Rust is essentially oxidation. It is a chemical interaction involving oxygen. When oxidation occurs, a thin film is formed as a result—such as the green layer that copper acquires or as iron— which shows rust as evidence of oxidation. If iron is exposed to an environment both oxygen–rich and friendly towards the catalyst, the oxidation process begins. The presence of salt in the water accelerates this process of oxidation because it increases the conductivity of water and in effect increases the concentration of ions in the water. This means electrons can move more easily. Since rusting is all about the movement of electrons, metal rusts more quickly in salt water.
Why does salt water make metal rust faster?
