Zinc chromate

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Zinc chromate
Identifiers
CAS number 13530-65-9 YesY
PubChem 26089
RTECS number GB3290000
Properties
Molecular formula ZnCrO4
Molar mass 181.403 g/mol
Appearance yellow-green crystals
Density 3.43 g/cm3
Melting point 316 °C
Boiling point 732 °C
Solubility in water insoluble
Hazards
EU classification not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
U.S. Permissible
exposure limit (PEL)
0.1 mg/m3[1]
LD50 0.5 to 5 g/kg
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references
B-25 Mitchell bombers, painted with zinc chromate undercoat, being assembled, 1942

Zinc chromate, ZnCrO4, is a chemical compound containing the chromate anion, appearing as odorless yellow solid powder.[2][3][4] It is used industrially in chromate conversion coatings, having been developed by Ford Motor Company in 1920s.[5] Exposure to zinc chromate can cause tissue ulceration and cancer.[1][3]

Its use as a corrosion resistant agent was applied to aluminium alloy parts first in commercial aircraft, and then in military ones. During the 1940 and 1950s it was typically found as the "paint" in the wheel wells of retractable landing gear on U.S. military aircraft to protect the aluminium from corrosion.

When used as a pigment, it is known as Zinc Yellow,[2] Buttercup Yellow or Yellow 36.[6] It is rarely used in art because the pigment degenerates into a brown color. This effect can be seen in Georges Seurat's famous painting: A Sunday Afternoon on the Island of La Grande Jatte.[7]

Zinc chromate putty was used as sealant in addition to two O-rings between sections of the failed solid rocket booster on Space Shuttle Challenger. Blowholes in this putty may have been a minor contributor to the loss of the shuttle.[8]

References[edit]

  1. ^ a b "OHSA Chemical Sampling Information for Zinc Chromate". Occupational Safety and Health Administration. Retrieved 24 March 2011. 
  2. ^ a b National Oceanic and Atmospheric Administration. "ZINC CHROMATE - CAMEO Chemicals". Retrieved 24 March 2011. 
  3. ^ a b "OHSA Guideline for Zinc Chromate". Occupational Safety and Health Administration. Retrieved 24 March 2011. 
  4. ^ Richard P. Pohanish (9 February 2004). HazMat data: for first response, transportation, storage, and security. John Wiley and Sons. p. 1155. ISBN 978-0-471-27328-8. Retrieved 24 March 2011. 
  5. ^ Waligorski, Martin. "Everything You Need to Know About Zinc Chromate". Retrieved 23 March 2011. 
  6. ^ "Basic Zinc Chromate". Chemical Land21. Retrieved 24 March 2011. 
  7. ^ Gage, John (1993). Color and Culture: Practice and Meaning from Antiquity to Abstraction. Boston: Little, Brown. pp. 220, 224. .
  8. ^ J.A. Hickman (1997). Polymeric Seals and Sealing Technology. iSmithers Rapra Publishing. p. 25. ISBN 978-1-85957-096-8. Retrieved 24 March 2011.