Question

explain why rusting of iron objects is faster in coastal areas then in desert ?

Answer 1

the reason that iron rusts anywhere is because oxygen and iron 
produce iron oxide, more commonly known as rust, in a chemical reaction.
Coastal areas tend to be more humid than other areas, so there is more 
moisture in the air.

Answer 2

it is because in coastal areas there is much amount of moisture in air due to water,
so rusting fastens because it reacts with water to form iron oxide and iron object corrodes easily