate 5 Water 450 Washed with cold water for 2 min, then immersed in the following solution for 3-12 min, temperature 55 °C: chromium oxide 45 sodium phosphate 8 water 450 washed in cold water for 2 min, then at 40 °C Dry 30min.
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 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 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, chemically treat in the following solution: concentrated sulfuric acid 27.3 Potassium dichromate 7.5 Water 65.2 After immersed in 60-65°C for 10-30 min, remove and rinse with water, dry or dry below 80°C; Or in the following solution and then washed after drying: Phosphoric acid 10 n-butanol 3 water 20 This method is suitable for phenolic - nylon rubber, etc., with good results.
[Method 3] Degreasing After 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 macerated at 25-40°C for 4.5-6 min , that is, washing and drying. 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 the degreasing, chemical treatment is performed 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, and then washed at 60-80°C, dry.
[Method 5] Anodizing in the following solution after degreasing: Concentrated sulfuric acid (22 g/l) was immersed for 10-15 min at a DC strength of 1-1.5 A/dm2 and then in a saturated potassium dichromate solution at 95- Immerse at 100°C for 5-20min, then wash and dry.
[Method 6] After the degreasing, chemical treatment was performed 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] Chemically treated in the following solution after degreasing: nitric acid (d=1.41) 3 hydrofluoric acid (42%) 1 was dipped at 20°C for 3s, ie, rinsed with cold water, and then used at 65°C. Wash with hot water, rinse with distilled water, and dry. 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 Raise the voltage from 0 V to 10 V at 40° C. within 10 min, hold for 20 min, and within 5 min. 10V was raised to 50V for 5 min, then washed with water and dried at 700C. Note: The free chromium oxide concentration must not exceed 30-35 g/l.
[Method 9] Chemical treatment in the following solution after degreasing: Sodium silicate 10 Non-ionic detergent 0.1 was immersed at 65°C for 5 minutes, then washed at 65°C or less, washed with distilled water and dried. Suitable for adhesive bonding of aluminum foil.
[Method 10] Chemical treatment in the following solution after degreasing: sodium fluoride 1 concentrated nitric acid 15 water 84 dipped at room temperature for 1 min, washed with water and then treated in the following solution: concentrated sulfuric acid 30 sodium dichromate 7.5 water 62.5 at room temperature Immerse for 1 min, wash and dry.
Second, magnesium and magnesium alloy surface treatment method
[Method 1] Degreasing treatment. Commonly used solvents are: trichloroethylene, acetone, ethyl acetate and butanone.
[Method 2] After degreased, immerse in the following solution at 70-75°C for 5 minutes: Sodium hydroxide 12 water 100 is rinsed with cold water, then immersed in the following solution at 20°C for 5 minutes: chromium oxide 10 water 100 anhydrous Sodium sulfate 2.8 was rinsed with cold water, washed with distilled water, and dried at 40C.
[Method 3] After degreased, immersed in a 6.3% sodium hydroxide solution at 70°C for 10 min, washed with water, and then immersed in the following solution at 55°C for 5 min: chromium oxide 13.8 calcium sulfate 1.2 water 85 washed with distilled water, Then in the following solution was immersed for 3 minutes at 55°C: Chromium oxide 10 Sodium sulfate 0.5 Water 89.5 After washing with water, dried below 60°C.
[Method 4] Immerse for 3 minutes in the following solution at 20°C: Chromium oxide 16.6 Sodium nitrate 20 Glacial acetic acid 105 Water 100 Rinse with cold water, wash with distilled water, dry below 40°C
[Method 5] Immerse in the following solution at 60-70°C for 3 minutes: sodium dichromate 10 magnesium sulfate 5 manganese sulfate 5 water 80 Rinse with cold water, wash with distilled water, and dry below 70°C.
[Method 6] After degreased, immersed in the following boiling solution for 20 minutes: sodium dichromate 1.5 ammonium sulfate 3 ammonia (d=0.88) 0.3 water 93.7 Rinse with warm water, wash with distilled water, and dry.
[Method 7] Anodizing in a 10% solution of ammonium hydrofluoride below 30°C to a current density of less than 0.45 A/m2 (one electrode panel), alternating voltage 90-120 V, followed by washing and drying.
[Method 8] Anodizing in the following solution at 20-30°C: potassium hydroxide 12 aluminum 0.75 anhydrous potassium fluoride 3.4 sodium phosphate 3.4 potassium permanganate 1.5 water 80 AC voltage 85 V, current density 1.1-1.4 A /m2, then wash with cold distilled water and dry.
[Method 9] After degreased, wash at 5 °C for 5-15 min at 70 °C in the following lye: Sodium hydroxide 23-34 water 400 was washed with cold water for 5 min, then immersed in the following solution for 5-15 min, temperature 55 °C: Oxidation Chromium 57-68 Calcium Nitrate 5 Water 450 Washed with cold water for 2 min, then immersed in the following solution for 3-12 min, temperature 55 °C: chromium oxide 45 sodium phosphate 8 water 450 washed in cold water for 2 min, then at 40 °C Dry 30min.
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