Zinc chromate , ZnCrO 4 , is a chemical compound containing chromate anion, appears as yellow odorless powder or yellow-green crystal, but, when used for coatings, pigments are often added. This industry is used in chromate conversion coating, which has been developed by Ford Motor Company in the 1920s.
Video Zinc chromate
Produksi
The process known as the Cronak process is used to make zinc chromate for use in industry. This process is carried out by placing zinc or zinc-coated metal in a solution of sodium dichromate and sulfuric acid for a few seconds. Zinc chromate can also be synthesized by using neutral potassium chromate (K 2 CrO 4 ) and zinc sulfate (ZnSO 4 ), which form the precipitate.
K 2 4 ZnSO 4 -> ZnCrO 4 K 2 SO 4
Maps Zinc chromate
Usage
The main use of Zinc Chromate is on industrial painting as a coating of iron or aluminum material. It was used extensively on planes by the US military, especially during the 1930s and 1940s. It is also used in various coats of paint for the aerospace and automotive industries. Its use as a corrosion-resistant agent is applied to the first aluminum alloy parts in commercial aircraft, and later in the military. During the 1940s and 1950s it was commonly found as "paint" in the wheels of dental landing gears drawn on US military aircraft to protect aluminum from corrosion. This compound is a useful coating because it is an anti-corrosive and anti-rust primer. Because it is highly toxic, it also destroys organic growth on the surface. Zinc chromate is also used in spray paint, paint artists, pigments in varnish, and in linoleum making.
When used as a pigment, it is known as Yellow Zinc, Yellow Buttercup or Yellow 36. It is rarely used in art because the pigments degenerate into brown. This effect can be seen in the famous painting Georges Seurat A Sunday Sore on La Grande Jatte Island . The degradation of yellow zinc in the painting of Surat was thoroughly investigated and these findings were later used in the digital rejuvenation of the painting.
Zinc chromate putty is used as a sealant next to two O-rings between parts of a solid rocket booster that fail in the Space Shuttle Challenger. The pits in this putty may be a small contributor to the loss of the disaster.
Toxicity
Recent research has shown that not only is the zinc chromate highly toxic, but also carcinogenic. Exposure to zinc chromate can lead to tissue ulceration and cancer. A study published in the British Journal of Industrial Medicine showed a significant correlation between the use of zinc chromate and lead chromate at the plant and the number of lung cancer cases experienced by the workers. Due to its toxicity, the use of zinc chromate has been greatly reduced in recent years.
References
Source of the article : Wikipedia
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