Niobium is a lustrous, light gray, ductile metal. It has numerous properties that make it an exciting material for jewelry designs.
- Niobium is hypoallergenic.
- Niobium is very malleable and easy to work with.
- An incredible range of colors can be rendered on the surface of niobium through a process called anodizing.
- Niobium is inexpensive.
Anodizing is a high-voltage, low-amperage process performed with non-toxic electrolytes that is used on reactive metals like niobium and titanium. It produces a transparent oxide film on the surface of the metal which results in what is called interference colors.
In contrast with titanium, niobium is easy as well as predictable to anodize. And a full range of colors can be produced on its surface. (The images illustrating this article feature jewelry made with niobium.) During anodizing, the metal is immersed into an electrolytic bath through which an electric current is passed, causing an oxide layer to form on the surface of the metal. The thickness of the oxide layer determines the resulting color.
The oxide layer is essentially a patina and should be treated as such... Jewelry designers do not usually coat anodized niobium with a protective finish. Since the colors depend on the high refractive index of the transparent oxide layer, any coating tends to dull the colors.