Anodising thickens the oxide layer on a metal surface. Which material is it most commonly used on, and what advantage does it provide?

• A. To improve electrical conductivity.
• B. To soften the surface.
• C. To apply a decorative color.
• D. To thicken the oxide layer, increasing corrosion resistance and allowing colour/finish control.

Answer: (D)

Anodising is used mainly on aluminum because it can grow a stable, adherent oxide layer that is much thicker than the natural film. This thicker oxide acts as a strong barrier, so the metal resists corrosion far better in harsh environments. At the same time, the anodic oxide on aluminum is porous enough to absorb dyes, allowing you to control the colour and finish after sealing. So the main benefit is a thicker oxide that boosts corrosion resistance while also giving you finish and colour options.