Zinc

Zinc is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. It’s the 24th most abundant element in the Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest mineable amounts are found in Australia, Asia, and the United States.

Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC.

Zinc is an essential mineral of "exceptional biologic and public health importance".  Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.  In children it causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhoea, contributing to the death of about 800,000 children worldwide per year.

The metal is most commonly used as an anti-corrosion agent.  Galvanization, which is the coating of iron or steel to protect the metals against corrosion, is the most familiar form of using zinc in this way.  Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.  A protective surface layer of oxide and carbonate forms as the zinc corrodes.  This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away.  The zinc is applied electrochemically or as molten zinc by hot-dip galvanizing or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, light posts, metal roofs, heat exchangers, and car bodies.

Zinc Oxide used in paint pigments

Zinc is useful for the human body and helps speed up the healing process after an injury.  It is also suspected of being beneficial to the body's immune system. Indeed, zinc deficiency may have effects on virtually all parts of the human immune system.

For more information visit:-

http://www.theguardian.com/science/punctuated-equilibrium/2011/sep/23/1?guni=Article:in%20body%20link

http://en.wikipedia.org/wiki/Zinc

What is Rust?

Rust is composed of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. Other forms of rust exist, like the result of reactions between iron and chloride in an environment deprived of oxygen.

Given sufficient time, oxygen, and water, any iron mass will eventually convert entirely to rust and disintegrate. Surface rust is flaky and friable, and provides no protection to the underlying iron, unlike the formation of patina on copper surfaces. Rusting is the common term for corrosion of iron and its alloys, such as steel. Many other metals undergo equivalent corrosion, but the resulting oxides are not commonly called rust.

Iron oxide, the chemical Fe₂O₃, is common because iron combines very readily with oxygen -- so readily, in fact, that pure iron is only rarely found in nature. Iron (or steel) rusting is an example of corrosion -- an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into metal cations in a form such as rust.

­For iron to become iron oxide, three things are required: iron, water and oxygen.

When a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces -- hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons. The electrons liberated from the anode portion of the iron flow to the cathode, which may be a piece of a metal less electrically reactive than iron, or another point on the piece of iron itself.

The chemical compounds found in liquids like acid rain, seawater and the salt-loaded spray from snow-bound roads make them better electrolytes than pure water, allowing their presence to speed the process of rusting on iron and other forms of corrosion on other metals.

For more information visit:-
http://en.wikipedia.org/wiki/Rust
http://science.howstuffworks.com/question4451.htm
http://en.wikipedia.org/wiki/Rustproofing