Experiences of Conductive Oxidation Processes for Aluminum and Aluminum Alloys

1 The oxide film is not conductive the reason: The oxidation time is too long and the oxide film is too thick. According to the process requirements of 30 ~ 60s operation, the obtained oxide film is light rainbow, the film conductivity is good, basically no resistance can be measured, if the oxidation time is too long, the film thickness increases, not only will affect the conductivity of the film Performance, the film will be khaki, look old. Solution: Operation time should be strictly controlled. 2 poor adhesion of oxide film the reason: 1 oxide film is too thick; 2 excessive oxidation solution concentration; 3 oxidation solution temperature is too high; 4 oxide film is not aged. Solution: The operator can adjust according to the above four factors that affect the adhesion of the oxide film to obtain satisfactory results. 3 Oxide parts are difficult to form oxide film around the hole the reason: 1 Washing is not complete after caustic washing; If the lye that enters the pores during alkaline washing fails to be washed cleanly, the lye will flow out of the pores after the oxidation treatment, causing the oxide film around the pores to be corroded. 2 There is butter around the holes of the workpiece; Aluminium tapping screw holes is very astringent, operators often use butter to improve lubrication, alkali washing when the lack of emulsifier alkali, butter is difficult to get rid of. Solution: 1 Wash it with gasoline before caustic washing, emulsifier should be added in caustic solution; 2 Wash the workpiece after caustic washing. 4 Part of the surface of the workpiece is not easy to generate oxide film This phenomenon mostly occurs on planes. The common causes are: 1 The surface of rolled plate often has dense coke paste, but it cannot be cleaned cleanly in alkaline washing; 2 The workpiece is not thoroughly rinsed in nitric acid after caustic washing; The partial surface of the workpiece is still alkaline, and a very thin natural oxide film will be quickly formed in the air. Since the conductive oxide solution is weak in acidity, the film cannot be removed when it is oxidized, so the conductive oxide film layer cannot be located here. Formed. Therefore, the workpiece must be fully washed in nitric acid after alkali cleaning, and then cleaned as much as possible, when the oxidation treatment, to prevent the workpiece from being subjected to natural oxidation between processes and affect the quality of the conductive oxide film. 3 Alkali wash accumulated excessive aluminum ions; The viscosity of the solution becomes large, and it is difficult to elute from the surface of the workpiece, blocking the affinity of the surface of the aluminum substrate with the oxidizing solution. As a result, yellow-and-white streaky quality often appears after oxidation (appears yellow surface due to the barrier The oxide film was removed by washing, and the white portion was unable to form an oxide film due to the presence of an aluminum hydroxide barrier on the surface). Solution: 1Aluminum parts are washed with fine sand before caustic washing to remove the coke paste; 2 Al parts after alkaline washing in nitric acid solution fully rinse; 3 Replace the alkaline wash solution. 5 Blind holes in the oxidized part and its surrounding dark yellow spots the reason: After oxidizing, it is not thoroughly rinsed in clean water, and the residual solution in the pores flows out during drying. Solution: After the workpiece has been oxidized, it must be rinsed vigorously, and the residual liquid should be thrown away. If necessary, a medical syringe can also be used to suck the above residue. 6 Occurrence of dark and light spots on the oxide film surface the reason: When the aluminum component is processed, part of the aluminum layer is cut off. The outer layer of aluminum is high quality aluminum. The inner layer of the package is a mixed aluminum. The two kinds of materials are quite different. Therefore, after the oxidation, "vitreous" spots appear. Solution: This phenomenon is often not understood by customers. Manufacturers should do more explanation work and clarify the details so as to avoid misunderstandings. 7 Photographs of joints on large area oxide films the reason: Aluminium pieces have a large area and are treated with a segmented oxidation. Solution: The overall treatment is carried out by taking a piece of plastic cloth and laying it on the ground. According to the size of the outer edge of the oxidation part, a pool of wood or brick is used to form a pool. The height of the pool can be about 100mm, and the general flat pieces can be in this pool. Direct operation, in case of three-dimensional shape parts, if the height of the pool is not enough, can also be taken in the pool surface treatment, that is, before and after, up and down, left and right in the solution in order to do so can get the same effect with the oxidation in a large tank. 8 Oxide film surface uneven color the reason: Aluminum parts are large in area and oscillate excessively in the oxidation bath. There is a big difference in the contact, renewal, and exchange between the edge and the center part and the solution, resulting in different colors of the oxide film. Solution: The oscillating amplitude of the workpiece during oxidation is small, static treatment can also be, but when the solution temperature is too low, it is easy to appear map-like variegation, it seems unnatural. 9 Gray photocopying of the lashings of the oxidized parts the reason: Use galvanized iron to bind the oxidizer. Solution: The wire must be removed before the wire is used.

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