Anodic oxidation of aluminum alloy material requirements and precautions

[China Aluminum Network] The composition and heat treatment of aluminum and aluminum alloys have a great influence on the appearance and appearance 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. Aluminium alloys containing high contents of copper or silicon cannot be hard anodized by the method of plaster, but must use a high-frequency hard oxide power source.

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 parts that are generally required for decoration, there is a large allowable content requirement for other components and impurities in aluminum materials, among which aluminum-magnesium alloys are preferred.

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.

When using oxidation equipment, you should also pay attention to:

When using a hard oxide power source, it is recommended to use a high-frequency hard oxide power water-cooled type, because the output waveform is a square wave, and the energy-saving effect is obviously fast on the film, it is recommended to use.

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