Pure metallic Zinc, which has the chemical symbol Zn, was first isolated by Marggraf in 1746, however brass which is an alloy of copper and zinc has been used since at least 1000BC. Zinc is in group 12 of the periodic table and reacts in a similar way to magnesium.
Zinc ore is mined in China, China, Peru and the USA, its most common ore is a sulfide called sphalerite or zinc blende. China is the world’s largest producing, responsible for about one third of the World’s production. Zinc ores are often found in combined deposits with the lead mineral, galena (PbS) and with silver ores. Only about 3 quarters of the Zinc used today is mined, the rest is recycled.
Applications for Zinc
Zinc is the 4th most common metal used today. It is used in as a pure metal, in various alloys and in certain compounds of zinc.
Pure Zinc applications
The main application for Zinc is corrosion resistance, the dip coating of iron in metallic zinc, known as galvanizing, or electrochemical application, produces a surface layer that will be oxidized first before the iron or steel. Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away As the zinc is oxidized it forms a protective layer that prevents further oxidation until the layer is scratched or damaged. The underlying iron or steel is protected from corrosion until the zinc corrodes away completely, which can take many years.
This form of corrosion protection, accounts for over half of the yearly usage of zinc, and is used in many applications such as bridges, street lamps. Car bodies, guard rails and chain link fences.
Other anti-corrosion uses for zinc include connecting zinc rods to underground pipelines. The zinc cathodically protects the pipeline, by slowly corroding itself instead of the pipe. Zinc can also be attached to ship keels, propellers and rudders to provide a sacrificial protection.
Other uses for zinc metal include as an anode material for batteries, both in powdered form and as sheets of zinc.
Zinc is the primary metal used in making American one cent coins since 1982.The zinc core is coated with a thin layer of copper to give the impression of a copper coin.
As a dense, inexpensive, easily worked material, zinc is used as a lead replacement in certain applications ranging from such as fishing lures, tire balances and flywheels.
Zinc Alloy Applications
The most widely used alloy containing zinc is brass, which is an alloy of zinc and copper containing between 3% and 45% zinc, depending upon the type of brass. Brass is significantly stronger and more corrosion resistant than copper alone and the important property of not creating sparks when struck.
Brass is used in water valves, musical instruments where its acoustic properties are appreciated, locks and gears where low friction is needed, in zippers in communications equipment and in tools that are used near explosive gases.
The second most used alloys of zinc are a series of so called “casting alloys” of zinc. Zinc is never used in casting due to its low strength. It is commonly used as an alloy that is composed of Zinc with alloying elements of Aluminum, Magnesium and Copper as well as other trace impurities.
Zinc casting alloys can be used for general industrial applications where strength, hardness, wear resistance or good pressure tightness is required. Zinc alloys often are employed to replace cast iron because of their similar properties
Certain alloys which contain various proportions of aluminum, magnesium, and copper are commonly known as ZAMAK alloys, ZAMAK is a previously trademarked term that comes from the alloy components Zinc, Aluminum, Magnesium and Kupfer (German for copper)
ZAMAK 2 (#2): This is the strongest and hardest ZAMAK alloy, generally used for die casting and is also known as KIRKSITE.
ZAMAK 3 (#3): This is the most commonly used ZAMAK alloy used for die casting. It has very good strength, ductility and impact strength and can be finished or plated to a high quality.
ZAMAK 5 (#5): Harder than ZAMAK 3.
ZAMAK 7 (#7): A purer form of ZAMAK 3 higher ductility so it is suitable for forming and bending.
Aluminum and zinc alloys are the most widely used casting alloys, zinc-aluminum (ZA) alloys are lightweight, offer good corrosion resistance, ease of casting, good mechanical properties and dimensional stability.
There are several standard ZA alloys
ZA-8: This is a cost effective alloy for casting and it provides improved performance over ZAMAK alloys in general ZA-8 can be sand or permanent mold cast.
ZA-12: This is the preferred alloy for permanent mold applications, although it can also be cal-chamber die cast with excellent results. It combines low temperature melting efficiency and thin wall capabilities with premium mechanical properties. ZA-21 can usually be poured directly into molds designed for aluminum and brass.
ZA-27: Components requiring optimum strength, hardness and light weight should be specified using ZA-27. ZA-27 also offers excellent bearing properties, comparable to those of aluminum-bronze.
Other widely used alloys that contain zinc include nickel silver, typewriter metal, soft and aluminum solder, and commercial bronze.
Zinc Compound applications
About 25% of the zinc used yearly is in the form of compounds.
Zinc oxide is used as a white pigment in paints. It also used in rubber production and protection. Its electrical properties make it useful for photocopying products.
Zinc Chloride is a fire retardant and wood preservative.
Zinc sulphide is used in luminescent paints
Cadmium zinc telluride (CZT) is a semiconductor alloy that can be used to detect gamma rays.
Zinc and in particular zinc alloys are widely in use for many applications today.