Corrosion takes place when the material loses electron and gets oxidized.
Corrosion is seen in metals as they tend to lose electrons to oxygen or water molecules present in the air.
While in case of plastic, they don't have free electrons to lose. So they do not react with air and water which are essential for corrosion.
As they tend to remain unreactive with strong chemicals, hence cleansing chemicals are stored in plastic bottles and not in metal containers.