Zinc Alloys – Properties, Occurrence, Compounds, Uses

Zinc is a chemical element with the symbol Zn and the atomic number 30. At room temperature, zinc is a slightly brittle metal with a silvery-greyish look when oxidation is removed. It is the first element in Periodic Table Group 12 of the periodic table (IIB). In certain ways, zinc and magnesium are chemically similar: both elements have only one normal oxidation state (+2). Zinc is the twenty-fourth most prevalent element in the Earth’s crust, with five stable isotopes. Sphalerite (zinc blende), a zinc sulphide mineral, is the most common zinc ore.

Physical properties

1. Zinc is a bluish-white, shiny, diamagnetic metal with a dull polish in the majority of commercial grades.
2. It has a hexagonal crystal structure with a deformed type of hexagonal tight packing and is somewhat less dense than iron.
3. At most temperatures, the metal is hard and brittle, although it becomes pliable between 100 and 150 °C.
4. At temperatures above 210°C, the metal reverts to brittleness and can be crushed by beating.
5. Zinc is a good electrical conductor.
6. Zinc has a low melting and boiling temperatures for a metal. Apart from mercury and cadmium, the melting point of all the d-block metals is the lowest; for this reason, zinc, cadmium, and mercury are frequently not considered transition metals like the rest of the d-block metals.
7. Many alloys, including brass, include zinc. Aluminium, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium, and sodium have long been known to make binary alloys with zinc.

Occurrence

Zinc constitutes around 75 ppm of the Earth’s crust. In ores, the element is typically found in combination with other base metals such as copper and lead. Zinc is a chalcophile, which means it is more likely to be found in minerals with sulphur and other heavy chalcogens than with the light chalcogen oxygen or non-chalcogen electronegative elements like halogens. Other minerals can be used to make zinc carbonate, zinc silicate, and so on. Zinc reserves are geologically defined ore deposits whose economic viability (location, grade, quality, and quantity) is determined at the time of determination. Because exploration and mine development are ongoing processes, the amount of zinc deposits are not fixed, and the sustainability of zinc ore supplies cannot be determined merely by extrapolating the total mine life of today’s zinc mines.

Compounds

Zinc(I) compounds

Zinc(I) compounds are uncommon and require bulky ligands to maintain their low oxidation state. The [Zn₂]²⁺ core is found in the majority of zinc(I) compounds. The ion’s diamagnetic properties validate its dimeric structure. The [Zn₂]²⁺ ion rapidly disproportionate into zinc metal and zinc(II), and only a yellow glass may be formed by cooling a metallic zinc solution in molten ZnCl2.

Zinc(II) Compounds

Except for noble gases, binary zinc compounds are known for the majority of metalloids and all nonmetals. ZnO is a white powder that is practically insoluble in neutral aqueous solutions but amphoteric, soluble in both strong basic and acidic solutions.

Alloys and Ores

Brass is a common zinc alloy in which copper is alloyed with anywhere from 3% to 45% zinc, depending on the type of brass. Brass is more ductile and stronger than copper, and it resists corrosion better. Because of these characteristics, it is useful in communication equipment, hardware, musical instruments, and water valves. Nickel silver, typewriter metal, soft and aluminium solder, and commercial bronze are all examples of zinc alloys that are frequently utilised. Zinc is also utilised as a substitute for the traditional lead/tin alloy in pipes in modern pipe organs.

Zinc alloys with trace amounts of copper, aluminium, and magnesium are helpful in die and spin casting, particularly in the automotive, electrical, and hardware sectors. The alloy’s low melting point, combined with its low viscosity, allows for the creation of microscopic and delicate shapes. Because of the low working temperature, the cast goods cool quickly and assembly is completed quickly. Prestel, which is made up of 78% zinc and 22% aluminium, is said to be nearly as strong as steel but as pliable as plastic. Because of the alloy’s superplasticity, it may be moulded using ceramic and cement die casts. Stamping dies made of 96 percent zinc and 4 percent aluminium alloy are utilised for a limited production run situations where ferrous metal dies would be prohibitively expensive.

Zinc ores can be found all over the world. Zinc sulphide is known as zinc blende or sphalerite (ZnS), a ferrous version of zinc blende known as marmatite, and zinc carbonate is known as calamine or smithsonite are the most prevalent zinc-containing minerals.

Zinc deposits have complicated geology. The majority of the time, hydrothermal methods were used, in which aqueous solutions were driven through porous strata at high temperatures and pressures to dissolve zinc, lead, and other minerals, which were then precipitated as sulphides. The zinc percentage of mined ore is typically between 3 and 10%. Almost all ores contain galena, a lead sulphide mineral, as well as trace amounts of cadmium sulphide. Chalcopyrite and copper-iron sulphide are frequently found. Calcite, dolomite, and quartz are the most prevalent gangue elements. The geology of zinc deposits is complex. In most cases, hydrothermal mechanisms were used to dissolve zinc, lead, and other minerals, which were then precipitated as sulphides after being driven through porous strata at high temperatures and pressures. Zinc concentration in mined ore is typically between 3% and 10%. Galena, a lead sulphide mineral, is found in almost all ores, as well as minor amounts of cadmium sulphide. Chalcopyrite and copper-iron sulphide are frequently found. Calcite, dolomite, and quartz are the most prevalent gangue elements.

Uses

1. The metal is utilised in industry, such as the production of roofing materials and zinc oxide.
2. The metallic element is utilised for a variety of applications, including sunscreens, solar cells, and nuclear reactors.
3. The element helps to keep the human body’s enzyme balance in check.
4. It’s a white pigment used in oil-based paints.
5. Another notable application for zinc oxide is as an addition to the rubber used in the manufacture of automotive tyres.
6. Zinc oxide can tolerate high temperatures and keeps tyres from collapsing when they get hot.

Sample Problems

Question 1: What are the advantages of zinc supplementation?

Solution: 

Zinc, a mineral contained in your body, helps your immune system and metabolism function properly. Zinc is also necessary for wound healing, as well as for your senses of taste and smell. A diversified diet provides your body with enough zinc.

Question 2: What are the disadvantages of zinc?

Solution: 

Just as a zinc deficiency can be harmful to one’s health, an excess of zinc can have the opposite impact. Excess zinc consumption is the most common form of zinc poisoning, which can induce both acute and chronic symptoms. Toxic symptoms include nausea and vomiting.

Question 3: What is zinc used for?

Solution:

Zinc is required for the human body to grow and sustain itself appropriately. It is present in a variety of systems and biological events and is necessary for immunological function, wound healing, blood clotting, thyroid function, and other functions.

Question 4:Why does zinc have a low melting point?

Solution:

The d orbital of iron is only partially filled, whereas the d orbital of zinc is totally filled. Regardless of the screening effect, Zn has a substantially larger size than Fe, which means that Zn’s valence electrons are less restricted to the nucleus.

Question 5: Does Zinc rust in water?

Solution: 

When exposed to air and water, zinc, like all ferrous metals, corrodes. Zinc, on the other hand, corrodes steel at a fraction of the pace. Zinc, like other ferrous metals, corrodes or rusts at variable rates depending on its environment.