Anodize Aluminum
Anodizing uses acid to create a corrosion and wear resistant layer on top of a metal. The process of anodizing changes the crystal structure near the surface of substances, like aluminum alloy, and allows you to dye the metal a bright color. Take extra precautions with caustic substances, like lye and sulfuric acid, when you anodize aluminum at home.
Contents
Steps
Collecting Supplies
- Buy some standard aluminum alloy metal parts. Anodizing works particularly well with aluminum, so, if careful, you can do it at home. Use small aluminum pieces to begin with so that you can submerge it in small quantities of acid.
- Buy a thick plastic tub to submerge your metal. Choose a type of plastic that is extremely hard and durable.
- Find some clothing dye at a local grocery store. During the anodizing process, you can dye the metal almost any color. This is the process Apple uses to color iPods.
- You can also buy special dye for anodizing that may produce better results.
- Purchase degreaser product , 2 long lead cathodes and a roll of aluminum wire at a hardware store.
- Purchase large amounts of distilled water, baking soda and rubber gloves.
- Find places to purchase several gallons of sulfuric acid (battery acid), lye and a constant power supply of at least 20 volts. The battery acid may be hard to find; however, it is usually available at auto parts stores. A large battery charger should work as a constant power supply.
Cleaning Aluminum
- Wash your metal with soap and water.
- Apply a degreaser with a cloth to remove any additional oil from the product.
- Mix 3 tbsp. (44 ml) of lye in 1 gallon (3.8 l) of distilled water. Use a smaller plastic tub or discarded metal bowl. Allow it to sit for 3 minutes, then remove it and rinse it well.
- The lye will remove any existing anodizing on the surface of the metal. Once it is removed, water should pour off the surface easily, instead of beading.
- Wear rubber gloves whenever working with lye.
- Do not use measuring spoons or cups that are used for food products. The materials used in this process are toxic.
Setting Up An Anodizing Bath
- Place your plastic tub in an area that is well ventilated and away from things that could be harmed during this process. Set it on a piece of plywood and/or a thick drop cloth in case of spills.
- For best results, do this when the indoor temperature is between 70 and 72 degrees Fahrenheit (21 to 22 degrees Celsius).
- Set up your power supply. Set it on a non-flammable material, like concrete, and make sure it is working consistently.
- You will need to connect the positive wire from your battery charger or rectifier to a wire that will be strung to your aluminum.
- You will need to connect your negative wire from your battery charger to an aluminum wire connected to 2 lead cathodes.
- Tie 1 end of the long aluminum wire to the aluminum part. 12-gauge aluminum wire works well for this use. Wrap it or connect it to the part on a place that is hidden.
- The area of the part that connects to the wire will not anodize.
- Make sure it is very tightly wrapped for a more consistent charge.
- Wrap the wire around a thin piece of wood that is wider than your plastic tub. This will give you leverage to lift it out when you are done. Make sure you have extra wire extending toward your power supply after you wrap it.
- Test the wooden handle to ensure your aluminum part will be fully submerged in the acid mix.
- Set a lead cathode on each side of your tank. String aluminum wire between the cathodes and connect them together on your small wood plank. You will attach the negatively charged power supply to this wire.
- Make sure the wire connecting the aluminum part and the lead cathodes does not touch.
- Pour 1 part distilled water to 1 part battery acid into your large plastic tub. The amount you use will depend upon the size of the metal part you want to anodize. Be very careful not to spill.
- Always pour the water in before the acid.
- If you spill any acid, cover it quickly with baking soda.
- Put on a mask or respirator before you start working with acid. Turn on a fan to ventilate the area.
- Connect the aluminum wire that leads from your aluminum part to the positive charge supply. Connect the aluminum wire that leads from the lead cathodes to the negative charge supply.
- Check to make sure there aren’t any spills, the power is safely connected and your skin is completely covered.
Anodizing and Dying Metal
- Turn the power source on. Slowly turn it up. You will want to use 12 amps per square foot of material.
- Increasing the power too fast or using too much can burn your aluminum wires.
- Keep the power supply constant for 45 minutes. You will see little oxidation bubbles start to form on the surface of the aluminum. It will also start to change color, turning brown, then yellow.
- Mix a colored dye during the anodizing process. Mix with distilled water and heat it to 100 to 140 degrees Fahrenheit (37 to 60 degrees Celsius).
- Turn off the power supply. Remove the metal part and rinse it with distilled water.
- Place the aluminum part in the warm dye bath. Let it sit for 15 minutes.
- Boil distilled water on a hot plate. Remove the aluminum part from the dye and place it in the boiling water for 30 minutes.
- Remove the hot metal carefully and allow it to dry. The surface should be sealed and dyed.
Warnings
- Beware that many of the supplies required for this project can be lethal if spilled or ingested. Make a workstation away from children and pets. Then, always wear thick work clothes, safety goggle and gloves.
- Never pour water into acid. It can result in boiling over and “blowing up.” The blow up is caused from the heat, and it can result in acid burns.
Things You'll Need
- Aluminum parts
- Thick work clothing
- Rubber gloves
- Safety glasses
- Thick plastic tub
- Mild soap
- Water
- Distilled water
- Plastic/metal bowl
- Degreaser
- Lye
- Sulfuric acid
- Small lead cathodes
- Old measuring spoons
- Baking soda
- Power supply (ex. car battery charger)
- Respirator/fan
- Old metal pan
- Hot plate/stove top
