How Does Zinc Phosphate Work in Everyday Chemistry?
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
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.
FAQs on Zinc Phosphate: Structure, Properties, and Applications
1. What is Zinc Phosphate and what is its chemical formula?
Zinc Phosphate is an inorganic chemical compound that serves as a salt of zinc and phosphoric acid. It is a white, crystalline solid that is insoluble in water. Its chemical formula is Zn₃(PO₄)₂, which indicates that it is composed of three zinc cations (Zn²⁺) and two phosphate anions (PO₄³⁻).
2. What are the main applications of Zinc Phosphate in industries and healthcare?
Zinc Phosphate has several important applications due to its unique properties. Its primary uses include:
Corrosion-Resistant Coating: It is widely used as a pigment in primers to prevent the rusting of steel and other metal surfaces.
Dental Cement: In dentistry, it is used for luting permanent metal restorations, such as crowns and bridges, and as a base under fillings.
Pigment and Filler: It can also be used as a non-toxic white pigment in paints and as a filler in certain materials.
3. How does Zinc Phosphate work as a corrosion-resistant coating on metals?
Zinc Phosphate functions as a corrosion inhibitor by a process called phosphating or passivation. When applied to a metal surface, it reacts to form a thin, insoluble, and non-conductive crystalline layer. This layer acts as a physical barrier that isolates the metal from environmental moisture and oxygen, effectively preventing the electrochemical process of rusting from starting.
4. What is the fundamental difference between Zinc Phosphate and Zinc Phosphide?
It is crucial not to confuse Zinc Phosphate with Zinc Phosphide as they have vastly different properties and uses. The key difference lies in their chemical composition and reactivity.
Zinc Phosphate (Zn₃(PO₄)₂): A stable, non-toxic salt used in anti-corrosion coatings and dental cements. It contains the phosphate ion (PO₄³⁻).
Zinc Phosphide (Zn₃P₂): A highly toxic compound used as a potent rodenticide. It contains the phosphide ion (P³⁻). When it reacts with acid, such as stomach acid, it releases extremely toxic phosphine gas (PH₃).
5. What are the key physical and chemical properties of Zinc Phosphate?
Zinc Phosphate exhibits several distinct properties relevant to its applications:
Appearance: It is a white, odourless, crystalline solid.
Solubility: It is practically insoluble in water but readily dissolves in mineral acids and acetic acid.
Melting Point: It has a high melting point of approximately 900°C, indicating strong ionic bonding.
Stability: It is a stable compound under normal conditions and is not flammable.
6. Why is Zinc Phosphate used as a dental cement, and what are its main disadvantages in this role?
Zinc Phosphate is used in dentistry because it offers good compressive strength and has a long track record of clinical success. However, it has notable disadvantages. The liquid component is phosphoric acid, making the initial mixture highly acidic (low pH), which can irritate the tooth's pulp. Additionally, the setting reaction is exothermic, meaning it releases heat, which can cause temporary discomfort for the patient.
7. How is Zinc Phosphate typically prepared in a laboratory setting?
A common method for preparing Zinc Phosphate involves a neutralization reaction. It is synthesized by reacting zinc oxide (ZnO) with phosphoric acid (H₃PO₄). The zinc oxide acts as a base, reacting with the acid to form the salt (zinc phosphate) and water. The balanced chemical equation for this reaction is: 3ZnO + 2H₃PO₄ → Zn₃(PO₄)₂ + 3H₂O.
8. Is Zinc Phosphate considered safe for humans and the environment?
The safety of Zinc Phosphate depends heavily on its application and exposure route. When used in its intended forms, such as a cured dental cement or as a component in a protective coating, it is stable and considered safe. However, ingesting the raw powder can be harmful, causing irritation to the digestive system. Environmentally, it is classified as very toxic to aquatic life, so its disposal must be managed carefully to prevent contamination of water bodies.
