Etching of aluminum alloy parts before oxidation

Etching of aluminum alloy parts before oxidation

Etching is the first step before the oxidation of aluminum and aluminum alloy parts, and it is one of the key steps to ensure the quality of the oxide film.

In order to ensure the quality of the etching, a series of pretreatments are required before etching, except that it needs to be removed to adsorb on the surface of the workpiece and cannot react chemically with the alkaline solution, or it can react chemically, but it will seriously affect the surface of the workpiece. In addition to all the impurities of the quality, it is necessary to perform organic solvent cleaning according to the degree of sticky oil on the surface of the product or to pretreat in a weak alkaline solution containing a surfactant to remove thick oil and other dirt.

Etching is not only a process of completely removing oil, but also a process of removing an oxide film. Therefore, each process before and after etching needs to be closely cooperated, and cleaning with a single organic solvent or cleaning in a weak alkaline solution can not meet the requirements of the oil removal process on the surface of the workpiece. If a strong alkaline etching treatment is applied directly to this part, the surface will be damaged due to the uneven surface oil contamination, and the etching solution cannot synchronously react on the surface of the aluminum part. In serious cases, pit inequality may also occur, which will seriously affect the appearance of the product. At the same time, it will also bring with it quality defects such as tolerance coordination. The lighter will be repaired and the weight will be scrapped. However, before alkali etching, not all of these processes are required, and it is also necessary to determine the surface conditions of the parts: If the surface conditions are good, parts without severe oily oil can be etched directly in the strong alkali solution.

After etching, it is necessary to perform light extraction (also called neutralization) treatment to remove alkaline substances that are left ash and hard to wash away during etching. In order to achieve a clean surface, the surface of the part is completely exposed to ensure that the next process solution is free of contamination and lays the foundation for obtaining a normal oxide film.

The steps that need to pass through the etching process are:

1 Remove the surface adhesive;

2 organic solvent cleaning;

3 chemical cleaning;

4 alkali etching;

5 light out.