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What Is Clear Anodizing?

Nov 23, 2015

Anodizing is a widely used process for treating aluminum parts to be used in a variety of  contexts.

Without a background in industrial practice or chemistry, it may be unclear what exactly clear anodizing is.



  • Clear anodizing is a process that creates a thin layer of aluminum oxide coating (typically under 0.025 mm) on aluminum metal. The oxide layer is clear in appearance and is filled with many microscopic pores that allow dyes and other substances to adhere to the surface. It protects the aluminum metal underneath from corrosion and wear.



  • To clear anodize a piece of aluminum, it is immersed in a bath of acid (typically sulfuric acid). The aluminum is hooked up to the positive terminal of a power source (making it the anode). The negative terminal is connected to a cathode that will not react much with the bath, such as carbon, lead or steel. Electrons flow from the aluminum, creating aluminum ions through the power source to the cathode. The aluminum ions react with oxygen in the water to make aluminum oxide and hydronium ions. The hydronium ions are then given electrons at the cathode to make hydrogen gas, completing the circuit.


  • Clear anodizing can create a finish on trim for cars, be used to make photolithography plates, and provide a base for paints, glues and dyes. It can also improve the performance of machinery parts by guarding against wear and corrosion.