What is corrosion?

What is corrosion in easy language?
Corrosion is when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the material.

What is the problem with corrosion?
Corrosion is a dangerous and extremely costly problem. Because of it, buildings and bridges can collapse, oil pipelines break, industrial plants leak, and plant catches fires.