Technical issues needing attention in aluminum oxide film formation process

[China Aluminum Industry Network] (1) Oxidation. Solution formulation and working conditions:

Chromium anhydride 4~5g/L

Temperature 25~35°C

Sodium fluoride 1~1.2g/L

Time 30~60s

Potassium ferricyanide 0.5~0.7g/L

After the pretreatment, it is immediately transferred to the oxidation process to prevent the formation of a natural oxide film due to the workpiece being left in the atmosphere for too long and affect the quality of the oxide layer. Re-soaking in fresh water is better than exposure to the atmosphere, but it should not be soaked for too long.

The temperature of the solution in the oxidation process is a critical process condition. The solution temperature is too high, the film formation speed is accelerated, and the oxide film is prone to powdering; the solution temperature is too low, the film formation speed is slow, and the resulting film is light in color tone. Poor efforts.

For the same type of lead to obtain a substantially uniform color on the surface, it should be treated at the same solution temperature for the same time.

In a certain range, the temperature is inversely proportional to time, that is, the higher the solution temperature, the shorter the required time, and vice versa.

The higher the purity of the aluminum material, the longer the oxidation treatment time required. Oxidation treatment time is insufficient, the resulting oxide film is too light; aluminum purity is low, oxidation time is shortened, otherwise the oxide film is obsolete, and even affect the conductivity of the film.

In order to obtain a uniform oxide film color, the small pieces may be shaken in the solution during oxidation, and the large pieces may be stirred or statically treated (without agitating the solution or shaking the workpiece) to prevent the peripheral parts of the workpiece from being exchanged with the solution. The center part of the workpiece has many uneven oxide film colors.

(2) flush with water. For parts with blind holes and slits, it is necessary to intensify the rinsing of these parts and to reject the residual solution inside to prevent the oxide solution from flowing out of the oxidized surface.

(3) Self-test. After the workpiece is rinsed with circulating water, it should be self-inspected. If it is found to be defective, it can be removed from the lye and re-oxidized after leaving.

Hanger Bolt

Hanger Bolts have threaded areas at both ends, a lag screw thread at one end and machine screw thread on the other. They are designed for insertion into a pre-drilled hole and are ideal for overhead application, usually in a wall or ceiling. Plain finish, or bare metal, may or may not have a coating of light oil to resist corrosion. Plain finish, or bare metal, may or may not have a coating of light oil to resist corrosion.