Rusting of iron happens when iron comes in contact with water/ moisture and oxygen for a period of time
– When the water is salty, rusting is much faster
– Therefore in coastal areas  cars underbody would rust faster . Rusted iron is called “Iron Oxide”. Once rusting starts, it is difficult to stop Car Underbody is also made of iron and comes in contact with plenty of water under various circumstances. In coastal areas, it is in contact with moisture in the air all the time. The presence of water/ moisture along with oxygen in the air causes rusting of car underbody.