Metallium, Inc.
The Anodizing Process
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Anodizing is a process that is used throughout industry for certain metal finishing operations. We tried this process first on our Niobium Element Series coins, and the outcome was spectacular! We were able to create most of the colors of the rainbow on the surfaces of the metal by adjusting the process to get the desired color. Purple, blue, green, yellow, and any in-between mixes of those colors can be created. Red is the only basic color that cannot be created. These color changes are permanent - not like paint or other coatings that can chip or wear off. The colors have a deep, iridescent appearance and are reflective and change appearance when you tilt the coin or adjust lighting.
The coating is actually an oxide layer that is deposited on the coin by the anodizing process. In a nutshell, the process works like this. An electrolysis setup is used, where a variable-voltage power supply is connected to a cathode metal (-) and the anode (+) is connected to the coin, or whatever is to be colored. Anode and cathode are placed in a mild electrolyte solution and power is applied. After a few seconds or minutes, the target metal piece will build a very thin oxide layer. As the layer gets thicker, it starts to retard the current and at some point will stop the current flow completely. The thickness of the oxide layer is controlled by the voltage setting of the power supply.
If the oxide layer is thin enough, it will cause light to reflect on the original metal surface and also the top surface of the oxide layer. These light patterns will interfere when they reflect, creating the vibrant colors, much like a thin oil slick on pavement will show a rainbow of colors.
See examples below of the results of this process:
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