when metal undergoes oxidation corrosion, it involes

Answer 1

Vague question. The question itself is essentially the answer. When a metal is oxidized it becomes the oxide of the metal. Now, if by 'corrosion' you're implying the breakdown of that oxide, it would next react with water (such as from rain) to form the hydroxide, which then would break away from the lower surfaces of the metal, exposing more surface area to the 'element' and continue corroding.