Aluminum Anodizing

Anodizing aluminum is an electrochemical process that produces a clear oxide layer on the surface of the metal. This oxide layer is extremely hard and porous, allowing the metal to accept color. The pore structure when viewed under a high-powered microscope looks like a honeycomb or metal sponge.

Dye, ink or paint can then be deposited into the pore structure and sealed to lock in the color and stabilize the surface. Colors are deeply embedded in the aluminum, not simply applied to the outside. The color actually becomes a part of the metal and won't chip off.

The formula for anodizing varies, but is basically controlled by time, temperature and current density. Anodizing insulates the surface and makes it non-conductive. For specific applications, engineers might design a part to have a dual purpose - areas that are anodized (non-conductive) and areas that are conductive for electrical contact.

Hard Coat Anodizing

Hard Coat Anodizing is different than conventional anodizing. Lowering the temperature and increasing the current density can build a thicker more compact layer on the surface of the metal. This process is ideal for parts that need extra protection under extreme conditions.

Hard Anodizing penetrates the metal as much as it builds up on the surface. The term "thickness" includes penetration and builds up. A typical hard-anodized job will increase a diameter by .002" (50 microns) - .001" penetrations and .001" build up. It is sometimes confusing to machinists who are more familiar with plating. In plating that same part would increase in dimension by .004". For specific questions on closer tolerance requirements, please contact our production manager.

The Benefits of Aluminum

• Aluminum is a light metal, about a third of the density of steel, copper, and brass.
• Aluminum has good corrosion resistance to common atmospheric and marine atmospheres. Its corrosion resistance and scratch resistance can be enhanced by anodizing.
• Aluminum has high reflectivity and can be used for decorative applications.
• Some aluminum alloys can match or even exceed the strength of common construction steel.
• Aluminum retains its toughness at very low temperatures, without becoming brittle like carbon steels.
• Aluminum is a good conductor of heat and electricity. When measured by equal cross-sectional area, electrical grade aluminum has conductivity which is approximately 62% of electrical grade annealed copper. However, when compared using equal weight, the conductivity of aluminum is 204% of copper.
• Aluminum is readily worked and formed using a wide variety of forming processes including deep-drawing and roll forming.
• Aluminum is non-toxic and is commonly used in contact with foodstuffs.
• Aluminum can be readily recycled.