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Is the piece to be treated pitting in the cleaning tank?

Release time:

2022-08-26 17:03

Sometimes after alkali etching and light treatment, due to the lack of tacit understanding between the upper and lower processes, it cannot be transferred to the next process immediately, so it has to bePlacing in cleaning tank to be treated. As everyone knows, this treatment is not very safe, when the cleaning tank in the following circumstances may occur pitting corrosion.

1, the cleaning tank contains Cl. General cleaning tanks contain a certain concentration of Cl, especially in the southern region, waterworks water from rivers, rivers, poor water quality. Good disinfection effect is not achieved, and excessive bleaching powder is added, so the Cl-concentration in tap water is relatively high. Because Cl-is corrosive, it is easy to penetrate the oxide film and cause pitting corrosion.

2. The cleaning tank contains metal ions with a positive potential than aluminum. These metal ions mainly include Fe2, Cu2, Ni2, etc., which will accelerate the pitting corrosion on the surface of aluminum, and the greater the potential difference, the more serious the pitting corrosion of aluminum.

Is aluminum stable in neutral salt solutions?Nor completely. Passivation can be obtained and protected, and corrosion may also occur due to the action of certain cations or anions.

If the semi-finished product isPrepare for Anodizing, it is recommended to throw away the free water after the environmental conditions are better to dry, keep can be anodic oxidation treatment in the next working day,For chemical conversion coating treatmentHowever, it cannot be dried, otherwise the quality of the conversion film that meets the quality requirements cannot be obtained.

In order to avoid the occurrence of the above phenomenon, in addition to the tacit coordination of the front and back processes, the parts that cannot be transferred to chemical conversion film treatment within a short period of time can be temporarily soaked in a solution containing oxidizing anions to form a passivation film on the surface to prevent punctate and other forms of corrosion.