A township electroplating factory, in order to meet customer needs, expand business, hastily patched together some old equipment, an additional aluminum anodizing process line. Since the plant personnel had not been exposed to the anodizing process technology in the past, they only read relevant books and lacked operating experience. Especially in the process of black dyeing after anodization, the surface of the processed workpiece is not green, red, or hairy, that is, the film is loose and powdered, and the fixture is burned or dyed. Too many defectives, unable to deliver, the factory is very anxious, invited the author to help solve. For this reason, the author went to understand the situation, and based on his own experience in anodizing and dyeing for many years, he introduced in writing the key points of the technology and gave it to the operator. After the author's discontinuous transmission for nearly two months, he helped him with At present, the personnel of the anodizing team of the plant can operate independently according to the process requirements, and the quality is very good. It has achieved both the satisfaction of the factory and the customer. The following is a summary of the technical aspects of the anodizing process. For peer reference. 1 Design and manufacture of fixtures 1.1 Characteristics of fixtures The fixtures used for anodizing are very different from the fixtures used for electroplating. It is not appropriate to use an anodizing fixture with a similar hook for electroplating because the anodizing fixture Oxide film will be quickly formed on the surface of the workpiece. During this process, slight loosening of the fixture and the workpiece will change the position of the contact and impede the current circulation. Therefore, the workpiece must be clamped with a flexible clamp. Only in this way can the anodizing process proceed normally. 1.2 Structure of the fixture The fixture structure is suitable for individual type. If the assembly type is used, the riveted or welded area will loosen due to corrosion after several times of use, which will hinder the normal circulation of current in the anodizing process. At the same time, the fixture should have a certain cross-sectional area. A certain section of the fixture also has enough elastic force and clamping force to keep the workpiece and the fixture in good contact, so as to ensure the normal current circulation when the workpiece is anodized. Avoid burning the workpiece due to bad heat. 1.3 Selection of Fixture Materials For the production of jigs, it is better to choose hard aluminum materials. The hard aluminum material has good elasticity and is durable and durable. 2 Fixture of the workpiece 2.1 Cleaning of the fixture Removing the film During the anodizing process, the fixture will also produce an oxide film. For this reason, be sure to remove the oxide film before using it again before using it again. The film can be removed in aluminum degreasing solution. It is also possible to remove the oxide film at the contact area between the jig and the workpiece with a trowel, and this method can also extend the service life of the jig for some jigs. 2.2 Selection of clamping position The position of the clamping workpiece must be properly selected. Generally, it should be clamped on the secondary side of the workpiece (that is, the non-decorative part). Otherwise, the contact area between the workpiece and the fixture cannot be covered with the oxide film due to being covered by the fixture. Of course, it will not be able to be dyed. This will show obvious white spots and affect the appearance quality. In addition, the question of whether the recessed parts suspended in the solution after the workpiece is clamped in the solution, such as the generation of gas, should also be considered. 2.3 to prevent the workpiece clamping deformation fixture is not the same, the clip has a certain degree of flexibility. In particular, care must be taken when clamping a deformed workpiece, and excessive deformation of the workpiece should be avoided. 2.4 To prevent the clamp from becoming too loose When the workpiece is clamped too loose, the current between the clamp and the workpiece will be broken. In this case, the workpiece is likely to be burned. 2.5 One by one to install anodized parts to be dyed. Some units apply anodization to some small parts by using screens or by other methods. Although this method can save man-hours and improve efficiency under certain conditions, it can only be used for certain anodizations with low quality requirements. Even if a small number of workpieces cannot form an oxide film at the mutual mask, they are not easily identified. But for workpieces that require black dyeing, this method of clamping is obviously not desirable. Must be installed one by one to ensure the quality of anodizing. 