Anodizing can create a colorful finish on aluminum objects.
Anodizing is a process commonly used to make aluminum harder and less likely to corrode. It involves using an electric current to create an oxide on the outside of an aluminum object. If you add a dye during the anodizing process, you can also make the oxide coating a decorative one. Home anodizing is used to add decorative and protective finishes to paintball components, car parts, computer parts and even telescopes.
The home anodizing process requires a few dangerous chemicals, and the use of electricity. These can be dangerous if you don’t observe the right procedures. Make sure to wear goggles or safety glasses when working with caustic substances or acids. Wear gloves when handling dangerous chemicals or hot water, and choose an apron or old clothes that won’t be damaged by chemical spills. Work in a well-ventilated room, or wear a chemical respirator, to avoid inhaling dangerous gases.
Tools and Materials
To anodize aluminum, you’ll need a nonreactive container, such as a plastic tub, large enough to hold the aluminum part and another piece of aluminum. Anodizing also requires an electrolyte, such as battery acid or 50 percent sulfuric acid, and a source of electricity, such as a vehicle battery charger. If you wish to add color to your anodized surface, you’ll also need a dye, such as commercial fabric dye or food coloring.
Clean all aluminum parts thoroughly before anodizing. Create a bath of one to two ounces of nitric acid or three tablespoons of lye added to a gallon of water. Always add the lye or acid to the water to prevent a dangerous chemical reaction. Immerse the part in this solution to remove oil and other contaminants. Fill the main container with a mixture of one part battery acid and three parts water, adding acid to water, not water to acid. Suspend the part to be anodized and another piece of aluminum — the cathode — in the acid solution. Attach the battery charger’s negative lead to the cathode, and the positive lead to the aluminum part, or anode.
Switch on the battery charger to begin anodizing. The greater the voltage, the stronger the anodizing effect, and the faster the process will go. If current is flowing correctly, the cathode will emit bubbles or a fog. Leave the setup with the power on for about two hours, or until the surface of the anode appears dull and slightly yellow. Remove the part from the acid bath and rinse it thoroughly in distilled water.
If you wish to color the part, mix water and dye in a nonreactive pot. The stronger the dye concentration, the darker the finished part will be. Place the aluminum part into the dye and heat it to 100 degrees Fahrenheit for about 15 minutes. While it’s heating, bring distilled water to a boil in a separate pot. Remove the part, rinse it in clean water, and add it to the boiling water. Keep the water at a boil for half an hour to seal the surface of the part.