Rusting of Iron - Elementary Science

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• published: 03 Sep 2012
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RUSTING OF IRON A common change we are familiar with is rusting of iron. A piece of iron left in the open for some time acquires a layer of brownish substance on its surface. This substance is called rust and the process is called rusting of iron. Iron gates of parks, iron benches kept in gardens, and many other articles of iron, kept in the open get rusted. In our homes too, we have observed the process of rusting on many of our iron articles. Rust is not iron. It is different from iron on which it gets deposited. Rusting is a chemical change that affects iron articles and slowly destroys them. Since iron is used in making bridges, ships, cars, truck bodies and many other articles, the monetary loss due to rusting is huge. The process of rusting can be shown by the following equation: Iron (Fe) + Oxygen (O2, from the air) + water (H2O) gives Rust (Iron Oxide Fe2O3) For rusting of iron to take place, both oxygen and water (or water vapor) need to be present in the atmosphere. In fact, the higher the moisture content in air, which means more humidity, the faster the rusting occurs. One can avoid rusting by preventing iron articles from coming in contact with oxygen, or water, or both. A simple solution would be to apply a coat of paint or grease. In fact, these coats should be applied regularly to prevent rusting. Another way is to deposit a layer of a metal like chromium or zinc on iron. This industrial process of applying a layer of zinc on iron is called galvanization. The iron pipes we use in our homes to carry water are galvanized to prevent rusting. Ships are made of iron with a part of them always under water. On the part above water level also, water drops are present on the ship's outer surface. Moreover, the water of the sea contains many salts. The salt water aides in the process of rust formation. Therefore, ships suffer a lot of damage from rusting in spite of being painted on. So much so, that replacing a major part of ship's iron every year is mandatory. Stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese. This prevents rusting of iron.