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Aluminum surface treatment aluminum anodic oxidation coloring bad cause solution

Release time:

2022-10-12 17:07

The oxide layer produced by anodic oxidation of aluminum parts has a strong adsorption capacity and is easy to color. Aluminum and its alloy anodic oxidation coloring, also known as dyeing, the purpose is to make aluminum products get bright and beautiful decorative appearance.

Since the coloring is formed by adsorption of the dye to the voids of the oxide film, the properties of the oxide film are not changed. The dyes used for coloring are organic dyes and inorganic dyes, but in actual production, organic dyes are mostly used for coloring. Because organic dyes are better than inorganic dyes in terms of firmness, coloring speed, hue vividness and implementation methods, they are the most widely used.

However, the anodizing coloring process of aluminum and its alloys is relatively strict. It requires that once the aluminum parts are oxidized, they must be cleaned and then colored immediately; the production process needs to maintain the cleanliness of the coloring liquid, dye concentration and pH to meet the process requirements. If there is a deviation, coloring failure is likely to occur.

Common coloring faults, cause analysis and troubleshooting methods

1. film is not colored causes

1. The dye used is not suitable or the dye has been decomposed.

2. The pH of the coloring liquid is too high (when the pH is increased to 7, the coloring is difficult to cause no coloring).

3. Insufficient oxide film thickness.

4. The oxidized parts are placed for a long time, causing the oxide film pores to be closed.

 

2. exclusion methods

1. Select the appropriate dye to reformulate the coloring liquid and replace the original coloring liquid.

2. Lower the pH to the process specification. The pH of the coloring liquid has a great influence on the coloring affinity. Therefore, an appropriate pH must be selected depending on the dye. The general pH value is 5~6. The pH can be adjusted with acetic acid and aqueous ammonia. If anthracene-soluble dyes are used, the pH should be controlled between 4 and 5.5. In this temperature range to improve acidity, fast color. But too high acidity will accelerate the failure of the dye.

3. Appropriately extend the anodic oxidation time to increase the thickness of the oxide film.

4. The aluminum parts should be colored immediately after oxidation, and the fresh oxide film is easy to color.