Class 3 No supplementary treatment. Class 4 Chemically converted. Excellent corrosion resistance. Almost as hard as chromium. Very good abrasion resistance.
Thicker coatings are very brittle.
Has high reflectivity. Used on silver for tarnish resistance. Applications range from electronics to nose cones-wherever wear, corrosion resistance, solderability, and reflectivity are important. Type I Over nickel, silver, gold, or platinum. Good corrosion resistance, depending on base metal.