Niobium is a hypo-allergenic material that is great to use in jewelry designs because it is safe for anyone to wear, especially those with metal allergies. With advancements in technology, we can create colorful earwires for fun elements instead of plain, grey components that need dressing up. How niobium earwires get painted with color is actually a surprising process, because they aren’t actually “colored” in the way you would think. Let’s take a look at the process.
First off, it’s important to know the components of niobium. Much like precious metals, niobium is very flexible and slowly hardens. It can be easily manipulated with a jeweler’s saw and has about twice the density of titanium, but is only about a third as dense as gold. At room temperatures, a thin, transparent and adherent oxide film forms on the metal’s surface. This protects the metal from corrosion and also protects the wearer from the metal. Niobium reacts with atmospheric oxygen and other gases at certain temperatures, making it a reactive metal. This element of the niobium is what aids in the coloring process. The color coating on niobium goes through a similar process like gold plating, but is extremely different. The color is anodized to the niobium, not plated.
The anodizing process works to increase the natural oxide layer of the metal by manipulating the electrodes found in niobium with an electric current. For this, wrought alloys are cleaned in either a hot soak cleaner or in a solvent bath mixed with sodium hydroxide or other acidic chemicals. The layer on the metal is increased by placing the metal in the electrolytic solution, with the metal acting as the anode (positive electrode) to complete the electric current.
Changing the voltage on the electrolytic solution is what determines the color of the niobium when it is submerged. This is because the voltage directly correlates to the thickness of the oxide layer. The oxide layer interferes with the light reflecting off its surface and then traveling through the underlying metal surface, thus determining the color you will see.
Since niobium starts out as a pewter grey color, it takes a higher voltage to create bright colors like hot pink and neon green as opposed to base metal colors like gold or copper. For example, it takes about 100 volts to create a purple-pink effect on niobium but only about 10 volts for a golden copper color. This process makes it possible to make a variety of different colors, although base metal tones are still the most popular in fashion trends. Check out our collection of niobium earwires available to use in designing decorative ideas.
Sources for all Photos: YouTube.