3 Anodic oxidation process conditions control 3.1 The relationship between the temperature and the voltage of the solution The lower the temperature of the solution within the rated range, the higher the required voltage, because the solution temperature is lower, the oxide film formation rate is slower, the film layer is more Dense, in order to obtain a certain thickness of oxide film, anodizing process needs to increase the voltage. When the temperature of the solution is high, the dissolution rate of the oxide film increases, and the resulting oxide film is loose. At this time, reducing the voltage can properly improve the quality of the oxide film. 3.2 The relationship between temperature and time of the anodizing solution The lower the temperature of the solution, the longer the anodizing time required. Because the temperature of the solution is low, the oxide film is slowly formed. As the temperature of the solution increases, the rate of oxide film formation increases. At this time to shorten the anodizing time, otherwise due to the increase of the outer layer of the oxide film resistance film layer dissolved, the size of the workpiece changes, the phenomenon of rough surface film. The above measures are only emergency measures taken under the condition that there is no cooling device and no heating device. 4 Formulation and preparation process of dyed black solution 4.1 Formulation and process conditions Acid wool ATT 20-30g/L Acid Lake Blue 2～3g/L Temperature 50～70°C Time 10～15min pH 3～3.5 (or 4.5) ~5. 5) 4.2 Formulation method First boil the solution to promote complete dissolution of the dye and ensure it is free from defects. After the solution is cooled, it is filtered with a filter paper to remove insoluble particles and oily substances floating on the liquid surface. The pH was later measured and adjusted to process requirements with cold acetic acid or ammonia. 5 Dyeing process should pay attention to matters 5.1 Strengthen the rinse before washing the workpiece from the anodic oxidation tank to be fully washed, especially the workpiece slits, blind holes, etc., otherwise the residual acid, alkali will slowly flow out during the dyeing process The pH of the dyeing solution is deviated from the normal range, and the surface of the residual acid-base portion is markedly different from the color of the clean portion, and even the oxide film is etched to show white color. 5.2 Immediately after anodization, the dyeings should be dyed after anodization. If the workpiece is anodized and exposed to air for an extended period of time, the pores of the film will shrink, and stains may get on the surface, causing difficulty in dyeing. If the dyeing tank is too small to be dyed in batches, the parts to be dyed should be soaked in clean water. 5.3 When the workpiece is not dyed during dyeing, the workpieces must not be overlapped, especially on the flat surface. Otherwise, the overlapping areas are covered to form the yin-yang plane. 5.4 Dyeing after rinsing If the surface of the workpiece is not washed clean, residual pigments will contaminate the assembly. 6 Cautions for cleaning work 6.1 Carefully remove the workpiece to prevent the workpiece from being scratched when the fixture is removed. Otherwise, a round of white marks will appear. The fixture should be loosened to free the workpiece to fall off. Never pull the workpiece hard before the fixture is released. 6.2 Workpiece Drying Method Firstly, the water in the hole of the workpiece should be thrown away to prevent residual water from contaminating the surface of the workpiece. It is better to dry the towel with a dry towel. In the rubbing process, the surface frost caused by the aluminum material or the operation process problem can also be wiped clean. 6.3 Packing requirements Packing is soft, clean paper is good, and it is packaged one by one to prevent rubbing each other. 7 Maintenance and Care of Stained Black Solutions Care and maintenance of the dyed black solution is mainly to maintain the pH of the solution. According to relevant information, acidic ATT dyes consist of acidic blue-black 10B and acidic orange II with different diffusion properties. When the pH value of the dyeing solution is in the range of 5-6 or 3-3.5, the absorption of Acid Orange II and Acid Blue Black 10B is better, and the amount absorbed by the oxide film is also larger. The amount meets the matching requirements and the color obtained is normal black. When the pH value is around 4, the effect of the oxidation film absorbing acidic orange II increases, and the absorption naturally increases. The acid orange II in the film is larger than the normal ratio, and the color appears reddish. When the pH is restored to the range of 3-5 or 5-5. 5, the absorption of acidic orange II by the oxide film will fall again, and the dyed workpiece will show normal black color. According to this, the pH of the dyed black liquid The accurate control of the value is very important.