Anodising (Topic: 14063)

Anodising is an electrolytic process. In the anodising process the aluminium extrusions are electrically connected as the anode, and the cathode may be flat bars of aluminium. The most common electrolyte used for architectural anodising is sulphuric acid. The concentration is between 160 and 200 g/l, the temperature is usually between 18 and 22°C, and the optimum current density is from 1,4 to 1,8 A/dm2.

Other process parameters are mentioned in "Anodising process parameters". To avoid too high temperature in the anodising bath, cooling and air agitation of the electrolyte is necessary.

Anodising tank with equipment mentioned above.

The anodic oxide grows at a rate of approximately 1 µm per 2ñ3 minutes. To build up an anodising layer of 20 µm, will take at least 40 minutes.

Pulse anodising is used to decrease the anodising time and to increase the quality of the anodic oxide layer.