In the process of various heat treatment, mechanical processing, transportation and storage, the metal surface will inevitably be oxidized, resulting in an uneven thickness of the oxide layer. At the same time, also susceptible to various types of oil pollution and adsorption of some other impurities. Oil stains and some adsorbents, the thinner oxide layer can be used solvent cleaning, chemical treatment and mechanical treatment, or directly with chemical treatment.
For severe oxidation of the metal surface, the oxide layer is thicker, you can not directly with the solvent cleaning and chemical treatment, and the better first mechanical treatment. Usually treated metal surfaces are highly reactive and more prone to re-contamination by dust, moisture, etc. For this purpose, the treated metal surface should be bonded as quickly as possible. The metal storage period after different treatments is as follows:
(1) aluminum alloy with wet sand blasting treatment, 72h;
(2) chromic acid-sulfuric acid treated aluminum alloy, 6h;
(3) anodized aluminum alloy, 30 days;
(4) stainless steel treated with sulfuric acid for 20 days;
(5) sand-blasted steel, 4h;
(6) wet sand blasted brass, 8h.
Methods for surface treatment of aluminum and aluminum alloys
[method 1] degreasing. With absorbent cotton wet solvent to wipe, remove oil, and then clean cotton cloth to wipe a few times. Common solvents: trichloroethylene, ethyl acetate, acetone, butanone and gasoline, etc.
Method  in the following after degreasing solution chemical treatment: potassium dichromate sulfuric acid 27.3 7.5 65.2 in the 60-65 ° C water dipping out 10 to 30 min after rinse, dry or drying under 80 ° C; Or washed in the following solution and then dried: 10 n butanol phosphate 3 water 20 this method is applicable to phenol-nylon adhesive, etc., the effect is good.
Method  in the following after degreasing solution chemical treatment: ammonium hydrogen fluoride 3-3.5 - chrome oxide 20 to 26 50 to 60 boric acid of sulfuric acid sodium phosphate 2-2.5-0.4-0.6 1000 in 25 to 40 ° C water dipping 4.5-6 min, namely for washing and drying. The adhesive strength of this method is high, and it can be used for epoxy adhesive and epoxy - butyronitrile adhesive within 4h after treatment.
Method  in the following after degreasing solution chemical treatment: alcohol phosphoric acid chrome oxide 7.5 7.5 5.0 formaldehyde (36-38%) of 80 in the 15 to 30 ° C impregnating 10-15 min, and then in the 60-80 ° C under water washing and drying.
Method  in the following after degreasing solution for anodized: 22 g/l in sulfuric acid under the dc intensity of 1-1.5 A/dm2 impregnated 10-15 min, again in saturated potassium dichromate solution, in 95-100 ° C under dipping 5 to 20 min, and then washed, dry.
Method  in the following after degreasing solution chemical treatment: potassium dichromate sulfuric acid (96%) of 66 to 666, 1000 water soaking under 70 ° C for 10 min, and then washed, dry.