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How to Anodize Aluminium

Updated April 17, 2017

Anodising aluminium, often spelt "aluminium" outside the U.S., is a quality way of metal finishing and colouring. Aluminium parts are used for various purposes and are found in cars, motorcycles, bicycles, cooking utensils and construction elements like windows and doors. If you want to colour an aluminium part or give it a strong, durable and attractive finish, consider anodising it. Unlike regular metal paint, a finish made by aluminium anodization can't be peeled off and is very hard to scratch.

Prepare the solution for the anodising process. Mix 7 parts of acid with 3 parts of water in a rubber bucket. Choose the amount according to the size of the aluminium part: the solution should be deep enough to cover it whole. Charge the solution with a 12-volt charger by putting both of its ends into the liquid.

Clean the aluminium part you want to anodise thoroughly. Use a soft yet thick brush, liquid soap and warm distilled water to remove any dirt or grease. Dry the aluminium part with a clean cloth to complete the first stage of cleaning.

Clean the aluminium part again, this time using nitric acid. Mix 59.1ml. of nitric acid with 1 gallon of distilled water. Pour the solution into a deep plastic bowl and soak the part for at least half an hour.

Rinse the part with distilled water and remove all traces of the cleaning solution.

Put the aluminium part into the anodising acid solution you made. Ensure that the whole surface of the metal is covered with liquid and that the negative ground of the battery charger doesn't touch the aluminium.

Heat the acid solution to 21.1 degrees C with the aluminium part soaking in it. Leave the solution for at least an hour.

Rinse the anodised aluminium part with boiling or distilled water. This will stop the oxidation process. If you want to dye the part, proceed with the next step.

Prepare a dye solution by mixing 2 parts water with 1 part fabric dye of your choice. Heat the solution to a temperature of 32.2 degrees C and then place the aluminium part inside. Use your power supply or battery charger to heat the solution.

Leave the anodised aluminium part in the dye solution for 30 minutes, while you increase the temperature slowly until it reaches 60 degrees C.

Rinse the dyed anodised aluminium part with boiling or distilled water and place it in an oven to dry. Set the oven to its lowest heat setting, around 43.3 degrees C for most ovens. Note that the temperature in the oven has to be only warm enough so that the dye sets gradually.

Tip

It is recommendable to work outside rather than in a closed space. For the acid solution you can use sulphuric acid.

Warning

Do not work near flammable materials or a source of ignition. Make the area you work in ventilated and try not to breathe in the solution and its components. Working with chemicals is always a dangerous job, so wear disposable rubber gloves, a protective mask and safety plastic goggles at all times.

Things You'll Need

  • Sulphuric acid
  • Rubber bucket
  • 12-volt battery charger
  • Brush and cloth
  • Liquid soap
  • Nitric acid
  • Distilled water
  • Fabric dye
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About the Author

Based in New Jersey, Susan Raphael has been writing technology-related articles since 1991. Her work has appeared in “Wired” magazine, and “Mac Addict” magazine. Raphael received the Janet B. Smith Literary Award in 2002. She holds a Bachelor of Science in journalism from New York University.