[China Aluminum Network] In order to meet the needs of users, aluminum construction materials can generally be put on the market after surface treatment. There are currently three methods for surface protection of architectural aluminum: (1) Anodizing, aluminum alloy doors and windows have been introduced in the 1950s, and are still common surface treatment measures for aluminum doors and windows; (2) Electrophoresis after anodization Acrylic resin, which was commercialized in Japan in the 1960s, began to be used in Europe in the 1970s and is currently used mainly in Asia. The technology has now been developed from transparent glossy film to matt transparent film and color film, the variety is more diversified, industrial control and product quality are relatively stable; (3) Electrostatic spraying after chemical conversion treatment includes electrostatic powder coating and electrostatic liquid phase Spraying, electrostatic liquid-phase spraying of fluorocarbon resin In the 1960s, the United States has achieved commercialization. The electrostatic powder coating thermosetting polyester coating was commercialized in Europe at the end of the 1960s. It is still a surface treatment method that is dominant in European countries. Today, the single anodized aluminum doors and windows are significantly reduced in Japan and the United States favored electrophoretic coating, white electrophoretic coating developed rapidly, and has been applied in Europe. Electrostatic powder coating 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 coating market is rapidly expanding in China.

1. Technology Development in the 1990s In the past 10 years, aluminum materials (especially aluminum profiles) in China have been developing 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 production technology has made new advances in anodizing process and equipment, and established new production lines such as electrostatic powder coating and electrostatic liquid coating and electrophoretic coating. The cutting-edge technology has sprouted in our country, with different degrees of development.

1.1 Anodizing Pretreatment Process The purpose of renewing the anodizing pretreatment is to remove the natural oxide film, grease and impurities on the surface and obtain a uniform and clean aluminum surface, which is conducive to the formation of a high-quality anodized film. Users in our country also require the removal of extrusion striations to achieve a uniform aesthetic appearance. Alkaline etching was used to obtain a matte surface in early stages, but excessive etching caused large aluminum loss, typically 3% to 5.5%. This not only increased costs, but also caused serious environmental problems. The formation of a matte surface was accompanied by the inherent nature of exposed profiles. The organizational flaws. Since then, Japan has introduced an acid etching method in our country (which is basically not used in aluminum profiles in Japan). Due to the low aluminum consumption (which can reach about 1%), the surface details were once welcomed by Chinese manufacturers. However, due to fluoride ions as the main bath, brought about more serious pollution, once caused heated discussions. The mechanical etching method has the advantages of low operating cost, good environmental benefits, and fine and no-scratch surface. It was first applied in European countries such as France and Italy. In the mid-1990s, Fujian Sanyuan Aluminum and Zhejiang Dongliang Aluminum introduced institutional shot blasting machines and mechanical polishing (stripping) machines and related processes from Italy and Spain, respectively, and they have been operating smoothly and received excellent results. Since then, many factories in Guangdong and Jiangsu provinces have successively imported more than one device from abroad. At the same time, China's self-made equipment has also entered the market. The price is only about 1/5 to 1/8 of the imported equipment. Whether mechanical shot blasting (or sandblasting) or mechanical polishing (mirror or satin finish), aluminum consumption can be controlled below 1%, and the appearance is even and detailed, and the decorative effect is good. According to the domestic and foreign production practices, the author recommends mechanical etching treatment instead of the traditional chemical etching (acid or alkali etching) in order to improve the appearance of aluminum profiles in China.

1.2 Anodizing Process and Equipment Progress The anodizing process has not changed fundamentally in the past 20 years. Hard anodizing technology has made many advances during this period. Breakthrough Anodizing The "spark" anodic oxidation and micro-arc oxidation of the Faraday zone have been commercialized. The recent development of high-speed and high-efficiency anodizing technology (HEA technology) of aluminum profiles has not yet obtained wide industrial applications.

