Method 1: Degreasing treatment. Wipe with absorbent cotton soaked in solvent. After removing oil, wipe with a clean cotton cloth several times. Commonly used solvents are: trichloroethylene, ethyl acetate, acetone, methyl ethyl ketone and gasoline.

Method 2: Chemical treatment in the following solution after degreasing: concentrated sulfuric acid 27.3 (mass fraction, the same below), potassium dichromate 7.5, water 65.2, immersed at 60～65℃ for 10～30min, taken out, rinsed with water, and dried Or dry below 80℃. Or wash in the following solution and then dry: phosphoric acid 10, n-butanol 3, water 20, this method is suitable for phenolic-nylon glue, etc., the effect is good.

Method 3: Chemical treatment in the following solution after degreasing: ammonium bifluoride 3 to 3.5, chromium oxide 20 to 26, sodium phosphate 2 to 2.5, concentrated sulfuric acid 50 to 60, boric acid 0.4 to 0.6, water 1000 at 25 to 40°C Immersed at temperature for 4.5-6min, then washed and dried. The method has high bonding strength, and the bonding within 4 hours after treatment is suitable for epoxy bonding and epoxy-butyronitrile bonding.

Method 4: Chemical treatment in the following solution after degreasing: phosphoric acid 7.5, chromium oxide 7.5, alcohol 5.0, formaldehyde (36-38%) 80, immersed at a temperature of 15-30°C for 10-15 minutes, and then at 60-80°C Wash in water and dry.

Method 5: Anodizing in the following solution after degreasing: concentrated sulfuric acid 22g/L, immersed in direct current intensity of 1～1.5A/dm2 for 10～15min, and then in saturated potassium dichromate solution, at 95～ Immerse at 100℃ for 5~20min, then wash with water and dry.

Method 6: After degreasing, chemical treatment in the following solution: potassium dichromate 66, sulfuric acid (96%666, water 1000, immersed at 70 ℃ for 10 minutes, then washed with water and dried.

Method 7: Chemical treatment in the following solution after degreasing: nitric acid (d=1.41) 3, hydrofluoric acid (42%) 1, soaked in cold water for 3s at 20℃, then washed with cold water at 65℃ Wash, rinse with distilled water, and dry. This method is suitable for cast aluminum alloys with high copper content.

Method 8: After sandblasting or sanding, anodize in the following solutions: chromium oxide 100, sulfuric acid 0.2, sodium chloride 0.2, and increase the voltage from 0V to 10V at 40℃ within 10min, hold for 20min, and then within 5min Increase from 10V to 50V, hold for 5min, then wash with water and dry at 700℃. Note: The concentration of free chromium oxide should not exceed 30 ~ 35g/L.

Method 9: Chemical treatment in the following solution after degreasing: sodium silicate 10, non-ionic detergent 0.1, immersed at 65°C for 5 min, then washed with water below 65°C, then washed with distilled water and dried. This method is suitable for the bonding of aluminum foil.

Method 10: Chemical treatment in the following solution after degreasing: sodium fluoride 1, concentrated nitric acid 15, water 84, immersed 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, immersed at room temperature for 1 min, washed with water and dried.