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Commonly used aluminum alloys and their oxidation

Release time:

2023-03-03 10:28

Series 1 aluminum alloy ("pure aluminum").

Pure aluminum is generally not used for hard anodizing. In bright anodic oxidation, after light brightening treatment and anodic oxidation, the higher the purity of aluminum, the better the light mirror reflectivity of the surface, that is, the smaller the so-called "light loss" after anodic oxidation. 1099 aluminum (aluminum content is not less than 99.99%), has the best light reflectivity. In general industrial applications, 1098 aluminum (aluminum content of not less than 99.98%) has been used for brightness and formability as the main purpose, regardless of mechanical properties. After mechanical polishing or chemical polishing of 1100 aluminum, the reflectivity of incandescent light can reach 86%.In the protective anodic oxidation treatment, the higher the purity of aluminum, the corrosion resistance of the anodic oxide film is also significantly improved.

2 series aluminum alloy (Al-Cu-Mg alloy).

The wrought aluminum alloy that can be heat treated and strengthened, and the varieties of material forms include plates, tubes, rods, types and wires.

The main alloying elements of this series of alloys are copper and magnesium, and also contain a small amount of Mn, Cr and Zr. The copper content is 2% ~ 10%, and the strength is the highest when the copper content is 4% ~ 6%. 2 is generally not suitable for bright anodic oxidation,Its mechanical properties are relatively high, mainly used in the aerospace industry.

Since the Al-Cu intermetallic compounds in the alloy are easily dissolved during anodic oxidation, it is difficult to generate denseanodic oxide filmAt the same time, its film-forming efficiency is also relatively low. in protective anodic oxidation,The corrosion resistance of anodic oxide film is worse than that of pure aluminum,Therefore, the anodic oxidation temperature should be appropriately reduced, and the anodic oxidation time of the same film thickness should be extended by 1/3.

2 series aluminum alloy hard anodic oxidation is more difficult, need to develop special technology, it is best to use pulse power supply or other special power supply, voltage rise should not be too fast, should control the step-by-step rise.

3 series aluminum alloy (Al-Mn alloy).

3 is a heat treatment can not strengthen the deformation of aluminum alloy, although there are extruded material, but mainly plate, 3004 aluminum alloy is the largest production of thin plate aluminum alloy.

Manganese can not only improve the mechanical properties of aluminum alloy, but also reduce the corrosion resistance of anodic oxide film.Because there are Al-Mn intermetallic compound particles in aluminum, the anodic oxide film is light gray or grayish brown.In bright anodic oxidation, with the increase of anodic oxide film thickness, the surface brightness decreased significantly, so the film thickness is generally controlled below 5um. The hard anodic oxidation of the 3 series aluminum alloy is less, and the anodic oxide film produced is darker.

4 series aluminum alloy (aluminum-Si alloy).

The aluminum alloy with silicon content of 5% in the 4 series has a gray anodic oxide film, and the color deepens with the increase of silicon content.

4043 aluminum alloy has a silicon content of about 5.2 percent and is used to make aluminum electrodes. 4032 aluminum alloys contain about 12.2 percent silicon and are used to machine forgings or make pistons or other high-temperature parts.

5 Series Aluminum Alloy (Al-Mg Alloy)

5 is a heat treatment can not strengthen the deformation of aluminum alloy, in industrial applications, the magnesium content of the alloy is generally not higher than 5.5%. This isWidely usedThe aluminum alloy system can not only manufacture bright products, but also be used in food industry, chemical industry, shipbuilding and marine environment.

5 series of corrosion resistance is better, and can be welded. Alloys with high aluminum content, such as 5043 and 5305, can be used to make bright products and decorative applications,When the magnesium content in aluminum alloy is high, it is difficult to form a bright oxide film on the surface of aluminum alloy..The corrosion resistance of 5 x x x series aluminum alloy after anodic oxidation is better, but the aluminum alloy with high magnesium content, such as 5154 and 5556, etc., unless the current density of anodic oxidation is carefully controlled and the bath solution is stirred well, the soft anodic oxide film with poor protection will be generated.

6 series aluminum alloy (Al-Mg-Si alloy)

6 is a deformed aluminum alloy that can be heat treated and strengthened, which is important for engineering applications,Mainly used for extruded profilesHigh strength such as 6061 aluminum alloy is also used in the production of plates. 6063 aluminum alloy is the most widely used extruded aluminum alloy. In bright anodizing, it is generally recommended to use a 6463 aluminum alloy having an aluminum content of at least 99.7 percent. The lower the impurity elements (such as iron and manganese) in the alloy, the smaller the brightness loss after anodizing.

In terms of protective anodic oxidation, the effect of 6063 aluminum alloy is also very good, and it has been widely used in the construction industry.It is recommended that the thickness of the anodic oxide film should not be higher than 10um, because the anodic oxide film loses light and darkens with the increase of film thickness and current density, and its anodic oxide film presents a light gray or yellow gray tone.

7 series aluminum alloy (Al-Zn-Mg alloy)

The 7 series aluminum alloy has the highest strength and is mainly developed for aerospace and military applications.However, its corrosion resistance is relatively poor. Corrosion sensitivity may occur in the atmosphere of anodic oxidation plants. Local corrosion occurs during alkali corrosion. Galvanic corrosion occurs when contacting with other metals (such as steel tanks) and has high stress corrosion sensitivity. Therefore, this is a series of aluminum alloys with special corrosion characteristics.

7 series aluminum alloy due to the high content of zinc and magnesium, in order to maintain the same current density anodic oxidation, need to significantly reduce the applied voltageImproper operation may produce soft powdery film. In hard anodizing, it is also important to control the speed of voltage rise, because if the current rise speed is too fast, the anodic oxide film will "burn".