There are two main types of aluminum alloys used in industry, namely deformed aluminum alloys and cast aluminum alloys.

 
Different grades of deformed aluminum alloys have different compositions, heat treatment processes, and corresponding processing forms, therefore they have different anodizing characteristics. According to the aluminum alloy series, from the lowest strength 1xxx pure aluminum to the highest strength 7xxx aluminum zinc magnesium alloy.

 
1xxx series aluminum alloy, also known as “pure aluminum”, is generally not used for hard anodizing. But it has good characteristics in bright anodizing and protective anodizing.

 
2xxx series aluminum alloy, also known as “aluminum copper magnesium alloy”, is difficult to form a dense anodic oxide film due to the easy dissolution of Al Cu intermetallic compounds in the alloy during anodizing. Its corrosion resistance is even worse during protective anodizing, so this series of aluminum alloys is not easy to anodize.

3xxx series aluminum alloy, also known as “aluminum manganese alloy”, does not reduce the corrosion resistance of the anodic oxide film. However, due to the presence of Al Mn intermetallic compound particles, the anodic oxide film may appear gray or gray brown.

 
4xxx series aluminum alloy, also known as “aluminum silicon alloy”, contains silicon, which causes the anodized film to appear gray. The higher the silicon content, the darker the color. Therefore, it is also not easily anodized.

 
5xxx series aluminum alloy, also known as “aluminum beauty alloy”, is a widely used aluminum alloy series with good corrosion resistance and weldability. This series of aluminum alloys can be anodized, but if the magnesium content is too high, its brightness may not be sufficient. Typical aluminum alloy grade: 5052.

 
6xxx series aluminum alloy, also known as “aluminum magnesium silicon alloy”, is particularly important in engineering applications, mainly used for extruding profiles. This series of alloys can be anodized, with a typical grade of 6063 6082 (mainly suitable for bright anodizing). The anodized film of 6061 and 6082 alloys with high strength should not exceed 10μm, otherwise it will appear light gray or yellow gray, and their corrosion resistance is significantly lower than that of 6063 and 6082.