Aluminum

Aluminum and aluminum alloys are the most commonly anodized materials. Aluminum is widely used in industrial processes because of its high strength to weight ratio and relative availability. Anodizing aluminum improves its overall performance and extends its working life. Numerous different aluminum anodizing processes exist.

Magnesium

The most common purpose for anodizing magnesium is as a paint primer, with thin films (as little as 5 μm) being sufficient for this use. Thicker anodic coatings (25 μm or more) can provide magnesium materials with improve corrosion resistance. These coatings must be sealed with oil, wax, or sodium silicate for optimum effectiveness.

Applicable standards for magnesium anodizing include AMS 2466, AMS 2478, AMS 2479, and ASTM B893.

Titanium

Anodized titanium is commonly used in dental and orthopedic implants. The anodizing process can create numerous colors without the use of dyes, making anodized titanium popular for art, costume jewelry, body piercing jewelry, and wedding rings. Color is dependent on the thickness of the oxide layer, which range from 30 nanometers to several micrometers. Thickness, in turn, is determined by the anodizing voltage.

Applicable standards for anodized titanium include AMS 2487 and 2488.

Niobium

Niobium can be anodized using chemistries and processes similar to titanium anodizing. A range of colors can be achieved by varying the coating thickness, which is, again, dependent on anodizing voltage. Anodized niobium is a popular material for costume and body jewelry, commemorative coins, and other highly aesthetic products.

Tantalum

Anodizing tantalum requires a similar process to those used for titanium and niobium. A wide array of attractive colors can be formed by altering the film thickness. Voltage required for anodizing tantalum typically ranges from 18-23 Angstroms per volt, depending on the chemical solution used and process temperature. Anodized tantalum is most often used in the manufacture of capacitors.

Zinc

Anodizing zinc can be a difficult process. A solution of ammonium phosphate, chromate, and fluoride, combined with voltages as high as 200V DC can produce anodized coatings as thick as 80 μm on zinc materials, adding hardness and corrosion resistance.

Chemical baths containing sodium silicate, sodium hydroxide, borax, sodium nitrate, and nickel sulphate, using lower voltages (20-30V DC), can be used to anodize zinc-plated steel materials.

Applicable standards for anodized zinc include MIL-A-81801.

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