In the anodizing treatment of aluminum, a series of problems are often encountered. These issues may arise from multiple aspects, including time control, raw material ratios, equipment performance, environmental factors, and batch differences. Next, we will delve into these five common issues.
�� 1. The concentration of aluminum ions in the solution is too high
Why does the anodized part feel sticky when touched by hand after drying during the anodizing process? This phenomenon is caused by the high concentration of aluminum ions in the anodizing solution. When the concentration of aluminum ions exceeds 30g/L, touching the anodized part with fingers may cause a sticky feeling, and white spots may appear on the surface of the oxide film, making it difficult to dye. The solution to this problem is to reduce the concentration of aluminum ions by replacing some of the solution. Specifically, some of the old solution can be extracted and placed in another tank for electrical treatment, allowing the accumulated copper ions to precipitate and reduce the concentration of copper ions to the lowest possible level. Afterwards, the solution can be used for etching steel parts or directly producing ferrous sulfate from iron filings to treat wastewater.
�� 2. Grey substance on the surface of the solution
During the anodizing process, a layer of gray substance often appears on the surface of the solution. What impact does this phenomenon have on the quality of the oxide film? Grey suspended solids are mainly silicon (Si), and excessive content can damage the color, transparency, and corrosion resistance of the oxide film. The methods to remove this substance include using fine mesh for retrieval or using filtering methods for removal. This silicon material mainly comes from the introduction of silicon containing aluminum alloys during the anodizing process, and incomplete light emission after alkali etching is the main reason for silicon accumulation.
�� 3. The oxide film is slightly yellow
What is the reason for the slight yellow color of the oxide film? If only a few parts in one slot appear slightly yellow, it may be related to the aluminum alloy material. But if this phenomenon occurs in multiple anodized parts, it may be related to the excessive addition of oxalic acid to the solution. In some process formulations, it is feasible to add an appropriate amount of oxalic acid to the solution to ensure continuous operation in high temperature environments.
�� 4. Black spot problem of oxide film
What are the reasons and countermeasures for black spots on the surface of oxide film? When black spots appear on the surface of the oxide film, possible reasons include impurities in the aluminum alloy material precipitating during anodizing, or impurities staining the oxide film during dyeing. Appropriate measures can be taken to address this issue, such as optimizing the pre-treatment process of aluminum alloy materials to ensure their purity, or strengthening control during the dyeing process to avoid impurities from staining the oxide film.
�� 5. Reasons for corrosion of anodized parts
What causes corrosion of anodized parts? This phenomenon is often related to the mixing of hydrochloric acid in sulfuric acid anodizing solution. In the early days, anodizing solutions were usually prepared from industrial grade sulfuric acid, and the clay jars containing these two acids were not strictly distinguished. Although this pollution may not have a significant impact on the corrosion of steel parts, it can have serious consequences in situations where aluminum anodizing or other electroplating solutions need to be prepared. When the sulfuric acid anodizing solution is contaminated with hydrochloric acid, a series of abnormal symptoms will occur during the anodizing process.