Machining aluminum oxide film forming process, technical requirements
(1) oxidation. Solution formulation and working conditions:
Aluminum pieces after pre-treatment immediately transferred to the oxidation step, to prevent the workpiece resting too long in the atmosphere but natural oxide film generated affect the quality of the oxide layer. Once again immersed in water exposed to the atmosphere, although superior, but should not be soaked for too long, if soaked in 3% dilute nitric acid generally soak l5 ~ 30min of oxidation can continue, but if it takes too long to film generation will be affected, in particular, contain impurities such as old copper nitrate.
Temperature of the oxidation process of aluminum manufactured components is critical solution process conditions, the solution temperature is too high, the film forming speed, the oxide film is prone to powder; solution temperature is too low, the deposition rate is slow, the generated tone film underweight, poor adhesion.
To obtain a substantially uniform surface color, it should be dealt with at the same time in the same solution at the same temperature model aluminum.
Within a certain range of temperature and time is inversely proportional to that solution, the higher the temperature, the shorter the time required, whereas the longer the time required.
When machining aluminum oxide, aluminum processing time, the higher purity needed for longer. Oxidation treatment time of less than an oxide film produced too pale; low-purity aluminum oxide, shortened, or the oxide film was stale, and even affect the electrical properties of the film.
In order to obtain a uniform color of the oxide film, the oxidation can be more small pieces of rock when in solution, can be taken large static or stirred solution treated (without stirring the solution, do not shake the workpiece), and the solution to prevent the edge portion of the workpiece than the switch the central portion of the workpiece to produce multi-color unevenness oxide film.
(2) circulating water. For blind holes, slits to strengthen the work of washing these parts, and thrown inside the net residual solution, oxidation solution to flow out of the surface oxide damaged.
(3) self-test. After washing the workpiece by circulating water quality self-test that is appropriate, such as may be found to be defective in alkaline stripping, re-oxidation of the light. If dry before stripping, repairing, stripping is more difficult, and easier to damage the substrate.
(4) Drying. Drying is critical to maintaining the quality of the oxide member need to be dried before rejection to the free water surface, and then in the sun exposure. Can also be baked at 45 ~ 50 ℃ drying conditions, the temperature is not too high, so as not to scorch, aging, cracks, color appearance looked old.
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