Coating Characteristics of Zinc Plating
Normal zinc-plated coatings are dull gray with a matte finish, although whiter, more lustrous coatings can be produced, depending on the process or agents added to the plating bath or through post-treatments. The coating is thin, ranging up to 1 mil (25 µm), restricting zinc-plated parts to very mild (indoor) exposures. ASTM Specification B 633 lists four classes of zinc-plating: Fe/Zn 5, Fe/Zn 8, Fe/Zn 12 and Fe/Zn 25. The number indicates the coating thickness in microns (µm). Zinc plating is typically used for screws and other light fasteners, light switch plates, and various small parts. Materials for use in moderate or severe environments must be chromate-conversion coated for additional corrosion protection.The coating is pure zinc, which has a hardness about one-third to one-half that of most steels.
Zinc Coatings Publication
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