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The chromate coating acts as paint does, protecting the zinc from white corrosion, thus making the part considerably more durable, depending on the chromate layer's thickness. [8] [9] [10] The protective effect of chromate coatings on zinc is indicated by color, progressing from clear/blue to yellow, gold, olive drab and black.
Immersion zinc plating is an electroless (non-electrolytic) coating process that deposits a thin layer of zinc on a less electronegative metal, by immersion in a solution containing a zinc or zincate ions, Zn(OH) 2− 4. A typical use is plating aluminum with zinc prior to electrolytic or electroless nickel plating.
Zinc chromate, Zn Cr O 4, is a chemical compound, a salt containing the chromate anion, appearing as odorless yellow powder or yellow-green crystals, but, when used for coatings, pigments are often added. [2] [3] [4] It is used industrially in chromate conversion coatings, having been developed by the Ford Motor Company in the 1920s. [5]
The specifications for zinc flake coatings are defined in international standard ISO 10683 and also in European standard EN 13858. ISO 10683 sets out the requirements for zinc flake coatings for threaded fasteners and EN 13858 describes the requirements for zinc flake coatings for fasteners with no thread and for other parts as well. There are ...
A phosphate coating is usually obtained by applying to the steel part a dilute solution of phosphoric acid, possibly with soluble iron, zinc, and/or manganese salts. The solution may be applied by sponging, spraying, or immersion. [6] Phosphate conversion coatings can also be used on aluminium, zinc, cadmium, silver and tin. [7] [8]
Such zinc electroplating or zinc alloy electroplating maintains a dominant position among other electroplating process options, based upon electroplated tonnage per annum. According to the International Zinc Association, more than 5 million tons are used yearly for both hot-dip galvanization and electroplating. [ 1 ]
Plating, cladding or other coating methods are used to form an outer layer of metal and are typically used to replace a more expensive metal while retaining the former appearance. For example, United States cents since 1982 are zinc with copper-plating, and thus retain their prior copper look while having a less expensive composition. [ 8 ]
Galvanization (also spelled galvanisation) [1] is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing , in which the parts are coated by submerging them in a bath of hot, molten zinc.