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The higher the purity of the aluminum, the longer the oxidation treatment time required. The oxidation treatment time is insufficient, and the formed oxide film is too light; the aluminum material has low purity and the oxidation time is shortened, otherwise the oxide film is old and even affects the conductivity of the film layer.
In order to obtain a uniform oxide film color, small parts can be shaken in solution when oxidized, and large parts can be stirred or statically treated (without stirring the solution or shaking the workpiece) to prevent the edge of the workpiece from being compared with the solution switch. There are many central parts of the workpiece and uneven color of the oxide film is produced.
(2) Rinse water rinse. For workpieces with blind holes and slits, the rinsing of these parts should be strengthened, and the residual solution inside should be cleaned to prevent the oxidation solution from flowing out of the oxidation surface.
(3) Self-test. After the workpiece is washed by circulating water, it should be self-checking quality. If it is found to be defective, it can be removed in the lye and reoxidized after light. If it is removed after re-drying and reworked, it is difficult to remove and it is easy to damage the substrate.
(4) Drying. Drying is the key to maintaining quality. The oxidized parts need to be freed from the free surface of the workpiece before drying and then exposed to sunlight. It can also be baked and dried at 45~50°C. The temperature should not be too high, so as to avoid scorching, aging, cracks, and the appearance of the color is old.
Large area chlorination
(1) Overall processing. According to the outer edge size of the oxidizing member (appropriately relaxing the margin), a wooden frame or brick is used to form a frame, and the plastic cloth is laid in the frame to form a concave pool. If the height of the plate is processed, there is 100MM. It can be left and right. When the workpiece is shaken up and down in the pool during operation, an oxide film can be formed on the surface.
(2) Sub-site treatment. The sub-site treatment means that the workpiece is rapidly changed or rotated sequentially in different parts in the tank (pool), and finally the entire workpiece surface is contacted with the solution multiple times to gradually form and thicken the oxide film.
By adopting the above two methods, it is possible to avoid large-scale plating tanks, prepare a large amount of solution, and reduce the waste caused by long-term use, and avoid the occupation of the production area in the workshop.
Three possible causes of uneven color of oxide film
(1) The workpiece area is too large, and the swing in the groove is too large during operation, and the contact, renewal, and exchange of the edge and the center portion are too large, resulting in inconsistent color of the oxide film.
Prevention method: The amplitude of the workpiece swing during oxidation is small, and static treatment is also possible. However, when the temperature of the solution is too low, it is easy to appear as a map-like spot, which is unnatural.
(2) When the aluminum package is processed, part of the aluminum coating is destroyed and cut off. The outer layer of aluminum is high-quality aluminum, and the inner layer of the package is miscellaneous aluminum. The difference between the two types of aluminum is large, so it appears after oxidation. A spot like a good wind. This phenomenon is often not understood by customers, manufacturers should do more explanation work, explain the original committee, so as not to cause misunderstanding.
(3) Problems in process operation
1 The alkali etching of the workpiece is not thorough, and the original oxide film and dirt are not removed at the local site;
2 After the alkali etching, the light treatment is not performed immediately, and the surface of the workpiece is still alkaline;
3 The workpiece has been exposed to foreign matter during the transfer.
When there is uneven color of the film layer, it is necessary to find the cause from various aspects and take targeted measures to solve it.
Failure caused by excessive accumulation of aluminum ions in the alkali etching solution
A reader called to inquire about the reason why it is difficult to obtain a conductive oxide film after alkali etching. After eliminating many factors that are difficult to form a conductive oxide film, considering whether there is a problem of excessive aluminum ion in the alkali etching solution, the other party said that the alkali etching solution Very thick. However, the rate of alkali etching is not fast. At that time, the author suggested replacing the alkali etching solution, because the alkali etching solution will accumulate too much aluminum ions after the use time is too long, and the aluminum ions are difficult to elute on the surface of the workpiece, thus affecting the contact between the surface of the aluminum piece and the conductive oxidation solution, thereby affecting Formation of an oxide film. Another suggestion is that if the alkali etching solution is unconditionally replaced at the time, the alkali-etched workpiece can be rinsed in flowing water immediately after being rinsed with hot water, then discharged in concentrated nitric acid containing hydrofluoric acid, and then fully rinsed to conduct electricity. Oxidation treatment. After the reader came to the phone, the effect of washing with hot water after alkali etching was very good.
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