Zinc chromate
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| General | |||||||||||||||||||
| Surname | Zinc chromate | ||||||||||||||||||
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| Molecular formula | ZnCrO 4 | ||||||||||||||||||
| Brief description |
lemon yellow powder |
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| properties | |||||||||||||||||||
| Molar mass | 181,38 g · mol -1 | ||||||||||||||||||
| Physical state |
firmly |
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| density |
3.40 g cm −3 |
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| Melting point |
316 ° C (decomposition from 440 ° C) |
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| solubility |
practically insoluble in cold water |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||||||||
Zinc chromate is a chemical compound (more precisely a chromate ) with the empirical formula ZnCrO 4 , which is mainly used as a yellow color pigment and anti-corrosion agent.
Extraction and presentation
Finely ground zinc oxide (zinc white) is partially converted to sulfate with sulfuric acid and then precipitated with potassium dichromate . After the precipitate has settled for a long time, it is filtered off and rinsed.
In some wood preservatives , zinc chromate is formed from the ingredients zinc hexafluorosilicate and CK salt (chromium-containing salts) in aqueous solution .
use
Zinc chromate is an anti-corrosive pigment with a basic reaction (i.e. a strong oxidizing agent ). It acts by neutralization of attacking acids , cathodic and anodic protection of the metal surface by redox reactions and by inactivating corrosive chloride - and sulfate ions by corresponding sparingly soluble salts forms (see also chromating ). In the past it was often used in "wash primers" (adhesion promoter between the material and other coatings), but also in corrosion protection primers. In the RAL color system it has the number 1018.
safety instructions
Zinc chromate has a carcinogenic and mutagenic effect (mostly through inhalation of dust).
See also
- Zinc hexafluorosilicate Zn [SiF 6 ]
- Zinc potassium chromate
- Zinc chromate hydroxide
- Tetrahydroxozinc chromate
Web links
- Zinc chromate in paints ( Memento from June 30, 2014 in the Internet Archive ) (PDF file; 65 kB)
Individual evidence
- ↑ a b c d e f Entry on zinc chromate in the GESTIS substance database of the IFA , accessed on January 28, 2020(JavaScript required) .
- ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling falls under the group entry zinc chromates including zinc potassium chromate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Wood protection. In: schadstoffberatung.de. Pollutant Advice Tübingen, December 2015, accessed on March 5, 2019 .
- ↑ External identifiers or database links for zinc chromate hydroxide: CAS number: 15930-94-6, GESTIS substance database : 491132 , PubChem : 27567 , ChemSpider : 32702056 , Wikidata : Q27256665 .