Anodized
an·od·ized | ˈa-nə-ˌdīz
verb
A process in which a metal object is placed in an acid bath and an electrical current is passed through the tank
This process causes oxygen atoms to bond to the surface of the metal, giving it a thin, protective film and lustrous sheen. This process has many benefits, including an increase in durability and resistance to corrosion for the lifetime of the piece. It can also help to highlight specific colors and patterns in the piece, it is generally safe to wear, and offers a smoother, more visible surface for the piece. Not all metals can be anodized due to how the different types of metal react to the process. The metals that can be anodized include zinc, magnesium, aluminum, titanium, niobium, and tantalum, and for the purposes of jewelry, it is most often titanium or niobium, as the other types of metal will eventually shed some of the layer that has been anodized. In these metals, the natural oxide layer that exists on the metal is thickened by the heating process, removing any debris and making the piece smoother.