Zinc phosphate

Zinc phosphate is an inorganic compound with the formula Zn3(PO4)2)(H2O)4. This white powder is widely 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][2] 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.[3]

Zinc phosphate
Names
IUPAC name
Zinc phosphate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.040
RTECS number
  • TD0590000
UNII
Properties
H4O12P2Zn3
Molar mass 454.11 g·mol−1
Appearance white solid
Density 3.998 g/cm3
Melting point 900 °C (1,650 °F; 1,170 K)
insoluble
−141.0·10−6

cm3/mol

1.595
Structure
monoclinic
Thermochemistry
− 2891.2 ± 3.3
Hazards
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
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).
Y verify (what is YN ?)
Infobox references

Minerals

Natural forms of zinc phosphate include minerals hopeite and parahopeite. 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.

Dentistry

Zinc phosphate dental cement is one of the oldest and widely used dental cements. It is commonly used for luting permanent metal and zirconium dioxide[4][5][6][7][8][9] 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. Etzrodt, G. (2012). "Pigments, Inorganic 5. Anticorrosive Pigments". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.n20_n04.
  3. Menke, Joseph T. "Zinc Phosphate Coatings on NonFerrous Substrates -- Part I". PFOnline. Retrieved 2006-08-07.
  4. Raab D: Befestigung von Zirkonoxidkeramiken. DENTALZEIZUNG 2007: 6; 32-34. http://www.zwp-online.info/archiv/pub/pim/dz/2007/dz0607/dz607_032_034_hoffmann.pdf
  5. Raab D: Befestigung von Vollkeramiken aus Zirkonoxid. ZAHNARZT WIRTSCHAFT PRAXIS 2007: 12; 98-101. http://www.zwp-online.info/archiv/pub/gim/zwp/2007/zwp1207/zwp1207_098_101_hoffmann.pdf
  6. Raab D: Fixation of all ceramic restorations – the advantages of cementation. DENTAL INC 2008: March / April 50-53.
  7. Raab D: Befestigung von Zirkonoxidkeramiken. ZAHN PRAX 2008: 11; 16-19.
  8. Raab D: Fixation of full ceramic restorations – the advantages of cementation. 全瓷修复的粘接 — 水门汀的优势. DENTAL INC Chinese Edition 2008: Sonderdruck.
  9. Raab D: Konventionelle Befestigung von Vollkeramikrestaurationen. ZAHN PRAX 2009: 12; 84-86.


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