Use any fade resistant dye to anodize flat colors on aluminum.
Anodizing is a process that uses electric current to create an oxide coating on the outside of aluminum objects. This coating is harder than the bare aluminum and prevents the metal underneath from corroding. Adding a dye during the anodizing process allows you to color the oxide coating as well. You can anodize a flat color–an even coating of just one color–on all kinds of aluminum objects, from telescope parts and paintball markers to car engine parts. The process is relatively straightforward and can be done using a few common materials.
1. Put on safety equipment of goggles and gloves and wear old clothes. Remove all contaminants from the object to be anodized. Combine three tablespoons of lye or one to two ounces of nitric acid with a gallon of water in a plastic tub. Add the lye or acid to the water. Place an aluminum object in this solution for a few minutes. The acid or lye solution will eat away oil and other contaminants that might cause uneven anodizing.
2. Mix the electrolyte. An electrolyte is any solution that electricity can travel through. The minerals in the electrolyte make it more effective at transmitting current than just water. Combine one part 50% sulfuric acid or battery acid with three parts water in a plastic tub. Choose a tub large enough to hold the object to be anodized and a piece of scrap aluminum.
3. Set up the parts. Use a wire or other corrosion-resistant material to suspend the cleaned aluminum object from Step 1 in the electrolyte. The liquid should cover it completely. Choose another piece of aluminum to be the cathode, or negative electrode. Suspend it in the electrolyte so that it doesn’t touch the first object.
4. Attach the leads. Clip the battery charger’s negative lead to the scrap aluminum cathode. Clip the positive lead to the object you wish to anodize. This object will become the anode, or positive electrode.
5. Switch on the battery charger. Use a rate of at least 2 volts. Higher voltages will allow the object to anodize more quickly. If power is flowing properly, you should see white fog, or a continuous stream of bubbles coming from the cathode.
6. Wait for the anodizing process to finish. Allow the parts to remain in the electrolyte with the current flowing for about two hours, or until you see a dull or yellowish tone on the surface of the anode. The bubbles coming from the cathode may change direction or become less frequent. You may need to leave large parts in the electrolyte for more than two hours, or use a higher voltage.
7. Turn off the power and use a pair of tongs or another corrosion-resistant tool to take the aluminum part out of the acid bath. Rinse the part thoroughly using distilled water.
8. Combine fabric dye and distilled water in a stainless steel pot or other non-reactive, heat-resistant vessel. Use a higher dye concentration for darker colors, and a lower concentration to produce lighter colors. Place the part into the dye solution, then heat the mixture on a stove or hot plate to 100 degrees Fahrenheit. Leave the pot on the heat for about 15 minutes, then remove the part. Rinse it with distilled water, but don’t scrub the surface. Scrubbing could remove the color.
9. Fill another stainless steel pot with distilled water. Bring the water to a boil, and add the aluminum object. Allow the object to boil for 30 minutes. This process is called hot water sealing, and will harden the anodized surface, sealing the color in permanently.
10. Remove the part from the water bath with the tongs. Allow it to cool and dry completely before use.