Analysis and Countermeasures of Main Defects of Anodized Coloring Products of Aluminum Profiles

Ⅰ. Yellowing of aluminum alloy profiles

1. Definition: Some impurities are mixed into the oxide film, causing the film to be yellow.

2. Phenomenon: When this film is used for electrolytic coloring, the color tone changes.

3. Reason:

a. Iron in the electrolyte or alloy materials, industrial aluminum profile silicon, etc. are mixed into the film, causing the film to be yellow.

b. The anodizing process conditions are not suitable, that is, low oxidation and high current density oxidation, resulting in the formation of a strange thick film.

4. Countermeasures:

a. Reduce the concentration of iron and silicon in the alloy and electrolyte.

b. Optimize the anodizing process conditions.

Ⅱ. The overlapping of aluminum alloy profiles

1. Definition: The material overlaps during oxidation, and the film is abnormally formed due to abnormal proximity.

2. Phenomenon: The imprint of the laminated profile can be seen from the part where the film does not occur and the thinned part at the end, and sometimes part of the rainbow (interference color) can be seen.

3. Reason: If the aluminum materials are arranged too densely in the electrolysis, abnormal contact may occur.

4. Countermeasures:

a. Maintain a proper binding spacing.

b. Clamping fixture.

c. Remove the deformed fixture.

d. Do not hoist deformed and bent profiles.

e. Adjust the amount of stirring and circulation.

Ⅲ. Accumulated gas (air bag) of aluminum alloy profiles

1. Definition: The gas generated in the electrolysis or the air used for stirring stays in the gaps or corners of the material, so it cannot form an oxide film, and usually it cannot be colored.

2. Phenomenon: In the gaps or corners of the material, the film is partially thin or absent, and uniform color cannot be obtained when electrolytic coloring is performed.

3. Reason: The angle of hoisting is not suitable or affected by the shape of the material. In the gap or corner of the material, the gas reacted by the aluminum alloy profile frame and the air used for stirring stay, which hinders the formation and coloring of the film.

4. Countermeasures: Adopt the hoisting angle and charging method that the gas is easy to discharge.

Ⅳ. The black spots of aluminum alloy profiles

1. Definition: Due to the local precipitation of β' intermediate phase, black or white spots appear after anodization.

2. Phenomenon: You may see black, white or gray spots with roughly equal spacing along the extrusion direction. These spots are mostly Mg2si precipitates with low hardness.

3. Reason: (Mg2si) intermediate phase precipitation occurs when the extruded material is in contact with the cooling bed during the process of rapid cooling and reheating. The aluminum surface where the mesophase is precipitated is roughened during the decontamination process, and a disordered film structure is formed by anodization.

4. Countermeasures:

a. Recuperation is suppressed by a cooling fan or the like.

b. Reduce the thermal conductivity of the material in contact with the extruded profile.

Ⅴ. Powdering (powder film) of aluminum alloy profiles

1. Definition: The white powder formed on the surface of the film after anodizing.

2. Phenomenon: After anodizing, the film is white powdery and opaque, and it is easy to wipe off the powder by hand rubbing.

3. Reason: long-term electrolysis in high temperature, high-concentration electrolyte, or long-term immersion after electrolysis, the film is chemically dissolved and pulverized.

4. Countermeasures:

a. Lower the electrolyte concentration and temperature.

b. Reduce the amount of aluminum ions.

c. Shorten the soaking time.

Ⅵ. Short circuit of aluminum alloy profiles (electric corrosion, film dissolution, ignition)

1. Definition: During electrification, the material is in contact with the pole, and a part of the material is dissolved.

2. Phenomenon: During the electrification process, the material and the counter electrode are short-circuited, and part of the material is dissolved due to excessive current.

3. Reason: The material is in contact with the pole, or short-circuited by the falling profile.

4. Countermeasures:

a. Improve the arrangement.

b. Prevent the material from swaying.

c. Remove the falling material.

d. Adjust the distance between poles.