Building aluminum is the main product of anodic aluminum oxidation treatment at present, of which 75% - 85% is treated by conventional sulfuric acid method. The thickness of aluminum oxide film is more than 10 according to the Chinese building profile standard μ m。 The optimum process parameters of anodic aluminum oxidation process of building aluminum in Suzhou oxidation plant are electrolyte sulfuric acid 15% ± 2%, aluminum ion content less than 5g / L, solution temperature 21 ± 10C, current density (1.3 ± 0.05) a / DM2, time (for LD31 alloy) 30min, then 10 μ m； 60 minutes, up to 18 μ M (Voltage 18V), the solution is prepared with pure water.

Other anodic aluminum oxidation 1. Most of the factors affecting oxalic acid anodic aluminum oxidation on sulfuric acid anodic aluminum oxidation are also applicable to oxalic acid anodic aluminum oxidation. Oxalic acid anodic aluminum oxidation can adopt DC, AC or AC / DC superposition. The film obtained by alternating current aluminum oxidation in Suzhou oxidation plant is softer and less elastic than that obtained by direct current under the same conditions; Pitting corrosion is easy to occur in direct current aluminum oxidation, which can be prevented by alternating current aluminum oxidation. With the increase of AC composition, the corrosion resistance of the film is improved, but the color is deepened and the colorability is worse than that of sulfuric acid film.

The concentration of free oxalic acid in the electrolyte of Suzhou oxidation plant is 3% - 10%, generally 3% - 5%. In the process of aluminum oxidation, about 0.13-0.14g is consumed per a · h. at the same time, 0.08-0.09g of aluminum is dissolved in the electrolyte to produce aluminum oxalate, which needs to consume 5 times the amount of aluminum. The aluminum ion concentration in the solution shall be controlled below 20g / L. when it contains 30g / L aluminum, the solution will fail. Oxalic acid electrolyte is very sensitive to chloride. When anodizing pure aluminum or aluminum alloy, the chloride content shall not exceed 0.04-0.02g/l respectively. The solution is best prepared with pure water.