Anodizing is a surface treatment only for aluminum metal fabrication products. By soaking the aluminum prototypes in the potion, they corrode as an oxidation reaction happens, resulting in changes in the color of the aluminum parts.
Aluminum oxide is a relatively stable substance and will not react with the oxygen in the air again. It can keep its color for a long time. There are two purposes of anodizing: one is to prevent the prototype from corrosion, and the other is to improve its aesthetics.
A range of colors is available for anodized aluminum parts, as shown below.
