1. Chemical pretreatment

1. Alkali etching method

This is the most common method. The surface after alkali etching is bright and delicate. In the past, alkali etching method was commonly used in my country to eliminate extrusion lines, but the aluminum consumption of this method was too high. Japan adopted an AL (OH) 3 recovery device, which achieved better results and benefits. However, due to reasons such as high equipment investment and mismatch in extrusion press tonnage, it has not been promoted in my country. Most of our countries use European methods to use corrosion inhibitors. The advantage of this method is to make the aluminum surface more refined, but the disadvantage is that the waste emissions will be very smelly in the future and meet environmental protection requirements.

2. Acid corrosion

The prototype of this technology existed in the 1950s and 1960s. Its principle is to use fluoride ions to have a relatively negative electrode potential under acidic conditions, which can attack aluminum. Pitting corrosion forms on the surface. This technology was first introduced from Japan by a manufacturer in Guangdong (this technology is used by a small number of aluminum industry groups in Japan). The characteristics of this technology are low aluminum consumption and uniform surface. The disadvantage is that the surface is not bright. Alkaline corrosion wastewater, which often requires adding one minute of acid corrosion, is more difficult to treat (not that it cannot be treated). The requirements for the composition of aluminum materials are relatively high, and operators must have strict safety protection. Despite this, because it is indeed very beautiful if matted electrophoretic paint is applied after acid etching, it will have a large market in Japan, China, and even Europe and the United States in the future.

3. Chemical polishing

The surface of chemical polishing can easily achieve a mirror effect, and because of the consistency between the decorative surface and the non-decorative surface, the grade of aluminum materials is improved. This technology is used in It is widely used in Europe, especially in Turkey. The disadvantages of this technology are: the cost of three-acid or two-acid polishing is high, the pollution is large, and some technical problems are difficult to solve (such as bath insulation, bath aging, etc.). At the same time, the essence of chemical polishing should be called chemical brightening method , because this method can indeed make the surface of the aluminum material bright, but it cannot remove the extrusion marks, but makes the extrusion marks more obvious.

2. Mechanical pretreatment

1. Mechanical polishing

Some manufacturers in my country have introduced some mechanical polishing machines from Spain. In fact, this technology is an early form of mechanical scanning. Extension of mechanical wire drawing technology. If aluminum can achieve a mirror effect through mechanical polishing, a polishing machine can only polish about two thousand tons of aluminum a year at most, so the output of mirror aluminum is not large. Some people polish the holes and then polish them again to achieve the brightness of electrophoretic coating. However, this kind of aluminum material often has a film thickness of only 6-7μ, and its corrosion resistance is too poor, so it is not worth promoting. Mechanical polishing can make the surface uniform, refine the texture, and reduce aluminum consumption. The disadvantage is that it consumes electricity, has low output, and cannot polish the decorative surface.

2. Mechanical shot blasting and mechanical sandblasting

This type of equipment was first used for surface treatment of steel plates or iron castings. Later, a manufacturer in Fujian, my country imported equipment from Italy for aluminum surface treatment and achieved excellent results. According to the raw materials used, this type of technology can be divided into four categories: stainless steel shot blasting, stainless iron shot blasting, aluminum shot blasting and quartz sand blasting. This kind of equipment has been domestically produced. This kind of technology can eliminate extrusion marks on the aluminum surface, reduce aluminum consumption, and achieve a matte effect on the surface. Recently, the author noticed that the doors of KFC fast food restaurants in the United States basically use shot blasting electrophoresis, which indeed looks noble.

3. Powder spraying

It should be said that powder spraying is becoming more and more popular among many aluminum manufacturers and mass consumers because of its various colors and not very strict requirements on substrate materials. Welcome, it also meets personalized design, selecting colors according to user preferences. The development and popularization of thermal insulation profiles has opened up an important space for powder coating profiles, and the appearance of powder coating is also more diverse. The transfer printing method allows us to easily make aluminum materials look like wood grain or marble. Today's grille spraying method can even directly spray a wood grain effect that feels like a hand. However, despite the rapid development of powder research in the world (fluorocarbon powder, transparent powder, etc. are now available), it is a matter of concern how many of these large powder coating manufacturers will bring excellent technologies to China for production. . Like electrophoretic coating, we have been producing it for so many years, but the quality has never been able to catch up with Japan.

4. Electrophoretic coating

1. Light and transparent electrophoresis

There are 160 groups of this kind of electrophoresis line in China, with different grades. This situation is more like the early 1990s, when aluminum was rapidly developing in China. At that time, there were those who strictly controlled the quality, and there were also those who sold it without oxidation or hole sealing. At present, more than 80% of domestic electrophoretic aluminum materials cannot be exported. This is also one of the main reasons why the corresponding national standards are relatively loose.

Whether the electrophoretic aluminum material is good or not, whether the coating film is up to standard, depends first on the coating he uses, and secondly, what equipment he uses. Nowadays, some domestic equipment is fully qualified, but everyone should pay attention to coatings. Even Japanese coating companies may not necessarily sell the best coatings to China. Therefore, you must be careful, ask for more advice, and do more testing before choosing.

2. Matte transparent electrophoresis

This product is very rare in Europe and the United States, but it has already occupied the market in Japan. Matt electrophoretic coating has better corrosion resistance and hardness than transparent electrophoretic coating, while avoiding hidden dangers such as light pollution. It looks more noble and elegant, so it is becoming more and more popular. Currently, only a factory in Guangdong has introduced one in China. production line.

3. Colored electrophoresis

In order to make up for the monotonous color of electrophoresis and the low yield rate of triple electrolytic coloring, Japan developed colored electrophoresis. At present, there are mainly white, milky white, creamy yellow, green, gray and soft color, especially the latter ones are composite colors. Take gray as an example. If the background color is silvery white, it will be light brown after electrophoresis; Only a manufacturer in Fujian has introduced one, while there are many white electrophoresis products.

4. Fluorocarbon electrophoresis

The use of fluorocarbon coatings for electrophoresis can be regarded as a Japanese invention. Currently, only Nippon Lighting's Funabashi Factory has such a machine in the world. production line, the electrophoresis is transparent matting electrophoresis, and the outdoor service life of its products has reached 15 years on offshore oil platforms without any abnormalities. This electrophoretic coating was developed by Japan's Nippon Paint. The price is 0 times that of transparent electrophoretic coating, but compared to fluorocarbon spraying, it is still much cheaper. It is about RMB 18 per square meter. It is the first choice for landmark buildings such as curtain walls and airports. First choice, Hong Kong Airport uses many of these products. Its only disadvantage is that it is transparent, that is, colorless, and not as colorful as fluorocarbon spray. Whether this technology can be introduced into China, the author is actively in contact with relevant parties in Japan.