Theory:

We come across many iron articles around us. Iron is used in making bridges, ships, cars, truck bodies, grills in windows, etc.
 
chain-566778_1280.jpg
Rusted iron chains
Iron turns into rust when exposed to air and moisture in the atmosphere. 
Rusting is an example of  a chemical change where the process cannot be reversed, and a new substance is formed. This is also called as a chemical reaction. Rusting becomes faster when there is humidity and high salt content in water.
 
Iron+Oxygen+WaterIronoxide(rust)Fe+O2+H2OFe2O3
 
Prevention:
 
1. Frequent coating of paint or grease on iron articles slower the process of rusting.ru2.jpg
Coating iron ship with paint
 
2. Galvanisation (depositing a layer of zinc on iron).
ru3.jpg
Galvanised iron sheets
 
3. Alloy (mixing iron with other metals).
ru4.jpg
Gold chain mixed with other metals
 
The iron galvanized pipes are used in our homes to carry water to prevent rusting. Ships suffer a lot of damage from rusting so to prevent its damage, stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese.
 
rust.jpg
Rusted iron ships