The composition of the aluminum and aluminum alloys and the thermal management sleeve have a great influence on the appearance and properties of the anodized film produced. For example, when anodizing with sulfuric acid, aluminum alloys with high copper content, due to the dissolution of CuAl:, make the film layer more porous and porous, and aluminum with high silicon content. Alloy film dark gray. Aluminum alloys with greater than 5% beryllium copper or with greater than 7.5% silicon content are not suitable for chromic acid anodization. Aluminum alloys containing high contents of copper or silicon cannot be hard anodized by the method of pastes, but must be selected from special waveform power sources. For decorative anodizing, the requirements for aluminum and aluminum alloy materials are higher. Generally only pure aluminum, aluminum, magnesium, aluminum manganese alloy can be dyed more vivid colors. For alloys containing higher silicon and iron, the dark color of the resulting oxide film can only be dyed dark. When decorating anodized aluminum and aluminum alloy parts, the following points should be noted in the material selection: For parts that require a mirror-state surface, high-purity aluminum or 5A66 aluminum-magnesium alloys with an aluminum content higher than 99.99% must be selected. After the parts are chemically or electrochemically polished, anodizing with sulfuric acid results in a colorless, transparent, bright film that can be dyed with various bright colors. For parts requiring lower surface brightness than the above, industrial high-purity aluminum with aluminum content higher than 99.9% and aluminum-magnesium alloy with LT65, LT67 can be selected. For general decorative parts, there is a large allowable content requirement for other components and impurities in aluminum. The values ​​are shown in Table 1. Among them, aluminum-magnesium alloys are preferred. Table 1 General decorative requirements Other materials and impurities in anodized aluminum element Fe Si Cu Mn Mg Zn Cr Ti Larger allowable content (mass fraction) (%) 0.5 2 to 3 1 to 2 0.5 to 0.8 7 6~8 0.3 0.3 When choosing aluminum, you should also pay attention to: 1) The surface of the selected aluminum should not have serious scratches, tissue defects and inclusions. They affect the appearance and corrosion resistance of the oxide film. 2) Some aluminum alloys should be heat treated using reasonable specifications. The grain size has a certain influence on the structure and properties of the oxide film. The coarse grains react non-uniformly during the oxidation process and often have an orange-like appearance. Therefore, it is generally desirable for the aluminum material to have a fine grain structure.