Reasons for uneven color of oxide film of industrial aluminum profile

There are three possible reasons for uneven color of air oxide film in aluminum profile processing:

(1) The total area of the workpiece is too large, the shaking in the tank is too large during actual operation, and the contact, upgrading and exchange between the edge and the management center and the aqueous solution experience great differences, resulting in inconsistent color of the air oxide film. Prevention method: when the air oxidizes, the shaking force of the workpiece should be small, and the static solution is OK, but when the temperature of the aqueous solution is too low, topographic map spots are very easy to occur, which looks unnatural.

(2) During the production and processing of die casting, part of the aluminum clad layer is damaged and drilled off. The surface aluminum clad is high-quality aluminum, and the tightly bound inner layer is waste aluminum. There is a great difference between the two kinds of aluminum, so there are black spots like "vitiligo" after air oxidation. This situation is usually not easy for customers to understand. Manufacturers should make more statements to show the causes and consequences, so as to prevent misunderstanding.

(3) Difficulties in practical operation of processing technology

1. The alkali corrosion of the workpiece is not completely solved, and the initial air oxide film and waste at some parts cannot be removed;

2. After alkali etching, no light treatment is carried out immediately, and the workpiece surface is still alkaline;

3. The workpiece has touched dirty things in the whole process of transmission.

In case of uneven film color, find the reason from all aspects and adopt purposeful countermeasures.

Common faults are caused by the high accumulation of aluminum ions in the alkali etching solution. One reader dialed the phone to understand the reason why it is difficult to obtain the conductive air oxide film after alkali etching. After cleaning up many elements that cannot be produced by the conductive air oxide film, he fully considered whether the alkali etching solution has experienced the problem of high aluminum ions. The other party said that the alkali etching solution is very thick. But the alkali etching rate is not satisfactory. At that time, it was proposed to remove and replace the alkali etching solution. Because the alkali etching solution will accumulate too many aluminum ions after being used for too long, the aluminum ions will be more difficult on the workpiece surface, which will endanger the contact between the die casting surface and the conductive air oxidation aqueous solution, and then endanger the generation of air oxidation film. Another proposal is that if there is no reason to remove and replace the alkali etching aqueous solution at that time, the alkali corroded workpiece can be immersed in flowing water immediately after being immersed in boiling water, and then light can be extracted in concentrated sulfuric acid with hydrochloric acid, and then conductive air oxidation can be carried out after sufficient immersion. Later, the reader called and said that the actual effect of washing wool with boiling water after alkali etching was very good. The working experience of Xiaobian is that after wool washing in boiling water, he quickly leaves the boiling water and immediately infiltrates into the water flow, so as to avoid damaging the generation of conductive air oxide film due to air oxidation after workpiece drying.