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Removal of oxide film on aluminum surface

Release time:

2021-07-09 13:54

Aluminum and its alloys will naturally form a layer of film in the atmosphere, and has the performance of corrosion resistance and beauty, but the film is very thin and easy to cut, so all kinds of aluminum workpieces in anodic oxidation or electroplating, chemical plating before the first to remove the incomplete film, otherwise it will affect the anodic oxidation, electroplating and other subsequent processes and product quality assurance.

Oxide film of 1. aluminum
Various products of aluminum and its alloys have good corrosion resistance in the atmosphere, mainly because this metal and alloy generates a thin and dense oxide film on the surface. This film with the extension of the parking time in the atmosphere and thickening, the greater the humidity in the atmosphere, the thicker the film. Depending on the alloy and humidity, the film thickness is in the range of 5 ~ 200nm ( 50 ~ 2000A):
In addition to the natural formation of oxide films in the atmosphere, aluminum and its alloys can also be oxidized by chemical methods, or electrochemical anodic oxidation and other methods to produce thicker oxide films. The film thickness obtained by chemical oxidation method is about 1 ~ 3μm, and the film produced by anodic oxidation can be greater than 100 μm, depending on the needs, which can be used for decoration, protection and wear-resistant components. Table 1 shows the thickness of the oxide film of aluminum under various conditions.



Table 1 Thickness of aluminum oxide film under various conditions

Removal of 2. aluminum oxide film
Aluminum and its alloys will naturally form a film in the atmosphere and have corrosion resistance and beautiful performance. However, this film is very thin and easy to cut. Therefore, the incomplete film must be removed before anodizing, electroplating and chemical plating of various aluminum workpieces, otherwise it will affect the subsequent processes such as anodizing and electroplating and the guarantee of product quality.
The removal of the aluminum oxide film is mainly removed in an alkaline chemical solution, but it can also be removed in an acidic solution, mainly based on the type of material and the surface of the aluminum workpiece. When there is little oil on the surface of the aluminum workpiece, the oil removal and the oxide film removal can be treated together. If the oil is very heavy or the oil layer is very thick, the oil should be removed first, and then the oxide film, otherwise it will cause the oil removal and film removal is not complete, affect the subsequent process, and may reduce the quality of surface treatment.

Removal of 3. aluminum anodic oxide film
After various workpieces or profiles of aluminum are anodized, some workpieces may be due to improper operation of anodizing, cleaning, sealing, coloring process or other reasons, resulting in unqualified anodizing film, which needs to be removed and anodized again to meet the requirements of product quality. The removal of anodic oxide film is different from that of natural film. The removal solution is mainly acidic, and alkali solution can also be used.

Aluminum anodic oxidation, additives, oxide film