Since the Mardi Gras doubloon was introduced, doubloons have been minted using a process called anodizing.

Many metals are structurally weakened by this process, but not aluminum. Aluminum throught the anodizing process is made much stronger. The same with Mardi Gras doubloons. Various dye can be used in this process to produce doubloons in many different colors. You have probably seen them or own some of these colors such as, green, gold, blue, orange, pink, purple, and many other colors.

The electrochemical process involves placing a sheet of metal into a chemical acid bath and the acid bath becomes negative. An electric current passes throught the acid causing the surface to oxidize. The oxidation forms a strong coating as it replaces the original aluminum on the surface. When the process is complete the surface becomes so durable that it can be compared to the hardness of a diamond.

You can probably look at some of your doubloon as see that many of the very old one still have the appearance of new strike.