First, chemical oxidation
The chemical oxidation treatment of aluminum and aluminum alloys can be divided into alkaline solutions and acidic solutions according to the nature of the solution. According to the nature of its film, it can be divided into oxide film, phosphate film, chromate film and chromate-phosphate film.
(1) Technical specifications.
1. Technical specifications for chemical oxidation of lye.
2. Anhydrous sodium carbonate (na2co 3) 50 g/L
3.5g/l sodium chromate (Na2Cr04)
4.25 g/L sodium hydroxide (NaOH)
5. Temperature 80 - 100 degrees Celsius
6. The time is 10-20 minutes.
The oxidized parts should be cleaned immediately, passivated in 20g/L chromic acid solution for 5 to 15 seconds at room temperature, then cleaned and dried. The color is golden yellow. The film thickness is 0.5~1um, suitable for pure aluminum, aluminum-magnesium, and aluminum-manganese alloys.
This method uses more phosphoric acid, so it is also called phosphating method. The color of the oxide film is colorless to light blue, and the film thickness is about 3-49m. The film layer is dense, the corrosion resistance is high, and the size of the parts does not change after oxidation. Applicable to all kinds of aluminum and its alloys.