The aluminium anodizing process includes mechanical polishing, degreasing, water washing, chemical polishing, water washing, anodizing, water washing, sealing, and mechanical brightening. The aluminum workpiece is suspended in an appropriate electrolyte solution and used as an anode for electrolysis. In the electrolysis process, the hydroxide ions in the water emit electrons at the anode to become water and new ecological oxygen, which oxidizes aluminum into a thicker aluminum oxide film. Because this process is oxidized by metal products as anodes, it is called anodization. After aluminum products are anodized, they are colored, sealed, and processed to become dyed products.
The pre-treated aluminum parts are stained with more grease, a small amount of abrasives, dust, and defective oxide films during multiple machining processes. These materials have poor electrical conductivity and cannot be anodized, so they need to be pre-treated. For anodization, the first step is the preparation of sulfuric acid electrolyte, which is a mixture of 18-20 kg of sulfuric acid and 80-82 kg of deionized water. At this time, the specific gravity of the solution is about 1.125-1.140. Sometimes in order to obtain a good protective anodic oxide film, a small amount of oxalic acid is usually added to the sulfuric acid electrolyte; the second is the aluminum anodic oxidation process, the line meters are installed, the aluminum parts to be dyed are used as anodes and all are immersed in the electrolyte, and then power it on. The electrolyte temperature is controlled at 12-25℃, the anode current density is 1-2 A/dm², and the cell voltage is between 13-23 volts. The time is about 30-40 minutes. After completing the above process, remove the aluminum parts from the electrolyte at any time, and rinse the acid with clean water. Pay more attention to the concave parts, otherwise white spots will appear. After the acid is cleaned, it is immersed in clean water for later use.
There are two types of dyes: inorganic dyes and organic dyes. Inorganic dyes are mostly composed of inorganic salts. When dyeing, the aluminum pieces are soaked in two compound solutions A and B respectively to generate colored compounds to achieve the purpose of dyeing.