Causes of Uneven Thickness of Aluminum Alloy Anodized Film
The temperature of the anodic oxidation solution has an important influence on the uniformity of the film thickness. High temperature will accelerate the dissolution rate of the anodized film, and the oxide film will be thinner. On the contrary, the oxide film will be thicker. The anodic oxidation reaction should be carried out at a lower temperature. In the production, it is completed by exchanging heat with cold water and the bath liquid. The bath liquid at the upper end of the oxidation tank passes through the heat exchanger and then is pumped back to the oxidation tank, and the bath liquid is drawn back to the original tank. There is a temperature difference in the oxidation tank. Due to the relatively large volume of the oxidation tank, the circulation of the tank solution is not enough, and the distribution of the withdrawn tank solution is uneven, which will cause a temperature difference in the oxidation tank solution. Taking the horizontal production line as an example, the film thickness at both ends of the same profile is different, which may be due to the temperature difference between the two ends of the bath, and the difference in film thickness between the top and bottom of the same hanging material may be due to the temperature difference between the top and bottom of the bath.
Whether the film is uniform on several surfaces of the same aluminum profile, or even in the groove, has a great relationship with the corresponding cathode area. The cathode area is large, so that the current density distributed in each part of the aluminum profile is uniform, so the film thickness is also uniform. In the production of horizontal line, sometimes the film thickness of the same part of each profile of the same hanging material is low. This is probably because the cathode plate corresponding to this part is loose or even falls off, which reduces the cathode area. , resulting in a lower film thickness.
In the actual production process, there are other reasons that can lead to uneven thickness of the oxide film, such as poor contact between the fixture and the profile, and the contact area is too small, which will make the oxide film incomplete or no oxide film. In addition, large-scale changes in sulfuric acid concentration will make the oxide film thickness of different bath materials different, and large-scale changes in sulfuric acid concentration will make the k in the empirical formula (δ=kIt) for calculating the thickness of the oxide film inaccurate, so the obtained oxide film The thickness is also inconsistent. In production, as long as the above problems are solved one by one, the uniform thickness of the oxide film can be guaranteed.
