This is one 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 represented by the following equation:
Iron (Fe) + Oxygen ( O2 , from the air) water (H2O) → rust (iron oxide Fe2O3 )
For rusting, the presence of both oxygen and water (or water vapour) is essential.
In fact, if the content of moisture in air is high, which means if it is more humid, rusting becomes faster.