(1) Anodizing, aluminum profiles have been introduced into aluminum alloy doors and windows in the 1950s, and are still a commonly used surface treatment measure for aluminum doors and windows;
(2) Electrophoretic acrylic resin after anodizing, which has been commercialized in Japan in the 1960s and started to be used in Europe to the 1970s. Currently it is mainly used in Asia. This technology has developed from transparent bright film to matte transparent film and color film, the variety is more diversified, and the industrial control and product quality are relatively stable;
(3) Electrostatic spraying after chemical conversion treatment includes electrostatic powder spraying and electrostatic liquid phase spraying. Electrostatic liquid phase spraying of fluorocarbon resin has been commercialized in the United States in the 1960s. The electrostatic powder sprayed thermosetting polyester coating has been commercialized in Europe at the end of the 1960s and is still the dominant surface treatment method in European countries. To this day, single anodized aluminum doors and windows have been significantly reduced in domestic and foreign markets. Japan favors electrophoretic coatings. White electrophoretic coatings have developed rapidly and are used in Europe. Electrostatic powder spraying has become the preferred surface treatment method in Europe and the United States due to its diverse colors, convenient control, environmental protection, and excellent performance. In recent years, the electrostatic powder spraying market has been expanding rapidly in China.
Technical development of aluminum profiles in the 1990s
In the past 10 years, China's aluminum products (especially aluminum profiles) have developed by leaps and bounds. The production scale of aluminum profiles has approached 1 million tons per year. Driven by advanced foreign technology and imported equipment, China's aluminum profile production technology has made new progress in anodizing processes and equipment, and has established electrostatic powder spraying, electrostatic liquid spraying, and electrophoretic coatings. The cutting-edge technology in China has sprouted up and has developed to varying degrees.
Anodizing pretreatment process
The purpose of anodizing pretreatment is to remove the natural oxide film, grease and impurities on the surface, to obtain a uniform and clean aluminum surface, which is beneficial to the formation of high-quality anodized film. Chinese users also require removing the squeezed stripes to obtain a uniform and beautiful surface. Early use of alkaline etching method to obtain a matte surface, but excessive etching caused a large loss of aluminum, generally reaching 3% to 5.5%, which not only increased costs, but also caused serious environmental problems, forming a matte surface accompanied by the inherent exposure of the profile itself Organizational defects. Since then, Japan has introduced the acid etching method in Japan (Japan basically does not use aluminum for aluminum profiles). Due to the low aluminum consumption (up to about 1%), the fine surface was once welcomed by Chinese manufacturers. However, due to the fluoride ion as the main body of the tank fluid, it brought more serious pollution, which once caused a heated discussion. The mechanical etching method has the advantages of low operating cost, good environmental benefits, and fine and no streaks on the surface. It was first promoted and applied in European countries such as France and Italy.