Common Process of Aluminum Anodic Oxidation
Release time:
2021-09-27 09:27
#Common Process#
The common processes of aluminum anodic oxidation are: sulfuric acid anodic oxidation process, chromic acid anodic oxidation process, oxalic acid anodic oxidation process and phosphoric acid anodic oxidation process. The most commonly used is sulfuric acid anodizing.
01 anodic oxidation of sulfuric acid
At present, the anodic oxidation process widely used at home and abroad is sulfuric acid anodic oxidation. Compared with other methods, it has great advantages in production cost, oxide film characteristics and performance. It has low cost, good film transparency, corrosion resistance and friction resistance. Good, easy coloring and so on. It is based on dilute sulfuric acid as electrolyte, anodic oxidation of the product, the thickness of the film can reach 5um-20um, the film has good adsorption, colorless and transparent, simple process and convenient operation.
The film obtained by chromic acid anodic oxidation is relatively thin, only 2-5um, which can maintain the original accuracy and surface roughness of the workpiece. The porosity is low and difficult to dye, and it can be used without sealing. The film is soft, with poor wear resistance but good elasticity. Strong corrosion resistance and small solubility of chromium to aluminum make the residual liquid in pinholes and crevices less corrosive to components, which is suitable for structural parts such as castings, the process is used more in the military. At the same time, the quality of the parts can be inspected, and the brown electrolyte will flow out at the crack, which is obvious.
03 oxalic acid anodic oxidation
Oxalic acid has small solubility in aluminum oxide film, so the porosity of oxide film is low, and the wear resistance and electrical insulation of the film are better than sulfuric acid film. However, the oxidation cost of oxalic acid is 3~5 times higher than that of sulfuric acid. At the same time, oxalic acid will be reacted at both cathode and anode, resulting in poor electrolyte stability. The color of oxalic acid oxide film is easy to change with process conditions, resulting in color difference, so the application. However, oxalic acid can be used as sulfuric acid oxidation additive.
The oxide film dissolves more in the phosphoric acid electrolyte than sulfuric acid, so the oxide film is thin (only 3um) and the pore size is large. Because the phosphoric acid film has strong water resistance, it can prevent the adhesive from aging due to hydration so that the bonding force of the adhesive is better, so it is mainly used for the surface treatment of printed metal plates and the pretreatment of aluminum workpiece bonding.
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