The author's experience is that after hot washing in hot water, the hot water is quickly removed and immediately immersed in the running water to prevent the formation of the conductive oxide film due to oxidation after the workpiece is dried.
The four reasons why the adhesion of the oxide film is poor may be:
(1) The oxide film is too thick (the oxidation time is too long);
(2) the concentration of the oxidizing solution is too large;
(3) the temperature of the oxidizing solution is too high;
(4) The oxide film is not aged.
The operator can adjust according to the above four factors that have an influence on the adhesion of the oxide film.
There are two main reasons for the formation of an oxide film in the perforation of the oxidized member and its surroundings.
(1) The workpiece is not thoroughly rinsed after caustic washing. If the lye entering the pores during the alkaline washing is not washed out, 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 hole of the workpiece. When the aluminum tapping hole is very sturdy, the operator often lubricates with butter. If the lye is lacking in emulsifier during alkaline washing, the butter is difficult to remove.
Solution:
(1) Washing with gasoline before alkali washing, an emulsifier should be added to the alkali washing solution;
(2) The workpiece should be rinsed clean after caustic washing.
Oxide film has poor conductivity
Cause: The oxidation time is too long and the oxide film is too thick. According to the process requirements of 30 ~ 60s, the obtained oxide film is light iridescent, the film layer is good in conductivity, basically no resistance is measured. If the oxidation time is too long, the thickness of the film layer will increase, which will not only affect the conductivity of the film layer. Performance, the film will also be khaki, appear old.
Prevention method: The operation time should be strictly controlled.
Four points to note in the post-processing
(1) Hot water rinse. The purpose of hot water washing is to age the film. However, the water temperature and time should be strictly controlled. When the water temperature is too high, the film layer is thinned and the color is lightened. If the treatment time is too long, the above similar problem will occur. The suitable temperature and time are: temperature 40 ~ 50 ° C time 0.5 ~ 1min.
(2) Drying. It is better to dry naturally to dry, and the workpiece washed by hot water is slanted on the shelf, so that the free water on the working surface flows downward in the vertical direction. The water droplets flowing to the lower corners are sucked off with a towel, and the color of the film layer dried by this method is not affected and appears natural.
(3) Aging. The aging method can be determined according to the climatic conditions. In the summer with sunlight, it can be exposed to sunlight, and in the rainy days or in winter, it can be baked in an oven. The process conditions are: temperature 40 to 50 ° C for 10 to 15 minutes.
(4) Rework of unqualified parts. Unqualified conductive oxide film parts should be picked out before drying and aging process. Because of drying and aging, the film layer is difficult to remove and will affect the surface roughness of the workpiece. This problem has been explored in the process. After several methods, it is found that the following methods are effective, the method is simple, and the surface quality of the workpiece is not affected. The specific process is as follows. Firstly, the unqualified workpiece is clamped on the fixture for aluminum anodizing, and then anodized according to the anodizing method of aluminum in sulfuric acid solution for 2 to 3 minutes. The film layer is soft and peeled off, and then slightly washed with alkali solution and nitric acid. Conductive anodization can be re-executed after light is emitted.
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