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.
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.
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.