Corrosion and its Prevention
Corrosion and its Prevention
Corrosion:
It is the slow process of eating away of metals by the reaction of atmospheric air and moisture, e.g. rusting of iron, tarnishing of silver, formation of green coating over copper etc.
When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The green material is a mixture of copper hydroxide and copper carbonate
. The reaction involved is
• Iron reacts with oxygen and moisture present in the atmosphere to form a brown, flaky substance called rust. Rusting of iron in an undesirable reaction because the layer of rust formed falls off, exposing the metal to further rusting.
Prevention of Corrosion:
Rusting of iron is prevented by galvanizing, by making alloys, painting greasing or oiling and tin- planting and chromium plating which are explained below:·
1. Galvanisation: The process of coating iron and steel objects with a thin layer of zinc is called galvanization. It is done by dipping the object in molten zinc.The galvanized article is protected against rusting even if the zinc coating is broken.·
Which of the following is/are necessary for rusting to take place ? | |||
| Right Option : B | |||
| View Explanation | |||
Silver articles become _________________ after some time when exposed to air. | |||
| Right Option : A | |||
| View Explanation | |||
Which of the following are correct : (a) The process of coating iron and steel objects with a thin layer of zinc is called galvanization. (b) The process of slow eating away of a metal due to the attack of atmospheric gases and moisture on its surface is called corrosion. (c) When grease or oil is applied to the surface of an it forms a coating on the surface of the metal and hence prevent corrosion. | |||
| Right Option : D | |||
| View Explanation | |||
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