Aluminum Extrusions  •  Fabrications  •   Finishing

What Is Anodizing?

Anodizing is a process by which metal is induced to form a surface layer of oxide by immersing it in a liquid electrolyte and applying electric current. The process is called anodizing because the piece being treated forms the anode of an electric circuit. Depending on the alloying metal and the thickness of the coating, this process may change the metal’s hardness, corrosion resistance, thermal or electrical properties. Many parts made by aluminum extrusion, such as those offered at, are often anodized to make them harder or for cosmetic reasons.

Anodizing begins with the cleaning of the metal piece when it leaves the aluminum extruder to remove any surface contaminants, after which the piece is subjected an electric current through a component called the cathode. This causes hydrogen to form on the cathode while a layer of oxygen forms on the anode. This creates a layer of oxide on the anode, making a barrier to further oxidation.

The oxide layer is smooth and shiny to the naked eye, giving the piece an attractive appearance. This smoothness is deceptive, since a microscopic examination will reveal a network of tiny fissures. These fissures allow dye to penetrate beneath the metal’s surface, so colors applied to the piece are bright, glossy and permanent. A negative side of the fissures is that they can allow reactive substances to penetrate to the metal substrate, encouraging corrosion. Though anodizing gives the metal some desirable properties, this pitting must sometimes be remedied by the application of protective coatings.

Aluminum alloys are good candidates for anodizing, since the alloying process often deprives them of aluminum’s ability to passivate naturally. Since passivation is the cause of aluminum’s corrosion resistance, the inability to passivate results in alloys that are prone to corrode. Anodizing after the piece leaves the aluminum extruder induces passivation, producing aluminum alloys with the same corrosion resistance as pure aluminum.

Anodized metals, especially aluminum, have many uses in industry and art. Metal panels on the exteriors of buildings are often made by anodized aluminum extrusion, as are railings and other outdoor features. The casings of appliances like refrigerators, microwaves and televisions are often anodized aluminum. Vent covers, awnings, light fixtures and so forth are also made from it, utilizing the metal’s weather resistance. Its lack of corrosion makes it ideal for kitchen items such as pots and pans.

As one of the largest value-added aluminum extruders in the country, Unique Extrusions, Inc. offers high-quality aluminum products and services nationwide.

One Of America’s Top-Rated Extruders Providing World-Class Service

"Our company builds industrial machinery, and we rely on Unique Extrusions to supply one of the most critical parts on our machine. They have always been completely professional and reliable, and their quality has been excellent. Additionally they are very good at reacting to our needs. A few years ago, our weekly demand increased to a level that was greater than what they could produce on the machine that ran our parts. In order to help us, they worked out a way to move our parts to a larger machine that could handle our demand. When our demand increased again, they came up with a way to run our parts at a higher speed while still keeping the same quality level. Whenever we have a problem, Frank is always there to help, and I know that he exhausts all possible options in working to meet our needs.

Overall, Unique is an excellent company, and we consider them to be one of our most valuable suppliers."

- Kimberley Riffe, Vanguard Pailung

"Safe Conveyor Inc. manufactures modular plastic belted lightweight conveyors using custom extruded aluminum sections supplied by Unique Extrusions Inc. Since the initial concept and design of our conveyor system, Unique has been most helpful in providing their expertise in extruding aluminum to meet our requirements. With our goal of maintaining low inventory, their quick response and fast delivery has allowed us to operate “just-in-time”. We have been very pleased with the quality of finished goods that have been carefully packed for shipment. We hope to continue purchasing from Unique Extrusions Inc. for many years to come."

- Gregory A. Ferguson - President of Safe Conveyor, Inc.

*The reviews listed are from actual Unique Extrusions customers. Individual results may vary. Reviews are not claimed to represent results for everyone.