1.2.1 The pulsed anodizing power source was widely publicized and introduced in the 70s and 80s. Since experimental data are mostly selected from hard films with high current density (eg, >3 A/d?) and subsequently applied in the anodizing process for building aluminum profiles, no significant effect has been obtained and thus no large-scale application has been achieved. Further practice shows that in the production of thick film (film thickness> 20μm), the pulse method is more favorable for the quality of the sealing hole, which shows that the current recovery effect can help the heat dissipation during the formation of the oxide film, reducing the film due to temperature rise Dissolution, to prevent the expansion of the oxide film orifice, is conducive to improving the hardness and density, but also help seal the hole. For the standard anodizing process of aluminum profiles, the current density is low (usually in the range of 1 to 1.5 A/d?), the film thickness requirement is only 10 μm, and the exothermic heat in the oxidation process is not serious, so no obvious advantages are shown. The authors believe that pulsed power is very practical in hard anodized or thick film production.

1.2.2 Ion exchange equipment for removal of aluminum ions Anion exchange equipment for the removal of aluminum ions in sulfate baths is of practical significance for the optimization of process measures. In the past, when the Al3+ in the sulfuric acid bath exceeded 20 g/L, the partial discharge liquid was readjusted, inevitably causing periodical fluctuations in the Al3+ content. In order to stabilize the content of Al3+ in the anodic oxidation bath, some imported lines in China in the 1980s imported Japanese or Italian Al3+ removal devices, which may not be widely used because of the limitations of the technological level and technical management at that time. In recent years, China's own production of "recovery of sulfuric acid automatically to Al3 + device", a device can remove about 100 kg of aluminum per day, thereby controlling the Al3 + in sulfuric acid in the set value, so that the oxidation process is more stable and accurate, and at the same time have a very good environment benefit.

1.3 Coloring Techniques The coloring of various aluminum profiles is traditionally performed using electrolytic coloring (the Asada method, which was invented by Japanese Asada, also known as secondary electrolysis). The interior decoration is also colored with a variety of colors (dyeing method is not suitable for outdoor use). In recent years, foreign countries have introduced multicolorization technology (that is, the use of light interference effect coloring, Japan called three electrolytic) composite coloring (staining after electrolytic coloring) technology, breaking the electrolytic coloring only bronze frame. However, industrial production has not yet been realized in our country.

1.3.1 Single nickel salt electrolytic coloring system Single nickel salt electrolytic coloring system has gradually increased. In Europe, tin salts have been used for coloration. Because tin salts and tin-nickel mixed salts have strong anti-impurity interference and have little environmental damage, industrial control is easy. China has always been based on tin salts (and tin-nickel mixed salts). Japan, on the Other hand, has always favored single nickel salts and is equipped with special power supply and bath purification (such as sodium and potassium) devices. Due to the small color difference of light nickel (imitation stainless steel and champagne) and the reproducibility of tones, nickel salts in China and Europe have developed single nickel salt coloring technology in recent years. The bath composition is in addition to MgSO4, H3BO3, and NiSO4. The content is generally high, about 100g / L, impurities sodium, potassium have to be controlled, depending on the process requirements and different, the Japanese process also controls the content of ammonium.

1.3.2 The introduction of new coloring power supply.

The power supply is not an isolated device, it must be a supporting device for a particular process. There are two kinds of electroless coloring techniques for single-nickel salt imported from Japan in Japan, namely the light UniNier method (uniform coloring meaning) and the new residence method. The power supply is not the same, and it can be generally considered as the different DC coloring of waveforms. . However, the coloring power supply used for single nickel salt in Europe is not a simple sine wave AC power supply. For example, Spain uses a DC (Direct Current)/AC (AC) power supply, and the United States has a DC/AC/Asymmetrical AC power supply. The ELCA company in Italy introduced a multi-functional coloring power supply that can output DC, variable frequency AC and DC and DC/AC superposition. This power source can be applied to various types of electrolytic coloring and polychromization techniques.

1.3.3 Requirements for diversification of colors The diversification of colors promotes the appearance of new electrolytic coloring baths. Titanium golden selenium salt solution, golden manganese salt solution has been quite common in China, but due to the long-term practice of nickel and tin salts, which are not domestically or internationally tested, these solution-colored aluminum materials are used to seal the hole quality, especially in use. The problem of discoloration and fading in color is still worthy of attention. In the process of anodic oxidation of aluminum materials in China, some practices that are inconsistent with foreign standard processes appear from time to time. They have not been scrutinized and tested (only to reduce costs). The author thinks that there is no effect on long-term use effects and production environment benefits. Less hidden dangers.

A4.Shower System

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