Dear Student
Corrosion is the process in which metals, are deteriorated by the action of air, moisture, chemicals etc. Corrosion causes damage to iron rail tracks.
When metals like Iron and copper come in contact with air and moisture they get corrode and forms a layer of oxides or carbonates on its surface, these layers deteriorate the metal. Corrosion in the case of Iron is called rusting, which can be explained by the following equation.
Fe+O2+x.H2O→Fe2O3.xH2O(rust)
This rust deteriorates the quality of railway tracks and hence a lot of costs are incurred every year to fix this.
To fix this, paint-coating can be done which will protect the metal from getting exposed to the moisture and oxygen.
Regards.