Precautions for dipping zinc parts
In the zinc immersion treatment of aluminum alloy parts, the following operations should be paid attention to:
(1) All materials of the zinc immersion solution need to be reagent grade to prevent other impurities from being replaced during the reaction, thereby affecting the quality and bonding force of the coating.
(2) It is forbidden to use hangers made of metals that are easily replaced by aluminum, such as copper and its alloy hangers, in order to prevent the contact between the workpiece and the hanger from blistering and skinning due to the replacement reaction. .
(3) If the zinc dipping layer has mottling and irregular gloss, it is necessary to re-dip the zinc after de-zincing. The workpiece after dezincification needs to be cleaned.
(4) The temperature of the zinc immersion solution should not be too high to prevent the crystallization of the zinc immersion layer from being rough, causing the aluminum and its alloy matrix to be easily corroded by the subsequent plating solution, resulting in poor bonding.
(5) The time of dipping zinc should not be too long or too short. The zinc immersion time is short and the zinc immersion layer is thin, which is beneficial to the improvement of the bonding force; but when the zinc immersion time is too short, the zinc immersion is incomplete, and it will also affect the bonding force of the coating.
(6) Frequently monitor the content of aluminum ion in the zinc immersion solution, and generally control it below 29/L. When the aluminum ion content is too high, the adhesion of the coating will decrease.
In the primary zinc immersion process, the zinc immersion time is about 30s-40s longer than the secondary zinc immersion. After the primary zinc immersion, the action will be faster in the pure water cleaning process (the exposure time in the air is good ≤10s), and the secondary zinc immersion After cleaning with pure water, it should enter the dark nickel solution as soon as possible for pre-plating (because zinc is amphiphilic, it is easy to react with oxygen in the air to form zinc oxide). The water washing after the zinc dipping process needs to be cleaned, and it can be cleaned with hot water at about 60°C to prevent contamination or poisoning of the subsequent plating solution.
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