Zinc phosphate

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Zinc phosphate
Zinc phosphate
Identifiers
CAS number 7779-90-0 YesY
PubChem 24519
ChemSpider 22927 YesY
UNII 1E2MCT2M62 YesY
RTECS number TD0590000
Jmol-3D images Image 1
Properties
Molecular formula Zn3(PO4)2
Molar mass 386.11 g/mol
Appearance white crystals
Density 3.998 g/cm3
Melting point 900 °C (1,650 °F; 1,170 K)
Solubility in water insoluble
1.595
Structure
Crystal structure monoclinic
Hazards
EU Index 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 hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
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

Zinc phosphate (Zn3(PO4)2) is an inorganic chemical compound used as a corrosion resistant coating on metal surfaces either as part of an electroplating process or applied as a primer pigment (see also red lead). Zinc phosphate coats better on a crystalline structure than bare metal, so a seeding agent is often used as a pre-treatment. One common agent is sodium pyrophosphate.[1]

Natural forms of zinc phosphate include minerals hopeite and parahopeite, Zn3(PO4)2·4H2O. A somewhat similar mineral is natural hydrous zinc phosphate called tarbuttite, Zn2(PO4)(OH). Both are known from oxidation zones of Zn ore beds and were formed through oxidation of sphalerite by the presence of phosphate-rich solutions. The anhydrous form has not yet been found naturally.

Zinc phosphate is formed from zinc phosphate cement and used in dentistry. Zinc phosphate dental cement is one of the oldest and widely used cements, and is commonly used for luting permanent metal restorations and as a base for dental restorations. Zinc phosphate cement is used for cementation of inlays, crowns, bridges, and orthodontic appliances and occasionally as a temporary restoration. It is prepared by mixing zinc oxide and magnesium oxide powders with a liquid consisting principally of phosphoric acid, water, and buffers. It is the standard cement to measure against. It has the longest track record of use in dentistry. It is still commonly used; however, resin-modified glass ionomer cements are more convenient and stronger when used in a dental setting.

References[edit]

  1. ^ Menke, Joseph T. "Zinc Phosphate Coatings on NonFerrous Substrates -- Part I". PFOnline. Retrieved 2006-08-07. 

External Links[edit]