Zinc phosphate

Zinc phosphate

Names
IUPAC name Zinc phosphate
Identifiers
CAS Number	7779-90-0 Y
ChemSpider	22927 Y
Jmol interactive 3D	Image
PubChem	24519
RTECS number	TD0590000
UNII	1E2MCT2M62 Y
InChI InChI=1S/2H3O4P.3Zn/c2*1-5(2,3)4;;;/h2*(H3,1,2,3,4);;;/q;;3*+2/p-6 Y Key: LRXTYHSAJDENHV-UHFFFAOYSA-H Y InChI=1/2H3O4P.3Zn/c2*1-5(2,3)4;;;/h2*(H3,1,2,3,4);;;/q;;3*+2/p-6 Key: LRXTYHSAJDENHV-CYFPFDDLAR
SMILES [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])(=O)[O-].[O-]P([O-])([O-])=O
Properties
Chemical 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
Refractive index (nD)	1.595
Structure
Crystal structure	monoclinic
Hazards
NFPA 704	0 2 0
Flash point	Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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). It has largely displaced toxic materials based on lead or chromium, and by 2006 it had become the most commonly used corrosion inhibitor.^[1] 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.^[2]

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

1. ↑ Kalendov´a, A.; Kalenda, P.; Vesel´y, D. (2006). "Comparison of the efficiency of inorganic nonmetal pigments with zinc powder in anticorrosion paints". Progress in Organic Coatings (Elsevier) 57: 1–10. doi:10.1016/j.porgcoat.2006.05.015. 
2. ↑ Menke, Joseph T. "Zinc Phosphate Coatings on NonFerrous Substrates -- Part I". PFOnline. Retrieved 2006-08-07. 

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