Anodizing is an electrochemical process that converts a metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing.

The anodic oxide structure originates from the aluminum substrate and is composed entirely of aluminum oxide. This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel. It has a highly ordered, porous structure that allows for secondary processes such as coloring and sealing.

Anodizing is accomplished by immersing the aluminum into an acid electrolyte bath and passing an electric current through the medium. A cathode is mounted to the inside of the anodizing tank; the aluminum acts as an anode, so that oxygen ions are released from the electrolyte to combine with the aluminum atoms at the surface of the part being anodized. Anodizing is, therefore, a matter of highly controlled oxidation—the enhancement of a naturally occurring phenomenon.  This process successfully combines science with nature to create one of the world’s best metal finishes.

The resulting finish, depending on the process, is the second hardest substance known to man, second only to the diamond.

Meets AAMA 611 specifications for anodizing.

Strengths of Anodizing

• Color stability
• Hardness, compared to a sapphire
• Anodize protects and maintains the structural integrity of the aluminum
• Non- hazardous, produces no harmful or dangerous by-products
• Ease of maintenance.

Weaknesses of Anodizing

• Limited color selection.  Because of the chemicals used in the anodizing process, you are greatly limited on the color selection for your next project or product.
• Anodizing does not offer you the extended warranties as Superior Pigmented Painted Products.
• Touch-up of anodized product that is severely damaged in your shop or the field is more noticeable than air dry touch up paint for painted products.

The Anodizing Process

• Pre-Treatment: Cleaning is done in a non-etching, alkaline detergent heated to approximately 145 degrees Fahrenheit. This process removes accumulated contaminants
  and light oils.
• Rinsing: Multiple rinses, some using strictly de-ionized water, follow each process step.
• Etching (Chemical Milling): Etching in caustic soda (sodium hydroxide) prepares the aluminum for anodizing by chemically removing a thin layer of aluminum. This alkaline bath gives the aluminum surface a matte appearance.
• Desmutting: Rinsing in an acidic solution removes unwanted surface alloy constituent particles not removed by the etching process.
• Anodizing: Aluminum is immersed in a tank containing an electrolyte having a 15% sulfuric acid concentration. Electric current is passed through the electrolyte and the aluminum is made through the anode in this electrolytic cell; the tank is the cathode. Voltage applied across the anode and cathode causes negatively charged anions to migrate to the anode where the oxygen in the anions combines with the aluminum to form aluminum oxide (Al2O3).
• Coloring: Anodic films are well suited to a variety of coloring methods including absorptive dyeing, both organic and inorganic dyestuffs, and electrolytic coloring, both the Sandocolor® and Anolok® processes.
• Sealing: In all the anodizing process, the proper sealing of the porous oxide coating is absolutely essential to the satisfactory performance of the coating. The pores must be rendered non-absorbent to provide maximum resistance to corrosion and stains.