Zinc Phosphate

What is Zinc Phosphate?

The Zn3(PO4)2 is an inorganic chemical compound having a chemical name Zinc Phosphate. The other names for Zinc Phosphate are Zinc orthophosphate, Trizinc phosphate, and Trizinc diphosphate. This white powder compound is widely used as a corrosion-resistant coating, which is applied on the metal surfaces, which are put as a part of electroplating or as a primer pigment. 

When compared to the bare metal, the trizinc phosphate coats better on a crystalline structure. Thus, a seeding agent like sodium pyrophosphate is used frequently as a pre-treatment. It has largely displaced toxic materials based on chromium or lead. It had become one of the most commonly used corrosion inhibitors by 2006. The common agent of this Zn3(PO4)2 is sodium pyrophosphate.

Zinc Phosphate Formula

As every chemical, organic compound, or substance, the Zinc Phosphate has also a chemical formula. The chemical formula for zinc phosphate is Zn3(PO4)2.

Zinc Phosphate properties

The chemical zinc phosphate properties are provided below.

Chemical Properties

Appearance of Zn3(PO4)2

White crystals

Crystal Structure of Zinc Phosphate


Density of Zn3(PO4)2

3.998 g/cm3

IUPAC/Chemical name for Zn3(PO4)2

Zinc Phosphate

Melting Point of Zinc Phosphate

900 °C

Molar Mass of Zn3(PO4)2

386.11 g/mol

Molecular Formula of Zn3(PO4)2


Solubility of Zn3(PO4)2


Flashpoint of Zinc Phosphate


Zinc Phosphate Structure - Zn3(PO4)2

The chemical structure of Zinc Phosphate is represented below.

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How to Make Zinc Phosphate?

Zinc Phosphate is prepared by mixing magnesium oxide and zinc oxide powders consisting of a liquid principally of water, phosphoric acid, and buffers. It is one of the standard types of cement to measure against. It has the longest track record of terms of dentistry. Still, it is commonly used, and however, the resin-modified glass ionomer types of cement are more stronger and convenient when used for dental settings.

Zinc Phosphate Coating

As it is said that the Zinc Phosphate is used as a corrosion-resistant coating which is applied on the metal surfaces, the process of coating is explained below.

Coating Process Using a Thermostatic Cell

The phosphating process creates a relatively inert film (Passivation) on the surface of a material, which prevents the interaction between the external agent and the metal. The chemical reaction is either reduced or impeded completely by increasing the adhesion of the paint on the metal surface. This will prevent corrosion and increase lubrication for creating or drawing processes. Also, it can act as a base for subsequent coatings or paints. 

The primary coating on the surface of carbon steel (1) was deposited by the thermostatic immersion cell (2) by using a phosphating solution (3). This process gives a primary coating with better paint adhesion. The phosphating solution passes through a latex tube (4) which is connected to the water bath (5) fixed at different temperatures ranging from 20 - 80 °C by using a regulator (6) to maintain the temperature at the required value as shown in the figure.

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The coating process can also be applied by using a mobile device.

Working of Zinc Phosphate

When zinc phosphide is eaten either by a person or an animal, the acid present in the stomach makes it release the toxic gas phosphine. Baits having zinc phosphide are primarily dangerous to animals that cannot vomit, such as rabbits, rats, and mice.

Then, the phosphine in the stomach crosses into the body cells and stops the cells from energy production, and this, in turn, causes the cells to die. Zinc phosphide affects all the cells, but targets cells in the lungs, liver, and even heart.

Symptoms when Exposed to Zinc Phosphide

Some of the symptoms of exposure to phosphine gas and zinc phosphide include dizziness, headache, breathing difficulties, and vomiting. The other problems like convulsions, liver and kidney failure, coma, and delirium may also occur if a person is exposed to excess phosphine.

Zinc phosphide also impacts animals in the same way as it can affect humans. Signs of poisoning in animals include anxiety, retching, and vomiting. Also, the animals may begin to stagger or lose their coordination. Such signs could start in just less than an hour after exposure if there is food in the stomach of the animal, or up to 12 hours if the stomach was empty. The vomit of poisoned dogs may also contain phosphine.

Environmental Effects of Zinc Phosphate

Zinc phosphide will break down when exposed to water or moist soil in the environment. Any phosphine that is emitted will be broken down by air.

Still, the pellets of Zinc Phosphide may release phosphine five weeks after being placed on damp soils, although the amount released is dependent on the pellets formulation.

Zinc Phosphate Uses

There are many of the Zinc Phosphate uses when considered, and a few of them are listed below.

  • Zinc phosphate (Zn3(PO4)2) is used in dentistry.

  • Used as a plating agent and as a surface treating agent as well.

  • Used in the production of rubber products.

  • Used as an anti-scaling agent.

  • Used in the preparation of dyes.

  • Used as a paint additive.

  • Can be used as a corrosion inhibitor.

  • Used for water treatment products.

Occurrence of Zinc phosphate

A few of the different forms of Zinc orthophosphate are minerals like parahopeite and hopeite. A similar mineral is a tarbuttite, Zn2(PO4)(OH).

This mineral originates from zinc phosphate cement. This cement is most commonly used as a base for dental restorations. It is used for cementation of inlays, crowns, bridges, as a temporary restoration, and for orthodontic appliances. It is made by mixing powders of zinc oxide and magnesium oxide with a liquid consisting of phosphoric acid, water, and buffers.

FAQ (Frequently Asked Questions)

1. What are the Disadvantages of Zinc Phosphate Cement?

It is quite important to understand that all dental cement classes dissolve in the mouth. As per Zinc Phosphate, there is an exothermic reaction that takes place when the cement gets settled. This can be damage to the pulp of living teeth. In general, it is not, but in some cases, it can be.

The main disadvantage of Zinc Phosphate has come from the acidic nature of the liquid (phosphoric acid), and it was not easy to mix, and many patients may have experienced discomfort after analgesia wore off before the full set of this compound material. It was difficult to mix potentially leaving much free acid in the mix than ideal, but that aspect may have improved well, and more patient-friendly luting types of cement are now used instead.

2. Mention some Environmental Effects of Zinc Phosphate?

Zinc phosphide will break down when exposed to water or moist soil in the environment. Any phosphine that is emitted will be broken down by air.

Still, the pellets of Zinc Phosphide may release phosphine five weeks after being placed on damp soils, although the amount released is dependent on the pellets formulation.

Zinc phosphide can break down to phosphine or phosphoric acid when exposed to highly acidic conditions. But, there is no information found on zinc phosphide and groundwater.