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A process known as the Cronak process is used to create zinc chromate for use in industry. This process is done by putting zinc or a zinc plated metal in a solution of sodium dichromate and sulfuric acid for a few seconds. [6] Zinc chromate can also be synthesized by using neutral potassium chromate (K 2 CrO 4) and zinc sulfate (ZnSO 4), which ...
The Cronak process is a conventional chromate conversion coating process developed in 1933 by The New Jersey Zinc Company. [1] It involves immersing a zinc or zinc-plated article for 5 to 15 seconds in a chromate solution, typically prepared from sodium dichromate and sulfuric acid. [2]
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.
A conversion coating is a chemical or electro-chemical treatment applied to manufactured parts that superficially converts the material into a thin adhering coating of an insoluble compound.
This process is not recommended for structural steel. Painting and gluing aluminum are especially important in the aircraft industry, which uses toxic zinc chromate primers and chromating to add the necessary adhesion properties. In addition, primer provides a smooth surface for the paint to adhere to, resulting in a professional-looking finish.
Mounted on a rack the parts get sprayed with the zinc flake material (spraying process) or, placed inside a container, they get dipped and spun (dip-spinning). The coating material forms a liquid, uniform layer on the parts' surface. In order to develop the excellent properties of zinc flake coatings, an annealing process is required.
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. [citation needed]
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 galvanizing and electroplating. [ 1 ]