After the oxidation of aluminum products, it has the advantages of stable technology, low cost and easy operation. In addition, it is possible to obtain a variety of beautiful or distinctive patterns through the improvement of the process and to increase the number of fancy varieties. Therefore, the dyeing process has always been the subject of aluminum oxidation workers. "Infiltration method with color technology" "Marbling dyeing process" and so on belong to this category. The osmotic method uses the chromic anhydride to fade the understained color, while the marble patterning uses the grease to seal the underline osmotic method. The specific method is to spray the aluminum products after oxidation and tinting with chromic anhydride (industrial pure 350-450 g/l) or oxalic acid (industrial-grade 200-300 g/l), using asbestos, glass fiber, etc. Chromium anhydride wettability auxiliary exhibition products, so that the auxiliary exhibition part faded, immediately after washing with water to stop the fading of the image reaction, and then dye the second time or repeated rubbing chromic acid rub, water, dyeing and other procedures. As a result, beautiful lines such as bright flowers, clouds and other colored lines can appear. As for the marble pattern dyeing method, aluminum oxide products are first stained with the first ground color and then immersed in water with a surface floating with grease (such as peanut oil). When lifting or immersing, due to the natural sagging of grease and water, the oxide layer is partially contaminated by irregular striped grease. When the second color is re-stained, the oxide film is The oil stained part is not stained, and the other part that is not contaminated with grease is dyed with a second color, which makes the surface of the aluminum product appear irregular and beautiful like a marble pattern. pattern.
Fourth, other surface treatment process
In addition to the oxidation dyeing of aluminum products, there are other surface treatment processes such as spray painting or spray painting. The painting process is to remove the aluminum products after oil washing and whitening, spray the amino baking varnish, air dry, and bake at 150-170°C for 15-20 minutes. Spray paint spray is used nitro-color paint, spray primer, and then sprayed on the pattern flower board, and finally spray varnish, and baked at 60 °C temperature for 2 minutes. Spray painting and spray painting processes are widely used in aluminum products such as aluminum buckets, bowls, washbasins, tea trays, etc. in Jiangsu Province and other provinces.
In recent years, a number of new aluminum surface treatment technologies have also been developed abroad, such as electrolytic coloring, coated PTFE and enamel technology, and have been applied in industrial production, making aluminum products more colorful and adaptable to various uses. Some domestic research institutes and factories have also tested and researched these processes. It is believed that these products will soon be available in the domestic market. Now these new processes are briefly described as follows:
(1) Electrolytic coloring
It is to add some additives directly in the oxidizing electrolyte, generally some organic acids such as thiosalicylic acid, cresol sulfonic acid, etc., to oxidize the colored oxide film. Strictly speaking, oxalic acid oxidation of yellow oxide film should also belong to this kind. The oxidized aluminum workpiece is also put into an electrolytic solution containing nickel, selenium, cobalt, tin and other metal salts to electrolyze the oxide film, and various colors can be obtained depending on the composition of the aluminum material and the electrolytic process. Although the color tone obtained by the electrolytic coloring method is still relatively monotonous and far less vivid than the organic dye, the electrolytic coloring is an oxidation film coloration, durability, and excellent weather resistance. Currently, electrolytically colored aluminum products have been widely used in building materials such as aluminum door and window frames.
(2) Process for coating resin such as polytetrafluoroethylene and polyphenylene sulfide
PTFE is a high-temperature resistant engineering plastic. It has high chemical stability, electrical insulation, and anti-adhesion. It can maintain good performance over a wide temperature range from -60°C to 250°C. Therefore, it is widely used. It is also very popular among aluminum products such as light industrial and civilian bedding. Coating process is generally: first by a certain ratio of PTFE resin ball mill filter, made of dispersion, sprayed on the sandblasted, degreasing, washing white aluminum products, and then by sintering, plasticizing, quenching to make. This process has been tested in Shanghai, Harbin, Beijing and other places.
