How to Anodize Aluminum at Home

Anodized clips or hooks

Anodizing is a process by which a protective film including dye can be deposited into the pores of a metal by means of an electric current. Aluminum is the most commonly anodized metal. Using this process, metal surfaces can be made into different colors and have a hardness similar to that of diamonds.

Things You'll Need

• Distilled water
• Detergent
• Plastic tub
• Sulfuric acid
• Lead strip
• Battery charger or DC power supply (25 volts / 12 amps)
• 12-gauge wire
• Thermometer
• Hot plate
• Large glass beaker
• Dye

Instructions

Surface Preparation

1. Clean the part to be anodized using a detergent.

2. Rinse the part with warm distilled water.

3. Mix sulfuric acid into distilled water slowly at a ratio of two parts of sulfuric acid to five parts of distilled water, in a plastic tub. This mixture will become extremely hot due to a chemical reaction if the acid is added too fast.

4. Measure the solution in the acid bath with a battery acid tester.

5. Place the lead strip vertically in the acid bath with the top of the strip sticking out.

6. Attach the negative cable of the battery charger to the part of the lead strip sticking out of the acid bath.

7. Bend a 12-gauge wire to create a hook and hang the part to be anodized on it.

8. Suspend the part to be anodized into the acid bath, taking care not to let the part rest against the side of the tub or the lead strip. The part should not be held or touched by any body part while suspended.

9. Connect the positive cable of the battery charger to the wire suspending the part to be anodized.

10. Set the power supply voltage to 25 volts and 12 amps.

11. Monitor the temperature of the acid bath using a thermometer to ensure the temperature is 65 to 75 degrees Fahrenheit. If it exceeds 80 degrees Fahrenheit reduce the voltage and amps. The temperature will rise approximately seven degrees for each hour of anodizing.

12. Add more distilled water if the water evaporates off. Use the baseline battery acid test measurement as a guide, and add water slowly in small amounts until the measurement is close to baseline.

13. Turn off the power supply and remove the part two to three minutes after the surface becomes milky in color.

14. Rinse the part in cool distilled water.

Adding Color

1. Pour enough dye into a glass beaker to fully cover the part.

2. Heat the dye to 140 degrees Fahrenheit.

3. Attach a wire to the part and submerge it in the hot dye for 30 minutes.

Sealing the Pores

1. Boil enough distilled water in a beaker to fully cover the part.

2. Submerge the part for 30 minutes.

3. Rinse with cool distilled water and dry with a soft towel.

Tips & Warnings

• The best dyes for anodizing are RIT fabric dyes.

• Once the part has been wet, do not let it dry until the end of the process.

• Bubbles will rise up from the lead strip and will interfere with the preparation of the surface. Keep the part away from the bubbles and the lead strip.

• Electrocution is possible when working with electricity.

• Always wear safety goggles, neoprene gloves and a rubber apron when working with chemicals.

• Never add water to an acid. Always add acid to water slowly. Adding in the wrong order or too fast can result in the acid being thrown out of the container.

• Always read the material safety data sheet before working with chemicals.

References

• Moonlite Telescope Accessories: Anodizing Aluminum