Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of the coin. Process subsequently increases resistance to corrasion and wear.
The wavelengths of the visible spectrum of light can reflect various colors depending on the thickness of the oxide coating. The rainbow affect is achieved by changing the voltage output during the anodization process. No paints or sprays are used. There are an infinite number of possibilities of how the coin’s design will finish. No two coins are alike.