Simple Definition:

Corrosion is the process of gradually damaging or destroying a material (such as metal) because of a chemical reaction with its environment (such as exposure to water or air). It typically results in the formation of a rust-like substance on the surface of the material.

Examples:

• When a metal fence is constantly exposed to rain, the water reacts with the metal, causing it to rust and weaken over time.
• If you leave a piece of iron outside, it will eventually start corroding and develop a reddish-brown layer called rust.

Very Simple Definition:

Corrosion is when metal gets damaged and turns rusty because of water or air.

Examples:

• When a metal gets wet and left outside for a long time, it can get rusty.
• If you leave a coin in water, it might start to change color and become rough.