How Anodizing Works
Aluminum is anodized to form a coating of aluminum oxide by immersing it in an acid electrolyte bath and applying direct current electrical current with the positively charged anodic work piece. This electrochemical process takes place with oxygen being attracted to the positively charged aluminum surfaces forming a coating of aluminum oxide. While the acid is used to conduct electricity, it will also attack the anodic film and tends to dissolve it – forming a coating that has microscopic holes that is very important in a manufacturing process. Freshly anodized aluminum sheets are immersed in a liquid dye solution.
The porous anodic coating absorbs the dye. The intensity of color is related to the thickness of the anodic film, the dye concentration, immersion time and temperature. The coating is then sealed to lock in the dye by closing the pores in the anodic coating, giving a surface resistant to staining and crazing.
What It Takes to Anodize Aluminum
There are a variety of acids such as phosphoric acid, boric acid, tartaric acid, sulfuric acid and chromic acid that can be used for anodizing aluminum depending on the applications. Sulfuric and chromic acid are most commonly used for aluminum anodizing. At Nelson-Miler, we used the conventional sulfuric acid anodizing process.
The anodizing process is a process which includes steps prior to and after the anodizing process. Typical sequence in the process would be cleaning, rinse, etch, rinse, desmut, rinse, anodize, rinse, neutralize, rinse, dye, rinse, seal and rinse. So if you ever wondered why anodized nameplates are more costly than screen printed or etching, this gives you an idea why.
Why Go With Anodized Nameplates
Anodized aluminum nameplates have extremely long life span and ease of maintenance and can be anodized in almost all colors except white (there’s no white anodize ink yet invented).
It offers corrosive resistance, hardness, wear resistance and provide great long term value for your investment.
In terms of health and safety, anodizing is a safe process that is not harmful to human health. The anodic coating is part of the metal and is non-toxic.
At Nelson-Miller, the aluminum oxide coating thickness and surface characteristics are tightly controlled to meet stringent process specifications. We are NADCAP certified and our anodized nameplates meet the following military specifications:
MIL-P-541 Comp A, Class II,
MIL-A-8625 Type II, Class I and II