Anodizing aluminum is a process to cover aluminum surface with oxide film of anodized aluminum. The layer of this oxide film is very thin and have transparent color. The transparent color of this layer make the color below this layer can be seen if any color attach on the below surface of oxide film. How to make color below this layer is already discussed at coloring of oxide film. Coloring agent to make this layer can use chemicals agent or by reaction of certain chemicals with aluminum surface. Coloring using dyeing agent can make more variety compare just with the chemical reaction with the surface of aluminum metal.
The process of anodizing itself using several process in sequence, such as below:
The process of anodizing itself using several process in sequence, such as below:
- Electropolishing of Aluminum: the process to make an old oxide film that already available in aluminum surface should be removed before the process of anodizing being started.
- Alkaline solution treatment: this process also have similar purpose like electropolishing, but on this process is used chemical solution to open the oxide film. Some other purpose of anodizing process can use other chemical substances.
- Rinsing: rising is a process that done in between of each process. Rising by fresh water is needed to make the surface of aluminum is clean and free from chemicals.
- Jigging: Jigging is extended process of rinsing by using of some solvent to clean the surface of aluminum. Some organic solvent can use to clean the surface of aluminum such as benzene or acetone if needed.
- The next process is anodizing process. Anodizing process is doing under DC electrict current in chemical solution. Bath solution on this process usually use sulfuric acid, but other purpose may use other kind of chemical solution.
- Racking and rinsing: after process of anodizing, then the object is being rinsing again and racking to make the object dry.
- Sealing and coloring: To make the surface of anodizing produce look interesting, this process is very important. First process of this step is coloring first can use dyeing agent from textile dyeing agent or use chemical that will react with chemicals that already stay on aluminum surface. For reaction method should doing in two step in order make coloring after reaction. After coloring of aluminum surface then the pore of aluminum surface is being closed by dipping in boiling water for several minutes.
- Polishing after anodized: the polishing process is apply to anodized aluminum involves the production of finishes resembling bronze, brass, gold, silver and their alloy. In such cases of suitable coloring materials, an important part is played by conditioning and preparation of the surface of the metal part to anodizing.