(3) Aluminum enamel process
The ordinary enamel powder used in steel enamels can be fused to the workpiece at 700-1000°C, while the melting point of aluminum and aluminum alloys is generally around 600°C. It is clear that ordinary enamels are not suitable for aluminum. Aluminium products, enamel temperature generally can not exceed 550 °C, it is also called low temperature enamel, which requires the use of some special enamel and special enamel method. It is said that Wuhu City Second Light Research Institute and Shandong Xintai Aluminum Products Factory have relatively comprehensive research on aluminum enamels, and preliminary tests have been successful.
Fifth, some superficial views
(1) The variety of aluminum products is annoying and the surface decoration requirements of the products are different. The conditions of manufacturers around the country are not the same. Therefore, we must choose new technologies and new technologies based on the environmental conditions, product requirements, and the actual production of the equipment. For example, the sulfuric acid-oxalic acid mixed acid oxidation method combines the advantages of the sulfuric acid oxalic acid method, has the advantages of energy saving, higher temperature, and thicker oxide film. However, it should be used flexibly in specific applications. Our factory (State-owned Yangjiang Knife Factory) has been using sulfuric acid oxidation to produce multiple dyeing methods to produce aluminum knife shanks with multiple patterns. In 1973, due to the destruction of the refrigeration equipment at the time, we used a sulfuric acid-oxalic acid mixed acid in a 1300-liter oxidation tank for test production. At that time, the practical process formulation was sulfuric acid 15%; oxalic acid 1%; bath temperature 26 to 33°C; current density 0.8 to 1 ampere/square decimetre; anodizing, the effect was good. However, during the test, we also observed that when the oxalic acid content exceeds 1.5%, although a yellowish film that does not affect the appearance of oxidized oxalic acid has yet to be produced, one-time dyeing performance is also acceptable, but when dyed multiple times by printing, it is difficult to produce. Dyeing phenomenon. Therefore, it is required to dye the decorative oxide film several times, and the content of oxalic acid in the mixed acid oxidation should not be too high. In the north, some factories producing aluminum cookers are oxidized by oxalic acid. The products have a thick oxide film, a natural yellowish color, and they are also popular with people without dyeing. Their experimental application of mixed acid oxidation aims to use less oxalic acid, save energy, and reduce costs. The composition of the mixed acid is oxalic acid 2 to 3%; sulfuric acid 5 to 10%. They also observed that when the content of oxalic acid is less than 2%, the oxide film no longer has a yellowish tone that gives a dense and thick feeling to the original oxidized oxalic acid, and some customers do not like the appearance of such products, affecting the product. market. So they use 3% oxalic acid, Zhuojia sulfuric acid oxidation method.
(2) Seriously learn from advanced organizations and help introduce new technologies and materials. In recent years, the aluminum oxide transfer printing method is one of the more advanced technologies. Many units compete for tests, but the test levels are uneven and the product quality is very different. In fact, the key to the transfer printing process is to transfer the production of printing paper. The production of transfer printing paper requires the assistance of the printing industry. The selection of ink and printing technology are not the specialty of professional oxidation workers. Some advanced units have trial-produced high-quality transfer printing papers, and the transfer printing process is relatively high (such as Shanghai, Qingdao, etc.), and they are willing to make transfer printing papers. Therefore, some small enterprises with poor conditions do not have to experiment from scratch. If they directly request the transfer of printing paper, they can shorten the trial production process and increase economic efficiency.
(3) Strengthen cooperation with universities and research institutes to develop new technologies and new technologies for surface treatment of aluminum products. The surface treatment of aluminum products has increasingly involved multidisciplinary technologies. Such as coating PTFE resin process, which has polymer chemical engineering issues. The scientific research department of universities and colleges has a complete set of disciplines, a large number of professional scientists and technicians, and a relatively high level. It is relatively easy to obtain support for them and it is relatively easy to produce results.
(4) Do a good job of scientific and technological intelligence exchanges. The aluminum products industry is divided into various departments, aviation, light industry, and building materials. It strengthens the exchange of scientific and technological information, and sends new technologies and new technologies at home and abroad to the factories for trial production as soon as possible, which will improve the technological level of the entire aluminum product industry. It is necessary to improve the quality of aluminum products.