There are three possible reasons for the uneven color of the elevator oxide film:

(1) The area of the workpiece is too large, the swing in the groove is too large during operation, and the contact, renewal and exchange between the edge and the center part and the solution are too different, resulting in inconsistent color of the oxide film. Prevention method: The swing of the workpiece should be small during oxidation, and static treatment is also possible, but when the temperature of the solution is too low, map-shaped spots are prone to appear, which is unnatural.

(2) Part of the aluminum cladding layer was damaged during the processing of the clad elevator parts and was cut off. The outer clad aluminum is high-quality aluminum, and the inner layer of the clad is miscellaneous aluminum. The difference between the two types of aluminum is large, so it appears after oxidation "Good vitiligo"-like spots. This phenomenon is often not understood by customers, and manufacturers should do more explanation work to explain the reason, so as not to cause misunderstandings.

(3) Problems in process operation: ① The alkaline etching treatment of the workpiece is not complete, and the original oxide film and dirt are not removed in some parts; ② The surface of the workpiece is still alkaline without immediate light extraction after the alkali etching; ③ The workpiece is in the transfer process. contact with foreign objects.