Analysis and Countermeasures of Main Defects of Aluminium Profile Anodizing and Coloring Products
1. Turn yellow
1, definition
some impurities are mixed into the oxide film, causing the film to become yellowish.
2. Phenomenon”
When this film is used for electrolytic coloring, the color tone changes.
3. Reason
a. Iron, silicon, etc. in the electrolyte or alloy materials are mixed into the film, causing the film to become yellowish.
b. The anodic oxidation process conditions are not suitable, that is, low oxidation and high current density oxidation, resulting in abnormal thick film.
4. Countermeasures
a. Reduce the concentration of iron and silicon in the alloy and electrolyte.
b. Optimize the anodic oxidation process.
Two, overlap
1, definition” When the materials overlap during oxidation, the film is abnormally formed due to the abnormal closeness.
2. Phenomenon From the part where the film does not occur and the part where the end part is thinned, the imprint of the laminated profile can be seen, and sometimes part of the rainbow (interference color) can be seen.
3. Reasons:In electrolysis, the arrangement of aluminum materials is too dense, and abnormal contact may occur.
4 countermeasures
a. Maintain a proper spacing between binding materials.
b. Clamp the fixture. c. Remove the deformed fixture.
d. Do not install deformed or bent profiles. e. Reduce the amount of mixing and circulation.
3. Gathering gas (air bag) "
1. Definition" The gas generated during electrolysis or the air used for stirring stays in the gaps or corners of the material, so no oxide film can be formed, and usually no coloration. "
2. Phenomenon" In the gaps or corners of the material, the film is partially thin or absent. When electrolytic coloring is performed, a uniform color cannot be obtained.
3. Reasons: The angle of hoisting is inappropriate or is affected by the shape of the material. In the gap or corner of the material, the reacting gas and the air for stirring stay in the gap or corner of the material, 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.
Four, dark spots
1, definition Because of the partial precipitation of β'intermediate phase, black or white spots appear after anodic oxidation.
2, Xiang may see black, white or gray spots approximately equally spaced along the extrusion direction. These spots are mostly Mg2si precipitates with low hardness.
3. Reason
The umbilical pressing material is located in the contact part of the cooling bed, which undergoes the process of rapid cooling and reheating, and the precipitation of the intermediate phase (Mg2si) occurs. The aluminum surface where the intermediate phase is precipitated is roughened during the decontamination process, and a messy film structure is formed by anodic oxidation.
4. Countermeasures
a. Use a cooling fan to suppress heat recovery.
b. Reduce the thermal conductivity of the material in contact with the extruded material.
5. Powdering (powder film) "
1. Definition" The white powder formed on the surface of the film after anodic oxidation.
2, Phenomenon” After anodizing, the film is white powdery and opaque. It is easy to wipe off the powder by rubbing it with your hand. 3. Reasons: Long-term electrolysis in a high-temperature, high-concentration electrolyte, or long-term immersion after electrolysis, chemically dissolves and powders the film.
4. Countermeasures
a. Lower the electrolyte concentration and temperature. b. Lower the amount of aluminum ion. c. Shorten the soaking time.
Six, short circuit (electric corrosion, film melting, sparking)
1, definition” When the material is in contact with the opposite poles, a part of the material is dissolved. "
2. Phenomenon" In the energization process, the material and the opposite electrode are short-circuited, and part of the material is dissolved due to excessive current.
3. Reasons” The material is in contact with the poles, or short-circuited by the dropped profile.
4. Countermeasures
a. Improve the arrangement.
b. Prevent the material from swinging.
c. Remove the dropped materials.
d. Adjust the distance between poles.
Seven, poor electrolysis (poor power supply)
1, definition In anodizing, the conductive contact is poor. Unlike the set current value, the specified current does not flow, and the film can hardly be formed.
2, Phenomenon” Sometimes rainbow phenomenon (interference color) can be seen on both sides, and electrolytic coloring cannot be performed normally.
3. Reason a. The electrolysis was interrupted due to power failure or power failure.
b. The fixture is deteriorated and contaminated and cannot be tightened.
c. The fixture contact area is insufficient.
d. The set current value is wrong.
4. Countermeasures
a. Strengthen the management of fixture nodes.
b. Increase the contact area.
c. Confirm the set current value.
Eight, milky white
1, definition The impurity is mixed into the anodic oxide film, and the film structure is different, resulting in milky white.
2, phenomenon The film lacks transparency and turns white.
3. Reason
a. Electrolysis treatment at high temperature.
b. Short hot water washing time.
c. Extrusion conditions (such as low extrusion temperature, etc.) are poor.
d. Fluctuations in the content of silicon, iron, manganese, etc.
4. Countermeasures
a. Normalization of anodizing treatment conditions
b. Normalization of washing conditions.
c. Confirm the set current value.
d. Adjust the alloy composition.
Nine, skin burns (burns)
1. Definitions: During anodizing, the current density is locally too large, resulting in a burn-like appearance. "
2. Phenomenon" In anodizing treatment, where the current is locally concentrated, the temperature increases and the thickness of the film increases, and it becomes a whitening and chalking state. Around the area where the skin wound occurs, the skin film will be thinned.
3, the reason a, insufficient contact area, too close to the opposite electrode and the material, etc., cause local current density to be too large.
b. The stirring ability is insufficient and uneven, and the aluminum ion concentration has exceeded the upper limit.
4. Countermeasures
a. Ensure proper contact area.
b. Improve the configuration of the opposite pole.
c. Increase the circulation volume of the tank liquid and be even.
d. Set an appropriate current density.
e. Optimize the process conditions, especially to determine the aluminum ion content.
Ten, the corrosion resistance is not good "
1. Main reason" The concentration of sulfuric acid is too high, and the aluminum ion content exceeds 20g/L. "
2. Solution" Keep the sulfuric acid concentration at 150-200 g/L. If it is confirmed that the aluminum ion exceeds 20 g/L, consider replacing the 1/2-3/4 bath.
11. The thin film in the hanging material causes the coloring to be light, or even unable to color
1, the main reason the material is not tied tightly or loosened after alkali corrosion, so that the material is in poor contact with the conductive rod.
2. Solution After alkaline etching, use pliers to further tighten the binding wire.
12. Partial burn of oxide film black
1, the main reason the aluminum part is in poor contact with the conductive rod or the contact area is not enough, the film on the conductive rod is not clean, or the cathode and anode contact are short-circuited.
2. Solution Improve the contact and eliminate the contact between the anode and the cathode.
13, the film is dark
1, the main reason there is a problem with the alloy composition, the current is interrupted during oxidation and the electricity is supplied again, the electrolyte concentration is low, the oxidation voltage is too high, and the pretreatment is not good.
2. Solution If it is a material problem, the quality of the ingot should be improved. If the treatment is not good, the pretreatment should be strengthened. Adjust the electrolyte content, adjust the sulfuric acid concentration, and appropriately reduce the voltage.
14. Fingerprints appear
1, the main reason the finger touches the unsealed anodic oxide film during operation (this is a phenomenon that exists in many factories)
2. Solution Wear clean gloves and try to avoid finger contact.
